/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {existsSync, readFileSync} from 'fs';
import * as multimatch from 'multimatch';
import {join} from 'path';
import {parse as parseYaml} from 'yaml';
import {bold, debug, error, info} from '../../utils/console';

import {BaseModule} from './base';

/** Information expressing the difference between the master and g3 branches */
export interface G3StatsData {
  insertions: number;
  deletions: number;
  files: number;
  commits: number;
}

export class G3Module extends BaseModule<G3StatsData|void> {
  async retrieveData() {
    const toCopyToG3 = this.getG3FileIncludeAndExcludeLists();
    const latestSha = this.getLatestShas();

    if (toCopyToG3 === null || latestSha === null) {
      return;
    }

    return this.getDiffStats(
        latestSha.g3, latestSha.master, toCopyToG3.include, toCopyToG3.exclude);
  }

  async printToTerminal() {
    const stats = await this.data;
    if (!stats) {
      return;
    }
    info.group(bold('g3 branch check'));
    if (stats.files === 0) {
      info(`${stats.commits} commits between g3 and master`);
      info('✅  No sync is needed at this time');
    } else {
      info(
          `${stats.files} files changed, ${stats.insertions} insertions(+), ${stats.deletions} ` +
          `deletions(-) from ${stats.commits} commits will be included in the next sync`);
    }
    info.groupEnd();
    info();
  }

  /** Fetch and retrieve the latest sha for a specific branch. */
  private getShaForBranchLatest(branch: string) {
    const {owner, name} = this.git.remoteConfig;
    /** The result fo the fetch command. */
    const fetchResult =
        this.git.runGraceful(['fetch', '-q', `https://github.com/${owner}/${name}.git`, branch]);

    if (fetchResult.status !== 0 &&
        fetchResult.stderr.includes(`couldn't find remote ref ${branch}`)) {
      debug(`No '${branch}' branch exists on upstream, skipping.`);
      return null;
    }
    return this.git.runGraceful(['rev-parse', 'FETCH_HEAD']).stdout.trim();
  }

  /**
   * Get git diff stats between master and g3, for all files and filtered to only g3 affecting
   * files.
   */
  private getDiffStats(
      g3Ref: string, masterRef: string, includeFiles: string[], excludeFiles: string[]) {
    /** The diff stats to be returned. */
    const stats = {
      insertions: 0,
      deletions: 0,
      files: 0,
      commits: 0,
    };

    // Determine the number of commits between master and g3 refs. */
    stats.commits =
        parseInt(this.git.run(['rev-list', '--count', `${g3Ref}..${masterRef}`]).stdout, 10);

    // Get the numstat information between master and g3
    this.git.run(['diff', `${g3Ref}...${masterRef}`, '--numstat'])
        .stdout
        // Remove the extra space after git's output.
        .trim()
        // Split each line of git output into array
        .split('\n')
        // Split each line from the git output into components parts: insertions,
        // deletions and file name respectively
        .map(line => line.trim().split('\t'))
        // Parse number value from the insertions and deletions values
        // Example raw line input:
        //   10\t5\tsrc/file/name.ts
        .map(line => [Number(line[0]), Number(line[1]), line[2]] as [number, number, string])
        // Add each line's value to the diff stats, and conditionally to the g3
        // stats as well if the file name is included in the files synced to g3.
        .forEach(([insertions, deletions, fileName]) => {
          if (this.checkMatchAgainstIncludeAndExclude(fileName, includeFiles, excludeFiles)) {
            stats.insertions += insertions;
            stats.deletions += deletions;
            stats.files += 1;
          }
        });
    return stats;
  }
  /** Determine whether the file name passes both include and exclude checks. */
  private checkMatchAgainstIncludeAndExclude(file: string, includes: string[], excludes: string[]) {
    return (
        multimatch.call(undefined, file, includes).length >= 1 &&
        multimatch.call(undefined, file, excludes).length === 0);
  }


  private getG3FileIncludeAndExcludeLists() {
    const angularRobotFilePath = join(this.git.baseDir, '.github/angular-robot.yml');
    if (!existsSync(angularRobotFilePath)) {
      debug('No angular robot configuration file exists, skipping.');
      return null;
    }
    /** The configuration defined for the angular robot. */
    const robotConfig = parseYaml(readFileSync(angularRobotFilePath).toString());
    /** The files to be included in the g3 sync. */
    const include: string[] = robotConfig?.merge?.g3Status?.include || [];
    /** The files to be expected in the g3 sync. */
    const exclude: string[] = robotConfig?.merge?.g3Status?.exclude || [];

    if (include.length === 0 && exclude.length === 0) {
      debug('No g3Status include or exclude lists are defined in the angular robot configuration');
      return null;
    }

    return {include, exclude};
  }

  private getLatestShas() {
    /** The latest sha for the g3 branch. */
    const g3 = this.getShaForBranchLatest('g3');
    /** The latest sha for the master branch. */
    const master = this.getShaForBranchLatest('master');

    if (g3 === null || master === null) {
      debug('Either the g3 or master was unable to be retrieved');
      return null;
    }

    return {g3, master};
  }
}