import { createHash, randomBytes, randomUUID, timingSafeEqual } from "node:crypto";
import { prisma } from "@/lib/db";
import {
  authorizePasswordReset,
  createSession,
  destroyPasswordResetAuthorization,
  getPasswordResetSession,
} from "@/lib/auth";

const PASSWORD_HASH_KEY = "admin_password_hash";
const RESET_TOKEN_KEY = "admin_password_reset";
const SESSION_GENERATION_KEY = "auth_session_generation";
const RESET_TOKEN_LIFETIME_MS = 15 * 60 * 1000;

interface ResetTokenRecord {
  digest: string;
  nonce: string;
  expiresAt: string;
}

export type LoginResult =
  | { ok: true }
  | { ok: false; status: 401 | 423; error: string };

function getLockoutDuration(failedAttempts: number): number {
  if (failedAttempts >= 20) return 24 * 60 * 60 * 1000;
  if (failedAttempts >= 15) return 30 * 60 * 1000;
  if (failedAttempts >= 10) return 5 * 60 * 1000;
  if (failedAttempts >= 5) return 60 * 1000;
  return 0;
}

function digestToken(token: string) {
  return createHash("sha256").update(token, "utf8").digest();
}

function parseResetTokenRecord(value: string | undefined): ResetTokenRecord | null {
  if (!value) return null;

  try {
    const parsed: unknown = JSON.parse(value);
    if (
      typeof parsed === "object" &&
      parsed !== null &&
      "digest" in parsed &&
      "nonce" in parsed &&
      "expiresAt" in parsed &&
      typeof parsed.digest === "string" &&
      typeof parsed.nonce === "string" &&
      typeof parsed.expiresAt === "string"
    ) {
      return parsed as ResetTokenRecord;
    }
  } catch {
    // A malformed reset record is treated as invalid.
  }

  return null;
}

async function getSessionGeneration(): Promise<number> {
  const setting = await prisma.setting.findUnique({
    where: { key: SESSION_GENERATION_KEY },
  });
  const generation = Number.parseInt(setting?.value ?? "1", 10);
  return Number.isSafeInteger(generation) && generation > 0 ? generation : 1;
}

async function getOrCreateSecurityRecord() {
  return prisma.authSecurity.upsert({
    where: { id: 1 },
    update: {},
    create: { id: 1 },
  });
}

export async function login(password: string): Promise<LoginResult> {
  const security = await getOrCreateSecurityRecord();

  if (security.lockedUntil && security.lockedUntil > new Date()) {
    const remainingMin = Math.ceil(
      (security.lockedUntil.getTime() - Date.now()) / 60_000
    );
    return {
      ok: false,
      status: 423,
      error: `Account locked. Try again in ${remainingMin} minute${remainingMin === 1 ? "" : "s"}.`,
    };
  }

  const passwordSetting = await prisma.setting.findUnique({
    where: { key: PASSWORD_HASH_KEY },
  });
  const argon2 = await import("argon2");
  let isValid = false;

  if (!passwordSetting) {
    await prisma.setting.create({
      data: { key: PASSWORD_HASH_KEY, value: await argon2.hash(password) },
    });
    isValid = true;
  } else {
    try {
      isValid = await argon2.verify(passwordSetting.value, password);
    } catch {
      isValid = false;
    }
  }

  if (!isValid) {
    const failedAttempts = security.failedAttempts + 1;
    const lockoutMs = getLockoutDuration(failedAttempts);
    await prisma.authSecurity.update({
      where: { id: 1 },
      data: {
        failedAttempts,
        lockedUntil: lockoutMs ? new Date(Date.now() + lockoutMs) : null,
        lastAttemptAt: new Date(),
      },
    });
    return { ok: false, status: 401, error: "Invalid password" };
  }

  await prisma.authSecurity.update({
    where: { id: 1 },
    data: { failedAttempts: 0, lockedUntil: null, lastAttemptAt: new Date() },
  });
  await createSession(await getSessionGeneration());
  return { ok: true };
}

export async function requestPasswordReset(): Promise<boolean> {
  const passwordSetting = await prisma.setting.findUnique({
    where: { key: PASSWORD_HASH_KEY },
  });
  if (!passwordSetting) return false;

  const token = randomBytes(24).toString("base64url");
  const expiresAt = new Date(Date.now() + RESET_TOKEN_LIFETIME_MS).toISOString();
  const record: ResetTokenRecord = {
    digest: digestToken(token).toString("hex"),
    nonce: randomUUID(),
    expiresAt,
  };

  await prisma.setting.upsert({
    where: { key: RESET_TOKEN_KEY },
    update: { value: JSON.stringify(record) },
    create: { key: RESET_TOKEN_KEY, value: JSON.stringify(record) },
  });

  console.info(`[password-reset] Token: ${token} (expires ${expiresAt})`);
  return true;
}

export async function verifyPasswordResetToken(token: string): Promise<boolean> {
  const setting = await prisma.setting.findUnique({ where: { key: RESET_TOKEN_KEY } });
  const record = parseResetTokenRecord(setting?.value);
  if (!record || new Date(record.expiresAt).getTime() <= Date.now()) return false;

  const submittedDigest = digestToken(token);
  const storedDigest = Buffer.from(record.digest, "hex");
  if (
    submittedDigest.length !== storedDigest.length ||
    !timingSafeEqual(submittedDigest, storedDigest)
  ) {
    return false;
  }

  await authorizePasswordReset(record.nonce, record.expiresAt);
  return true;
}

export async function completePasswordReset(password: string): Promise<boolean> {
  const resetSession = await getPasswordResetSession();
  if (!resetSession.nonce || !resetSession.expiresAt) {
    await destroyPasswordResetAuthorization();
    return false;
  }

  const argon2 = await import("argon2");
  const passwordHash = await argon2.hash(password);
  const completed = await prisma.$transaction(async (transaction) => {
    const setting = await transaction.setting.findUnique({
      where: { key: RESET_TOKEN_KEY },
    });
    const record = parseResetTokenRecord(setting?.value);
    if (
      !record ||
      resetSession.nonce !== record.nonce ||
      resetSession.expiresAt !== record.expiresAt ||
      new Date(record.expiresAt).getTime() <= Date.now()
    ) {
      return false;
    }

    const generationSetting = await transaction.setting.findUnique({
      where: { key: SESSION_GENERATION_KEY },
    });
    const parsedGeneration = Number.parseInt(generationSetting?.value ?? "1", 10);
    const currentGeneration =
      Number.isSafeInteger(parsedGeneration) && parsedGeneration > 0
        ? parsedGeneration
        : 1;

    await transaction.setting.upsert({
      where: { key: PASSWORD_HASH_KEY },
      update: { value: passwordHash },
      create: { key: PASSWORD_HASH_KEY, value: passwordHash },
    });
    await transaction.setting.upsert({
      where: { key: SESSION_GENERATION_KEY },
      update: { value: String(currentGeneration + 1) },
      create: { key: SESSION_GENERATION_KEY, value: String(currentGeneration + 1) },
    });
    await transaction.setting.delete({ where: { key: RESET_TOKEN_KEY } });
    await transaction.authSecurity.upsert({
      where: { id: 1 },
      update: { failedAttempts: 0, lockedUntil: null, lastAttemptAt: new Date() },
      create: { id: 1 },
    });
    return true;
  });

  await destroyPasswordResetAuthorization();
  return completed;
}