Read the emphasis, the links and the lone image CommonMark spells (#34)

AGENTS.md

@@ -148,7 +148,9 @@ live Atlassian APIs; property-generated ADF trees; the CommonMark spec suite aga
 - `src/adf/` holds ADF's own knowledge and imports no format. Each format directory (`markdown/`,
   `html/`) parts into `emit/` (ADF→format) and `parse/` (format→ADF), its root holding what both
   directions read. A construct's reader lives in that root beside the regex the emitter escapes
-  against, so the two cannot drift; a reader with no emit counterpart goes in `parse/`. A rule both
+  against, so the two cannot drift; a reader with no emit counterpart goes in `parse/`, unless it is
+  part of a construct the root already holds — a grammar stays in one file rather than splitting
+  across the seam. A rule both
   directions must answer alike — whether a list marker interrupts a paragraph — is one function
   there too, never a copy per direction, however conservative the copy would be.
 - The attribute vocabulary is ADF's: `adf/` walks it and narrows each value to its kind, and a
@@ -180,7 +182,8 @@ One-line commit messages and PR titles; short PR summaries. No AI-attribution ma
 
 No wiki markup (§1), no network or filesystem I/O, no name→id resolution (§3), no ADF schema
 validation or exported validator — a refusal that keeps the round-trip is not schema validation,
-so the one a spelled node carrying the same mark type twice earns stays, no shipped CSS (§4), no
+so the one a spelled node carrying the same mark type twice earns stays, and input nesting a
+spelling inside its own kind (`*(*a*)*`) names that mark once, no shipped CSS (§4), no
 streaming APIs, no performance budget past §11's scanning rule — nothing here is tuned, and no
 figure is promised. A CLI is a later goal (`todo.md`), not a non-goal.
 

corpus/errors/image-in-text.error

@@ -0,0 +1 @@
+unmappable-image

corpus/errors/image-in-text.md

@@ -0,0 +1 @@
+See ![the moon](https://example.com/moon.png) tonight.

corpus/normalization/emphasis-spellings.json

@@ -0,0 +1,88 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "em"
+            }
+          ],
+          "text": "Torque",
+          "type": "text"
+        },
+        {
+          "text": " the ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "strong"
+            }
+          ],
+          "text": "M8 bolt",
+          "type": "text"
+        },
+        {
+          "text": " to 25 Nm, then ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "em"
+            },
+            {
+              "type": "strong"
+            }
+          ],
+          "text": "log it",
+          "type": "text"
+        },
+        {
+          "text": ".",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "text": "Un",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "em"
+            }
+          ],
+          "text": "bolt",
+          "type": "text"
+        },
+        {
+          "text": "ing needs a ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "strike"
+            }
+          ],
+          "text": "10 mm",
+          "type": "text"
+        },
+        {
+          "text": " 13 mm spanner.",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/normalization/emphasis-spellings.md

@@ -0,0 +1,3 @@
+*Torque* the __M8 bolt__ to 25 Nm, then ***log it***.
+
+Un*bolt*ing needs a ~~10 mm~~ 13 mm spanner.

corpus/normalization/link-references.json

@@ -0,0 +1,64 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "text": "See ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "attrs": {
+                "href": "https://example.com/changelog"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "the changelog",
+          "type": "text"
+        },
+        {
+          "text": " and ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "attrs": {
+                "href": "https://example.com/guide",
+                "title": "Setup guide"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "the guide",
+          "type": "text"
+        },
+        {
+          "text": ", or mail ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "attrs": {
+                "href": "mailto:ops@example.com"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "ops@example.com",
+          "type": "text"
+        },
+        {
+          "text": ".",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/normalization/link-references.md

@@ -0,0 +1,4 @@
+See [the changelog][changes] and [the guide], or mail <ops@example.com>.
+
+[changes]: https://example.com/changelog
+[the guide]: https://example.com/guide "Setup guide"

corpus/round-trip/commonmark-subset/link-destination-parenthesis.md

@@ -0,0 +1 @@
+[The torque table](https://example.com/a\)b)

corpus/round-trip/commonmark-subset/link-title-quote.md

@@ -0,0 +1 @@
+[The torque table](https://example.com/torque "He said \"hi\"")

corpus/unspellable/link-destination-parenthesis.error

@@ -1 +0,0 @@
-unspellable-link-destination

corpus/unspellable/link-title-quote.error

@@ -1 +0,0 @@
-unspellable-link-title

spec/flavour.md

@@ -37,9 +37,10 @@ normalizes to it through the round-trip.
   CommonMark admits no spelling — the end of a block, inside an ATX heading — or where the node
   carries an attribute, it is the inline directive.
 - An empty paragraph — real payloads carry them — is `::paragraph`.
-- Links `[text](url)`; `<…>` around a destination containing spaces; title in double quotes.
-  `<url>` autolink form only when the text equals the destination and the destination is a valid
-  CommonMark autolink (absolute URI).
+- Links `[text](url)`; `<…>` around a destination containing spaces; title in double quotes. A
+  backslash escapes a parenthesis the destination leaves unbalanced, and a quote inside the title;
+  a balanced pair stays bare. `<url>` autolink form only when the text equals the destination and
+  the destination is a valid CommonMark autolink (absolute URI).
 - Paragraphs on one line — no soft wrapping; a soft line break in input becomes a single space.
 - Entity references in input decode to their characters; output backslash-escapes only where text
   would otherwise parse as syntax, scanning the assembled line rather than each text node: escape
@@ -244,7 +245,8 @@ The moon, at night.
 
 **The CommonMark image.** A paragraph whose entire inline content is one image `![alt](url)` is
 a `mediaSingle` with attrs exactly `{"layout":"center"}` holding an `external` `media` — `url`
-from the destination, `alt` the description's plain-text content when non-empty. `adfToMarkdown`
+from the destination, `alt` the description's plain-text content when non-empty — a link or image
+inside it contributing its own text, and a break of either kind a space. `adfToMarkdown`
 emits the image form for exactly that shape — those attrs and no others, no marks on either
 node, no caption, and a `media` carrying nothing beyond `alt`, `type` and `url` — and only where
 CommonMark spells the pair: a destination or a description the image form cannot hold, an empty

src/adf/editor-normal.ts

@@ -0,0 +1,32 @@
+import type { AdfMark, AdfNode } from './document.ts'
+import { serializeCanonicalJson } from '../canonical-json.ts'
+
+export function sameMark(candidate: AdfMark, mark: AdfMark): boolean {
+  return markKey(candidate) === markKey(mark)
+}
+
+// AGENTS.md §2: adjacent text nodes carrying identical marks are one node.
+export function mergeAdjacentText(nodes: readonly AdfNode[]): AdfNode[] {
+  const merged: AdfNode[] = []
+  for (const node of nodes) {
+    const previous = merged[merged.length - 1]
+    if (previous !== undefined && previous.type === 'text' && node.type === 'text' && sameMarks(previous, node)) {
+      merged[merged.length - 1] = { ...previous, text: `${previous.text ?? ''}${node.text ?? ''}` }
+      continue
+    }
+    merged.push(node)
+  }
+  return merged
+}
+
+function sameMarks(previous: AdfNode, node: AdfNode): boolean {
+  return marksKey(previous.marks ?? []) === marksKey(node.marks ?? [])
+}
+
+function marksKey(marks: readonly AdfMark[]): string {
+  return marks.map(markKey).join('\n')
+}
+
+function markKey(mark: AdfMark): string {
+  return `${mark.type} ${serializeCanonicalJson(mark.attrs ?? {}, 'compact')}`
+}

src/markdown/backtick-runs.ts

@@ -1,7 +1,7 @@
+import { runLength } from './emphasis-matching.ts'
+
 export function backtickRun(text: string, index: number): number {
-  let length = 0
-  while (text.charAt(index + length) === '`') length += 1
-  return length
+  return text.charAt(index) === '`' ? runLength(text, index) : 0
 }
 
 // Where the run of exactly `opener` backticks closing a code span begins, `undefined` where none does.

src/markdown/commonmark-grammar.ts

@@ -56,7 +56,10 @@ const pipeClaim = /^\|/
 const bulletListOpener = /^[*+-](?:[ \t]|$)/
 // A superset of what the parser claims: over-escaping a line is safe, under-escaping one breaks the round-trip.
 const firstCharacterOpeners = [atxHeadingOpener, /^>/, bulletListOpener, codeFenceOpener, /^:{2,}/, pipeClaim]
-const emailAutolink = /<[^\s<>@]+@[^\s<>@]+>/y
+// CommonMark 0.31.2, Autolinks: the email production, whose label may not open or close with a hyphen.
+const emailNameSource = "[A-Za-z0-9.!#$%&'*+/=?^_`{|}~-]+"
+const emailLabelSource = '[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?'
+const emailAutolink = new RegExp(`<${emailNameSource}@${emailLabelSource}(?:\\.${emailLabelSource})*>`, 'y')
 const orderedListOpener = /^(\d{1,9})([.)])(?:[ \t]|$)/
 const setextUnderline = /^(=+|-+)[ \t]*$/
 const thematicBreak = /^(?:(?:\*[ \t]*){3,}|(?:-[ \t]*){3,}|(?:_[ \t]*){3,})$/
@@ -197,13 +200,21 @@ export function openingHtmlBlock(line: string, interrupting: boolean): OpenHtmlB
 }
 
 export function opensBracketedAutolink(text: string, index: number): boolean {
-  bracketedAutolink.lastIndex = index
-  return bracketedAutolink.test(text)
+  return readBracketedAutolink(text, index) !== undefined
 }
 
 export function opensEmailAutolink(text: string, index: number): boolean {
+  return readEmailAutolink(text, index) !== undefined
+}
+
+export function readBracketedAutolink(text: string, index: number): number | undefined {
+  bracketedAutolink.lastIndex = index
+  return bracketedAutolink.exec(text)?.[0].length
+}
+
+export function readEmailAutolink(text: string, index: number): number | undefined {
   emailAutolink.lastIndex = index
-  return emailAutolink.test(text)
+  return emailAutolink.exec(text)?.[0].length
 }
 
 export function setextHeadingLevel(line: string): number | undefined {

src/markdown/emit/adf-to-markdown.test.ts

@@ -76,7 +76,6 @@ test('spells a code block language no info string holds as an attribute', () =>
 
 test('refuses a link destination CommonMark cannot spell', () => {
   const link = (href: string): AdfDocument => document(paragraph({ marks: [{ attrs: { href }, type: 'link' }], text: 't', type: 'text' }))
-  assert.equal(code(adfToMarkdown(link('https://example.com/a)b'))), 'unspellable-link-destination')
   assert.equal(code(adfToMarkdown(link('https://example.com/a b>c'))), 'unspellable-link-destination')
   assert.equal(code(adfToMarkdown(link('<https://example.com/'))), 'unspellable-link-destination')
   assert.equal(code(adfToMarkdown(link('https://example.com/a\\b'))), 'unspellable-link-destination')
@@ -84,14 +83,23 @@ test('refuses a link destination CommonMark cannot spell', () => {
   assert.equal(code(adfToMarkdown(link('https://example.com/a\nb'))), 'unspellable-link-destination')
   const entity = 'https://example.com/?a=1&amp;b=2'
   assert.equal(code(adfToMarkdown(document(paragraph({ marks: [{ attrs: { href: entity }, type: 'link' }], text: entity, type: 'text' })))), 'unspellable-link-destination')
-  assert.equal(markdown(adfToMarkdown(link('https://en.example.com/a_(b)'))), '[t](https://en.example.com/a_(b))\n')
 })
 
-test('refuses a link title CommonMark cannot spell', () => {
+test('escapes the parenthesis a link destination leaves unbalanced, and no other', () => {
+  const link = (href: string): string => markdown(adfToMarkdown(document(paragraph({ marks: [{ attrs: { href }, type: 'link' }], text: 't', type: 'text' }))))
+  assert.equal(link('https://en.example.com/a_(b)'), '[t](https://en.example.com/a_(b))\n')
+  assert.equal(link('https://example.com/a)b'), '[t](https://example.com/a\\)b)\n')
+  assert.equal(link('https://example.com/a(b'), '[t](https://example.com/a\\(b)\n')
+  assert.equal(link('https://example.com/)(') , '[t](https://example.com/\\)\\()\n')
+  assert.equal(link('https://example.com/a (b'), '[t](<https://example.com/a (b>)\n')
+})
+
+test('escapes the quote a link title holds, and refuses the rest', () => {
   const titled = (title: string): AdfDocument =>
     document(paragraph({ marks: [{ attrs: { href: 'https://example.com/', title }, type: 'link' }], text: 't', type: 'text' }))
-  assert.equal(code(adfToMarkdown(titled('He said "hi"'))), 'unspellable-link-title')
+  assert.equal(markdown(adfToMarkdown(titled('He said "hi"'))), '[t](https://example.com/ "He said \\"hi\\"")\n')
   assert.equal(code(adfToMarkdown(titled('a\nb'))), 'unspellable-link-title')
+  assert.equal(code(adfToMarkdown(titled('a\\b'))), 'unspellable-link-title')
 })
 
 test('carries a link mark the link spelling cannot write', () => {

src/markdown/emit/destination-spelling.ts

@@ -1,38 +0,0 @@
-import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
-import { holdsControlCharacter } from '../commonmark-grammar.ts'
-import { holdsEntityReference } from '../entity-references.ts'
-
-export function spellDestination(href: string, path: ConvertErrorPath): Result<string> {
-  if (holdsControlCharacter(href)) return failure('unspellable-link-destination', 'a link destination holds a control character', path)
-  if (href.includes('\\')) return failure('unspellable-link-destination', 'no canonical escape spells a backslash in a link destination', path)
-  if (holdsEntityReference(href)) {
-    return failure('unspellable-link-destination', 'a link destination holds an entity reference that decodes on the way back', path)
-  }
-  if (href.includes(' ')) {
-    if (/[<>]/.test(href)) {
-      return failure('unspellable-link-destination', 'no canonical escape spells an angle bracket beside a space in a link destination', path)
-    }
-    return success(`<${href}>`)
-  }
-  if (href.startsWith('<')) return failure('unspellable-link-destination', 'a bare link destination cannot begin with an angle bracket', path)
-  if (!balanced(href)) return failure('unspellable-link-destination', 'no canonical escape spells an unbalanced parenthesis in a link destination', path)
-  return success(href)
-}
-
-export function spellTitle(title: string, path: ConvertErrorPath): Result<string> {
-  if (/["\n\r\\]/.test(title)) {
-    return failure('unspellable-link-title', 'no canonical escape spells a quote, backslash or newline in a link title', path)
-  }
-  if (holdsEntityReference(title)) return failure('unspellable-link-title', 'a link title holds an entity reference that decodes on the way back', path)
-  return success(` "${title}"`)
-}
-
-function balanced(href: string): boolean {
-  let depth = 0
-  for (const character of href) {
-    if (character === '(') depth += 1
-    if (character === ')') depth -= 1
-    if (depth < 0) return false
-  }
-  return depth === 0
-}

src/markdown/emit/inline-line.ts

@@ -9,9 +9,9 @@ import { inlineDirective } from '../../adf/inline-directives.ts'
 import { largestNesting } from '../../nesting.ts'
 import { longestBacktickRun } from '../backtick-runs.ts'
 import { markSpelling, spellMarkAttributes } from '../mark-spellings.ts'
-import { serializeCanonicalJson } from '../../canonical-json.ts'
+import { sameMark } from '../../adf/editor-normal.ts'
 import { spellAttributes, spellStringAttribute } from '../directive-attributes.ts'
-import { spellDestination, spellTitle } from './destination-spelling.ts'
+import { spellDestination, spellTitle } from '../link-syntax.ts'
 import { spellInlineNodeAttributes } from './inline-directive-spelling.ts'
 
 type EmittedLine = { line: string; segments: InlineSegment[] }
@@ -297,7 +297,3 @@ function emitLink(nodes: readonly AdfNode[], mark: AdfMark, depth: number, range
   return success({ segments: [syntax('['), ...inner.value.segments, syntax(`](${destination.value}${spelledTitle.value})`)] })
 }
 
-function sameMark(candidate: AdfMark, mark: AdfMark): boolean {
-  if (candidate.type !== mark.type) return false
-  return serializeCanonicalJson(candidate.attrs ?? {}, 'compact') === serializeCanonicalJson(mark.attrs ?? {}, 'compact')
-}

src/markdown/emit/line-escaping.ts

@@ -1,5 +1,5 @@
 import { backtickRun, closingBacktickRun } from '../backtick-runs.ts'
-import { delimiterFlags, isWordCharacter, matchEmphasis } from '../emphasis-matching.ts'
+import { delimiterFlags, isWordCharacter, matchEmphasis, runLength } from '../emphasis-matching.ts'
 import { backslashEscape, escapesLineClaim, inlineHtmlConstruct, opensBracketedAutolink, opensEmailAutolink, type LinePosition } from '../commonmark-grammar.ts'
 import { opensInlineDirective } from '../directive-attributes.ts'
 import { readEntityReference } from '../entity-references.ts'
@@ -260,13 +260,6 @@ function startsRun(scan: string, index: number, escaped: ReadonlySet<number>): b
   return scan.charAt(index - 1) !== scan.charAt(index)
 }
 
-function runLength(scan: string, index: number): number {
-  const character = scan.charAt(index)
-  let length = 0
-  while (scan.charAt(index + length) === character) length += 1
-  return length
-}
-
 function charAt(text: string, index: number): string {
   return index < 0 ? '' : text.charAt(index)
 }

src/markdown/emphasis-matching.ts

@@ -2,7 +2,7 @@ import { isUnicodeWhitespace } from './commonmark-grammar.ts'
 
 type DelimiterRun = { canClose: boolean; canOpen: boolean; character: string; length: number }
 
-type EmphasisPairing<Run> = { closer: Run; closerOffset: number; opener: Run; openerOffset: number; used: number }
+export type EmphasisPairing<Run> = { closer: Run; closerOffset: number; opener: Run; openerOffset: number; used: number }
 
 type Candidate<Run> = {
   head: number
@@ -64,6 +64,13 @@ export function matchEmphasis<Run extends DelimiterRun>(runs: readonly Run[]): E
   return pairings
 }
 
+export function runLength(text: string, index: number): number {
+  const character = text.charAt(index)
+  let length = 0
+  while (text.charAt(index + length) === character) length += 1
+  return length
+}
+
 function candidates<Run extends DelimiterRun>(runs: readonly Run[]): Candidate<Run> | undefined {
   let first: Candidate<Run> | undefined
   let previous: Candidate<Run> | undefined

src/markdown/link-syntax.ts

@@ -0,0 +1,129 @@
+import { backslashEscape, decodeTextEscapes, holdsControlCharacter } from './commonmark-grammar.ts'
+import { failure, success, type ConvertErrorPath, type Result } from '../result.ts'
+import { holdsEntityReference } from './entity-references.ts'
+
+export type LinkDefinition = { destination: string; title?: string }
+
+export type LinkPart = { length: number; value: string }
+
+const bracketedDestination = /<((?:[^\n<>\\]|\\[^\n])*)>/y
+const linkLabel = /\[((?:[^[\]\\]|\\[\s\S]){0,999})\]/y
+const titleClosers: Readonly<Record<string, string>> = { '"': '"', "'": "'", '(': ')' }
+
+// The label is matched by its normalized raw text, escapes and all.
+export function readLabel(text: string, offset: number): LinkPart | undefined {
+  linkLabel.lastIndex = offset
+  const value = linkLabel.exec(text)?.[1]
+  return value === undefined ? undefined : { length: value.length + 2, value }
+}
+
+export function normalizeLabel(raw: string): string {
+  return raw
+    .replace(/^[ \t\n]+|[ \t\n]+$/g, '')
+    .replace(/[ \t\n]+/g, ' ')
+    .toLowerCase()
+}
+
+export function readDestination(text: string, offset: number): LinkPart | undefined {
+  bracketedDestination.lastIndex = offset
+  const bracketed = bracketedDestination.exec(text)?.[0]
+  if (bracketed !== undefined) return { length: bracketed.length, value: decodeTextEscapes(bracketed.slice(1, -1)) }
+  if (text.charAt(offset) === '<') return undefined
+  let depth = 0
+  let index = offset
+  while (index < text.length) {
+    const character = text.charAt(index)
+    if (character === ' ' || holdsControlCharacter(character)) break
+    if (backslashEscape(text, index) !== undefined) {
+      index += 2
+      continue
+    }
+    if (character === '(') depth += 1
+    if (character === ')') {
+      depth -= 1
+      if (depth < 0) break
+    }
+    index += 1
+  }
+  return index <= offset ? undefined : { length: index - offset, value: decodeTextEscapes(text.slice(offset, index)) }
+}
+
+// `offset` sits on the `(` a link text closes into.
+export function readInlineTarget(text: string, offset: number): { definition: LinkDefinition; length: number } | undefined {
+  let index = skipLinkWhitespace(text, offset + 1)
+  let destination = ''
+  if (text.charAt(index) !== ')') {
+    const read = readDestination(text, index)
+    if (read === undefined) return undefined
+    destination = read.value
+    index += read.length
+  }
+  const afterDestination = index
+  index = skipLinkWhitespace(text, index)
+  const title = index > afterDestination ? readTitle(text, index) : undefined
+  if (title !== undefined) index = skipLinkWhitespace(text, index + title.length)
+  if (text.charAt(index) !== ')') return undefined
+  return { definition: title === undefined ? { destination } : { destination, title: title.value }, length: index + 1 - offset }
+}
+
+export function readTitle(text: string, offset: number): LinkPart | undefined {
+  const opener = text.charAt(offset)
+  const closer = titleClosers[opener]
+  if (closer === undefined) return undefined
+  let index = offset + 1
+  while (index < text.length) {
+    const character = text.charAt(index)
+    if (backslashEscape(text, index) !== undefined) {
+      index += 2
+      continue
+    }
+    if (character === closer) return { length: index + 1 - offset, value: decodeTextEscapes(text.slice(offset + 1, index)) }
+    if (character === opener) return undefined
+    index += 1
+  }
+  return undefined
+}
+
+// The label, the destination and the title each take at most one line ending with them.
+export function skipLinkWhitespace(text: string, offset: number): number {
+  const rest = text.slice(offset)
+  return offset + rest.length - rest.replace(/^[ \t]*\n?[ \t]*/, '').length
+}
+
+export function spellDestination(href: string, path: ConvertErrorPath): Result<string> {
+  if (holdsControlCharacter(href)) return failure('unspellable-link-destination', 'a link destination holds a control character', path)
+  if (href.includes('\\')) return failure('unspellable-link-destination', 'no canonical escape spells a backslash in a link destination', path)
+  if (holdsEntityReference(href)) {
+    return failure('unspellable-link-destination', 'a link destination holds an entity reference that decodes on the way back', path)
+  }
+  if (href.includes(' ')) {
+    if (/[<>]/.test(href)) {
+      return failure('unspellable-link-destination', 'no canonical escape spells an angle bracket beside a space in a link destination', path)
+    }
+    return success(`<${href}>`)
+  }
+  if (href.startsWith('<')) return failure('unspellable-link-destination', 'a bare link destination cannot begin with an angle bracket', path)
+  return success(escapeUnbalanced(href))
+}
+
+export function spellTitle(title: string, path: ConvertErrorPath): Result<string> {
+  if (/[\n\r\\]/.test(title)) {
+    return failure('unspellable-link-title', 'no canonical escape spells a backslash or newline in a link title', path)
+  }
+  if (holdsEntityReference(title)) return failure('unspellable-link-title', 'a link title holds an entity reference that decodes on the way back', path)
+  return success(` "${title.replaceAll('"', '\\"')}"`)
+}
+
+function escapeUnbalanced(href: string): string {
+  const open: number[] = []
+  const unbalanced = new Set<number>()
+  for (let index = 0; index < href.length; index += 1) {
+    const character = href.charAt(index)
+    if (character === '(') open.push(index)
+    if (character === ')' && open.pop() === undefined) unbalanced.add(index)
+  }
+  for (const index of open) unbalanced.add(index)
+  let spelled = ''
+  for (let index = 0; index < href.length; index += 1) spelled += (unbalanced.has(index) ? '\\' : '') + href.charAt(index)
+  return spelled
+}

src/markdown/parse/blocks.test.ts

@@ -1,7 +1,7 @@
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import type { LinkDefinition } from './link-reference-definitions.ts'
+import type { LinkDefinition } from '../link-syntax.ts'
 import { parseBlocks } from './blocks.ts'
 
 function definitions(markdown: string): [string, LinkDefinition][] {
@@ -21,9 +21,10 @@ test('keeps the link reference definitions a paragraph gives up, the first of a
   ])
   assert.deepEqual(definitions('[a\\]b]: /url\n'), [['a\\]b', { destination: '/url' }]])
   assert.deepEqual(definitions('[a]: /url(x)y\n'), [['a', { destination: '/url(x)y' }]])
-  assert.deepEqual(definitions('[a]: /url\\(x\n'), [['a', { destination: '/url\\(x' }]])
+  assert.deepEqual(definitions('[a]: /url\\(x\n'), [['a', { destination: '/url(x' }]])
+  assert.deepEqual(definitions('[a]: /url&x\n'), [['a', { destination: '/url&x' }]])
   assert.deepEqual(definitions('[a]: <>\n'), [['a', { destination: '' }]])
-  assert.deepEqual(definitions('[a]: /url "He said \\"hi\\""\n'), [['a', { destination: '/url', title: 'He said \\"hi\\"' }]])
+  assert.deepEqual(definitions('[a]: /url "He said \\"hi\\""\n'), [['a', { destination: '/url', title: 'He said "hi"' }]])
   assert.deepEqual(definitions('[a]: /url\\\n[b]: /b\n'), [
     ['a', { destination: '/url\\' }],
     ['b', { destination: '/b' }],
@@ -47,6 +48,7 @@ test('leaves the paragraph a line no definition spells', () => {
   assert.deepEqual(definitions('[a]: /url "One" and more\n'), [])
   assert.deepEqual(definitions('[a]:\n'), [])
   assert.deepEqual(definitions('[a]: /url "unclosed\n'), [])
+  assert.deepEqual(definitions('[a]: /url (a(b)\n'), [])
   assert.deepEqual(kinds('[a]: /url\nPart.\n'), ['paragraph'])
 })
 

src/markdown/parse/blocks.ts

@@ -1,4 +1,4 @@
-import type { LinkDefinition } from './link-reference-definitions.ts'
+import type { LinkDefinition } from '../link-syntax.ts'
 import {
   atxHeading,
   claimsDirectiveLine,

src/markdown/parse/inline-content.ts

@@ -1,69 +1,326 @@
-import type { AdfNode } from '../../adf/document.ts'
-import { backslashEscape, decodeTextEscapes, inlineHtmlConstruct } from '../commonmark-grammar.ts'
+import type { AdfMark, AdfNode } from '../../adf/document.ts'
+import type { EmphasisPairing } from '../emphasis-matching.ts'
+import type { LinkDefinition } from '../link-syntax.ts'
+import { backslashEscape, decodeTextEscapes, inlineHtmlConstruct, readBracketedAutolink, readEmailAutolink } from '../commonmark-grammar.ts'
 import { backtickRun, closingBacktickRun } from '../backtick-runs.ts'
+import { delimiterFlags, matchEmphasis, runLength } from '../emphasis-matching.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
+import { mergeAdjacentText } from '../../adf/editor-normal.ts'
+import { normalizeLabel, readInlineTarget, readLabel } from '../link-syntax.ts'
 
-type Run = { nodes: AdfNode[]; text: string; undecodedFrom: number }
+export type InlineContent = { image: AdfNode; nodes?: undefined } | { image?: undefined; nodes: AdfNode[] }
+
+export type LinkDefinitions = ReadonlyMap<string, LinkDefinition>
+
+type Bracket = { active: boolean; image: boolean; kind: 'open'; start: number }
+
+type Pairing = EmphasisPairing<Run>
+
+type Piece =
+  | Bracket
+  | { alt: string; kind: 'image'; node: AdfNode }
+  | { kind: 'nodes'; nodes: AdfNode[] }
+  | { canClose: boolean; canOpen: boolean; character: string; kind: 'run'; length: number }
+
+type Run = { canClose: boolean; canOpen: boolean; character: string; index: number; length: number }
+
+type Scan = { definitions: LinkDefinitions; path: ConvertErrorPath; pending: string; pieces: Piece[]; source: string }
 
 const hardBreakSpaces = / {2,}$/
+const imageAlone = 'an image fits only as a paragraph of its own'
 const trailingSpace = /[ \t]+$/
 
-export function parseInlineContent(source: string, path: ConvertErrorPath): Result<AdfNode[]> {
-  const run: Run = { nodes: [], text: '', undecodedFrom: 0 }
+export function parseInlineContent(source: string, definitions: LinkDefinitions, path: ConvertErrorPath): Result<InlineContent> {
+  const scan: Scan = { definitions, path, pending: '', pieces: [], source }
   let index = 0
   while (index < source.length) {
-    const character = source.charAt(index)
-    if (character === '\\' && source.charAt(index + 1) === '\n') {
-      // CommonMark strips the spaces the two-space break is spelled with, and keeps those before a backslash.
-      takeRun(run, source, index, index + 2, false)
-      pushNode(run, { type: 'hardBreak' })
-      index += 2
-      continue
+    switch (source.charAt(index)) {
+      case '\\':
+        index = readBackslash(scan, index)
+        break
+      case '\n':
+        index = readLineEnding(scan, index)
+        break
+      case '`':
+        index = readBackticks(scan, index)
+        break
+      case '<': {
+        const angle = readAngle(scan, index)
+        if (!angle.ok) return angle
+        index = angle.value
+        break
       }
-    if (character === '\n') {
-      const hard = hardBreakSpaces.test(source.slice(run.undecodedFrom, index))
-      takeRun(run, source, index, index + 1, true)
-      if (hard) pushNode(run, { type: 'hardBreak' })
-      else run.text += ' '
+      case '!':
+      case '[':
+        index = openBracket(scan, index)
+        break
+      case ']': {
+        const closed = closeBracket(scan, index)
+        if (!closed.ok) return closed
+        index = closed.value
+        break
+      }
+      case '*':
+      case '_':
+      case '~':
+        index = readDelimiterRun(scan, index)
+        break
+      default:
+        scan.pending += source.charAt(index)
         index += 1
-      continue
     }
-    if (character === '`') {
-      const span = readCodeSpan(source, index)
+  }
+  flush(scan, true)
+  return assemble(scan)
+}
+
+function readBackslash(scan: Scan, index: number): number {
+  if (scan.source.charAt(index + 1) === '\n') {
+    // CommonMark strips the spaces the two-space break is spelled with, and keeps those before a backslash.
+    flush(scan, false)
+    pushNode(scan, { type: 'hardBreak' })
+    return index + 2
+  }
+  const width = backslashEscape(scan.source, index) === undefined ? 1 : 2
+  scan.pending += scan.source.slice(index, index + width)
+  return index + width
+}
+
+function readLineEnding(scan: Scan, index: number): number {
+  const hard = hardBreakSpaces.test(scan.pending)
+  flush(scan, true)
+  if (hard) pushNode(scan, { type: 'hardBreak' })
+  else scan.pending = ' '
+  return index + 1
+}
+
+function readBackticks(scan: Scan, index: number): number {
+  const span = readCodeSpan(scan.source, index)
   if (span === undefined) {
-        index += backtickRun(source, index)
-        continue
+    const run = backtickRun(scan.source, index)
+    scan.pending += scan.source.slice(index, index + run)
+    return index + run
   }
-      takeRun(run, source, index, span.end, false)
-      pushNode(run, { marks: [{ type: 'code' }], text: span.text, type: 'text' })
-      index = span.end
-      continue
-    }
-    if (character === '<') {
-      const construct = inlineHtmlConstruct(source, index)
-      if (construct !== undefined) return failure('unmappable-html', `no ADF node carries ${construct}`, path)
-    }
-    index += backslashEscape(source, index) === undefined ? 1 : 2
-  }
-  takeRun(run, source, source.length, source.length, true)
-  pushText(run)
-  return success(run.nodes)
+  flush(scan, false)
+  pushNode(scan, { marks: [{ type: 'code' }], text: span.text, type: 'text' })
+  return span.end
 }
 
-function takeRun(run: Run, source: string, end: number, resume: number, strip: boolean): void {
-  const raw = source.slice(run.undecodedFrom, end)
-  run.text += decodeTextEscapes(strip ? raw.replace(trailingSpace, '') : raw)
-  run.undecodedFrom = resume
+function readAngle(scan: Scan, index: number): Result<number> {
+  const autolink = readAutolink(scan.source, index)
+  if (autolink !== undefined) {
+    flush(scan, false)
+    pushNode(scan, autolink.node)
+    return success(index + autolink.length)
+  }
+  const construct = inlineHtmlConstruct(scan.source, index)
+  if (construct !== undefined) return failure('unmappable-html', `no ADF node carries ${construct}`, scan.path)
+  scan.pending += '<'
+  return success(index + 1)
 }
 
-function pushText(run: Run): void {
-  if (run.text !== '') run.nodes.push({ text: run.text, type: 'text' })
-  run.text = ''
+function openBracket(scan: Scan, index: number): number {
+  const image = scan.source.charAt(index) === '!'
+  if (image && scan.source.charAt(index + 1) !== '[') {
+    scan.pending += '!'
+    return index + 1
+  }
+  const width = image ? 2 : 1
+  flush(scan, false)
+  scan.pieces.push({ active: true, image, kind: 'open', start: index + width })
+  return index + width
 }
 
-function pushNode(run: Run, node: AdfNode): void {
-  pushText(run)
-  run.nodes.push(node)
+function flush(scan: Scan, strip: boolean): void {
+  const raw = strip ? scan.pending.replace(trailingSpace, '') : scan.pending
+  scan.pending = ''
+  if (raw !== '') scan.pieces.push({ kind: 'nodes', nodes: [{ text: decodeTextEscapes(raw), type: 'text' }] })
+}
+
+function pushNode(scan: Scan, node: AdfNode): void {
+  scan.pieces.push({ kind: 'nodes', nodes: [node] })
+}
+
+function assemble(scan: Scan): Result<InlineContent> {
+  const only = scan.pieces[0]
+  if (scan.pieces.length === 1 && only?.kind === 'image') return success({ image: only.node })
+  if (holdsImage(scan.pieces)) return failure('unmappable-image', imageAlone, scan.path)
+  return success({ nodes: resolveNodes(scan.pieces) })
+}
+
+function holdsImage(pieces: readonly Piece[]): boolean {
+  return pieces.some((piece) => piece.kind === 'image')
+}
+
+function readDelimiterRun(scan: Scan, index: number): number {
+  const character = scan.source.charAt(index)
+  const length = runLength(scan.source, index)
+  const flags = delimiterFlags(character, scan.source.charAt(index - 1), scan.source.charAt(index + length))
+  if ((character === '~' && length !== 2) || (!flags.canOpen && !flags.canClose)) scan.pending += scan.source.slice(index, index + length)
+  else {
+    flush(scan, false)
+    scan.pieces.push({ canClose: flags.canClose, canOpen: flags.canOpen, character, kind: 'run', length })
+  }
+  return index + length
+}
+
+function readAutolink(source: string, index: number): { length: number; node: AdfNode } | undefined {
+  const bracketed = readBracketedAutolink(source, index)
+  if (bracketed !== undefined) return { length: bracketed, node: linkedText(source.slice(index + 1, index + bracketed - 1), '') }
+  const email = readEmailAutolink(source, index)
+  if (email === undefined) return undefined
+  return { length: email, node: linkedText(source.slice(index + 1, index + email - 1), 'mailto:') }
+}
+
+function linkedText(text: string, scheme: string): AdfNode {
+  return { marks: [{ attrs: { href: `${scheme}${text}` }, type: 'link' }], text, type: 'text' }
+}
+
+function closeBracket(scan: Scan, index: number): Result<number> {
+  flush(scan, false)
+  const open = lastBracket(scan.pieces)
+  if (open === undefined) return success(literalClose(scan, index))
+  const target = open.bracket.active ? resolveTarget(scan, open.bracket, index) : undefined
+  if (target === undefined) return success(unopened(scan, open, index))
+  const inner = scan.pieces.slice(open.index + 1)
+  if (open.bracket.image) {
+    const closed = closeImage(scan, open.index, inner, target.definition)
+    if (!closed.ok) return closed
+    return success(index + 1 + target.length)
+  }
+  const closed = closeLink(scan, open.index, inner, target.definition)
+  if (!closed.ok) return closed
+  return success(closed.value ? index + 1 + target.length : unopened(scan, open, index))
+}
+
+function literalClose(scan: Scan, index: number): number {
+  scan.pending += ']'
+  return index + 1
+}
+
+function unopened(scan: Scan, open: { bracket: Bracket; index: number }, index: number): number {
+  scan.pieces[open.index] = { kind: 'nodes', nodes: bracketNodes(open.bracket) }
+  return literalClose(scan, index)
+}
+
+function bracketNodes(bracket: Bracket): AdfNode[] {
+  return [{ text: bracket.image ? '![' : '[', type: 'text' }]
+}
+
+function lastBracket(pieces: readonly Piece[]): { bracket: Bracket; index: number } | undefined {
+  for (let index = pieces.length - 1; index >= 0; index -= 1) {
+    const piece = pieces[index]
+    if (piece?.kind === 'open') return { bracket: piece, index }
+  }
+  return undefined
+}
+
+function resolveTarget(scan: Scan, bracket: Bracket, index: number): { definition: LinkDefinition; length: number } | undefined {
+  const after = index + 1
+  if (scan.source.charAt(after) === '(') {
+    const inline = readInlineTarget(scan.source, after)
+    if (inline !== undefined) return { definition: inline.definition, length: inline.length }
+  }
+  const label = scan.source.charAt(after) === '[' ? readLabel(scan.source, after) : undefined
+  const name = label === undefined || label.value === '' ? scan.source.slice(bracket.start, index) : label.value
+  const definition = scan.definitions.get(normalizeLabel(name))
+  if (definition === undefined) return undefined
+  return { definition, length: label?.length ?? 0 }
+}
+
+// `false` where the link text is empty: the mark has no node to ride, so the brackets stay text.
+function closeLink(scan: Scan, at: number, inner: readonly Piece[], definition: LinkDefinition): Result<boolean> {
+  if (holdsImage(inner)) return failure('unmappable-image', imageAlone, scan.path)
+  const nodes = resolveNodes(inner)
+  if (nodes.length === 0) return success(false)
+  const attrs = definition.title === undefined ? { href: definition.destination } : { href: definition.destination, title: definition.title }
+  scan.pieces.length = at
+  // CommonMark: no link nests inside another, though an image's description holds one.
+  for (const piece of scan.pieces) if (piece.kind === 'open' && !piece.image) piece.active = false
+  scan.pieces.push({ kind: 'nodes', nodes: applyMark(nodes, { attrs, type: 'link' }) })
+  return success(true)
+}
+
+function closeImage(scan: Scan, at: number, inner: readonly Piece[], definition: LinkDefinition): Result<null> {
+  if (definition.title !== undefined) return failure('unmappable-image', 'no media node carries a link title', scan.path)
+  const alt = imageAlt(inner)
+  const attrs = alt === '' ? { type: 'external', url: definition.destination } : { alt, type: 'external', url: definition.destination }
+  scan.pieces.length = at
+  scan.pieces.push({ alt, kind: 'image', node: { attrs: { layout: 'center' }, content: [{ attrs, type: 'media' }], type: 'mediaSingle' } })
+  return success(null)
+}
+
+function imageAlt(inner: readonly Piece[]): string {
+  return resolveNodes(inner)
+    .map((node) => (node.type === 'hardBreak' ? ' ' : (node.text ?? '')))
+    .join('')
+}
+
+function resolveNodes(pieces: readonly Piece[]): AdfNode[] {
+  const nodes = pieces.map(pieceNodes)
+  const runs = delimiterRuns(pieces)
+  const pairings = matchEmphasis(runs)
+  writeUnpaired(nodes, runs, pairings)
+  markPairings(nodes, pairings)
+  return mergeAdjacentText(nodes.flat())
+}
+
+// Only `imageAlt` reaches the image arm: everywhere else an image amid other content is refused first.
+function pieceNodes(piece: Piece): AdfNode[] {
+  switch (piece.kind) {
+    case 'image':
+      return piece.alt === '' ? [] : [{ text: piece.alt, type: 'text' }]
+    case 'nodes':
+      return piece.nodes
+    case 'open':
+      return bracketNodes(piece)
+    case 'run':
+      return []
+  }
+}
+
+function delimiterRuns(pieces: readonly Piece[]): Run[] {
+  const runs: Run[] = []
+  for (const [index, piece] of pieces.entries()) {
+    if (piece.kind === 'run') runs.push({ canClose: piece.canClose, canOpen: piece.canOpen, character: piece.character, index, length: piece.length })
+  }
+  return runs
+}
+
+// A run gives its delimiters up from the head closing and the tail opening; what is left between them is text.
+function writeUnpaired(nodes: AdfNode[][], runs: readonly Run[], pairings: readonly Pairing[]): void {
+  const heads = new Map<Run, number>()
+  const tails = new Map<Run, number>()
+  for (const pairing of pairings) {
+    heads.set(pairing.closer, pairing.closerOffset + pairing.used)
+    tails.set(pairing.opener, pairing.openerOffset)
+  }
+  for (const run of runs) {
+    const head = heads.get(run) ?? 0
+    const tail = tails.get(run) ?? run.length
+    if (tail > head) nodes[run.index] = [{ text: run.character.repeat(tail - head), type: 'text' }]
+  }
+}
+
+// Innermost pairing first, so prepending leaves the marks array outermost first (spec/flavour.md, Marks).
+function markPairings(nodes: AdfNode[][], pairings: readonly Pairing[]): void {
+  for (const pairing of pairings) {
+    const mark: AdfMark = { type: markType(pairing.opener.character, pairing.used) }
+    for (let index = pairing.opener.index + 1; index < pairing.closer.index; index += 1) nodes[index] = applyMark(nodes[index] ?? [], mark)
+  }
+}
+
+function markType(character: string, used: number): string {
+  if (character === '~') return 'strike'
+  return used === 2 ? 'strong' : 'em'
+}
+
+// A node cannot carry one mark type twice (AGENTS.md §14).
+function applyMark(nodes: readonly AdfNode[], mark: AdfMark): AdfNode[] {
+  return nodes.map((node) => {
+    const marks = node.marks ?? []
+    return marks.some((carried) => carried.type === mark.type) ? node : { ...node, marks: [mark, ...marks] }
+  })
 }
 
 function readCodeSpan(source: string, index: number): { end: number; text: string } | undefined {

src/markdown/parse/link-reference-definitions.ts

@@ -1,14 +1,9 @@
-import { holdsControlCharacter, isAsciiPunctuation } from '../commonmark-grammar.ts'
-
-export type LinkDefinition = { destination: string; title?: string }
+import type { LinkDefinition, LinkPart } from '../link-syntax.ts'
+import { normalizeLabel, readDestination, readLabel, readTitle, skipLinkWhitespace } from '../link-syntax.ts'
 
 type ReadDefinition = { definition: LinkDefinition; label: string; length: number }
-type ReadValue = { length: number; value: string }
 
-const bracketedDestination = /^<((?:[^\n<>\\]|\\[^\n])*)>/
-const label = /^\[((?:[^[\]\\]|\\[\s\S]){1,999})\]:/
 const restOfLine = /^[ \t]*(?:\n|$)/
-const titleClosers: Readonly<Record<string, string>> = { '"': '"', "'": "'", '(': ')' }
 
 export function readLinkDefinitions(definitions: Map<string, LinkDefinition>, text: string): string {
   let rest = text
@@ -22,11 +17,11 @@ export function readLinkDefinitions(definitions: Map<string, LinkDefinition>, te
 }
 
 function readDefinition(text: string): ReadDefinition | undefined {
-  const matched = label.exec(text)
-  if (matched === null) return undefined
-  const name = normalizeLabel(matched[1] ?? '')
+  const label = readLabel(text, 0)
+  if (label === undefined || text.charAt(label.length) !== ':') return undefined
+  const name = normalizeLabel(label.value)
   if (name === '') return undefined
-  const afterLabel = skipSpace(text, matched[0].length)
+  const afterLabel = skipLinkWhitespace(text, label.length + 1)
   const destination = readDestination(text, afterLabel)
   if (destination === undefined) return undefined
   const afterDestination = afterLabel + destination.length
@@ -37,15 +32,8 @@ function readDefinition(text: string): ReadDefinition | undefined {
   return { definition: { destination: destination.value }, label: name, length: plain }
 }
 
-function normalizeLabel(raw: string): string {
-  return raw
-    .replace(/^[ \t\n]+|[ \t\n]+$/g, '')
-    .replace(/[ \t\n]+/g, ' ')
-    .toLowerCase()
-}
-
-function readTitledEnd(text: string, offset: number): ReadValue | undefined {
-  const afterSpace = skipSpace(text, offset)
+function readTitledEnd(text: string, offset: number): LinkPart | undefined {
+  const afterSpace = skipLinkWhitespace(text, offset)
   if (afterSpace === offset) return undefined
   const title = readTitle(text, afterSpace)
   if (title === undefined) return undefined
@@ -53,58 +41,6 @@ function readTitledEnd(text: string, offset: number): ReadValue | undefined {
   return end === undefined ? undefined : { length: end, value: title.value }
 }
 
-function readDestination(text: string, offset: number): ReadValue | undefined {
-  const bracketed = bracketedDestination.exec(text.slice(offset))
-  if (bracketed !== null) return { length: bracketed[0].length, value: bracketed[0].slice(1, -1) }
-  if (text.charAt(offset) === '<') return undefined
-  let depth = 0
-  let index = offset
-  while (index < text.length) {
-    const character = text.charAt(index)
-    if (character === ' ' || holdsControlCharacter(character)) break
-    if (escapesNext(text, index)) {
-      index += 2
-      continue
-    }
-    if (character === '(') depth += 1
-    if (character === ')') {
-      depth -= 1
-      if (depth < 0) break
-    }
-    index += 1
-  }
-  return index <= offset ? undefined : { length: index - offset, value: text.slice(offset, index) }
-}
-
-function readTitle(text: string, offset: number): ReadValue | undefined {
-  const opener = text.charAt(offset)
-  const closer = titleClosers[opener]
-  if (closer === undefined) return undefined
-  let index = offset + 1
-  while (index < text.length) {
-    const character = text.charAt(index)
-    if (escapesNext(text, index)) {
-      index += 2
-      continue
-    }
-    if (character === closer) return { length: index + 1 - offset, value: text.slice(offset + 1, index) }
-    if (character === opener) return undefined
-    index += 1
-  }
-  return undefined
-}
-
-// A backslash escapes ASCII punctuation only, so a line ending always ends the destination it follows.
-function escapesNext(text: string, index: number): boolean {
-  return text.charAt(index) === '\\' && isAsciiPunctuation(text.charAt(index + 1))
-}
-
-// The label, the destination and the title each take at most one line ending with them.
-function skipSpace(text: string, offset: number): number {
-  const rest = text.slice(offset)
-  return offset + rest.length - rest.replace(/^[ \t]*\n?[ \t]*/, '').length
-}
-
 function endOfLine(text: string, offset: number): number | undefined {
   const rest = restOfLine.exec(text.slice(offset))?.[0]
   return rest === undefined ? undefined : offset + rest.length

src/markdown/parse/markdown-to-adf.test.ts

@@ -1,10 +1,14 @@
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import type { AdfDocument, AdfNode } from '../../adf/document.ts'
+import type { AdfDocument, AdfMark, AdfNode } from '../../adf/document.ts'
 import type { Result } from '../../result.ts'
 import { markdownToAdf } from './markdown-to-adf.ts'
 
+const em: AdfMark = { type: 'em' }
+const strike: AdfMark = { type: 'strike' }
+const strong: AdfMark = { type: 'strong' }
+
 function code(result: Result<AdfDocument>): string {
   return result.ok ? `built ${JSON.stringify(result.value)}` : result.error.code
 }
@@ -49,6 +53,19 @@ function quote(...content: AdfNode[]): AdfNode {
   return content.length === 0 ? { type: 'blockquote' } : { content, type: 'blockquote' }
 }
 
+function marked(value: string, ...marks: AdfMark[]): AdfNode {
+  return { marks, text: value, type: 'text' }
+}
+
+function link(href: string, title?: string): AdfMark {
+  return { attrs: title === undefined ? { href } : { href, title }, type: 'link' }
+}
+
+function image(url: string, alt?: string): AdfNode {
+  const media: AdfNode = { attrs: alt === undefined ? { type: 'external', url } : { alt, type: 'external', url }, type: 'media' }
+  return { attrs: { layout: 'center' }, content: [media], type: 'mediaSingle' }
+}
+
 test('builds an empty document from input holding no block', () => {
   assert.deepEqual(markdownToAdf(''), { ok: true, value: { type: 'doc', version: 1 } })
   assert.deepEqual(content(markdownToAdf('\n \n\t\n')), [])
@@ -323,3 +340,142 @@ test('leaves the angle bracket that opens no HTML construct to the text it sits
   assert.deepEqual(content(markdownToAdf('`<span>`\n')), [{ content: [codeSpan('<span>')], type: 'paragraph' }])
   assert.deepEqual(content(markdownToAdf('\\<span>\n')), [paragraph('<span>')])
 })
+
+test('reads the emphasis CommonMark matches, the marks nesting outermost first', () => {
+  assert.deepEqual(content(markdownToAdf('*a*\n')), [{ content: [marked('a', em)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('_a_\n')), [{ content: [marked('a', em)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('**a**\n')), [{ content: [marked('a', strong)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('__a__\n')), [{ content: [marked('a', strong)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('***a***\n')), [{ content: [marked('a', em, strong)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('*a **b** c*\n')), [
+    { content: [marked('a ', em), marked('b', em, strong), marked(' c', em)], type: 'paragraph' },
+  ])
+  assert.deepEqual(content(markdownToAdf('a*b*c\n')), [{ content: [text('a'), marked('b', em), text('c')], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('# *a*\n')), [{ attrs: { level: 1 }, content: [marked('a', em)], type: 'heading' }])
+})
+
+test('leaves a delimiter run CommonMark pairs with nothing in the text it sits in', () => {
+  assert.deepEqual(content(markdownToAdf('a_b_c\n')), [paragraph('a_b_c')])
+  assert.deepEqual(content(markdownToAdf('*a\n')), [paragraph('*a')])
+  assert.deepEqual(content(markdownToAdf('a * b\n')), [paragraph('a * b')])
+  assert.deepEqual(content(markdownToAdf('**a*\n')), [{ content: [text('*'), marked('a', em)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('*a**\n')), [{ content: [marked('a', em), text('*')], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('\\*a\\*\n')), [paragraph('*a*')])
+  assert.deepEqual(content(markdownToAdf('`*a*`\n')), [{ content: [codeSpan('*a*')], type: 'paragraph' }])
+})
+
+test('reads two tildes as strike, a single tilde and a longer run literal', () => {
+  assert.deepEqual(content(markdownToAdf('~~a~~\n')), [{ content: [marked('a', strike)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('a ~b~ c\n')), [paragraph('a ~b~ c')])
+  assert.deepEqual(content(markdownToAdf('a ~~~b~~~ c\n')), [paragraph('a ~~~b~~~ c')])
+  assert.deepEqual(content(markdownToAdf('~~a **b**~~\n')), [{ content: [marked('a ', strike), marked('b', strike, strong)], type: 'paragraph' }])
+})
+
+test('reads an inline link, its destination and title', () => {
+  assert.deepEqual(content(markdownToAdf('[a](/url)\n')), [{ content: [marked('a', link('/url'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](/url "t")\n')), [{ content: [marked('a', link('/url', 't'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](\n/url\n"t" )\n')), [{ content: [marked('a', link('/url', 't'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](<u v>)\n')), [{ content: [marked('a', link('u v'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a]()\n')), [{ content: [marked('a', link(''))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](/x(y))\n')), [{ content: [marked('a', link('/x(y)'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[**a**](/u)\n')), [{ content: [marked('a', link('/u'), strong)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a `b`](/u)\n')), [
+    { content: [marked('a ', link('/u')), { marks: [link('/u'), { type: 'code' }], text: 'b', type: 'text' }], type: 'paragraph' },
+  ])
+})
+
+test('decodes the escapes and the references a destination and a title hold', () => {
+  assert.deepEqual(content(markdownToAdf('[a](/x\\)y)\n')), [{ content: [marked('a', link('/x)y'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](/u "He said \\"hi\\"")\n')), [{ content: [marked('a', link('/u', 'He said "hi"'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a](/x&amp;y)\n')), [{ content: [marked('a', link('/x&y'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a][r]\n\n[r]: /x\\)y "He said \\"hi\\""\n')), [
+    { content: [marked('a', link('/x)y', 'He said "hi"'))], type: 'paragraph' },
+  ])
+})
+
+test('leaves the bracket pair no link parses as the text it holds', () => {
+  assert.deepEqual(content(markdownToAdf('[a\n')), [paragraph('[a')])
+  assert.deepEqual(content(markdownToAdf('[a] (/u)\n')), [paragraph('[a] (/u)')])
+  assert.deepEqual(content(markdownToAdf('a ] b\n')), [paragraph('a ] b')])
+  assert.deepEqual(content(markdownToAdf('[a](/u\n')), [paragraph('[a](/u')])
+  assert.deepEqual(content(markdownToAdf('[a](/u x)\n')), [paragraph('[a](/u x)')])
+  assert.deepEqual(content(markdownToAdf('[a](<u\n')), [paragraph('[a](<u')])
+  assert.deepEqual(content(markdownToAdf('![a\n')), [paragraph('![a')])
+  assert.deepEqual(content(markdownToAdf('[a [b](/u) c](/v)\n')), [
+    { content: [text('[a '), marked('b', link('/u')), text(' c](/v)')], type: 'paragraph' },
+  ])
+})
+
+test('reads the reference links a definition resolves, and leaves the rest literal', () => {
+  assert.deepEqual(content(markdownToAdf('[a][r]\n\n[r]: /url\n')), [{ content: [marked('a', link('/url'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a][]\n\n[a]: /url\n')), [{ content: [marked('a', link('/url'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a]\n\n[a]: /url\n')), [{ content: [marked('a', link('/url'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[Foo\nBar][]\n\n[foo   bar]: /url\n')), [{ content: [marked('Foo Bar', link('/url'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('[a][z]\n\n[a]: /url\n')), [paragraph('[a][z]')])
+  assert.deepEqual(content(markdownToAdf('[a]\n')), [paragraph('[a]')])
+  assert.deepEqual(content(markdownToAdf('[][]\n')), [paragraph('[][]')])
+})
+
+test('reads an autolink, the email form as the mailto link it means', () => {
+  assert.deepEqual(content(markdownToAdf('<https://example.com/>\n')), [
+    { content: [marked('https://example.com/', link('https://example.com/'))], type: 'paragraph' },
+  ])
+  assert.deepEqual(content(markdownToAdf('a <a@b.example.com> c\n')), [
+    { content: [text('a '), marked('a@b.example.com', link('mailto:a@b.example.com')), text(' c')], type: 'paragraph' },
+  ])
+  assert.deepEqual(content(markdownToAdf('a <a@b-c.example.com> d\n')), [
+    { content: [text('a '), marked('a@b-c.example.com', link('mailto:a@b-c.example.com')), text(' d')], type: 'paragraph' },
+  ])
+  assert.deepEqual(content(markdownToAdf('a <b@-c.example.com> d\n')), [paragraph('a <b@-c.example.com> d')])
+  assert.deepEqual(content(markdownToAdf('a <b[c@example.com> d\n')), [paragraph('a <b[c@example.com> d')])
+  assert.deepEqual(content(markdownToAdf('<https://example.com/?a=\\*>\n')), [
+    { content: [marked('https://example.com/?a=\\*', link('https://example.com/?a=\\*'))], type: 'paragraph' },
+  ])
+  assert.equal(code(markdownToAdf('<https://example.com/> <span>\n')), 'unmappable-html')
+})
+
+test('reads a lone image as the media the flavour spells for it', () => {
+  assert.deepEqual(content(markdownToAdf('![The moon](https://example.com/moon.png)\n')), [
+    image('https://example.com/moon.png', 'The moon'),
+  ])
+  assert.deepEqual(content(markdownToAdf('![](/u)\n')), [image('/u')])
+  assert.deepEqual(content(markdownToAdf('![*a*](/u)\n')), [image('/u', 'a')])
+  assert.deepEqual(content(markdownToAdf('- ![a](/u)\n')), [bulletList(item(image('/u', 'a')))])
+})
+
+test('flattens the description of a lone image to the plain text alt holds', () => {
+  assert.deepEqual(content(markdownToAdf('![a [b](/u) c](/v)\n')), [image('/v', 'a b c')])
+  assert.deepEqual(content(markdownToAdf('![a ![b](/c) d](/e)\n')), [image('/e', 'a b d')])
+  assert.deepEqual(content(markdownToAdf('![a\nb](/u)\n')), [image('/u', 'a b')])
+  assert.deepEqual(content(markdownToAdf('![a  \nb](/u)\n')), [image('/u', 'a b')])
+  assert.deepEqual(content(markdownToAdf('![a `b`](/u)\n')), [image('/u', 'a b')])
+})
+
+test('leaves the brackets of an empty link text the text they are', () => {
+  assert.deepEqual(content(markdownToAdf('[](/u)\n')), [paragraph('[](/u)')])
+  assert.deepEqual(content(markdownToAdf('a [](/u) b\n')), [paragraph('a [](/u) b')])
+  // The pair gives the label back the way an unresolved one does, so the shortcut behind it still reads.
+  assert.deepEqual(content(markdownToAdf('[][r]\n\n[r]: /u\n')), [{ content: [text('[]'), marked('r', link('/u'))], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('![](/u)\n')), [image('/u')])
+})
+
+test('refuses the image no ADF node carries where it sits', () => {
+  assert.equal(content(markdownToAdf('![a](/u "t")\n')), 'unmappable-image: no media node carries a link title')
+  assert.equal(content(markdownToAdf('See ![a](/u).\n')), 'unmappable-image: an image fits only as a paragraph of its own')
+  assert.equal(code(markdownToAdf('# ![a](/u)\n')), 'unmappable-image')
+  assert.equal(code(markdownToAdf('*![a](/u)*\n')), 'unmappable-image')
+  assert.equal(code(markdownToAdf('[![a](/u)](/v)\n')), 'unmappable-image')
+  assert.equal(code(markdownToAdf('![a](/u)![b](/v)\n')), 'unmappable-image')
+  assert.equal(code(markdownToAdf('![a ![b](/c) d\n')), 'unmappable-image')
+  assert.deepEqual(path(markdownToAdf('Part.\n\nSee ![a](/u).\n')), ['content', 1])
+  assert.deepEqual(content(markdownToAdf('![a]\n')), [paragraph('![a]')])
+  assert.deepEqual(content(markdownToAdf('a ! b\n')), [paragraph('a ! b')])
+})
+
+test('carries the mark a spelling nested inside its own kind names once', () => {
+  assert.deepEqual(content(markdownToAdf('*(*a*)*\n')), [{ content: [marked('(a)', em)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf(`${'*'.repeat(600)}a${'*'.repeat(600)}\n`)), [{ content: [marked('a', strong)], type: 'paragraph' }])
+  assert.deepEqual(content(markdownToAdf('*a **b** c*\n')), [
+    { content: [marked('a ', em), marked('b', em, strong), marked(' c', em)], type: 'paragraph' },
+  ])
+})

src/markdown/parse/markdown-to-adf.ts

@@ -1,60 +1,62 @@
 import type { AdfDocument, AdfNode } from '../../adf/document.ts'
 import type { Block, ClaimedConstruct } from './blocks.ts'
+import type { LinkDefinitions } from './inline-content.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
 import { largestNesting } from '../../nesting.ts'
 import { parseBlocks } from './blocks.ts'
 import { parseInlineContent } from './inline-content.ts'
 
 export function markdownToAdf(markdown: string): Result<AdfDocument> {
-  const content = blockNodes(parseBlocks(markdown).blocks, [], 0)
+  const parsed = parseBlocks(markdown)
+  const content = blockNodes(parsed.blocks, parsed.definitions, [], 0)
   if (!content.ok) return content
   return success(content.value.length === 0 ? { type: 'doc', version: 1 } : { content: content.value, type: 'doc', version: 1 })
 }
 
-function blockNodes(blocks: readonly Block[], path: ConvertErrorPath, depth: number): Result<AdfNode[]> {
+function blockNodes(blocks: readonly Block[], definitions: LinkDefinitions, path: ConvertErrorPath, depth: number): Result<AdfNode[]> {
   if (depth > largestNesting) return failure('unsupported-nesting-depth', `the input nests deeper than the ${largestNesting} levels the parser carries`, path)
   const content: AdfNode[] = []
   for (const [index, block] of blocks.entries()) {
-    const node = blockNode(block, [...path, 'content', index], depth)
+    const node = blockNode(block, definitions, [...path, 'content', index], depth)
     if (!node.ok) return node
     content.push(node.value)
   }
   return success(content)
 }
 
-function blockNode(block: Block, path: ConvertErrorPath, depth: number): Result<AdfNode> {
+function blockNode(block: Block, definitions: LinkDefinitions, path: ConvertErrorPath, depth: number): Result<AdfNode> {
   switch (block.kind) {
     case 'blockquote':
-      return containerNode({ type: 'blockquote' }, block.blocks, path, depth)
+      return containerNode({ type: 'blockquote' }, block.blocks, definitions, path, depth)
     case 'bulletList':
-      return listNode({ type: 'bulletList' }, block.items, path, depth)
+      return listNode({ type: 'bulletList' }, block.items, definitions, path, depth)
     case 'claim':
       return claimFailure(block.construct, path)
     case 'code':
       return success(codeBlockNode(block.language, block.text))
     case 'heading':
-      return contentNode({ attrs: { level: block.level }, type: 'heading' }, block.text, path)
+      return contentNode({ attrs: { level: block.level }, type: 'heading' }, block.text, definitions, path)
     case 'html':
       return failure('unmappable-html', `no ADF node carries ${block.construct}`, path)
     case 'orderedList':
-      return listNode({ attrs: { order: block.start }, type: 'orderedList' }, block.items, path, depth)
+      return listNode({ attrs: { order: block.start }, type: 'orderedList' }, block.items, definitions, path, depth)
     case 'paragraph':
-      return contentNode({ type: 'paragraph' }, block.text, path)
+      return contentNode({ type: 'paragraph' }, block.text, definitions, path)
     case 'rule':
       return success({ type: 'rule' })
   }
 }
 
-function containerNode(node: AdfNode, blocks: readonly Block[], path: ConvertErrorPath, depth: number): Result<AdfNode> {
-  const content = blockNodes(blocks, path, depth + 1)
+function containerNode(node: AdfNode, blocks: readonly Block[], definitions: LinkDefinitions, path: ConvertErrorPath, depth: number): Result<AdfNode> {
+  const content = blockNodes(blocks, definitions, path, depth + 1)
   if (!content.ok) return content
   return success(content.value.length === 0 ? node : { ...node, content: content.value })
 }
 
-function listNode(node: AdfNode, items: readonly Block[][], path: ConvertErrorPath, depth: number): Result<AdfNode> {
+function listNode(node: AdfNode, items: readonly Block[][], definitions: LinkDefinitions, path: ConvertErrorPath, depth: number): Result<AdfNode> {
   const content: AdfNode[] = []
   for (const [index, blocks] of items.entries()) {
-    const item = containerNode({ type: 'listItem' }, blocks, [...path, 'content', index], depth)
+    const item = containerNode({ type: 'listItem' }, blocks, definitions, [...path, 'content', index], depth)
     if (!item.ok) return item
     content.push(item.value)
   }
@@ -75,8 +77,13 @@ function codeBlockNode(language: string, text: string): AdfNode {
   return text === '' ? node : { ...node, content: [{ text, type: 'text' }] }
 }
 
-function contentNode(node: AdfNode, text: string, path: ConvertErrorPath): Result<AdfNode> {
-  const content = parseInlineContent(text, path)
+// spec/flavour.md, The CommonMark image: only a paragraph gives an image the block it needs.
+function contentNode(node: AdfNode, text: string, definitions: LinkDefinitions, path: ConvertErrorPath): Result<AdfNode> {
+  const content = parseInlineContent(text, definitions, path)
   if (!content.ok) return content
-  return success(content.value.length === 0 ? node : { ...node, content: content.value })
+  const image = content.value.image
+  if (image !== undefined) {
+    return node.type === 'paragraph' ? success(image) : failure('unmappable-image', `no ADF node carries an image inside a ${node.type}`, path)
+  }
+  return success(content.value.nodes.length === 0 ? node : { ...node, content: content.value.nodes })
 }

src/result.ts

@@ -3,6 +3,7 @@ export type ConvertErrorCode =
   | 'malformed-pipe-table'
   | 'not-an-adf-document'
   | 'unmappable-html'
+  | 'unmappable-image'
   | 'unspellable-adjacent-lists'
   | 'unspellable-character'
   | 'unspellable-line-start'

todo.md

@@ -240,7 +240,7 @@ detail is settled at its own milestone.
         autolink parting off as 3e's own predicate: refusing on the superset would refuse
         `1 <b 2`, a fourth carve-out §4 and the README do not list. `holdsEntityReference` reads
         the table for the same reason, so `&notareference;` is emitted bare.
-  - [ ] **3e — Emphasis and links.** `_`, `*` and `~~` runs through `matchEmphasis` to the `em`,
+  - [x] **3e — Emphasis and links.** `_`, `*` and `~~` runs through `matchEmphasis` to the `em`,
         `strong` and `strike` marks; links inline and reference, 3b's definitions resolved here,
         autolinks, and the image gap's named errors — a titled image, and one amid other text.
         `spec/flavour.md` does not yet pin `~`'s `can_open`/`can_close`, which is transcription
@@ -252,6 +252,22 @@ detail is settled at its own milestone.
         where nothing else works, so each construct keeps one spelling and a destination holding
         both composes. `link-destination-parenthesis` and `link-title-quote` become round-trip
         pairs.
+        **Settled** (the maintainer, 2026-08-31): the destination escapes only the parenthesis it
+        leaves unbalanced, so `/wiki/Foo_(bar)` keeps its bytes, and the backslash stays refused in
+        both the destination and the title — which leaves `[a](/a\b)` a §2 hole 3k's exception list
+        answers, as `<http://x?a=1&amp;b=2>` is, autolinks decoding neither escapes nor references.
+        The image gap mints `unmappable-image`, mirroring `unmappable-html` — a construct in input
+        no ADF node carries. And the CommonMark image shape lands here rather than at 3h: once
+        `[…](…)` reads, a lone `![alt](url)` would otherwise misparse as text plus a link, so 3h
+        keeps the rest of the media family and loses only that line.
+        **Settled** (the maintainer, 2026-08-31, on the review): an empty link text — `[](/u)` —
+        leaves the brackets the text they are rather than minting a refusal or dropping the
+        destination, giving the label back the way an unresolved pair does, so the shortcut behind
+        `[][r]` still reads. A description holding an image flattens to that image's own alt, which
+        is what alt text means and what keeps the documented gap to mid-text and titled images; a
+        break of either kind inside one reads as a space. And a destination or title whose entity
+        reference decodes to a control character — `[a](/x&#10;y)` — joins 3k's exception list
+        beside the two above: the reader takes cmark's reading, the emitter has no spelling for it.
   - [ ] **3f — The directive grammar.** The three forms — inline `:name[content]{attrs}`,
         container `:::name arg {attrs}`, leaf `::name arg {attrs}` — the attribute grammar with
         its quoting and escapes, the fence-length and nesting rules, and the malformed list
@@ -269,9 +285,9 @@ detail is settled at its own milestone.
         guard is built here if the answer there was yes.
   - [ ] **3h — The block nodes.** `block-nodes/` reads back: the plain-versus-directive choice 2f
         settles, read from the other side; the `codeBlock` directive's fenced body and the
-        `language` attribute a bare fence leaves it; the media family's composition and the
-        CommonMark image shape; both table forms, the pipe table's cell split and its named
-        errors; and the one paragraph an inline body takes.
+        `language` attribute a bare fence leaves it; the media family's composition; both table
+        forms, the pipe table's cell split and its named errors; and the one paragraph an inline
+        body takes.
         **Settled** (the maintainer, 2026-08-27): 1d's last pick, the one
         `container-block-separation` holds — a CommonMark block and a directive block sit adjacent
         in a container body with no blank line between them. That reduces the three cases to one
@@ -300,7 +316,9 @@ detail is settled at its own milestone.
         canonical fixpoint: a named error, or markdown that parses and emits to itself byte for
         byte. That HTML's text, tags stripped and entities decoded, against the parsed document's
         concatenated `text`. And a count of the dozen elements the CommonMark subset covers
-        against the marks and nodes they map to. The fixpoint alone is self-consistency a parser
+        against the marks and nodes they map to — counting distinct mark types per text node, since
+        3e collapses a spelling nested inside its own kind and `*(*a*)*` is two `<em>` against one
+        `em`. The fixpoint alone is self-consistency a parser
         returning the empty document passes, and the text alone one dropping every emphasis; the
         counts close both. The exception list stays the maintainer's. One outcome is no
         exception and must not be filed as one: valid CommonMark parsing to a document