Emitter 2a: the corpus runner, the canonical serializer and the CommonMark subset

src/canonical-json.ts

@@ -0,0 +1,38 @@
+export type JsonValue = JsonValue[] | boolean | null | number | string | { [key: string]: JsonValue }
+
+export type JsonSpelling = 'compact' | 'two-space'
+
+export function isJsonValue(value: unknown): value is JsonValue {
+  if (value === null) return true
+  if (typeof value === 'boolean' || typeof value === 'string') return true
+  if (typeof value === 'number') return Number.isFinite(value)
+  if (Array.isArray(value)) return value.every(isJsonValue)
+  if (typeof value === 'object') return Object.values(value).every(isJsonValue)
+  return false
+}
+
+export function serializeCanonicalJson(value: JsonValue, spelling: JsonSpelling): string {
+  return serialize(value, spelling === 'compact' ? '' : '  ', 0)
+}
+
+function serialize(value: JsonValue, indent: string, depth: number): string {
+  if (Array.isArray(value)) {
+    if (value.length === 0) return '[]'
+    const items = value.map((item) => serialize(item, indent, depth + 1))
+    return `[${join(items, indent, depth)}]`
+  }
+  if (value !== null && typeof value === 'object') {
+    const keys = Object.keys(value).sort()
+    if (keys.length === 0) return '{}'
+    const separator = indent === '' ? ':' : ': '
+    const entries = keys.map((key) => `${JSON.stringify(key)}${separator}${serialize(value[key] ?? null, indent, depth + 1)}`)
+    return `{${join(entries, indent, depth)}}`
+  }
+  return JSON.stringify(value)
+}
+
+function join(parts: readonly string[], indent: string, depth: number): string {
+  if (indent === '') return parts.join(',')
+  const inner = `\n${indent.repeat(depth + 1)}`
+  return `${inner}${parts.join(`,${inner}`)}\n${indent.repeat(depth)}`
+}