import { randomBytes, scrypt, timingSafeEqual } from "node:crypto";
import { Buffer } from "node:buffer";
import { jwtVerify, SignJWT } from "@panva/jose";

import {
  type AuthPayload,
  isAuthPayload,
  isPasswordResetPayload,
  type PasswordResetPayload,
} from "../model/interfaces.ts";
import { JWT_SECRET } from "../config.ts";

if (!JWT_SECRET) {
  throw new Error(
    "GERBEUR_JWT_SECRET environment variable is required. Generate one with: openssl rand -hex 32",
  );
}
const JWT_KEY = new TextEncoder().encode(JWT_SECRET);

// ── Password reset tokens ─────────────────────────────────────────────────────

export async function createPasswordResetToken(
  userId: string,
): Promise<string> {
  return await new SignJWT({ purpose: "password-reset", userId })
    .setProtectedHeader({ alg: "HS256" })
    .setJti(crypto.randomUUID())
    .setExpirationTime("1h")
    .sign(JWT_KEY);
}

export async function verifyPasswordResetToken(
  token: string,
): Promise<PasswordResetPayload | null> {
  try {
    const { payload } = await jwtVerify(token, JWT_KEY);
    if (!isPasswordResetPayload(payload)) return null;
    return payload as PasswordResetPayload;
  } catch {
    return null;
  }
}

// ── Auth tokens ───────────────────────────────────────────────────────────────

export async function createJWT(
  payload: Omit<AuthPayload, "exp">,
): Promise<string> {
  return await new SignJWT(payload)
    .setProtectedHeader({ alg: "HS256" })
    // `iat` is what a password change revokes against (users.tokens_valid_after).
    .setIssuedAt()
    .setExpirationTime("7d")
    .sign(JWT_KEY);
}

// ── Media tokens ──────────────────────────────────────────────────────────────

// Media elements can't send an Authorization header, so a private dump's file
// and thumbnail URLs carry a token in the query string, where it lands in
// access logs and browser history. That token is this one: it only reads media,
// so a leaked URL exposes the owner's private files, not their account.
export async function createMediaToken(userId: string): Promise<string> {
  return await new SignJWT({ purpose: "media", userId })
    .setProtectedHeader({ alg: "HS256" })
    .setIssuedAt()
    .setExpirationTime("7d")
    .sign(JWT_KEY);
}

export async function verifyMediaToken(
  token: string,
): Promise<{ userId: string; iat?: number } | null> {
  try {
    const { payload } = await jwtVerify(token, JWT_KEY);
    if (payload.purpose !== "media" || typeof payload.userId !== "string") {
      return null;
    }
    return { userId: payload.userId, iat: payload.iat };
  } catch {
    return null;
  }
}

export async function verifyJWT(token: string): Promise<AuthPayload | null> {
  try {
    const { payload } = await jwtVerify(token, JWT_KEY);

    if (!isAuthPayload(payload)) {
      return null;
    }

    return payload;
  } catch (err) {
    console.error("JWT verification failed:", err);
    return null;
  }
}

export function hashPassword(password: string): Promise<string> {
  const salt = randomBytes(16).toString("hex");

  return new Promise((resolve, reject) => {
    scrypt(password, salt, 64, (err, derivedKey) => {
      if (err) reject(err);
      else resolve(`${derivedKey.toString("hex")}.${salt}`);
    });
  });
}

export function verifyPassword(
  password: string,
  storedHash: string,
): Promise<boolean> {
  const [hash, salt] = storedHash.split(".");

  return new Promise((resolve, reject) => {
    scrypt(password, salt, 64, (err, derivedKey) => {
      if (err) reject(err);
      else {
        const expected = Buffer.from(hash ?? "", "hex");
        resolve(
          expected.length === derivedKey.length &&
            timingSafeEqual(expected, derivedKey),
        );
      }
    });
  });
}