context.ts

import path from "path";

import { Endpoints } from "@octokit/types";
import { EventNames, EventPayloads, WebhookEvent } from "@octokit/webhooks";
import merge from "deepmerge";
import yaml from "js-yaml";

import type { Logger } from "pino";

import { ProbotOctokit } from "./octokit/probot-octokit";
import { aliasLog } from "./helpers/alias-log";
import { DeprecatedLogger } from "./types";

type ReposGetContentsParams = Endpoints["GET /repos/:owner/:repo/contents/:path"]["parameters"];

const CONFIG_PATH = ".github";
const BASE_KEY = "_extends";
const BASE_REGEX = new RegExp(
  "^" +
  "(?:([a-z\\d](?:[a-z\\d]|-(?=[a-z\\d])){0,38})/)?" + // org
  "([-_.\\w\\d]+)" + // project
  "(?::([-_./\\w\\d]+\\.ya?ml))?" + // filename
    "$",
  "i"
);
const DEFAULT_BASE = ".github";

export type MergeOptions = merge.Options;

interface WebhookPayloadWithRepository {
  [key: string]: any;
  repository?: EventPayloads.PayloadRepository;
  issue?: {
    [key: string]: any;
    number: number;
    html_url?: string;
    body?: string;
  };
  pull_request?: {
    [key: string]: any;
    number: number;
    html_url?: string;
    body?: string;
  };
  sender?: {
    [key: string]: any;
    type: string;
  };
  action?: string;
  installation?: {
    id: number;
    [key: string]: any;
  };
}

/**
 * The context of the event that was triggered, including the payload and
 * helpers for extracting information can be passed to GitHub API calls.
 *
 *  ```js
 *  module.exports = app => {
 *    app.on('push', context => {
 *      context.log.info('Code was pushed to the repo, what should we do with it?');
 *    });
 *  };
 *  ```
 *
 * @property {github} github - A GitHub API client
 * @property {payload} payload - The webhook event payload
 * @property {logger} log - A logger
 */
export class Context<E extends WebhookPayloadWithRepository = any>
  implements WebhookEvent<E> {
  public name: EventNames.StringNames;
  public id: string;
  public payload: E;

  public github: InstanceType<typeof ProbotOctokit>;
  public log: DeprecatedLogger;

  constructor(
    event: WebhookEvent<E>,
    github: InstanceType<typeof ProbotOctokit>,
    log: Logger
  ) {
    this.name = event.name;
    this.id = event.id;
    this.payload = event.payload;

    this.github = github;
    this.log = aliasLog(log);
  }

  // Maintain backward compatibility
  public get event(): string {
    return this.name;
  }

  /**
   * Return the `owner` and `repo` params for making API requests against a
   * repository.
   *
   * ```js
   * const params = context.repo({path: '.github/config.yml'})
   * // Returns: {owner: 'username', repo: 'reponame', path: '.github/config.yml'}
   * ```
   *
   * @param object - Params to be merged with the repo params.
   *
   */
  public repo<T>(object?: T) {
    const repo = this.payload.repository;

    if (!repo) {
      throw new Error(
        "context.repo() is not supported for this webhook event."
      );
    }

    return Object.assign(
      {
        owner: repo.owner.login || repo.owner.name!,
        repo: repo.name,
      },
      object
    );
  }

  /**
   * Return the `owner`, `repo`, and `issue_number` params for making API requests
   * against an issue. The object passed in will be merged with the repo params.
   *
   *
   * ```js
   * const params = context.issue({body: 'Hello World!'})
   * // Returns: {owner: 'username', repo: 'reponame', issue_number: 123, body: 'Hello World!'}
   * ```
   *
   * @param object - Params to be merged with the issue params.
   */
  public issue<T>(object?: T) {
    const payload = this.payload;
    return Object.assign(
      {
        issue_number: (payload.issue || payload.pull_request || payload).number,
      },
      this.repo(object)
    );
  }

  /**
   * Return the `owner`, `repo`, and `issue_number` params for making API requests
   * against an issue. The object passed in will be merged with the repo params.
   *
   *
   * ```js
   * const params = context.pullRequest({body: 'Hello World!'})
   * // Returns: {owner: 'username', repo: 'reponame', pull_number: 123, body: 'Hello World!'}
   * ```
   *
   * @param object - Params to be merged with the pull request params.
   */
  public pullRequest<T>(object?: T) {
    const payload = this.payload;
    return Object.assign(
      {
        pull_number: (payload.issue || payload.pull_request || payload).number,
      },
      this.repo(object)
    );
  }

  /**
   * Returns a boolean if the actor on the event was a bot.
   * @type {boolean}
   */
  get isBot() {
    return this.payload.sender!.type === "Bot";
  }

  /**
   * Reads the app configuration from the given YAML file in the `.github`
   * directory of the repository.
   *
   * For example, given a file named `.github/config.yml`:
   *
   * ```yml
   * close: true
   * comment: Check the specs on the rotary girder.
   * ```
   *
   * Your app can read that file from the target repository:
   *
   * ```js
   * // Load config from .github/config.yml in the repository
   * const config = await context.config('config.yml')
   *
   * if (config.close) {
   *   context.github.issues.comment(context.issue({body: config.comment}))
   *   context.github.issues.edit(context.issue({state: 'closed'}))
   * }
   * ```
   *
   * You can also use a `defaultConfig` object:
   *
   * ```js
   * // Load config from .github/config.yml in the repository and combine with default config
   * const config = await context.config('config.yml', {comment: 'Make sure to check all the specs.'})
   *
   * if (config.close) {
   *   context.github.issues.comment(context.issue({body: config.comment}));
   *   context.github.issues.edit(context.issue({state: 'closed'}))
   * }
   * ```
   *
   * Config files can also specify a base that they extend. `deepMergeOptions` can be used
   * to configure how the target config, extended base, and default configs are merged.
   *
   * For security reasons, configuration is only loaded from the repository's default branch,
   * changes made in pull requests from different branches or forks are ignored.
   *
   * @param fileName - Name of the YAML file in the `.github` directory
   * @param defaultConfig - An object of default config options
   * @param deepMergeOptions - Controls merging configs (from the [deepmerge](https://github.com/TehShrike/deepmerge) module)
   * @return Configuration object read from the file
   */
  public async config<T>(
    fileName: string,
    defaultConfig?: T,
    deepMergeOptions?: MergeOptions
  ): Promise<T | null> {
    const params = this.repo({ path: path.posix.join(CONFIG_PATH, fileName) });

    const config = await this.loadYaml(params);

    let baseRepo;
    if (config == null) {
      baseRepo = DEFAULT_BASE;
    } else if (config != null && BASE_KEY in config) {
      baseRepo = config[BASE_KEY];
      delete config[BASE_KEY];
    }

    let baseConfig;
    if (baseRepo) {
      if (typeof baseRepo !== "string") {
        throw new Error(`Invalid repository name in key "${BASE_KEY}"`);
      }

      const baseParams = this.getBaseParams(params, baseRepo);
      baseConfig = await this.loadYaml(baseParams);
    }

    if (config == null && baseConfig == null && !defaultConfig) {
      return null;
    }

    return (merge.all(
      // filter out null configs
      [defaultConfig, baseConfig, config].filter((conf) => conf),
      deepMergeOptions
    ) as unknown) as T;
  }

  /**
   * Loads a file from GitHub
   *
   * @param params Params to fetch the file with
   * @return The parsed YAML file
   */
  private async loadYaml<T>(params: ReposGetContentsParams): Promise<any> {
    try {
      // https://docs.github.com/en/rest/reference/repos#get-repository-content
      const response = await this.github.request(
        "GET /repos/{owner}/{repo}/contents/{path}",
        params
      );

      // Ignore in case path is a folder
      // - https://developer.github.com/v3/repos/contents/#response-if-content-is-a-directory
      if (Array.isArray(response.data)) {
        return null;
      }

      // we don't handle symlinks or submodule
      // - https://developer.github.com/v3/repos/contents/#response-if-content-is-a-symlink
      // - https://developer.github.com/v3/repos/contents/#response-if-content-is-a-submodule
      // tslint:disable-next-line
      if (typeof response.data.content !== "string") {
        return;
      }

      return (
        yaml.safeLoad(
          Buffer.from(response.data.content, "base64").toString()
        ) || {}
      );
    } catch (e) {
      if (e.status === 404) {
        return null;
      }

      throw e;
    }
  }

  /**
   * Computes parameters for the repository specified in base
   *
   * Base can either be the name of a repository in the same organization or
   * a full slug "organization/repo".
   *
   * @param params An object containing owner, repo and path
   * @param base A string specifying the base repository
   * @return The params of the base configuration
   */
  private getBaseParams(
    params: ReposGetContentsParams,
    base: string
  ): ReposGetContentsParams {
    const match = base.match(BASE_REGEX);
    if (match === null) {
      throw new Error(`Invalid repository name in key "${BASE_KEY}": ${base}`);
    }

    return {
      owner: match[1] || params.owner,
      path: match[3] || params.path,
      repo: match[2],
    };
  }
}