feat(session): default JSONL writes to packed rows

scripts/session-fixture-layout.ts

@@ -0,0 +1,120 @@
+/** Canonical packed-row layout helpers for repository session fixtures. */
+
+import { deepStrictEqual } from 'node:assert'
+import { execFileSync } from 'node:child_process'
+import { existsSync, readFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+import { decodeStorageRecord, packChunkRuns, type SessionEvent } from '@deepseek-ai/dsh-session'
+
+/** One repository session fixture and its canonical packed representation. */
+export interface SessionFixtureLayout {
+  /** Repository-relative path with `/` separators. */
+  path: string
+  /** Current fixture bytes decoded as UTF-8. */
+  source: string
+  /** Canonical packed fixture bytes. */
+  canonical: string
+}
+
+interface RecordLine {
+  line: number
+  text: string
+}
+
+function recordLines(content: string): RecordLine[] {
+  return content.split(/\r?\n/).flatMap((text, index) => (
+    text.trim().length === 0 ? [] : [{ line: index + 1, text }]
+  ))
+}
+
+function parseRecord(line: RecordLine, label: string): unknown {
+  try {
+    return JSON.parse(line.text) as unknown
+  } catch (error) {
+    const detail = error instanceof Error ? error.message : String(error)
+    throw new Error(`${label}:${line.line}: invalid JSON: ${detail}`, { cause: error })
+  }
+}
+
+function isSessionHeader(value: unknown): boolean {
+  return value !== null && typeof value === 'object' && (value as { type?: unknown }).type === 'session'
+}
+
+function decodeBody(lines: readonly RecordLine[], label: string): SessionEvent[] {
+  return lines.flatMap(line => decodeStorageRecord(parseRecord(line, label)))
+}
+
+function renderFixture(headerLine: string, events: readonly SessionEvent[]): string {
+  return [
+    headerLine,
+    ...packChunkRuns(events).map(record => JSON.stringify(record)),
+    '',
+  ].join('\n')
+}
+
+/**
+ * Canonicalize one JSONL document when its first record is a session header.
+ * The header line remains byte-identical; body records decode to logical events
+ * and re-encode with {@link packChunkRuns}. Non-session JSONL returns undefined.
+ *
+ * @param content - JSONL source text.
+ * @param label - path-like diagnostic label.
+ * @returns Canonical text for a session fixture, otherwise undefined.
+ */
+export function canonicalSessionFixture(content: string, label = '<session-fixture>'): string | undefined {
+  const lines = recordLines(content)
+  const header = lines[0]
+  if (header === undefined) return undefined
+
+  let headerValue: unknown
+  try {
+    headerValue = JSON.parse(header.text) as unknown
+  } catch {
+    return undefined
+  }
+  if (!isSessionHeader(headerValue)) return undefined
+
+  const events = decodeBody(lines.slice(1), label)
+  const canonical = renderFixture(header.text, events)
+  const canonicalLines = recordLines(canonical)
+  const decoded = decodeBody(canonicalLines.slice(1), label)
+  try {
+    deepStrictEqual(decoded, events)
+  } catch (error) {
+    throw new Error(`${label}: packed rewrite changed the decoded event stream`, { cause: error })
+  }
+  if (renderFixture(header.text, decoded) !== canonical) {
+    throw new Error(`${label}: packed rewrite is not idempotent`)
+  }
+  return canonical
+}
+
+/**
+ * Discover tracked and unignored untracked JSONL files through Git.
+ *
+ * @param root - repository root.
+ * @returns Stable repository-relative paths.
+ */
+export function discoverJsonlFiles(root: string): string[] {
+  return execFileSync(
+    'git',
+    ['ls-files', '-z', '--cached', '--others', '--exclude-standard', '--', '*.jsonl'],
+    { cwd: root, encoding: 'utf8' },
+  ).split('\0')
+    .filter(path => path.length > 0 && existsSync(resolve(root, path)))
+    .sort()
+}
+
+/**
+ * Inspect every repository JSONL whose first record is a session header.
+ *
+ * @param root - repository root.
+ * @returns Session fixtures with current and canonical text.
+ */
+export function inspectSessionFixtureLayouts(root: string): SessionFixtureLayout[] {
+  return discoverJsonlFiles(root).flatMap((path) => {
+    const source = readFileSync(resolve(root, path), 'utf8')
+    const canonical = canonicalSessionFixture(source, path)
+    return canonical === undefined ? [] : [{ path, source, canonical }]
+  })
+}