import type { ForgeType, RepoMetadata } from "@tasks/shared/connected-repos";

export type ForgeAdapterContext = {
  apiBaseUrl: string;
  owner: string;
  repo: string;
  token?: string;
};

export type CreatePullRequestInput = {
  base: string;
  head: string;
  title: string;
  body: string;
  draft: boolean;
};

export type CreatePullRequestResult = {
  url: string;
  number: number;
};

export interface ForgeAdapter {
  readonly forgeType: ForgeType;
  fetchRepoMetadata(ctx: ForgeAdapterContext): Promise<RepoMetadata>;
  createPullRequest(
    ctx: ForgeAdapterContext,
    input: CreatePullRequestInput,
  ): Promise<CreatePullRequestResult>;
}

async function readJsonResponse(response: Response): Promise<unknown> {
  const text = await response.text();
  if (!text) {
    return null;
  }
  try {
    return JSON.parse(text) as unknown;
  } catch {
    throw new Error(`Forge API returned non-JSON response (${response.status}).`);
  }
}

function authHeaders(token: string | undefined): HeadersInit {
  if (!token) {
    return {};
  }
  return { Authorization: `Bearer ${token}` };
}

async function createGithubPullRequest(
  ctx: ForgeAdapterContext,
  input: CreatePullRequestInput,
): Promise<CreatePullRequestResult> {
  const url = `${ctx.apiBaseUrl.replace(/\/$/, "")}/repos/${ctx.owner}/${ctx.repo}/pulls`;
  const response = await fetch(url, {
    method: "POST",
    headers: {
      Accept: "application/vnd.github+json",
      "Content-Type": "application/json",
      ...authHeaders(ctx.token),
    },
    body: JSON.stringify({
      title: input.title,
      body: input.body,
      head: input.head,
      base: input.base,
      draft: input.draft,
    }),
  });
  const body = await readJsonResponse(response);
  if (!response.ok) {
    const message =
      typeof body === "object" &&
      body !== null &&
      "message" in body &&
      typeof (body as { message: unknown }).message === "string"
        ? (body as { message: string }).message
        : `GitHub API error (${response.status})`;
    throw new Error(message);
  }
  const htmlUrl =
    typeof body === "object" &&
    body !== null &&
    "html_url" in body &&
    typeof (body as { html_url: unknown }).html_url === "string"
      ? (body as { html_url: string }).html_url
      : typeof body === "object" &&
          body !== null &&
          "url" in body &&
          typeof (body as { url: unknown }).url === "string"
        ? (body as { url: string }).url
        : `${ctx.apiBaseUrl.replace(/\/$/, "")}/${ctx.owner}/${ctx.repo}/pulls/unknown`;
  const number =
    typeof body === "object" &&
    body !== null &&
    "number" in body &&
    typeof (body as { number: unknown }).number === "number"
      ? (body as { number: number }).number
      : 0;
  return { url: htmlUrl, number };
}

async function createForgejoPullRequest(
  ctx: ForgeAdapterContext,
  input: CreatePullRequestInput,
): Promise<CreatePullRequestResult> {
  const url = `${ctx.apiBaseUrl.replace(/\/$/, "")}/repos/${ctx.owner}/${ctx.repo}/pulls`;
  const response = await fetch(url, {
    method: "POST",
    headers: {
      Accept: "application/json",
      "Content-Type": "application/json",
      ...authHeaders(ctx.token),
    },
    body: JSON.stringify({
      title: input.title,
      body: input.body,
      head: input.head,
      base: input.base,
      draft: input.draft,
    }),
  });
  const body = await readJsonResponse(response);
  if (!response.ok) {
    const message =
      typeof body === "object" &&
      body !== null &&
      "message" in body &&
      typeof (body as { message: unknown }).message === "string"
        ? (body as { message: string }).message
        : `Forge API error (${response.status})`;
    throw new Error(message);
  }
  const htmlUrl =
    typeof body === "object" &&
    body !== null &&
    "html_url" in body &&
    typeof (body as { html_url: unknown }).html_url === "string"
      ? (body as { html_url: string }).html_url
      : typeof body === "object" &&
          body !== null &&
          "url" in body &&
          typeof (body as { url: unknown }).url === "string"
        ? (body as { url: string }).url
        : `${ctx.apiBaseUrl.replace(/\/api\/v1$/, "")}/${ctx.owner}/${ctx.repo}/pulls/${typeof body === "object" && body !== null && "number" in body ? String((body as { number: unknown }).number) : "unknown"}`;
  const number =
    typeof body === "object" &&
    body !== null &&
    "number" in body &&
    typeof (body as { number: unknown }).number === "number"
      ? (body as { number: number }).number
      : 0;
  return { url: htmlUrl, number };
}

export const githubForgeAdapter: ForgeAdapter = {
  forgeType: "github",
  async fetchRepoMetadata(ctx) {
    const url = `${ctx.apiBaseUrl.replace(/\/$/, "")}/repos/${ctx.owner}/${ctx.repo}`;
    const response = await fetch(url, {
      headers: {
        Accept: "application/vnd.github+json",
        ...authHeaders(ctx.token),
      },
    });
    const body = await readJsonResponse(response);
    if (!response.ok) {
      const message =
        typeof body === "object" &&
        body !== null &&
        "message" in body &&
        typeof body.message === "string"
          ? body.message
          : `GitHub API error (${response.status})`;
      throw new Error(message);
    }
    if (
      typeof body !== "object" ||
      body === null ||
      !("default_branch" in body) ||
      typeof body.default_branch !== "string"
    ) {
      throw new Error("GitHub API response missing default_branch.");
    }
    const cloneUrl =
      typeof body === "object" &&
      body !== null &&
      "clone_url" in body &&
      typeof body.clone_url === "string"
        ? body.clone_url
        : `https://github.com/${ctx.owner}/${ctx.repo}.git`;
    const description =
      typeof body === "object" &&
      body !== null &&
      "description" in body &&
      typeof body.description === "string"
        ? body.description
        : undefined;
    return {
      defaultBranch: body.default_branch,
      cloneUrl,
      description,
    };
  },
  async createPullRequest(ctx, input) {
    return createGithubPullRequest(ctx, input);
  },
};

export const forgejoForgeAdapter: ForgeAdapter = {
  forgeType: "forgejo",
  async fetchRepoMetadata(ctx) {
    const url = `${ctx.apiBaseUrl.replace(/\/$/, "")}/repos/${ctx.owner}/${ctx.repo}`;
    const response = await fetch(url, {
      headers: {
        Accept: "application/json",
        ...authHeaders(ctx.token),
      },
    });
    const body = await readJsonResponse(response);
    if (!response.ok) {
      const message =
        typeof body === "object" &&
        body !== null &&
        "message" in body &&
        typeof body.message === "string"
          ? body.message
          : `Forge API error (${response.status})`;
      throw new Error(message);
    }
    if (
      typeof body !== "object" ||
      body === null ||
      !("default_branch" in body) ||
      typeof body.default_branch !== "string"
    ) {
      throw new Error("Forge API response missing default_branch.");
    }
    const cloneUrl =
      typeof body === "object" &&
      body !== null &&
      "clone_url" in body &&
      typeof body.clone_url === "string"
        ? body.clone_url
        : `${ctx.apiBaseUrl.replace(/\/api\/v1$/, "")}/${ctx.owner}/${ctx.repo}.git`;
    const description =
      typeof body === "object" &&
      body !== null &&
      "description" in body &&
      typeof body.description === "string"
        ? body.description
        : undefined;
    return {
      defaultBranch: body.default_branch,
      cloneUrl,
      description,
    };
  },
  async createPullRequest(ctx, input) {
    return createForgejoPullRequest(ctx, input);
  },
};

const ADAPTERS: Record<ForgeType, ForgeAdapter> = {
  github: githubForgeAdapter,
  forgejo: forgejoForgeAdapter,
  gitlab: forgejoForgeAdapter,
  bitbucket: forgejoForgeAdapter,
};

export function getForgeAdapter(forgeType: ForgeType): ForgeAdapter {
  return ADAPTERS[forgeType];
}