#!/usr/bin/env bun
/**
 * release-notes.ts — turn a commit range into capability-level release notes
 * using the TRACES graph instead of raw commit subjects.
 *
 * Usage:
 *   bun run scripts/release-notes.ts [<range>]
 *   bun run scripts/release-notes.ts v0.0.15..HEAD
 *
 * With no argument it uses <latest tag>..HEAD (or the whole history if untagged).
 *
 * How it works:
 *   1. `git diff --name-only <range>` → files the range changed.
 *   2. Read each changed file's `TRACES:` comments → requirement IDs.
 *   3. Resolve IDs to descriptions from docs/requirements.md.
 *   4. Group: UR → Features, DR/IR → Improvements. Deduped, so many commits
 *      touching one requirement collapse to one line.
 *
 * This is a drafting aid for docs/release-checklist.md — review the output,
 * it does not invent descriptions for untraced changes (those are listed
 * separately so nothing is silently dropped).
 */

import { execSync } from "node:child_process";
import { readFileSync, existsSync } from "node:fs";

const TRACE_RE = /TRACES:\s*([^\n*]+)/g;
const ID_RE = /\b(UR|IR|DR|JA|UT|IT)-\d+\b/g;
const REQ_ROW_RE = /^\|\s*((?:UR|IR|DR|JA)-\d+)\s*\|\s*([^|]+?)\s*\|/;

function sh(cmd: string): string {
  return execSync(cmd, { encoding: "utf8" }).trim();
}

function defaultRange(): string {
  try {
    const tag = sh("git describe --tags --abbrev=0");
    return `${tag}..HEAD`;
  } catch {
    return ""; // no tags: fall through to whole-history diff
  }
}

/** Map requirement ID → human description, parsed from docs/requirements.md. */
function loadRequirementDescriptions(): Map<string, string> {
  const map = new Map<string, string>();
  const text = readFileSync("docs/requirements.md", "utf8");
  for (const line of text.split("\n")) {
    const m = line.match(REQ_ROW_RE);
    // First definition wins: the descriptive tables come before the later
    // cross-reference tables, whose cells hold linked IDs (or "-"), not prose.
    if (m && !map.has(m[1])) map.set(m[1], m[2].trim());
  }
  return map;
}

/**
 * Commit subjects whose changes carry no requirement meaning.
 *
 * `chore(format)` / `style` rewrite files without changing behaviour;
 * `chore(deps)` moves lockfiles. Anything else — including a bare `chore:` and
 * `chore(release):` — is assumed to mean something and is kept.
 *
 * Anchored at the start of the subject on purpose: "fix(duration): format times
 * over 24 hours" is a real fix to formatting *code*, not a formatting commit.
 */
const COSMETIC_SUBJECT = /^(chore\(format\)|chore\(deps\)|style)(\([^)]*\))?\s*:/i;

/**
 * Does this commit subject describe a change with no requirement meaning?
 *
 * Exported for scripts/release-notes.test.ts.
 *
 * TRACES: | DR-219
 */
export function isCosmeticCommit(subject: string): boolean {
  return COSMETIC_SUBJECT.test(subject.trim());
}

/**
 * Files the range changed, excluding those touched only by cosmetic commits.
 *
 * Why not a plain `git diff --name-only <range>`: that is what this did, and a
 * single repo-wide `prettier --write` inside the range made it report 199 files
 * whose TRACES comments resolved to nearly the entire requirement matrix. The
 * generated notes for v0.9.2 claimed the release had added the whole
 * application — and build-release.yml publishes this output, so the noise would
 * have shipped.
 *
 * Walking commit by commit and skipping the cosmetic ones keeps a file that a
 * sweep *and* a real change both touched: it is still listed by the real
 * commit. Only files touched exclusively by cosmetic commits drop out, which is
 * exactly the intent.
 *
 * Merge commits produce no output from `git diff-tree` without `-m`, and are
 * skipped deliberately: everything they merge is already in the range as its
 * own commit, so including them would double-count.
 */
function changedFiles(range: string): string[] {
  // Untagged repo: describe everything currently traced.
  if (!range) {
    return sh("git ls-files")
      .split("\n")
      .filter((f) => f && existsSync(f));
  }

  // NUL between hash and subject so a subject containing anything at all is safe.
  const log = sh(`git log --no-merges --format=%H%x00%s ${range}`);
  if (!log) return [];

  const files = new Set<string>();
  let skipped = 0;

  for (const line of log.split("\n")) {
    const [sha, ...subjectParts] = line.split("\u0000");
    const subject = subjectParts.join("\u0000");
    if (!sha) continue;

    if (isCosmeticCommit(subject)) {
      skipped++;
      continue;
    }

    for (const f of sh(`git diff-tree --no-commit-id --name-only -r ${sha}`).split("\n")) {
      if (f && existsSync(f)) files.add(f);
    }
  }

  if (skipped > 0) {
    // Say what was dropped rather than silently reporting a smaller set.
    console.error(
      `ℹ️  Skipped ${skipped} cosmetic commit(s) (formatting/deps) when deriving notes.`,
    );
  }

  return [...files];
}

/** Collect requirement IDs referenced by TRACES comments in the given files. */
function idsFromFiles(files: string[]): Set<string> {
  const ids = new Set<string>();
  for (const file of files) {
    let content: string;
    try {
      content = readFileSync(file, "utf8");
    } catch {
      continue;
    }
    for (const trace of content.matchAll(TRACE_RE)) {
      for (const id of trace[1].matchAll(ID_RE)) ids.add(id[0]);
    }
  }
  return ids;
}

function main() {
  const range = process.argv[2] ?? defaultRange();
  const descriptions = loadRequirementDescriptions();
  const files = changedFiles(range);
  const ids = idsFromFiles(files);

  const features: string[] = []; // UR
  const improvements: string[] = []; // DR / IR
  const unknown: string[] = []; // traced but not in requirements.md

  for (const id of [...ids].sort()) {
    const desc = descriptions.get(id);
    if (id.startsWith("UT") || id.startsWith("IT")) continue; // tests aren't notes
    if (!desc) {
      if (!id.startsWith("UT") && !id.startsWith("IT")) unknown.push(id);
      continue;
    }
    const line = `- ${desc} (${id})`;
    if (id.startsWith("UR")) features.push(line);
    else improvements.push(line);
  }

  const header = range || "(entire history — no tags found)";
  const out: string[] = [`## Release notes — ${header}`, ""];

  if (features.length) out.push("### ✨ Features", ...features, "");
  if (improvements.length) out.push("### 🚀 Improvements", ...improvements, "");
  if (unknown.length)
    out.push(
      "### ⚠️ Traced IDs missing from requirements.md",
      ...unknown.map((id) => `- ${id}`),
      "",
    );

  const untraced = files.filter((f) => {
    try {
      return !/TRACES:/.test(readFileSync(f, "utf8"));
    } catch {
      return false;
    }
  });
  if (untraced.length)
    out.push(
      `### 📝 Changed files without TRACES (${untraced.length}) — review manually`,
      ...untraced.map((f) => `- ${f}`),
      "",
    );

  if (!features.length && !improvements.length)
    out.push("_No traced requirements in this range._", "");

  console.log(out.join("\n"));
}

// Guarded so this module stays importable from release-notes.test.ts.
if (import.meta.main) {
  main();
}