// lib/validators/intent-approval.mjs
// Intent approval marker — the gate /trekplan passes before it plans anything.
//
// A brief carries two optional frontmatter fields once the operator has
// approved its intent in /trekbrief (Phase 4h, or `/trekbrief --approve`):
//
//   intent_approved_hash: "sha256:<64 hex>"   hash over ## Intent + ## Goal
//   intent_approved_at:   "<ISO-8601>"        when the stamp was written
//
// The hash binds the approval to the EXACT intent text: each section is
// normalized (lines trimmed, whitespace runs collapsed, blank lines dropped)
// and the pair is hashed. Reflowing a paragraph keeps the approval; changing
// a word in ## Intent or ## Goal after approval makes it stale, and /trekplan
// stops until the operator approves the new text.
//
// WHAT THE MARKER DOES NOT PROVE. Same user, same machine: any session with
// write access to the brief can run `--stamp` itself, or write the two fields
// by hand. The marker is a TRACE that the approval step ran against this text,
// NOT a signature binding a person — the same limit as the order queue's
// `--from`. It catches drift (intent edited after approval) and omission (no
// approval step at all); it does not catch a session that approves on the
// operator's behalf.
//
// trekreview briefs are exempt: they are produced from a review of an already
// planned brief and carry no ## Intent of their own.
//
// CLI:
//   node lib/validators/intent-approval.mjs --check [--json] <brief.md>
//     exit 0 = approved and current; exit 1 = stop (errors); exit 2 = usage
//   node lib/validators/intent-approval.mjs --stamp <brief.md>
//     writes the marker and emits `brief-approved`; exit 0 stamped, 1 refused

import { createHash } from 'node:crypto';
import { existsSync, readFileSync, renameSync, writeFileSync } from 'node:fs';
import { homedir } from 'node:os';
import { basename, dirname, join } from 'node:path';
import { parseDocument } from '../util/frontmatter.mjs';
import { issue } from '../util/result.mjs';
import { emit } from '../stats/event-emit.mjs';

export const INTENT_HASH_FIELD = 'intent_approved_hash';
export const INTENT_APPROVED_AT_FIELD = 'intent_approved_at';
export const INTENT_SECTIONS = Object.freeze(['Intent', 'Goal']);
const HASH_RE = /^sha256:[0-9a-f]{64}$/;
const STATS_FILENAME = 'trekexecute-stats.jsonl'; // where event-emit writes lifecycle events

const APPROVE_HINT = 'Run /trekbrief --approve <project-dir> — the operator reads ## Intent + ## Goal and answers "Approve".';

function extractSection(body, heading) {
  const re = new RegExp(`^##\\s+${heading}\\b.*$`, 'm');
  const m = re.exec(body);
  if (!m) return null;
  const after = body.slice(m.index + m[0].length);
  const next = after.search(/^##\s/m);
  return next === -1 ? after : after.slice(0, next);
}

function normalize(text) {
  return text.split(/\r?\n/)
    .map((l) => l.trim().replace(/\s+/g, ' '))
    .filter(Boolean)
    .join('\n');
}

/**
 * Hash ## Intent + ## Goal of a brief body.
 * @returns {{ hash: string|null, missing: string[] }} hash is null when a section is absent or empty.
 */
export function computeIntentHash(body) {
  const parts = [];
  const missing = [];
  for (const h of INTENT_SECTIONS) {
    const s = extractSection(body || '', h);
    const n = s === null ? '' : normalize(s);
    if (!n) missing.push(h);
    parts.push(n);
  }
  if (missing.length) return { hash: null, missing };
  const hex = createHash('sha256').update(JSON.stringify(parts), 'utf8').digest('hex');
  return { hash: `sha256:${hex}`, missing };
}

/** Check the approval marker of a brief's text. Returns a validator Result. */
export function checkIntentApprovalContent(text) {
  const doc = parseDocument(text);
  if (!doc.valid) return doc;
  const fm = doc.parsed.frontmatter || {};
  const body = doc.parsed.body || '';
  const errors = [];
  const result = () => ({ valid: errors.length === 0, errors, warnings: [], parsed: { frontmatter: fm } });

  if (fm.type === 'trekreview') return result();

  if (!(INTENT_HASH_FIELD in fm)) {
    errors.push(issue(
      'BRIEF_INTENT_NOT_APPROVED',
      'The brief\'s intent has not been approved — /trekplan does not plan against an unapproved intent.',
      APPROVE_HINT,
    ));
    return result();
  }
  const recorded = String(fm[INTENT_HASH_FIELD]);
  if (!HASH_RE.test(recorded)) {
    errors.push(issue(
      'BRIEF_INTENT_APPROVAL_INVALID',
      `${INTENT_HASH_FIELD} "${recorded}" is not "sha256:<64 hex>" — the marker is malformed.`,
      APPROVE_HINT,
    ));
    return result();
  }
  const { hash, missing } = computeIntentHash(body);
  if (!hash) {
    errors.push(issue(
      'BRIEF_INTENT_APPROVAL_INVALID',
      `The approval cannot bind: ## ${missing.join(' and ## ')} is missing or empty.`,
      'Write the missing section(s), then ' + APPROVE_HINT,
    ));
    return result();
  }
  if (hash !== recorded) {
    errors.push(issue(
      'BRIEF_INTENT_APPROVAL_STALE',
      '## Intent or ## Goal changed after the intent was approved — the approval covers the old text, not this one.',
      APPROVE_HINT,
    ));
  }
  return result();
}

/**
 * Write the approval marker into a brief's frontmatter (replacing any prior one).
 * @returns {{ stamped: boolean, text: string, hash?: string, approvedAt?: string, reason?: string }}
 */
export function stampIntentApproval(text, now = new Date()) {
  const doc = parseDocument(text);
  if (!doc.valid) return { stamped: false, text, reason: 'frontmatter does not parse' };
  const { hash, missing } = computeIntentHash(doc.parsed.body || '');
  if (!hash) return { stamped: false, text, reason: `## ${missing.join(' and ## ')} missing or empty` };
  const m = /^(?---\r?\n)([\s\S]*?)(\r?\n---)/.exec(text);
  if (!m) return { stamped: false, text, reason: 'no frontmatter block' };
  const approvedAt = now.toISOString();
  const kept = m[2].split(/\r?\n/).filter((l) =>
    !l.startsWith(`${INTENT_HASH_FIELD}:`) && !l.startsWith(`${INTENT_APPROVED_AT_FIELD}:`));
  kept.push(`${INTENT_HASH_FIELD}: "${hash}"`, `${INTENT_APPROVED_AT_FIELD}: "${approvedAt}"`);
  const out = m[1] + kept.join('\n') + m[3] + text.slice(m.index + m[0].length);
  return { stamped: true, text: out, hash, approvedAt };
}

/**
 * Where the brief-approved record goes. CLAUDE_PLUGIN_DATA when the harness
 * provides it; otherwise the plugin data dir the hooks write to and
 * scripts/yardstick.mjs reads — the Bash tool env carries no CLAUDE_PLUGIN_DATA,
 * and event-emit's own fallback is a silent skip, which is how brief-approved
 * reached 0 records.
 */
export function resolveApprovalDataDir(env = process.env) {
  if (env.CLAUDE_PLUGIN_DATA) return env.CLAUDE_PLUGIN_DATA;
  const home = env.HOME && env.HOME.length > 0 ? env.HOME : homedir();
  return join(home, '.claude', 'plugins', 'data', 'voyage-ktg-plugin-marketplace');
}

if (import.meta.url === `file://${process.argv[1]}`) {
  const args = process.argv.slice(2);
  const file = args.find((a) => !a.startsWith('--'));
  const mode = args.includes('--stamp') ? 'stamp' : args.includes('--check') ? 'check' : null;
  if (!file || !mode) {
    process.stderr.write('Usage: intent-approval.mjs --check [--json] <brief.md> | --stamp <brief.md>\n');
    process.exit(2);
  }
  let text = null;
  if (existsSync(file)) {
    try { text = readFileSync(file, 'utf8'); } catch { text = null; }
  }

  if (mode === 'check') {
    const r = text === null
      ? { valid: false, errors: [issue('BRIEF_NOT_FOUND', `Cannot read brief: ${file}`)], warnings: [] }
      : checkIntentApprovalContent(text);
    if (args.includes('--json')) {
      process.stdout.write(JSON.stringify({ valid: r.valid, errors: r.errors, warnings: r.warnings }, null, 2) + '\n');
    } else {
      process.stdout.write(`intent-approval: ${r.valid ? 'APPROVED' : 'STOP'} ${file}\n`);
      for (const e of r.errors) process.stderr.write(`  ERROR  [${e.code}] ${e.message}\n         ${e.hint || ''}\n`);
    }
    process.exit(r.valid ? 0 : 1);
  }

  // --stamp
  if (text === null) {
    process.stdout.write(JSON.stringify({ stamped: false, reason: `cannot read ${file}` }) + '\n');
    process.exit(1);
  }
  const s = stampIntentApproval(text);
  if (!s.stamped) {
    process.stdout.write(JSON.stringify({ stamped: false, reason: s.reason }) + '\n');
    process.exit(1);
  }
  const tmp = join(dirname(file), `.${basename(file)}.approve.tmp`);
  writeFileSync(tmp, s.text);
  renameSync(tmp, file);
  const fm = parseDocument(s.text).parsed.frontmatter || {};
  const record = emit('brief-approved',
    { project: dirname(file), slug: fm.slug ?? null, intent_hash: s.hash },
    { path: join(resolveApprovalDataDir(), STATS_FILENAME) });
  process.stdout.write(JSON.stringify({
    stamped: true, intent_hash: s.hash, approved_at: s.approvedAt, record,
  }) + '\n');
  process.exit(0);
}