'use strict'

const mongoVersionList = require('mongodb-version-list');
const core = require('@actions/core');
const semver = require('semver');
const yaml = require('yaml');
const fs = require('fs').promises;

/*******************************************************************
 * Settings
********************************************************************/
// The path to the GitHub workflow YAML file that contains the tests.
const pathToCiYml = './.github/workflows/ci.yml';
// The key path in the CI YAML file to the environment specifications.
const ciKeyEnvironments = 'jobs.check-mongo.strategy.matrix.include';
// The key in the CI YAML file to determine the MongoDB version.
const ciKeyVersion = 'MONGODB_VERSION';
// The versions to ignore when checking whether the CI tests against
// the newest versions. This can be used in case there is a MongoDB
// release for which Parse Server compatibility is not required.
const ignoreReleasedVersions = [
  '4.7.0' // This is a development release according to MongoDB support
];
/*******************************************************************/

/**
 * Returns the released versions of MongoDB by MongoDB; this also
 * includes pre-releases.
 * @return {Array<String>} The released versions.
 */
async function getReleasedVersions () {
  return new Promise((resolve, reject) => {
    mongoVersionList(function(error, versions) {
      if (error) {
        reject(error);
      }
      resolve(versions);
    });
  });
}

/**
 * Returns the test environments in the Github CI as specified in the
 * GitHub workflow YAML file.
 */
async function getTests() {
  try {
    // Get CI workflow
    const ciYaml = await fs.readFile(pathToCiYml, 'utf-8');
    const ci = yaml.parse(ciYaml);

    // Extract MongoDB versions
    let versions = ciKeyEnvironments.split('.').reduce((o,k) => o !== undefined ? o[k] : undefined, ci);
    versions = Object.entries(versions)
      .map(entry => entry[1])
      .filter(entry => entry[ciKeyVersion]);

    return versions;
  } catch (e) {
    throw 'Failed to determine MongoDB versions from CI YAML file with error: ' + e;
  }
}

/**
 * Returns all minor and major MongoDB versions against which Parse Server
 * is not tested in the CI.
 * @param {Array<String>} releasedVersions The released versions.
 * @param {Array<String>} testedVersions The tested versions.
 * @returns {Array<String>} The untested versions.
 */
function getUntestedMinorsAndMajors(releasedVersions, testedVersions) {
  // Get highest tested version
  const highestTested = semver.maxSatisfying(testedVersions, '*');

  // Get all higher released versions (minor & major)
  const higherReleased = releasedVersions.reduce((m, v) => {
    // If the version is a pre-release, skip it
    if ((semver.prerelease(v) || []).length > 0) {
      return m;
    }
    // If the version is not greater than the highest tested version, skip it
    if (!semver.gt(v, highestTested)) {
      return m;
    }
    // If the same or a newer version has already been added, skip it
    if (semver.maxSatisfying(m, `^${v}`) == v) {
      return m;
    }
    // If there is a higher minor released version, skip it
    if (semver.maxSatisfying(releasedVersions, `^${v}`) != v) {
      return m;
    }
    // If version should be ignored, skip it
    if (semver.satisfies(v, ignoreReleasedVersions.join(' || '))) {
      return m;
    }
    // Add version
    m.push(v);
    return m;
  }, []);

  return higherReleased;
}

/**
 * Returns the newest patch version for a given version.
 * @param {Array<String>} versions The versions in which to search.
 * @param {String} version The version for which a newer patch
 * version should be searched.
 * @returns {String|undefined} The newer patch version.
 */
function getNewerPatch(versions, version) {
  const latest = semver.maxSatisfying(versions, `~${version}`);
  return semver.gt(latest, version) ? latest : undefined;
}

/**
 * Runs the check.
 */
async function check() {
  try {
    // Get released MongoDB versions
    const releasedVersions = await getReleasedVersions();

    // Get tested MongoDB versions from CI
    const tests = await getTests();

    // Is true if any of the checks failed
    let failed = false;

    // Check whether each tested version is the latest patch
    for (const test of tests) {
      const version = test[ciKeyVersion];
      const newer = getNewerPatch(releasedVersions, version);
      if (newer) {
        console.log(`❌ CI environment '${test.name}' uses an old MongoDB patch version ${version} instead of ${newer}.`);
        failed = true;
      } else {
        console.log(`✅ CI environment '${test.name}' uses the newest MongoDB patch version ${version}.`);
      }
    }

    // Check whether there is a newer minor version available that is not tested
    const testedVersions = tests.map(test => test[ciKeyVersion]);
    const untested = getUntestedMinorsAndMajors(releasedVersions, testedVersions);
    if (untested.length > 0) {
      console.log(`❌ CI does not have environments using the following versions of MongoDB: ${untested.join(', ')}.`);
      failed = true;
    } else {
      console.log(`✅ CI environments use all recent major and minor releases of MongoDB.`);
    }

    if (failed) {
      core.setFailed(
        'CI environments are not up-to-date with newest MongoDB versions.' +
         '\n\nCheck the error messages above and update the MongoDB versions in the CI YAML ' +
         'file. There may be versions of MongoDB that have reached their official MongoDB end-of-life ' +
         'support date and should be removed from the CI; see https://www.mongodb.com/support-policy.'
      );
    }

  } catch (e) {
    core.setFailed('Failed to check MongoDB versions with error: ' + e);
    throw 'Failed to check MongoDB versions with error: ' + e;
  }
}

check();