// tests/helpers/plan-v18-builder.mjs
// Builds plan_version 1.8 plans for the plan-contract tests (K3 gate, K4 step
// fields, the design part, the scope sweep). One builder, many variants, so a
// test states only the difference it is about.
//
// Raw options on step() write a field the generated form cannot (the
// plan_version 1.9 grammar tests): `filesRaw` is the `Files:` value written
// verbatim after `- **Files:** `; `testFirstRaw` is the whole `Test first:`
// `File:` line written verbatim in place of `  - File: `<test>` (new)`. Without
// them the output is unchanged.

function manifest(paths) {
  return [
    '- **Manifest:**',
    '  ```yaml',
    '  manifest:',
    '    expected_paths:',
    ...paths.map(p => `      - ${p}`),
    `    min_file_count: ${paths.length}`,
    '    commit_message_pattern: "^feat\\\\(x\\\\):"',
    '    bash_syntax_check: []',
    '    forbidden_paths: []',
    '    must_contain: []',
    '  ```',
  ].join('\n');
}

export function step(n, opts = {}) {
  const file = opts.file ?? `src/mod${n}.mjs`;
  const test = opts.test ?? `tests/mod${n}.test.mjs`;
  const lines = [
    `### Step ${n}: ${opts.title ?? `Build module ${n}`}`,
    '',
    opts.filesRaw !== undefined ? `- **Files:** ${opts.filesRaw}` : `- **Files:** \`${file}\``,
    `- **Changes:** Add \`run${n}()\` to \`${file}\`. (new file)`,
  ];
  if (opts.interfaceIn !== undefined) lines.push(`- **Interface in:** ${opts.interfaceIn}`);
  if (opts.interfaceOut !== undefined) lines.push(`- **Interface out:** ${opts.interfaceOut}`);
  if (opts.reviewFocus !== undefined) lines.push(`- **Review focus:** ${opts.reviewFocus}`);
  if (opts.testFirst !== false) {
    lines.push(
      '- **Test first:**',
      opts.testFirstRaw !== undefined ? opts.testFirstRaw : `  - File: \`${test}\` (new)`,
      `  - Verifies: run${n}() returns the value the next step reads`,
      '  - Pattern: `tests/lib/plan-schema.test.mjs`',
    );
  }
  if (opts.endToEnd) lines.push(`- **End-to-end:** \`${opts.endToEnd}\` → expected: exit 0 and the CLI prints a result`);
  lines.push(
    `- **Verify:** \`node --test ${test}\` → expected: pass`,
    `- **On failure:** revert — \`git checkout -- ${file}\``,
    `- **Checkpoint:** \`git commit -m "feat(x): step ${n}"\``,
    manifest(opts.manifestPaths ?? [file, test]),
  );
  return lines.join('\n');
}

export const DESIGN = [
  '## Design',
  '',
  '### Architecture',
  'Two modules: a parser and a CLI on top of it.',
  '',
  '### Data Flow',
  'CLI argv → parser → result JSON on stdout.',
  '',
  '### Interfaces',
  '`parse(text) → {ok, items}`',
  '',
  '### Data Models',
  '`Item = {name: string, n: number}`',
  '',
  '### Error Handling',
  'Unreadable input → exit 2; invalid input → exit 1.',
  '',
  '### Module Map',
  '```mermaid',
  'graph TD',
  '  cli[src/cli.mjs] --> parser[src/parser.mjs]',
  '  parser --> util[src/util.mjs]',
  '```',
  '',
  '### Architecture Rules',
  '| Rule | Enforced by | Proof |',
  '|------|-------------|-------|',
  '| The parser never imports the CLI | checked by `node_modules/.bin/depcruise --config .dependency-cruiser.cjs src` | Step 1 |',
  '| Prefer pure functions in the parser | advisory — `.claude/rules/parser.md` | — |',
  '',
  '### Requirements Check',
  'No conflicts or gaps found between the brief\'s requirements.',
].join('\n');

/**
 * Build a plan.
 * @param {object} o
 * @param {string} [o.version='1.8']
 * @param {string|null} [o.ceremony] - header value; null = omit (→ architectural)
 * @param {boolean} [o.design=true]
 * @param {string} [o.designText]
 * @param {Array<object>} [o.steps] - step() option objects
 */
export function buildPlan(o = {}) {
  const version = o.version ?? '1.8';
  const ceremony = o.ceremony === undefined ? 'architectural' : o.ceremony;
  const header = ceremony === null
    ? `> Generated by trekplan v6.1.1 on 2026-10-06 — \`plan_version: ${version}\``
    : `> Generated by trekplan v6.1.1 on 2026-10-06 — \`plan_version: ${version}\` · \`ceremony: ${ceremony}\``;
  const stepOpts = o.steps ?? [{}, { endToEnd: 'bash tests/e2e.sh' }];
  const parts = [
    '# Test plan',
    '',
    '> **Plan quality: A** (92/100) — APPROVE',
    '>',
    header,
    '',
    '## Context',
    '',
    'Why: the brief asks for a parser CLI.',
    '',
  ];
  if (o.design !== false) parts.push(o.designText ?? DESIGN, '');
  parts.push('## Implementation Plan', '');
  stepOpts.forEach((s, i) => parts.push(step(i + 1, s), ''));
  parts.push(
    '## Test Strategy',
    '',
    '- **Framework:** node:test',
    '',
    '## Verification',
    '',
    '- [ ] `npm test` → expected: exit 0',
    // Each End-to-end command also stands here: Phase 7 runs this section.
    ...[...new Set(stepOpts.filter(s => s.endToEnd).map(s => s.endToEnd))].map(c => `- [ ] \`${c}\` → expected: exit 0`),
    '',
  );
  return parts.join('\n');
}