import { createHash, randomBytes } from "node:crypto";
import type { Express, RequestHandler } from "express";
import { z } from "zod";

type RegisterAuthApiRoutesOptions = {
  app: Express;
  prisma: any;
  authHandler: RequestHandler;
  requireSession: RequestHandler;
  extractSessionToken: (cookieHeader: string | undefined) => string | null;
  providersAvailability: Record<string, boolean>;
  sessionCookieName: string;
  sessionCookieSecure: boolean;
  extraCookieNamesToClear?: string[];
  messages?: Partial<AuthRouteMessages>;
  authBasePath?: string;
  authApiBasePath?: string;
  mePath?: string;
  normalizeEmail?: (email: string) => string;
  passwordHasher?: (password: string) => Promise<string>;
  passwordComparator?: (password: string, passwordHash: string) => Promise<boolean>;
  passwordReset?: {
    enabled: boolean;
    tokenTtlMs?: number;
    identifierPrefix?: string;
    buildResetUrl: (token: string) => string;
    sendMessage: (input: {
      user: { id: string; email: string; name: string | null; passwordHash: string | null };
      resetUrl: string;
      isPasswordCreation: boolean;
      expiresAt: Date;
    }) => Promise<void>;
  };
  onUserRegistered?: (user: { id: string; email: string | null; name: string | null }) => Promise<void> | void;
  onPasswordResetConfirmed?: (user: { id: string; email: string | null; name: string | null }) => Promise<void> | void;
};

type AuthRouteMessages = {
  invalidPayload: string;
  emailAlreadyUsed: string;
  accountNotFound: string;
  externalAccountOnly: string;
  invalidPassword: string;
  passwordResetUnavailable: string;
  invalidResetLink: string;
  expiredResetLink: string;
};

const defaultNormalizeEmail = (email: string) => email.trim();
const defaultPasswordResetIdentifierPrefix = "password-reset:";
const defaultMessages: AuthRouteMessages = {
  invalidPayload: "Invalid payload",
  emailAlreadyUsed: "Email already used",
  accountNotFound: "Account not found",
  externalAccountOnly: "This account uses an external sign-in provider.",
  invalidPassword: "Invalid password",
  passwordResetUnavailable: "Email service is not configured.",
  invalidResetLink: "Invalid reset link",
  expiredResetLink: "Invalid or expired reset link"
};

function hashPasswordResetToken(token: string): string {
  return createHash("sha256").update(token).digest("hex");
}

function buildPasswordResetIdentifier(prefix: string, userId: string): string {
  return `${prefix}${userId}`;
}

export function registerAuthApiRoutes(options: RegisterAuthApiRoutesOptions): void {
  const authBasePath = options.authBasePath ?? "/auth";
  const authApiBasePath = options.authApiBasePath ?? "/api/auth";
  const mePath = options.mePath ?? "/api/me";
  const normalizeEmail = options.normalizeEmail ?? defaultNormalizeEmail;
  const passwordHasher = options.passwordHasher ?? ((password: string) => Promise.resolve(password));
  const passwordComparator = options.passwordComparator ?? ((password: string, hash: string) => Promise.resolve(password === hash));
  const passwordResetIdentifierPrefix = options.passwordReset?.identifierPrefix ?? defaultPasswordResetIdentifierPrefix;
  const messages = { ...defaultMessages, ...(options.messages ?? {}) };

  const findUserByEmail = async (email: string) => {
    const normalized = normalizeEmail(email);
    const lowered = normalized.toLowerCase();

    return options.prisma.user.findFirst({
      where: {
        OR: lowered === normalized ? [{ email: normalized }] : [{ email: normalized }, { email: lowered }]
      },
      select: {
        id: true,
        email: true,
        name: true,
        image: true,
        passwordHash: true,
        emailVerified: true
      }
    });
  };

  const getPasswordResetContext = async (
    rawToken: string
  ): Promise<
    | {
        verificationToken: { identifier: string; expires: Date };
        user: { id: string; email: string | null; name: string | null; passwordHash: string | null; emailVerified: Date | null };
      }
    | null
  > => {
    const verificationToken = await options.prisma.verificationToken.findUnique({
      where: { token: hashPasswordResetToken(rawToken) },
      select: { identifier: true, expires: true }
    });

    if (
      !verificationToken ||
      verificationToken.expires <= new Date() ||
      !verificationToken.identifier.startsWith(passwordResetIdentifierPrefix)
    ) {
      return null;
    }

    const userId = verificationToken.identifier.slice(passwordResetIdentifierPrefix.length);
    if (!userId) {
      return null;
    }

    const user = await options.prisma.user.findUnique({
      where: { id: userId },
      select: {
        id: true,
        email: true,
        name: true,
        passwordHash: true,
        emailVerified: true
      }
    });

    if (!user?.email) {
      return null;
    }

    return { verificationToken, user };
  };

  options.app.use(authBasePath, options.authHandler);

  options.app.get(`${authApiBasePath}/providers`, (_req, res) => {
    res.json(options.providersAvailability);
  });

  options.app.post(`${authApiBasePath}/register`, async (req, res) => {
    const parsed = z
      .object({
        name: z.string().min(2).max(60),
        email: z.string().email(),
        password: z.string().min(8)
      })
      .safeParse(req.body);

    if (!parsed.success) {
      return res.status(400).json({ error: messages.invalidPayload });
    }

    const email = normalizeEmail(parsed.data.email);
    const exists = await findUserByEmail(email);
    if (exists) {
      return res.status(409).json({ error: messages.emailAlreadyUsed });
    }

    const passwordHash = await passwordHasher(parsed.data.password);
    const created = await options.prisma.user.create({
      data: {
        name: parsed.data.name,
        email,
        passwordHash
      },
      select: { id: true, email: true, name: true }
    });

    await options.onUserRegistered?.(created);
    return res.status(201).json(created);
  });

  options.app.post(`${authApiBasePath}/login`, async (req, res) => {
    const parsed = z
      .object({
        email: z.string().email(),
        password: z.string().min(8)
      })
      .safeParse(req.body);

    if (!parsed.success) {
      return res.status(400).json({ error: messages.invalidPayload });
    }

    const email = normalizeEmail(parsed.data.email);
    const user = await findUserByEmail(email);
    if (!user) {
      return res.status(404).json({ error: messages.accountNotFound });
    }

    if (!user.passwordHash) {
      return res.status(400).json({ error: messages.externalAccountOnly });
    }

    const valid = await passwordComparator(parsed.data.password, user.passwordHash);
    if (!valid) {
      return res.status(401).json({ error: messages.invalidPassword });
    }

    const sessionToken = randomBytes(32).toString("hex");
    const expires = new Date(Date.now() + 30 * 24 * 60 * 60 * 1000);

    await options.prisma.session.create({
      data: {
        sessionToken,
        userId: user.id,
        expires
      }
    });

    res.cookie(options.sessionCookieName, sessionToken, {
      httpOnly: true,
      sameSite: "lax",
      secure: options.sessionCookieSecure,
      path: "/",
      expires
    });

    return res.status(200).json({ ok: true });
  });

  options.app.post(`${authApiBasePath}/password-reset/request`, async (req, res) => {
    const parsed = z
      .object({
        email: z.string().email()
      })
      .safeParse(req.body);

    if (!parsed.success) {
      return res.status(400).json({ error: messages.invalidPayload });
    }

    if (!options.passwordReset?.enabled) {
      return res.status(503).json({ error: messages.passwordResetUnavailable });
    }

    const email = normalizeEmail(parsed.data.email);
    const user = await findUserByEmail(email);
    if (!user?.email) {
      return res.status(200).json({ ok: true });
    }

    const rawToken = randomBytes(32).toString("hex");
    const identifier = buildPasswordResetIdentifier(passwordResetIdentifierPrefix, user.id);
    const expiresAt = new Date(Date.now() + (options.passwordReset.tokenTtlMs ?? 2 * 60 * 60 * 1000));
    const resetUrl = options.passwordReset.buildResetUrl(rawToken);
    const isPasswordCreation = !user.passwordHash;

    await options.prisma.verificationToken.deleteMany({
      where: {
        OR: [{ identifier }, { expires: { lt: new Date() } }]
      }
    });

    await options.prisma.verificationToken.create({
      data: {
        identifier,
        token: hashPasswordResetToken(rawToken),
        expires: expiresAt
      }
    });

    await options.passwordReset.sendMessage({
      user: {
        id: user.id,
        email: user.email,
        name: user.name,
        passwordHash: user.passwordHash
      },
      resetUrl,
      isPasswordCreation,
      expiresAt
    });

    return res.status(200).json({ ok: true });
  });

  options.app.get(`${authApiBasePath}/password-reset/validate`, async (req, res) => {
    if (!options.passwordReset?.enabled) {
      return res.status(400).json({ error: messages.expiredResetLink });
    }

    const parsed = z.object({ token: z.string().min(1) }).safeParse({
      token: Array.isArray(req.query.token) ? req.query.token[0] : req.query.token
    });

    if (!parsed.success) {
      return res.status(400).json({ error: messages.invalidResetLink });
    }

    const context = await getPasswordResetContext(parsed.data.token);
    if (!context) {
      return res.status(400).json({ error: messages.expiredResetLink });
    }

    return res.status(200).json({
      ok: true,
      email: context.user.email,
      mode: context.user.passwordHash ? "reset" : "create"
    });
  });

  options.app.post(`${authApiBasePath}/password-reset/confirm`, async (req, res) => {
    if (!options.passwordReset?.enabled) {
      return res.status(400).json({ error: messages.expiredResetLink });
    }

    const parsed = z
      .object({
        token: z.string().min(1),
        password: z.string().min(8)
      })
      .safeParse(req.body);

    if (!parsed.success) {
      return res.status(400).json({ error: messages.invalidPayload });
    }

    const context = await getPasswordResetContext(parsed.data.token);
    if (!context) {
      return res.status(400).json({ error: messages.expiredResetLink });
    }

    const passwordHash = await passwordHasher(parsed.data.password);
    await options.prisma.$transaction([
      options.prisma.verificationToken.deleteMany({
        where: { identifier: context.verificationToken.identifier }
      }),
      options.prisma.session.deleteMany({
        where: { userId: context.user.id }
      }),
      options.prisma.user.update({
        where: { id: context.user.id },
        data: {
          passwordHash,
          emailVerified: context.user.emailVerified ?? new Date()
        }
      })
    ]);

    await options.onPasswordResetConfirmed?.(context.user);
    return res.status(200).json({ ok: true });
  });

  options.app.post(`${authApiBasePath}/logout`, async (req, res) => {
    const token = options.extractSessionToken(req.headers.cookie);

    if (token) {
      await options.prisma.session.deleteMany({ where: { sessionToken: token } });
    }

    const cookieNamesToClear = [
      options.sessionCookieName,
      ...(options.extraCookieNamesToClear ?? []),
      "authjs.session-token",
      "__Secure-authjs.session-token",
      "next-auth.session-token",
      "__Secure-next-auth.session-token"
    ];

    for (const cookieName of cookieNamesToClear) {
      res.clearCookie(cookieName, { path: "/" });
    }

    return res.status(200).json({ ok: true });
  });

  options.app.get(mePath, options.requireSession, async (req, res) => {
    res.json({ user: (req as { authUser?: unknown }).authUser });
  });
}