// lib/review/verdict-gate.mjs
// K7 — the review verdict gate (ordre 5, P11).
//
// One command decides on the verdict written in review.md, so whatever stops a
// merge or a release reads a file and an exit code, never a model's summary:
//
//   node lib/review/verdict-gate.mjs [--json] <review.md>
//     0 = ALLOW or WARN
//     1 = BLOCK
//     2 = could not decide: missing/unreadable file, not a review, no verdict,
//         an unknown verdict, a file that contradicts its own verdict, a
//         finding lowered or marked against the brief outside the one legal
//         shape (coordinator-contract `illegalBriefLowering`), or a
//         WARN because a reviewer or engine did not run (`missing-reviewer:` /
//         `unattributable-payload` in allow_blocked_by — operator decision
//         2026-10-06: a review not performed in full stops a merge).
//         Exit 2 is NEVER green.
//
// Fail-closed reading: a missing `verdict` is exit 2, never ALLOW. A verdict
// that is GREENER than the file's own findings (ALLOW/WARN over a BLOCKER, or a
// frontmatter verdict the trailing JSON block disagrees with) is exit 2 as well
// — the file cannot be trusted for the direction that would let work through.
// BLOCK always exits 1: a stricter-than-supported verdict is still a stop.
//
// Borrowed: the verdict goes to a file and a command check gates on it
// (Kiro `feature-pipeline`, https://kiro.dev/docs/workflows/patterns); the
// executor may read the verdict but never write it (Spec Kit
// `templates/checklist-template.md:8-9`, MIT). The blocking itself is Voyage's
// own design — neither source blocks on its own.

import { readFileSync, existsSync } from 'node:fs';
import { validateReviewContent, VERDICT_VALUES } from '../validators/review-validator.mjs';
import { fencedBlocks, isJsonBlock } from './findings-schema.mjs';
import { illegalBriefLowering } from './coordinator-contract.mjs';
import { isMain } from '../util/is-main.mjs';

export const EXIT = Object.freeze({ PASS: 0, BLOCK: 1, UNDECIDED: 2 });

function undecided(reason, verdict = null) {
  return { exit: EXIT.UNDECIDED, verdict, reason };
}

/**
 * Decide on review.md text. Pure: no I/O.
 * @param {string} text
 * @returns {{ exit: 0|1|2, verdict: string|null, reason: string }}
 */
export function decideVerdict(text) {
  const r = validateReviewContent(text, { strict: false });
  const fm = r.parsed?.frontmatter ?? {};
  if (!r.valid) {
    const codes = (r.errors ?? []).map((e) => e.code).join(', ');
    return undecided(`not a readable review.md (${codes || 'parse failure'})`);
  }
  const verdict = fm.verdict;
  if (verdict === undefined || verdict === null || verdict === '') {
    return undecided('review.md carries no verdict (K7: required) — never read as ALLOW');
  }
  if (!VERDICT_VALUES.includes(verdict)) {
    return undecided(`unknown verdict ${JSON.stringify(verdict)}`);
  }
  if (verdict === 'BLOCK') {
    return { exit: EXIT.BLOCK, verdict, reason: 'verdict BLOCK' };
  }

  // ALLOW / WARN: the file must back the greener direction, from every place a
  // BLOCKER can be written. A shape the gate cannot read is exit 2, never 0.
  const body = r.parsed.body ?? '';
  const fmText = text.slice(0, Math.max(0, text.indexOf('\n---', 3)));
  if ((fmText.match(/^verdict\s*:/gm) ?? []).length > 1) {
    return undecided('frontmatter carries more than one verdict line', verdict);
  }
  // The last fenced block, its info string and its body from one reading
  // (findings-schema `fencedBlocks`): a gate that took the language from one
  // reader and the body from another passed a BLOCKER in a last block opened
  // as ```json {x} (release review of 6.3.0, round 9).
  const last = fencedBlocks(body).at(-1);
  if (last === undefined) {
    return undecided(`verdict ${verdict} has no trailing JSON block to back it`, verdict);
  }
  if (!last.closed) {
    return undecided(`the last fenced block ("${last.info || '(no language)'}") is never closed, so it runs to the end of the file`, verdict);
  }
  if (!isJsonBlock(last)) {
    return undecided(`the last fenced block is "${last.info || '(no language)'}", not the trailing \`json\` block`, verdict);
  }
  let payload;
  try {
    payload = JSON.parse(last.body);
  } catch (e) {
    return undecided(`trailing JSON block does not parse: ${e.message}`, verdict);
  }
  const shape = checkPayloadShape(payload);
  if (shape) return undecided(`trailing JSON block: ${shape}`, verdict);
  if (payload.verdict !== verdict) {
    return undecided(`frontmatter verdict ${verdict} disagrees with the JSON block verdict ${payload.verdict}`, verdict);
  }
  const blockerFindings = payload.findings.filter((f) => String(f.severity).toUpperCase() === 'BLOCKER').length;
  const blockerCount = Object.entries(payload.counts)
    .filter(([k]) => k.toUpperCase() === 'BLOCKER')
    .reduce((n, [, v]) => n + Number(v || 0), 0);
  const blockerSection = blockerSectionEntries(body);
  if (blockerFindings > 0 || blockerCount > 0 || blockerSection > 0) {
    return undecided(`verdict ${verdict} over BLOCKER finding(s) (json: ${blockerFindings}, counts: ${blockerCount}, ## Findings (BLOCKER): ${blockerSection})`, verdict);
  }
  // The brief-conflict rule (coordinator-contract `illegalBriefLowering`, the
  // one place it lives): a finding lowered or marked outside the one legal
  // shape means the verdict may be greener than the findings — never green.
  const illegal = payload.findings.filter((f) => illegalBriefLowering(f)).map((f) => f.id);
  if (illegal.length > 0) {
    return undecided(`verdict ${verdict} over a brief-conflict lowering outside the one legal shape (finding ${illegal.join(', ')})`, verdict);
  }
  const fmIds = new Set(Array.isArray(fm.findings) ? fm.findings : []);
  const jsonIds = new Set(payload.findings.map((f) => f.id));
  if (fmIds.size !== jsonIds.size || [...fmIds].some((id) => !jsonIds.has(id))) {
    return undecided('frontmatter findings: list and the JSON block finding ids differ', verdict);
  }
  // A review in which a reviewer or engine never reported was not performed in
  // full: that is "could not decide", not a passable warning (operator
  // decision 2026-10-06, ordre 5). A 1.1 review must carry the list.
  if (atLeastVersion(fm.review_version, 1, 1) && !Array.isArray(payload.allow_blocked_by)) {
    return undecided('trailing JSON block lacks allow_blocked_by (required from review_version 1.1)', verdict);
  }
  const warnReasons = Array.isArray(payload.allow_blocked_by) ? payload.allow_blocked_by.map(String) : [];
  const notRun = warnReasons.filter((w) => w.startsWith('missing-reviewer:') || w.startsWith('unattributable-payload'));
  if (notRun.length > 0) {
    return undecided(`a control did not run: ${notRun.join(', ')}`, verdict);
  }
  return { exit: EXIT.PASS, verdict, reason: `verdict ${verdict}`, warn_reasons: warnReasons };
}

function atLeastVersion(v, major, minor) {
  const m = typeof v === 'string' ? v.match(/^(\d+)\.(\d+)$/) : null;
  return Boolean(m) && (Number(m[1]) > major || (Number(m[1]) === major && Number(m[2]) >= minor));
}

/** The JSON block shape the gate needs; returns an error string or null. */
function checkPayloadShape(p) {
  if (p === null || typeof p !== 'object' || Array.isArray(p)) return 'not an object';
  if (!VERDICT_VALUES.includes(p.verdict)) return `verdict must be one of ${VERDICT_VALUES.join('|')}`;
  if (p.counts === null || typeof p.counts !== 'object' || Array.isArray(p.counts)) return 'counts must be an object';
  if (!Array.isArray(p.findings)) return 'findings must be an array';
  for (const [i, f] of p.findings.entries()) {
    if (f === null || typeof f !== 'object' || typeof f.severity !== 'string' || typeof f.id !== 'string') {
      return `findings[${i}] needs a string id and severity`;
    }
  }
  return null;
}

/** Number of `### ` entries under `## Findings (BLOCKER)`. */
function blockerSectionEntries(body) {
  const start = body.search(/^##\s+Findings\s*\(BLOCKER\)/im);
  if (start === -1) return 0;
  const rest = body.slice(start).replace(/^[^\n]*\n/, '');
  const next = rest.search(/^##\s+/m);
  const section = next === -1 ? rest : rest.slice(0, next);
  return (section.match(/^###\s+\S/gm) ?? []).length;
}

/**
 * Decide on a review.md path.
 * @param {string} filePath
 */
export function decideVerdictFile(filePath) {
  if (!filePath || !existsSync(filePath)) return undecided(`file not found: ${filePath}`);
  let text;
  try {
    text = readFileSync(filePath, 'utf-8');
  } catch (e) {
    return undecided(`cannot read ${filePath}: ${e.message}`);
  }
  return decideVerdict(text);
}

if (isMain(import.meta.url)) {
  const args = process.argv.slice(2);
  const files = args.filter((a) => !a.startsWith('--'));
  const filePath = files[0];
  if (files.length !== 1) {
    // Exactly one file: a glob would otherwise gate on its first match only.
    process.stderr.write('Usage: verdict-gate.mjs [--json] <review.md>  (exactly one file)\n');
    process.exit(EXIT.UNDECIDED);
  }
  let result;
  try {
    result = decideVerdictFile(filePath);
  } catch (e) {
    result = undecided(`gate crashed: ${e.message}`);
  }
  if (args.includes('--json')) {
    process.stdout.write(JSON.stringify({ path: filePath, ...result }) + '\n');
  } else {
    const label = result.exit === EXIT.UNDECIDED ? 'UNDECIDED (not green)' : result.verdict;
    process.stdout.write(`verdict-gate: ${label} — ${result.reason} — ${filePath}\n`);
  }
  process.exit(result.exit);
}