import {
  createOAuthUserAuth,
  createAppAuth,
  type OAuthWebFlowAuthOptions,
  type InstallationAuthOptions,
} from "@octokit/auth-app";
import { Octokit } from "octokit";
import pluralize from "pluralize";
import {
  IntegrationService,
  IntegrationType,
  JSONObject,
  UnfurlResourceType,
} from "@shared/types";
import Logger from "@server/logging/Logger";
import { Integration, User } from "@server/models";
import { UnfurlSignature } from "@server/types";
import env from "./env";

const requestPlugin = (octokit: Octokit) => ({
  requestPR: async (params: ReturnType<typeof GitHub.parseUrl>) =>
    octokit.request(`GET /repos/{owner}/{repo}/pulls/{id}`, {
      owner: params?.owner,
      repo: params?.repo,
      id: params?.id,
      headers: {
        Accept: "application/vnd.github.text+json",
        "X-GitHub-Api-Version": "2022-11-28",
      },
    }),

  requestIssue: async (params: ReturnType<typeof GitHub.parseUrl>) =>
    octokit.request(`GET /repos/{owner}/{repo}/issues/{id}`, {
      owner: params?.owner,
      repo: params?.repo,
      id: params?.id,
      headers: {
        Accept: "application/vnd.github.text+json",
        "X-GitHub-Api-Version": "2022-11-28",
      },
    }),

  /**
   * Fetches app installations accessible to the user
   *
   * @returns {Array} Containing details of all app installations done by user
   */
  requestAppInstallations: async () =>
    octokit.paginate("GET /user/installations"),

  /**
   * Fetches details of a GitHub resource, e.g, a pull request or an issue
   *
   * @param resource Contains identifiers which are used to construct resource endpoint, e.g, `/repos/{params.owner}/{params.repo}/pulls/{params.id}`
   * @returns Response containing resource details
   */
  requestResource: async function requestResource(
    resource: ReturnType<typeof GitHub.parseUrl>
  ): Promise<{ data?: JSONObject }> {
    switch (resource?.type) {
      case UnfurlResourceType.PR:
        return this.requestPR(resource);
      case UnfurlResourceType.Issue:
        return this.requestIssue(resource);
      default:
        return { data: undefined };
    }
  },

  /**
   * Uninstalls the GitHub app from a given target
   *
   * @param installationId Id of the target from where to uninstall
   */
  requestAppUninstall: async (installationId: number) =>
    octokit.request("DELETE /app/installations/{id}", {
      id: installationId,
    }),
});

const CustomOctokit = Octokit.plugin(requestPlugin);

export class GitHub {
  private static appId = env.GITHUB_APP_ID;
  private static appKey = env.GITHUB_APP_PRIVATE_KEY
    ? Buffer.from(env.GITHUB_APP_PRIVATE_KEY, "base64").toString("ascii")
    : undefined;

  private static clientId = env.GITHUB_CLIENT_ID;
  private static clientSecret = env.GITHUB_CLIENT_SECRET;

  private static appOctokit: Octokit;

  private static supportedResources = Object.values(UnfurlResourceType);

  /**
   * Parses a given URL and returns resource identifiers for GitHub specific URLs
   *
   * @param url URL to parse
   * @returns {object} Containing resource identifiers - `owner`, `repo`, `type` and `id`.
   */
  public static parseUrl(url: string) {
    const { hostname, pathname } = new URL(url);
    if (hostname !== "github.com") {
      return;
    }

    const parts = pathname.split("/");
    const owner = parts[1];
    const repo = parts[2];
    const type = parts[3]
      ? (pluralize.singular(parts[3]) as UnfurlResourceType)
      : undefined;
    const id = parts[4];

    if (!type || !GitHub.supportedResources.includes(type)) {
      return;
    }

    return { owner, repo, type, id, url };
  }

  private static authenticateAsApp = () => {
    if (!GitHub.appOctokit) {
      GitHub.appOctokit = new CustomOctokit({
        authStrategy: createAppAuth,
        auth: {
          appId: GitHub.appId,
          privateKey: GitHub.appKey,
          clientId: GitHub.clientId,
          clientSecret: GitHub.clientSecret,
        },
      });
    }

    return GitHub.appOctokit;
  };

  /**
   * [Authenticates as a GitHub user](https://github.com/octokit/auth-app.js/?tab=readme-ov-file#authenticate-as-installation)
   *
   * @param code Temporary code received in callback url after user authorizes
   * @param state A string received in callback url to protect against CSRF
   * @returns {Octokit} User-authenticated octokit instance
   */
  public static authenticateAsUser = async (
    code: string,
    state?: string | null
  ) =>
    GitHub.authenticateAsApp().auth({
      type: "oauth-user",
      code,
      state,
      factory: (options: OAuthWebFlowAuthOptions) =>
        new CustomOctokit({
          authStrategy: createOAuthUserAuth,
          auth: options,
        }),
    }) as Promise<InstanceType<typeof CustomOctokit>>;

  /**
   * [Authenticates as a GitHub app installation](https://github.com/octokit/auth-app.js/?tab=readme-ov-file#authenticate-as-installation)
   *
   * @param installationId Id of an installation
   * @returns {Octokit} Installation-authenticated octokit instance
   */
  public static authenticateAsInstallation = async (installationId: number) =>
    GitHub.authenticateAsApp().auth({
      type: "installation",
      installationId,
      factory: (options: InstallationAuthOptions) =>
        new CustomOctokit({
          authStrategy: createAppAuth,
          auth: options,
        }),
    }) as Promise<InstanceType<typeof CustomOctokit>>;

  /**
   *
   * @param url GitHub resource url
   * @param actor User attempting to unfurl resource url
   * @returns An object containing resource details e.g, a GitHub Pull Request details
   */
  public static unfurl: UnfurlSignature = async (url: string, actor: User) => {
    const resource = GitHub.parseUrl(url);

    if (!resource) {
      return;
    }

    const integration = (await Integration.findOne({
      where: {
        service: IntegrationService.GitHub,
        teamId: actor.teamId,
        "settings.github.installation.account.name": resource.owner,
      },
    })) as Integration<IntegrationType.Embed>;

    if (!integration) {
      return;
    }

    try {
      const client = await GitHub.authenticateAsInstallation(
        integration.settings.github!.installation.id
      );
      const { data } = await client.requestResource(resource);
      if (!data) {
        return;
      }
      return { ...data, type: resource.type };
    } catch (err) {
      Logger.warn("Failed to fetch resource from GitHub", err);
      return;
    }
  };
}