// lib/validators/architecture-discovery.mjs
// EXTERNAL CONTRACT — drift-WARN, never drift-FAIL.
//
// The architecture/ directory is owned by the separate `ultra-cc-architect`
// plugin. ultraplan-local validates only DISCOVERY (file present at canonical
// path) and tolerates internal-format drift via warnings.
//
// Never read body content beyond first heading. Never assert frontmatter shape.

import { existsSync, readdirSync, statSync, readFileSync } from 'node:fs';
import { join } from 'node:path';
import { issue } from '../util/result.mjs';

const CANONICAL_OVERVIEW = 'overview.md';
const CANONICAL_GAPS = 'gaps.md';
const KNOWN_ALTERNATIVES = ['architecture-overview.md', 'overview.markdown', 'README.md'];

export function discoverArchitecture(projectDir) {
  const archDir = projectDir ? join(projectDir, 'architecture') : null;
  const result = {
    found: false,
    overview: null,
    gaps: null,
    looseFiles: [],
    warnings: [],
  };

  if (!archDir || !existsSync(archDir) || !statSync(archDir).isDirectory()) {
    return result;
  }

  const overviewPath = join(archDir, CANONICAL_OVERVIEW);
  if (existsSync(overviewPath) && statSync(overviewPath).isFile()) {
    result.found = true;
    result.overview = overviewPath;
  } else {
    for (const alt of KNOWN_ALTERNATIVES) {
      const altPath = join(archDir, alt);
      if (existsSync(altPath) && statSync(altPath).isFile()) {
        result.found = true;
        result.overview = altPath;
        result.warnings.push(issue(
          'ARCH_NON_CANONICAL_OVERVIEW',
          `Architecture file at non-canonical path: ${alt}`,
          `Canonical contract is architecture/overview.md. The ultra-cc-architect plugin may have drifted; this is a warning, not a blocker.`,
        ));
        break;
      }
    }
  }

  const gapsPath = join(archDir, CANONICAL_GAPS);
  if (existsSync(gapsPath) && statSync(gapsPath).isFile()) result.gaps = gapsPath;

  const all = readdirSync(archDir).filter(f => /\.md$/i.test(f));
  result.looseFiles = all
    .filter(f => f !== CANONICAL_OVERVIEW && f !== CANONICAL_GAPS && !KNOWN_ALTERNATIVES.includes(f))
    .map(f => join(archDir, f));

  if (result.looseFiles.length > 0) {
    result.warnings.push(issue(
      'ARCH_LOOSE_FILES',
      `Found ${result.looseFiles.length} unrecognized architecture file(s)`,
      `Architecture contract expects overview.md (+ optional gaps.md). Loose files may indicate format drift in ultra-cc-architect.`,
    ));
  }

  if (result.found && result.overview) {
    try {
      const text = readFileSync(result.overview, 'utf-8');
      const firstHeading = text.match(/^#\s+(.+?)\s*$/m);
      result.firstHeading = firstHeading ? firstHeading[1] : null;
    } catch { /* ignore — only sniff */ }
  }

  return result;
}

if (import.meta.url === `file://${process.argv[1]}`) {
  const projectDir = process.argv[2];
  const wantJson = process.argv.includes('--json');
  if (!projectDir) {
    process.stderr.write('Usage: architecture-discovery.mjs <project-dir> [--json]\n');
    process.exit(2);
  }
  const r = discoverArchitecture(projectDir);
  if (wantJson) {
    process.stdout.write(JSON.stringify(r, null, 2) + '\n');
  } else {
    process.stdout.write(`architecture-discovery: ${r.found ? 'FOUND' : 'NONE'} ${r.overview || projectDir}\n`);
    for (const w of r.warnings) process.stderr.write(`  WARN   [${w.code}] ${w.message}\n`);
  }
  process.exit(0);
}