import { randomBytes, randomUUID, timingSafeEqual } from "node:crypto";

import type { Application, Request, Response } from "express";
import { Router } from "express";
import { rateLimit } from "express-rate-limit";
import type { z } from "zod/v4";

import type { SessionResponseDTO } from "../../../common";
import {
  BootstrapAdminRequestSchema,
  ChangePasswordRequestSchema,
  CreateUserRequestSchema,
  LoginRequestSchema,
  ResetPasswordRequestSchema,
  UpdateUserRequestSchema,
  UserParamsRequestSchema,
} from "../../../common";
import type { IdentityUseCases } from "../../application/identity.use-cases";
import { buildUserResponse } from "../../application/user-response.builder";
import type { IdentityError } from "../../domain/identity-error";

import type { AuthenticatedSession } from "./session-types";

function sendError(response: Response, code: string, status: number): void {
  response
    .status(status)
    .json({ code, requestId: response.getHeader("x-request-id")?.toString() ?? randomUUID() });
}

function businessError(response: Response, error: IdentityError): void {
  const statuses = {
    INVALID_REQUEST: 400,
    INVALID_CREDENTIALS: 401,
    UNAUTHENTICATED: 401,
    FORBIDDEN: 403,
    SETUP_CLOSED: 409,
    EMAIL_EXISTS: 409,
    USER_NOT_FOUND: 404,
    ADMIN_PROTECTED: 409,
  };

  sendError(response, error.code, statuses[error.code]);
}

function getContext(request: Request): AuthenticatedSession | undefined {
  const { userId, authVersion } = request.session;

  return userId && authVersion !== undefined ? { userId, authVersion } : undefined;
}

function saveSession(request: Request): Promise<void> {
  return new Promise((resolve, reject) =>
    request.session.save((error) => (error ? reject(error) : resolve()))
  );
}

async function signIn(request: Request, userId: string, authVersion: number): Promise<void> {
  await new Promise<void>((resolve, reject) =>
    request.session.regenerate((error) => (error ? reject(error) : resolve()))
  );
  request.session.userId = userId;
  request.session.authVersion = authVersion;
  request.session.csrfToken = randomBytes(32).toString("hex");
  await saveSession(request);
}

export function registerIdentityRoutes(
  app: Application,
  useCases: IdentityUseCases,
  origin: string
): void {
  const router = Router();

  router.get("/auth/session", (request, response, next) => {
    const handle = async () => {
      request.session.csrfToken ??= randomBytes(32).toString("hex");
      const user = await useCases.session(getContext(request));

      if (!user) {
        request.session.userId = undefined;
        request.session.authVersion = undefined;
      }
      const snapshot: SessionResponseDTO = {
        user: user ? buildUserResponse(user) : null,
        setupRequired: await useCases.setupRequired(),
        csrfToken: request.session.csrfToken,
      };

      await saveSession(request);
      response.json(snapshot);
    };

    handle().catch(next);
  });
  router.use((request, response, next) => {
    if (request.method === "GET") {
      next();

      return;
    }
    const token = request.get("x-csrf-token");
    const expected = request.session.csrfToken;

    if (
      request.get("origin") !== origin ||
      !token ||
      !expected ||
      !/^[a-f0-9]{64}$/.test(token) ||
      !timingSafeEqual(Buffer.from(token), Buffer.from(expected))
    ) {
      sendError(response, "FORBIDDEN", 403);

      return;
    }
    next();
  });
  const authLimiter = rateLimit({
    windowMs: 15 * 60 * 1000,
    limit: 10,
    standardHeaders: "draft-8",
    legacyHeaders: false,
    skipSuccessfulRequests: true,
    handler: (_request, response) => sendError(response, "TOO_MANY_REQUESTS", 429),
  });

  router.use(["/auth/login", "/auth/bootstrap"], authLimiter);

  const registerBody = <T>(
    path: string,
    schema: z.ZodType<T>,
    execute: (dto: T, request: Request, response: Response) => Promise<void>
  ) => {
    router.post(path, (request, response, next) => {
      const parsed = schema.safeParse(request.body);

      if (!parsed.success) {
        sendError(response, "INVALID_REQUEST", 400);

        return;
      }
      execute(parsed.data, request, response).catch(next);
    });
  };

  registerBody("/auth/bootstrap", BootstrapAdminRequestSchema, async (dto, request, response) => {
    const result = await useCases.bootstrap(dto);

    if (!result.isSuccess) {
      businessError(response, result.error);

      return;
    }
    await signIn(request, result.data.id.toPrimitive(), result.data.authVersion);
    response.status(201).json({ user: buildUserResponse(result.data) });
  });
  registerBody("/auth/login", LoginRequestSchema, async (dto, request, response) => {
    const result = await useCases.login(dto);

    if (!result.isSuccess) {
      businessError(response, result.error);

      return;
    }
    await signIn(request, result.data.id.toPrimitive(), result.data.authVersion);
    response.json({ user: buildUserResponse(result.data) });
  });
  registerBody(
    "/auth/logout",
    BootstrapAdminRequestSchema.pick({}),
    async (_dto, request, response) => {
      await new Promise<void>((resolve, reject) =>
        request.session.destroy((error) => (error ? reject(error) : resolve()))
      );
      response.clearCookie("metis.sid", { httpOnly: true, sameSite: "strict", path: "/" });
      response.json({ success: true });
    }
  );
  registerBody(
    "/auth/change-password",
    ChangePasswordRequestSchema,
    async (dto, request, response) => {
      const context = getContext(request);

      if (!context) {
        sendError(response, "UNAUTHENTICATED", 401);

        return;
      }
      const result = await useCases.changePassword(dto, context);

      if (!result.isSuccess) {
        businessError(response, result.error);

        return;
      }
      await signIn(request, result.data.id.toPrimitive(), result.data.authVersion);
      response.json({ user: buildUserResponse(result.data) });
    }
  );
  router.use("/users", (request, response, next) => {
    const handle = async () => {
      const user = await useCases.session(getContext(request));

      if (!user) {
        sendError(response, "UNAUTHENTICATED", 401);

        return;
      }
      if (!user.isInitialAdmin) {
        sendError(response, "FORBIDDEN", 403);

        return;
      }
      next();
    };

    handle().catch(next);
  });
  router.get("/users", (request, response, next) => {
    const context = getContext(request);

    if (!context) {
      sendError(response, "UNAUTHENTICATED", 401);

      return;
    }
    useCases
      .list(context)
      .then((result) => {
        if (!result.isSuccess) {
          businessError(response, result.error);

          return;
        }
        response.json({ users: result.data.map(buildUserResponse) });
      })
      .catch(next);
  });
  registerBody("/users", CreateUserRequestSchema, async (dto, request, response) => {
    const context = getContext(request);

    if (!context) {
      sendError(response, "UNAUTHENTICATED", 401);

      return;
    }
    const result = await useCases.create(dto, context);

    if (!result.isSuccess) {
      businessError(response, result.error);

      return;
    }
    response.status(201).json({ user: buildUserResponse(result.data) });
  });
  registerBody("/users/:id/update", UpdateUserRequestSchema, async (dto, request, response) => {
    const context = getContext(request);
    const params = UserParamsRequestSchema.safeParse(request.params);

    if (!(context && params.success)) {
      sendError(response, "INVALID_REQUEST", 400);

      return;
    }
    const result = await useCases.update(params.data.id, dto, context);

    if (!result.isSuccess) {
      businessError(response, result.error);

      return;
    }
    response.json({ user: buildUserResponse(result.data) });
  });

  registerBody(
    "/users/:id/reset-password",
    ResetPasswordRequestSchema,
    async (dto, request, response) => {
      const context = getContext(request);
      const params = UserParamsRequestSchema.safeParse(request.params);

      if (!(context && params.success)) {
        sendError(response, "INVALID_REQUEST", 400);

        return;
      }
      const result = await useCases.resetPassword(params.data.id, dto, context);

      if (!result.isSuccess) {
        businessError(response, result.error);

        return;
      }
      response.json({ user: buildUserResponse(result.data) });
    }
  );
  app.use("/api", router);
}