Read the leaf blocks, ahead of any inline parsing

2026-08-27 23:23:29 +02:00
parent 90632c6711
commit 5fc4272155
19 changed files with 681 additions and 2 deletions
@@ -0,0 +1,100 @@
+import { holdsControlCharacter } from '../commonmark-grammar.ts'
+
+export type LinkDefinition = { destination: string; title?: string }
+
+type ReadDefinition = { definition: LinkDefinition; label: string; length: number }
+type ReadValue = { length: number; value: string }
+
+const bracketedDestination = /^<((?:[^\n<>\\]|\\[\s\S])*)>/
+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
+  let read = readDefinition(rest)
+  while (read !== undefined) {
+    if (!definitions.has(read.label)) definitions.set(read.label, read.definition)
+    rest = rest.slice(read.length)
+    read = readDefinition(rest)
+  }
+  return rest
+}
+
+function readDefinition(text: string): ReadDefinition | undefined {
+  const matched = label.exec(text)
+  if (matched === null) return undefined
+  const raw = matched[1] ?? ''
+  if (raw.trim() === '') return undefined
+  const afterLabel = skipSpace(text, matched[0].length)
+  const destination = readDestination(text, afterLabel)
+  if (destination === undefined) return undefined
+  const afterDestination = afterLabel + destination.length
+  const name = raw.replace(/[ \t\n]+/g, ' ').trim().toLowerCase()
+  const titled = readTitledEnd(text, afterDestination)
+  if (titled !== undefined) return { definition: { destination: destination.value, title: titled.value }, label: name, length: titled.length }
+  const plain = endOfLine(text, afterDestination)
+  if (plain === undefined) return undefined
+  return { definition: { destination: destination.value }, label: name, length: plain }
+}
+
+function readTitledEnd(text: string, offset: number): ReadValue | undefined {
+  const afterSpace = skipSpace(text, offset)
+  if (afterSpace === offset) return undefined
+  const title = readTitle(text, afterSpace)
+  if (title === undefined) return undefined
+  const end = endOfLine(text, afterSpace + title.length)
+  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 (character === '\\') {
+      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 (character === '\\') {
+      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
+}
+
+// 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
+}