import {spawnSync, SpawnSyncReturns} from 'child_process';

/**
 * Class that can be used to execute Git commands within a given project directory.
 *
 * Relying on the working directory of the current process is not good because it's not
 * guaranteed that the working directory is always the target project directory.
 */
export class GitClient {
  constructor(public projectDir: string, public remoteGitUrl: string) {}

  /**
   * Spawns a child process running Git. The "stderr" output is inherited and will be printed
   * in case of errors. This makes it easier to debug failed commands.
   */
  private _spawnGitProcess(args: string[], printStderr = true): SpawnSyncReturns<string> {
    return spawnSync('git', args, {
      cwd: this.projectDir,
      stdio: ['pipe', 'pipe', printStderr ? 'inherit' : 'pipe'],
      encoding: 'utf8',
    });
  }

  /** Gets the currently checked out branch for the project directory. */
  getCurrentBranch() {
    return this._spawnGitProcess(['symbolic-ref', '--short', 'HEAD']).stdout.trim();
  }

  /** Gets the commit SHA for the specified remote repository branch. */
  getRemoteCommitSha(branchName: string): string {
    return this._spawnGitProcess(['ls-remote', this.remoteGitUrl, '-h', `refs/heads/${branchName}`])
        .stdout.split('\t')[0]
        .trim();
  }

  /** Gets the latest commit SHA for the specified git reference. */
  getLocalCommitSha(refName: string) {
    return this._spawnGitProcess(['rev-parse', refName]).stdout.trim();
  }

  /** Gets whether the current Git repository has uncommitted changes. */
  hasUncommittedChanges(): boolean {
    return this._spawnGitProcess(['diff-index', '--quiet', 'HEAD']).status !== 0;
  }

  /** Checks out an existing branch with the specified name. */
  checkoutBranch(branchName: string): boolean {
    return this._spawnGitProcess(['checkout', branchName]).status === 0;
  }

  /** Creates a new branch which is based on the previous active branch. */
  checkoutNewBranch(branchName: string): boolean {
    return this._spawnGitProcess(['checkout', '-b', branchName]).status === 0;
  }

  /** Stages all changes by running `git add -A`. */
  stageAllChanges(): boolean {
    return this._spawnGitProcess(['add', '-A']).status === 0;
  }

  /** Creates a new commit within the current branch with the given commit message. */
  createNewCommit(message: string): boolean {
    // Disable pre-commit hooks when creating a commit. Developers might not have set up
    // their Git configuration for the "git-clang-format" pre-commit hook.
    return this._spawnGitProcess(['commit', '--no-verify', '-m', message]).status === 0;
  }

  /** Gets the title of a specified commit reference. */
  getCommitTitle(commitRef: string): string {
    return this._spawnGitProcess(['log', '-n1', '--format="%s"', commitRef]).stdout.trim();
  }

  /** Creates a tag for the specified commit reference. */
  createTag(commitRef: string, tagName: string, message: string): boolean {
    return this._spawnGitProcess(['tag', tagName, '-m', message]).status === 0;
  }

  /** Checks whether the specified tag exists locally. */
  hasLocalTag(tagName: string) {
    return this._spawnGitProcess(['rev-parse', `refs/tags/${tagName}`], false).status === 0;
  }

  /** Gets the Git SHA of the specified local tag. */
  getShaOfLocalTag(tagName: string) {
    // We need to use the "^{}" suffix to instruct Git to deference the tag to
    // the actual commit. See: https://www.git-scm.com/docs/git-rev-parse
    return this._spawnGitProcess(['rev-parse', `refs/tags/${tagName}^{}`]).stdout.trim();
  }

  /** Gets the Git SHA of the specified remote tag. */
  getShaOfRemoteTag(tagName: string): string {
    // We need to use the "^{}" suffix to instruct Git to deference the tag to
    // the actual commit. See: https://www.git-scm.com/docs/git-rev-parse
    return this._spawnGitProcess(['ls-remote', this.remoteGitUrl, '-t', `refs/tags/${tagName}^{}`])
        .stdout.split('\t')[0]
        .trim();
  }

  /** Pushes the specified tag to the remote git repository. */
  pushTagToRemote(tagName: string, remoteName: string = this.remoteGitUrl): boolean {
    return this._spawnGitProcess(['push', remoteName, `refs/tags/${tagName}`]).status === 0;
  }

  /** Checks whether the given remote has been set up. */
  hasRemote(remoteName: string): boolean {
    return this._spawnGitProcess(['remote', 'get-url', remoteName], false).status == 0;
  }

  /** Gets a list of all available remotes set up. */
  getAvailableRemotes(): string[] {
    // Note that "git" always uses a line feed for new lines.
    return this._spawnGitProcess(['remote']).stdout.trim().split('\n');
  }
}