import * as core from '@actions/core';
import { exec } from '@actions/exec';
import NotImplementedException from './error/not-implemented-exception';
import ValidationError from './error/validation-error';
import System from './system';

export default class Versioning {
  static get strategies() {
    return { None: 'None', Semantic: 'Semantic', Tag: 'Tag', Custom: 'Custom' };
  }

  /**
   * Get the branch name of the (related) branch
   */
  static get branch() {
    return this.headRef || this.ref.slice(11);
  }

  /**
   * For pull requests we can reliably use GITHUB_HEAD_REF
   */
  static get headRef() {
    return process.env.GITHUB_HEAD_REF;
  }

  /**
   * For branches GITHUB_REF will have format `refs/heads/feature-branch-1`
   */
  static get ref() {
    return process.env.GITHUB_REF;
  }

  /**
   * Regex to parse version description into separate fields
   */
  static get descriptionRegex() {
    return /^v([\d.]+)-(\d+)-g(\w+)-?(\w+)*/g;
  }

  static async determineVersion(strategy, inputVersion) {
    // Validate input
    if (!Object.hasOwnProperty.call(this.strategies, strategy)) {
      throw new ValidationError(
        `Versioning strategy should be one of ${Object.values(this.strategies).join(', ')}.`,
      );
    }

    let version;
    switch (strategy) {
      case this.strategies.None:
        version = 'none';
        break;
      case this.strategies.Custom:
        version = inputVersion;
        break;
      case this.strategies.Semantic:
        version = await this.generateSemanticVersion();
        break;
      case this.strategies.Tag:
        version = await this.generateTagVersion();
        break;
      default:
        throw new NotImplementedException(`Strategy ${strategy} is not implemented.`);
    }

    return version;
  }

  /**
   * Automatically generates a version based on SemVer out of the box.
   *
   * The version works as follows: `<major>.<minor>.<patch>` for example `0.1.2`.
   *
   * The latest tag dictates `<major>.<minor>`
   * The number of commits since that tag dictates`<patch>`.
   *
   * @See: https://semver.org/
   */
  static async generateSemanticVersion() {
    await this.fetchAll();

    if (await this.isDirty()) {
      throw new Error('Branch is dirty. Refusing to base semantic version on uncommitted changes');
    }

    if (!(await this.hasAnyVersionTags())) {
      const version = `0.0.${await this.getTotalNumberOfCommits()}`;
      core.info(`Generated version ${version} (no version tags found).`);
      return version;
    }

    const { tag, commits, hash } = await this.parseSemanticVersion();
    core.info(`Found semantic version ${tag}.${commits} for ${this.branch}@${hash}`);

    return `${tag}.${commits}`;
  }

  /**
   * Generate the proper version for unity based on an existing tag.
   */
  static async generateTagVersion() {
    let tag = await this.getTag();

    if (tag.charAt(0) === 'v') {
      tag = tag.slice(1);
    }

    return tag;
  }

  /**
   * Parses the versionDescription into their named parts.
   */
  static async parseSemanticVersion() {
    const description = await this.getVersionDescription();
    const [match, tag, commits, hash] = this.descriptionRegex.exec(description);

    if (!match) {
      throw new Error(`Failed to parse git describe output: "${description}"`);
    }

    return {
      match,
      tag,
      commits,
      hash,
    };
  }

  static async fetchAll() {
    await exec('git', ['fetch', '--all']);
  }

  /**
   * Retrieves information about the branch.
   *
   * Format: `v0.12-24-gd2198ab`
   *
   * In this format v0.12 is the latest tag, 24 are the number of commits since, and gd2198ab
   * identifies the current commit.
   */
  static async getVersionDescription() {
    return System.run('git', ['describe', '--long', '--tags', '--always', `origin/${this.branch}`]);
  }

  /**
   * Returns whether there are uncommitted changes that are not ignored.
   */
  static async isDirty() {
    const output = await System.run('git', ['status', '--porcelain']);

    return output !== '';
  }

  /**
   * Get the tag if there is one pointing at HEAD
   */
  static async getTag() {
    return System.run('git', ['tag', '--points-at', 'HEAD']);
  }

  /**
   * Whether or not the repository has any version tags yet.
   */
  static async hasAnyVersionTags() {
    const numberOfVersionCommits = await System.run('git', [
      '--list',
      '--merged',
      'HEAD',
      '|',
      'grep v[0-9]*',
      '|',
      'wc -l',
    ]);

    return numberOfVersionCommits !== '0';
  }

  /**
   * Get the total number of commits on head.
   */
  static async getTotalNumberOfCommits() {
    const numberOfCommitsAsString = await System.run('git', ['rev-list', '--count', 'HEAD']);

    return parseInt(numberOfCommitsAsString, 10);
  }
}