/**
 * CI quality baseline test — locks in the [E00-S05-T01] required PR stages of
 * the committed workflow (`.gitea/workflows/ci.yml`).
 *
 * The baseline (issue #187 acceptance criteria):
 *   - "CI runs frozen install before later stages" → `frozen-install` is the
 *     first job and every later stage declares `needs` on its predecessor, so
 *     the pipeline runs the required stages strictly in order and nothing
 *     proceeds past a failed stage.
 *   - "CI runs typecheck, formatting/lint, unit, architecture and PostgreSQL
 *     integration tests" → the five stage jobs exist with the expected
 *     commands: `pnpm typecheck`, `pnpm lint`, and the unit / architecture /
 *     postgres-integration `node --test` suite runs.
 *   - "CI builds the admin and server applications" → the `build-apps` stage
 *     compiles the whole apps group (`./apps/**` — apps/server today, the
 *     admin app when E06-S01 lands) and verifies the compiled server
 *     artifact.
 *   - every committed test suite under tests/ is wired into exactly one stage
 *     (`pnpm lint` runs the formatting-policy suite; every other suite is
 *     named by a `node --test` run in the unit, architecture or
 *     postgres-integration stage).
 *
 * Mutation probes prove the assertions are non-vacuous: removing a stage,
 * breaking the `needs` chain, or dropping a suite from its stage all fail.
 *
 * Run: `node --test tests/ci-stages.test.mjs`
 * (node:test — built into Node >= 18; no dependencies, lockfile untouched.)
 */

import test from 'node:test';
import assert from 'node:assert/strict';
import { readFileSync, readdirSync } from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const REPO_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');

const read = (relPath) => readFileSync(path.join(REPO_ROOT, relPath), 'utf8');

/** The workflow file under test. */
const WORKFLOW = '.gitea/workflows/ci.yml';

/** The required PR stages, in the order the pipeline must run them. */
const REQUIRED_STAGES = [
  'frozen-install',
  'typecheck',
  'formatting-lint',
  'unit',
  'architecture',
  'postgres-integration',
  'build-apps',
];

/** The root lint command the formatting-lint stage must run. */
const LINT_SCRIPT = 'node --test tests/formatting-policy.test.mjs';

/**
 * Parses the workflow's `jobs:` section (the committed file is 2-space
 * indented YAML) into `{ order, jobs }` where `order` lists job keys in
 * document order and each job carries its `needs` value and `run:` commands.
 * Comments and blank lines are skipped; unknown keys under a job are ignored.
 */
function parseWorkflowJobs(yamlText) {
  const lines = yamlText.split('\n');
  const jobsIndex = lines.findIndex((line) => line === 'jobs:');
  assert.ok(jobsIndex >= 0, 'the workflow must declare a top-level jobs: section');

  const order = [];
  const jobs = {};
  let current = null;

  for (let i = jobsIndex + 1; i < lines.length; i++) {
    const line = lines[i];
    const trimmed = line.trim();
    if (trimmed === '' || trimmed.startsWith('#')) continue;
    const indent = line.length - line.trimStart().length;
    if (indent === 2) {
      const key = /^([A-Za-z0-9_-]+):/.exec(trimmed);
      assert.ok(key, `unexpected jobs: entry at indent 2: "${line}"`);
      current = key[1];
      order.push(current);
      jobs[current] = { needs: null, runs: [] };
      continue;
    }
    if (current && indent > 2) {
      const needs = /^needs:\s*(.+)$/.exec(trimmed);
      if (needs) jobs[current].needs = needs[1].trim().replace(/^\[|\]$/g, '');
      const run = /^run:\s*(.+)$/.exec(trimmed);
      if (run) jobs[current].runs.push(run[1].trim());
    }
  }

  return { order, jobs };
}

/** Extracts the tests/*.test.mjs suite names named by `node --test` runs. */
function suitesNamedInRuns(runs) {
  const out = [];
  for (const run of runs) {
    for (const token of run.split(/\s+/)) {
      if (token.startsWith('tests/') && token.endsWith('.test.mjs')) {
        out.push(token.slice('tests/'.length));
      }
    }
  }
  return out;
}

/**
 * Asserts the whole E00-S05-T01 baseline for a parsed workflow. Throws an
 * AssertionError describing the first violated invariant.
 */
function assertBaseline({ order, jobs }) {
  // Every required stage exists.
  for (const stage of REQUIRED_STAGES) {
    assert.ok(jobs[stage], `required CI stage "${stage}" is missing from the workflow`);
  }

  // The required stages run in order (their relative order is preserved).
  const present = order.filter((name) => REQUIRED_STAGES.includes(name));
  assert.deepEqual(
    present,
    REQUIRED_STAGES,
    `the required CI stages must run in order: ${REQUIRED_STAGES.join(' -> ')}`,
  );

  // Frozen install runs before later stages: every later stage gates on its
  // predecessor, so the pipeline is strictly ordered.
  for (let i = 1; i < REQUIRED_STAGES.length; i++) {
    assert.equal(
      jobs[REQUIRED_STAGES[i]].needs,
      REQUIRED_STAGES[i - 1],
      `stage "${REQUIRED_STAGES[i]}" must gate on the previous stage "${REQUIRED_STAGES[i - 1]}"`,
    );
  }

  // Stage commands.
  assert.ok(
    jobs['frozen-install'].runs.some((run) => run.includes('pnpm install --frozen-lockfile')),
    'frozen-install must run the frozen lockfile install',
  );
  assert.ok(
    jobs['typecheck'].runs.some((run) => run.includes('pnpm typecheck')),
    'the typecheck stage must run pnpm typecheck',
  );
  assert.ok(
    jobs['formatting-lint'].runs.some((run) => run.includes('pnpm lint')),
    'the formatting-lint stage must run pnpm lint',
  );

  // The build stage compiles the apps group and verifies the server artifact.
  const buildRuns = jobs['build-apps'].runs;
  assert.ok(
    buildRuns.some((run) => run.includes('run build') && run.includes('./apps/**')),
    'build-apps must build the apps group (pnpm --filter "./apps/**" run build)',
  );
  assert.ok(
    buildRuns.some((run) => run.includes('apps/server/dist/index.js')),
    'build-apps must verify the compiled server application artifact',
  );

  // Every committed test suite is wired into exactly one stage.
  const staged = [
    ...suitesNamedInRuns(jobs['unit'].runs),
    ...suitesNamedInRuns(jobs['architecture'].runs),
    ...suitesNamedInRuns(jobs['postgres-integration'].runs),
  ];
  const allSuites = readdirSync(path.join(REPO_ROOT, 'tests'))
    .filter((file) => file.endsWith('.test.mjs'))
    .sort();
  // The formatting-policy suite is run by the formatting-lint stage via the
  // root lint script rather than by a node --test run in a test stage.
  const expected = allSuites.filter((file) => file !== 'formatting-policy.test.mjs');
  assert.equal(
    staged.length,
    expected.length,
    'each test suite must be wired into exactly one CI stage run ' +
      `(staged: ${staged.join(', ')}; expected: ${expected.join(', ')})`,
  );
  assert.deepEqual(
    [...new Set(staged)].sort(),
    expected,
    'every committed test suite must be wired into exactly one CI stage ' +
      `(staged: ${staged.join(', ')}; expected: ${expected.join(', ')})`,
  );
}

/** Removes the whole `  <jobName>:` block from a workflow text (probe helper). */
function removeJobBlock(yamlText, jobName) {
  const lines = yamlText.split('\n');
  const start = lines.findIndex((line) => line === `  ${jobName}:`);
  assert.ok(start >= 0, `job ${jobName} must exist in the workflow text`);
  let end = lines.length;
  for (let i = start + 1; i < lines.length; i++) {
    const trimmed = lines[i].trim();
    if (
      trimmed !== '' &&
      !trimmed.startsWith('#') &&
      lines[i].length - lines[i].trimStart().length === 2 &&
      /^[A-Za-z0-9_-]+:/.test(trimmed)
    ) {
      end = i;
      break;
    }
  }
  return [...lines.slice(0, start), ...lines.slice(end)].join('\n');
}

// ---------------------------------------------------------------------------
// Real-workflow baseline
// ---------------------------------------------------------------------------

test('the committed CI workflow runs the required PR stages in order', () => {
  assertBaseline(parseWorkflowJobs(read(WORKFLOW)));
});

test('the workflow triggers on pull requests and pushes to main', () => {
  const text = read(WORKFLOW);
  assert.match(text, /^on:$/m, 'the workflow must declare an on: trigger block');
  assert.match(text, /pull_request:/, 'PRs must trigger the CI workflow');
  assert.match(text, /push:/, 'pushes must trigger the CI workflow');
  assert.match(text, /branches:\s*\[main\]/, 'the push trigger must cover main');
});

test('the root lint script runs the formatting-policy suite', () => {
  const scripts = JSON.parse(read('package.json')).scripts ?? {};
  assert.equal(
    scripts.lint,
    LINT_SCRIPT,
    `root package.json must declare scripts.lint exactly as "${LINT_SCRIPT}"`,
  );
});

// ---------------------------------------------------------------------------
// Mutation probes — the baseline assertions are non-vacuous
// ---------------------------------------------------------------------------

test('removing a required stage fails the baseline (mutation probe)', () => {
  const mutated = removeJobBlock(read(WORKFLOW), 'unit');
  assert.throws(() => assertBaseline(parseWorkflowJobs(mutated)), /required CI stage "unit"/);
});

test('breaking the needs chain fails the baseline (mutation probe)', () => {
  const text = read(WORKFLOW);
  const mutated = text.replace('needs: formatting-lint', 'needs: typecheck');
  assert.notEqual(mutated, text, 'the probe must mutate the workflow');
  assert.throws(
    () => assertBaseline(parseWorkflowJobs(mutated)),
    /must gate on the previous stage/,
  );
});

test('dropping a suite from its stage fails the coverage assertion (mutation probe)', () => {
  const text = read(WORKFLOW);
  const mutated = text.replace('tests/config-schema.test.mjs', '');
  assert.notEqual(mutated, text, 'the probe must mutate the workflow');
  assert.throws(
    () => assertBaseline(parseWorkflowJobs(mutated)),
    /must be wired into exactly one CI stage/,
  );
});

test('reordering the stages fails the baseline (mutation probe)', () => {
  const text = read(WORKFLOW);
  // Swap the typecheck and formatting-lint job blocks so their document order
  // no longer matches the required stage order.
  const typecheckBlock = text.slice(text.indexOf('  typecheck:'), text.indexOf('  formatting-lint:'));
  const lintBlock = text.slice(text.indexOf('  formatting-lint:'), text.indexOf('  unit:'));
  const mutated = text.replace(typecheckBlock + lintBlock, lintBlock + typecheckBlock);
  assert.notEqual(mutated, text, 'the probe must mutate the workflow');
  assert.throws(() => assertBaseline(parseWorkflowJobs(mutated)), /must run in order/);
});