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

type PR =
  Endpoints["GET /repos/{owner}/{repo}/pulls/{pull_number}"]["response"]["data"];
type Issue =
  Endpoints["GET /repos/{owner}/{repo}/issues/{issue_number}"]["response"]["data"];
type Installation =
  Endpoints["GET /app/installations/{installation_id}"]["response"]["data"];

type ParsedIssueOrPR = {
  owner: string;
  repo: string;
  type: UnfurlResourceType.Issue | UnfurlResourceType.PR;
  id: number;
  url: string;
};

type ParsedProject = {
  owner: string;
  ownerType: "orgs" | "users";
  type: UnfurlResourceType.Project;
  projectNumber: number;
  url: string;
};

type GitHubResource = ParsedIssueOrPR | ParsedProject;

type GitHubProject = {
  number: number;
  title: string;
  description: string | null;
  url: string;
  createdAt: string;
  closed: boolean;
};

const requestPlugin = (octokit: Octokit) => ({
  requestRepos: () =>
    octokit.paginate.iterator(
      octokit.rest.apps.listReposAccessibleToInstallation,
      {
        headers: {
          Accept: "application/vnd.github+json",
          "X-GitHub-Api-Version": "2022-11-28",
        },
      }
    ),

  requestPR: async (params: ParsedIssueOrPR) =>
    octokit.request(`GET /repos/{owner}/{repo}/pulls/{pull_number}`, {
      owner: params.owner,
      repo: params.repo,
      pull_number: params.id,
      headers: {
        Accept: "application/vnd.github.text+json",
        "X-GitHub-Api-Version": "2022-11-28",
      },
    }),

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

  /**
   * Fetches details of a GitHub ProjectV2 using the GraphQL API.
   *
   * @param params Parsed project URL identifiers.
   * @returns Project data or undefined if not found.
   */
  requestProject: async (
    params: ParsedProject
  ): Promise<GitHubProject | undefined> => {
    const ownerField = params.ownerType === "orgs" ? "organization" : "user";

    const query = `query($login: String!, $number: Int!) {
      ${ownerField}(login: $login) {
        projectV2(number: $number) {
          number
          title
          shortDescription
          url
          createdAt
          closed
        }
      }
    }`;

    const result = await octokit.graphql<
      Record<
        string,
        {
          projectV2: {
            number: number;
            title: string;
            shortDescription: string | null;
            url: string;
            createdAt: string;
            closed: boolean;
          } | null;
        }
      >
    >(query, { login: params.owner, number: params.projectNumber });

    const project = result[ownerField]?.projectV2;
    if (!project) {
      return undefined;
    }

    return {
      number: project.number,
      title: project.title,
      description: project.shortDescription,
      url: project.url,
      createdAt: project.createdAt,
      closed: project.closed,
    };
  },

  /**
   * 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: GitHubResource | undefined
  ): Promise<OctokitResponse<Issue | PR> | undefined> {
    switch (resource?.type) {
      case UnfurlResourceType.PR:
        return this.requestPR(resource) as Promise<OctokitResponse<PR>>;
      case UnfurlResourceType.Issue:
        return this.requestIssue(resource) as Promise<OctokitResponse<Issue>>;
      default:
        return;
    }
  },

  /**
   * Fetches details of a specific GitHub app installation
   *
   * @param installationId Id of the installation to fetch
   * @returns Response containing installation details
   */
  requestAppInstallation: async (
    installationId: number
  ): Promise<OctokitResponse<Installation>> =>
    octokit.request("GET /app/installations/{installation_id}", {
      installation_id: installationId,
      headers: {
        Accept: "application/vnd.github+json",
        "X-GitHub-Api-Version": "2022-11-28",
      },
    }),

  /**
   * 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 = [
    UnfurlResourceType.Issue,
    UnfurlResourceType.PR,
  ];

  /**
   * 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): GitHubResource | undefined {
    try {
      const { hostname, pathname } = new URL(url);
      if (hostname !== "github.com") {
        return;
      }

      const parts = pathname.split("/");

      // Handle project URLs: /orgs/{org}/projects/{number} or /users/{user}/projects/{number}
      if (
        (parts[1] === "orgs" || parts[1] === "users") &&
        parts[3] === "projects"
      ) {
        const ownerType = parts[1] as "orgs" | "users";
        const owner = parts[2];
        const projectNumber = Number(parts[4]);

        if (!owner || isNaN(projectNumber)) {
          return;
        }

        return {
          owner,
          ownerType,
          type: UnfurlResourceType.Project,
          projectNumber,
          url,
        };
      }

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

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

      return {
        owner,
        repo,
        type: type as UnfurlResourceType.Issue | UnfurlResourceType.PR,
        id,
        url,
      };
    } catch (_err) {
      // Invalid URL format
      return;
    }
  }

  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 || !actor) {
      return;
    }

    // Find integration, prioritizing one where the installation account matches the resource owner
    const integration = (await Integration.findOne({
      where: {
        service: IntegrationService.GitHub,
        teamId: actor.teamId,
      },
      order: [
        [
          Sequelize.literal(
            `CASE WHEN "settings"->'github'->'installation'->'account'->>'name' = :owner THEN 0 ELSE 1 END`
          ),
          "ASC",
        ],
      ],
      replacements: {
        owner: resource.owner,
      },
    })) as Integration<IntegrationType.Embed>;

    if (!integration) {
      return;
    }

    try {
      const client = await GitHub.authenticateAsInstallation(
        integration.settings.github!.installation.id
      );

      if (resource.type === UnfurlResourceType.Project) {
        return GitHub.unfurlProject(client, resource);
      }

      const res = await client.requestResource(resource);
      if (!res) {
        return { error: "Resource not found" };
      }

      return GitHub.transformData(res.data, resource.type);
    } catch (err) {
      Logger.warn("Failed to fetch resource from GitHub", err);
      return { error: err.message || "Unknown error" };
    }
  };

  private static async unfurlProject(
    client: InstanceType<typeof CustomOctokit>,
    resource: ParsedProject
  ) {
    let project: GitHubProject | undefined;
    try {
      project = await client.requestProject(resource);
    } catch (err) {
      Logger.warn("Failed to fetch project from GitHub", err);
      return { error: "Resource not found" };
    }

    if (!project) {
      return { error: "Resource not found" };
    }

    const state = project.closed ? "completed" : "open";

    return {
      type: UnfurlResourceType.Project,
      url: project.url,
      id: `#${project.number}`,
      name: project.title,
      color: GitHubUtils.getColorForStatus(state),
      description: project.description,
      lead: null,
      state: {
        type: state,
        name: state,
        color: GitHubUtils.getColorForStatus(state),
      },
      labels: [],
      createdAt: project.createdAt,
      targetDate: null,
    } satisfies UnfurlProject;
  }

  private static transformData(data: Issue | PR, type: UnfurlResourceType) {
    if (type === UnfurlResourceType.Issue) {
      const issue = data as Issue;
      const issueState =
        issue.state === "closed"
          ? issue.state_reason === "completed"
            ? "completed"
            : "canceled"
          : issue.state;
      return {
        type: UnfurlResourceType.Issue,
        url: issue.html_url,
        id: `#${issue.number}`,
        title: issue.title,
        description: issue.body_text ?? null,
        author: {
          name: issue.user?.login ?? "",
          avatarUrl: issue.user?.avatar_url ?? "",
        },
        labels: issue.labels.map((label: { name: string; color: string }) => ({
          name: label.name,
          color: `#${label.color}`,
        })),
        state: {
          name: issueState,
          color: GitHubUtils.getColorForStatus(issueState),
        },
        createdAt: issue.created_at,
      } satisfies UnfurlIssueOrPR;
    }

    const pr = data as PR;
    const prState = pr.merged ? "merged" : pr.state;
    return {
      type: UnfurlResourceType.PR,
      url: pr.html_url,
      id: `#${pr.number}`,
      title: pr.title,
      description: pr.body,
      author: {
        name: pr.user.login,
        avatarUrl: pr.user.avatar_url,
      },
      state: {
        name: prState,
        color: GitHubUtils.getColorForStatus(prState, !!pr.draft),
        draft: pr.draft,
      },
      createdAt: pr.created_at,
    } satisfies UnfurlIssueOrPR;
  }
}