#!/usr/bin/env node
'use strict';

/**
 * Docs-required lint (#3213).
 *
 * Mirrors scripts/changeset/lint.cjs. Pure verdict function
 * evaluateLint({ changedFiles, fragments, labels, malformed }) returns
 * { ok, reason, triggering } using the LINT_REASON enum. The CLI wrapper
 * reads the PR diff (`git diff --name-only origin/${base}...HEAD`), parses
 * each touched `.changeset/*.md` fragment, then calls evaluateLint.
 *
 * Tests assert on the structured verdict, never on free text.
 */

const { parseFragment, FRAGMENT_ERROR } = require('./changeset/parse.cjs');
const { ExitError, runMain } = require('./lib/cli-exit.cjs');

const LINT_REASON = Object.freeze({
  OK_NO_TRIGGERING_FRAGMENTS: 'ok_no_triggering_fragments',
  OK_DOCS_UPDATED: 'ok_docs_updated',
  OK_OPT_OUT_LABEL: 'ok_opt_out_label',
  OK_FRAGMENTS_EXEMPT: 'ok_fragments_exempt',
  FAIL_DOCS_MISSING: 'fail_docs_missing',
  FAIL_MALFORMED_FRAGMENT: 'fail_malformed_fragment',
});

const OPT_OUT_LABEL = 'no-docs';

// Fragment types that require a docs update. `Fixed` and `Security` are
// bug-class — they describe regressions or vulnerabilities, not new
// behavior to document.
const TRIGGERING_TYPES = new Set(['Added', 'Changed', 'Deprecated', 'Removed']);

const DOCS_PREFIX = 'docs/';

function isFragmentPath(file) {
  return /^\.changeset\/[^/]+\.md$/.test(file) && !file.endsWith('/README.md');
}

function isDocsFile(file) {
  return file.startsWith(DOCS_PREFIX);
}

// Per-fragment escape hatch: parse.cjs extracts `<!-- docs-exempt: <reason> -->`
// from the body into `fragment.docsExempt` (a non-empty reason string when the
// marker was present and well-formed; `null` otherwise). A non-empty audit
// trail is required — the lint defends in depth here too: even if a caller
// constructs a fragment with `docsExempt: ''`, that does not count as exempt.
function isExemptFragment(fragment) {
  return typeof fragment.docsExempt === 'string' && fragment.docsExempt.trim().length > 0;
}

/**
 * Pure verdict — no fs, no git.
 *
 * Malformed fragments fail closed: a triggering fragment with bad frontmatter
 * cannot silently bypass docs enforcement. The changeset-required lint only
 * checks fragment _presence_, not _validity_, so docs lint takes responsibility
 * for any fragment it tries to consume.
 *
 * @param {object} args
 * @param {string[]} args.changedFiles  - file paths changed in the PR
 * @param {Array<{ path: string, type: string, body: string, docsExempt: string|null }>} args.fragments
 *   - parsed records for well-formed `.changeset/*.md` files in `changedFiles`
 * @param {Array<{ path: string, reason: string }>} [args.malformed]
 *   - records for `.changeset/*.md` files that failed `parseFragment`
 * @param {string[]} args.labels        - PR labels
 * @returns {{ ok: boolean, reason: string, triggering: string[], malformed?: Array<{path:string,reason:string}> }}
 */
function evaluateLint({ changedFiles, fragments, labels, malformed = [] }) {
  if (malformed.length > 0) {
    return {
      ok: false,
      reason: LINT_REASON.FAIL_MALFORMED_FRAGMENT,
      triggering: [],
      malformed,
    };
  }

  const triggering = fragments.filter((f) => TRIGGERING_TYPES.has(f.type));
  const triggeringPaths = triggering.map((f) => f.path);

  if (triggering.length === 0) {
    return { ok: true, reason: LINT_REASON.OK_NO_TRIGGERING_FRAGMENTS, triggering: [] };
  }

  // Per-fragment exempt path: every triggering fragment must carry the marker.
  // Partial exemption fails closed — one un-marked Added fragment still requires docs.
  if (triggering.every(isExemptFragment)) {
    return { ok: true, reason: LINT_REASON.OK_FRAGMENTS_EXEMPT, triggering: triggeringPaths };
  }

  if (labels.includes(OPT_OUT_LABEL)) {
    return { ok: true, reason: LINT_REASON.OK_OPT_OUT_LABEL, triggering: triggeringPaths };
  }

  if (changedFiles.some(isDocsFile)) {
    return { ok: true, reason: LINT_REASON.OK_DOCS_UPDATED, triggering: triggeringPaths };
  }

  return { ok: false, reason: LINT_REASON.FAIL_DOCS_MISSING, triggering: triggeringPaths };
}

function readFragmentsFromDisk(changedFiles, rootDir) {
  const fs = require('node:fs');
  const path = require('node:path');
  const fragments = [];
  const malformed = [];
  for (const rel of changedFiles) {
    if (!isFragmentPath(rel)) continue;
    const abs = path.join(rootDir, rel);
    if (!fs.existsSync(abs)) continue; // fragment deleted in PR — skip
    let src;
    try {
      src = fs.readFileSync(abs, 'utf8');
    } catch (e) {
      malformed.push({ path: rel, reason: 'read_error', detail: e.code || e.message });
      continue;
    }
    const parsed = parseFragment(src);
    if (!parsed.ok) {
      malformed.push({ path: rel, reason: parsed.reason, detail: parsed.detail || null });
      continue;
    }
    fragments.push({
      path: rel,
      type: parsed.fragment.type,
      body: parsed.fragment.body,
      docsExempt: parsed.fragment.docsExempt,
    });
  }
  return { fragments, malformed };
}

function main() {
  const fs = require('node:fs');
  const cp = require('node:child_process');
  const path = require('node:path');

  const rootDir = path.join(__dirname, '..');

  const eventPath = process.env.GITHUB_EVENT_PATH;
  let labels = [];
  if (eventPath && fs.existsSync(eventPath)) {
    try {
      const event = JSON.parse(fs.readFileSync(eventPath, 'utf8'));
      labels = (event.pull_request?.labels || []).map((l) => l.name);
    } catch { /* fall through */ }
  }

  const base = process.env.GITHUB_BASE_REF || 'main';
  let changedFiles = [];
  try {
    // execFileSync with argv — no shell, so a malicious GITHUB_BASE_REF
    // cannot inject shell syntax. Git's own ref-name validator rejects
    // any metacharacters it would otherwise interpret.
    const out = cp.execFileSync(
      'git',
      ['diff', '--name-only', `origin/${base}...HEAD`],
      { encoding: 'utf8', cwd: rootDir },
    );
    changedFiles = out.split('\n').filter(Boolean);
  } catch (e) {
    throw new ExitError(2, `could not compute diff: ${e.message}`);
  }

  const { fragments, malformed } = readFragmentsFromDisk(changedFiles, rootDir);
  const verdict = evaluateLint({ changedFiles, fragments, labels, malformed });

  if (process.argv.includes('--json')) {
    process.stdout.write(
      JSON.stringify({ ...verdict, changedFiles, fragments, malformed, labels }, null, 2) + '\n',
    );
  } else if (verdict.ok) {
    process.stdout.write(`ok docs-lint: ${verdict.reason}\n`);
  } else if (verdict.reason === LINT_REASON.FAIL_MALFORMED_FRAGMENT) {
    process.stderr.write(`\nERROR docs-lint: ${verdict.reason}\n`);
    process.stderr.write(
      `${malformed.length} changeset fragment(s) failed to parse — docs lint cannot consume them:\n`,
    );
    for (const m of malformed) {
      process.stderr.write(`  ${m.path}  (reason: ${m.reason}${m.detail ? `, detail: ${m.detail}` : ''})\n`);
    }
    process.stderr.write(
      `\nFix the fragment frontmatter (\`type:\` + \`pr:\`) before this PR can pass.\n`,
    );
  } else {
    process.stderr.write(`\nERROR docs-lint: ${verdict.reason}\n`);
    process.stderr.write(
      `${verdict.triggering.length} changeset fragment(s) require documentation updates:\n`,
    );
    for (const f of fragments.filter((f) => TRIGGERING_TYPES.has(f.type))) {
      process.stderr.write(`  ${f.path}  (type: ${f.type})\n`);
    }
    process.stderr.write(`\nNo files under docs/ were modified in this PR.\n\n`);
    process.stderr.write(
      `Update the relevant docs/ file(s), or add the \`${OPT_OUT_LABEL}\` label if this change\n`,
    );
    process.stderr.write(
      `is genuinely internal-only (infrastructure, refactor, test-only). Per-fragment\n`,
    );
    process.stderr.write(
      `exemption via \`<!-- docs-exempt: <reason> -->\` inside the fragment body also works.\n`,
    );
  }
  return verdict.ok ? 0 : 1;
}

if (require.main === module) runMain(main);

module.exports = {
  evaluateLint,
  readFragmentsFromDisk,
  LINT_REASON,
  OPT_OUT_LABEL,
  TRIGGERING_TYPES,
  FRAGMENT_ERROR,
  isFragmentPath,
  isDocsFile,
  isExemptFragment,
};