/**
 * .env.example test — locks in the [E00-S04-T05] guarantee that the committed
 * `.env.example` template at the repo root contains placeholders only and no
 * real secret values.
 *
 * Acceptance criteria covered (each test fails without the committed state):
 *   - ".env.example contains placeholders only" → the file exists at the repo
 *     root and every assignment value is a placeholder (an explicit
 *     `change-me`/`<…>`-style marker) or a benign non-secret default (bind
 *     address, port, local database/user name); no value is a long
 *     random-looking token without a placeholder marker, no value embeds a
 *     credential URI, every line is a comment, a blank line, or a well-formed
 *     `KEY=value` assignment, no variable is repeated, and the file documents
 *     every configuration environment source (`HOST`/`PORT`/`DATABASE_URL`/
 *     `EPPP_SESSION_SECRET`).
 *   - "no real secret values appear in the example file" → the same value
 *     predicate rejects secret-shaped values, the compose dev-default
 *     credential value appears nowhere in the file (values or comments), and
 *     `.gitignore` keeps real `.env` files ignored while un-ignoring the
 *     committed `.env.example`. The mutation probes below prove the
 *     assertions are non-vacuous (a secret-looking value, a credential URI, a
 *     compose default credential, a missing required variable, a dropped
 *     `!.env.example` negation, or a malformed line all break the criterion).
 *
 * Run: `node --test tests/env-example.test.mjs`
 * (node:test — built into Node >= 18; no dependencies, lockfile untouched.)
 */

import test from 'node:test';
import assert from 'node:assert/strict';
import { existsSync, readFileSync } 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');
const exists = (relPath) => existsSync(path.join(REPO_ROOT, relPath));

const ENV_EXAMPLE_PATH = '.env.example';

/** The config schema's environment sources (E00-S04-T01/T04) the template must document. */
const REQUIRED_VARS = ['HOST', 'PORT', 'DATABASE_URL', 'EPPP_SESSION_SECRET'];

/** Compose dev-default credential values that must never appear in the template. */
const FORBIDDEN_VALUES = ['postgres://eppp:eppp@db:5432/eppp'];

/** A long random-looking value (JWT/API-key/token-shaped literal). */
const LONG_SECRET_RE = /^[A-Za-z0-9+/=_-]{32,}$/;

/** A credential URI (`scheme://user:pass@host`) embedded as a literal value. */
const CREDENTIAL_URI_RE = /:\/\/[^/\s]+:[^@\s]+@/;

/** Explicit placeholder markers a value may carry. */
const PLACEHOLDER_MARKERS = [
  'change-me',
  'changeme',
  'change_me',
  'your-',
  'replace',
  'example',
  'xxx',
  '<',
  '>',
];

/** Benign non-secret defaults the template may show as values. */
const BENIGN_VALUES = new Set([
  '0.0.0.0', // HOST container default
  '3000', // PORT / APP_PORT default
  '5432', // POSTGRES_PORT default
  'localhost', // local bind/db host
  'eppp', // local database/user name (non-secret)
  'postgres://localhost:5432/eppp', // DATABASE_URL shape without embedded credentials
]);

/**
 * True when an assignment value is a placeholder, never a real secret.
 *
 * A value is a placeholder when it is a benign non-secret default or carries
 * an explicit placeholder marker; a marked value is still rejected when it
 * embeds a credential URI or reproduces a compose default credential. Any
 * other value — including a long random-looking token — is not a placeholder.
 */
function isPlaceholderValue(value) {
  if (value === '') return false;
  if (BENIGN_VALUES.has(value)) return true;
  if (PLACEHOLDER_MARKERS.some((marker) => value.includes(marker))) {
    return !CREDENTIAL_URI_RE.test(value) && !FORBIDDEN_VALUES.includes(value);
  }
  return false;
}

/**
 * Parses the template into `{ key, value }` assignments, ignoring blank lines
 * and `#` comment lines. Throws a descriptive Error on a malformed line so a
 * stray non-assignment line cannot silently pass.
 */
function parseAssignments(content) {
  const assignments = [];
  content.split(/\r?\n/).forEach((raw, index) => {
    const line = raw.trim();
    if (line === '' || line.startsWith('#')) return;
    const match = /^([A-Z][A-Z0-9_]*)=(.*)$/.exec(line);
    if (!match) {
      throw new Error(
        `line ${index + 1} is not a comment, blank line, or KEY=value assignment: "${raw}"`,
      );
    }
    assignments.push({ key: match[1], value: match[2] });
  });
  return assignments;
}

/**
 * Asserts the acceptance criteria for the given template content — used by
 * the committed-state test and by the mutation probes (which must make it
 * throw).
 */
function assertTemplateHasPlaceholdersOnly(content) {
  for (const forbidden of FORBIDDEN_VALUES) {
    assert.ok(
      !content.includes(forbidden),
      `the template must not contain the compose default credential value "${forbidden}"`,
    );
  }

  const assignments = parseAssignments(content);
  assert.ok(assignments.length > 0, 'the template must contain at least one assignment');

  const keys = assignments.map(({ key }) => key);
  assert.equal(new Set(keys).size, keys.length, 'the template must not repeat a variable');

  for (const required of REQUIRED_VARS) {
    assert.ok(
      keys.includes(required),
      `the template must document the required variable "${required}"`,
    );
  }

  for (const { key, value } of assignments) {
    assert.ok(
      isPlaceholderValue(value),
      `"${key}" must be a placeholder value, got: "${value}"`,
    );
  }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

test('a committed .env.example exists at the repo root', () => {
  assert.ok(exists(ENV_EXAMPLE_PATH), `"${ENV_EXAMPLE_PATH}" must exist at the repo root`);
});

test('.gitignore keeps real .env files ignored while un-ignoring the committed example', () => {
  const gitignore = read('.gitignore');
  assert.ok(gitignore.includes('.env'), 'real .env files must stay git-ignored');
  assert.ok(gitignore.includes('.env.*'), 'real .env.* files must stay git-ignored');
  assert.ok(
    gitignore.includes('!.env.example'),
    'the committed .env.example must be un-ignored (negation pattern)',
  );
});

test('.env.example contains placeholders only and no real secret values', () => {
  assertTemplateHasPlaceholdersOnly(read(ENV_EXAMPLE_PATH));
});

// ---------------------------------------------------------------------------
// Non-vacuous probes — the assertions above really do fail on violations
// ---------------------------------------------------------------------------

test('a compose default credential value in the template fails the criterion (mutation probe)', () => {
  const content = read(ENV_EXAMPLE_PATH);
  const mutated = content.replace(
    'DATABASE_URL=postgres://localhost:5432/eppp',
    'DATABASE_URL=postgres://eppp:eppp@db:5432/eppp',
  );
  assert.notEqual(mutated, content, 'the mutation must actually replace the DATABASE_URL value');
  assert.throws(
    () => assertTemplateHasPlaceholdersOnly(mutated),
    /compose default credential|placeholder/,
  );
});

test('a long secret-looking value fails the criterion (mutation probe)', () => {
  const content = read(ENV_EXAMPLE_PATH);
  const mutated = content.replace(
    'EPPP_SESSION_SECRET=change-me-to-a-random-32-character-secret',
    'EPPP_SESSION_SECRET=aB3dE9fG0hI1jK2lM3nO4pQ5rS6tU7vW8xY9zA0',
  );
  assert.notEqual(mutated, content, 'the mutation must actually replace the session secret');
  assert.throws(() => assertTemplateHasPlaceholdersOnly(mutated), /placeholder/);
});

test('a credential URI value fails the criterion (mutation probe)', () => {
  const content = read(ENV_EXAMPLE_PATH);
  const mutated = content.replace(
    'DATABASE_URL=postgres://localhost:5432/eppp',
    'DATABASE_URL=postgres://alice:supersecret@db.example.com:5432/eppp',
  );
  assert.notEqual(mutated, content, 'the mutation must actually replace the DATABASE_URL value');
  assert.throws(() => assertTemplateHasPlaceholdersOnly(mutated), /placeholder/);
});

test('a missing required variable fails the criterion (mutation probe)', () => {
  const content = read(ENV_EXAMPLE_PATH);
  const mutated = content.replace(/^EPPP_SESSION_SECRET=.*$/m, '');
  assert.notEqual(
    mutated,
    content,
    'the mutation must actually remove the EPPP_SESSION_SECRET assignment',
  );
  assert.throws(() => assertTemplateHasPlaceholdersOnly(mutated), /EPPP_SESSION_SECRET/);
});

test('dropping the !.env.example negation fails the criterion (mutation probe)', () => {
  const gitignore = read('.gitignore');
  const mutated = gitignore.replace('!.env.example', '');
  assert.notEqual(mutated, gitignore, 'the mutation must actually drop the negation pattern');
  assert.throws(
    () => {
      assert.ok(mutated.includes('!.env.example'), 'the committed .env.example must be un-ignored');
    },
    /un-ignored/,
  );
});

test('a malformed non-assignment line fails the criterion (mutation probe)', () => {
  const content = read(ENV_EXAMPLE_PATH);
  const mutated = `${content}\nTHIS IS NOT A VALID LINE\n`;
  assert.throws(() => assertTemplateHasPlaceholdersOnly(mutated), /not a comment/);
});