import { createElement } from "react";
import { compare, hash } from "bcryptjs";
import { z } from "zod";
import { prisma } from "@/lib/prisma";
import { serializableTransaction } from "@/lib/transaction";
import { hashToken, newToken } from "@/lib/tokens";
import { passwordSchema } from "@/lib/password";
import { sendAppEmail } from "@/lib/mail";
import { PasswordResetEmail } from "@/emails/PasswordResetEmail";
import { UserFacingError } from "@/lib/action-error";

const RESET_PREFIX = "password-reset:";
const resetScope = (userId: string) =>
  `${RESET_PREFIX}${Buffer.from(userId).toString("base64url")}:`;
function resetIdentity(identifier: string) {
  const match = /^password-reset:([a-zA-Z0-9_-]+):(\d+)$/.exec(identifier);
  if (!match) return null;
  const sessionVersion = Number(match[2]);
  if (!Number.isSafeInteger(sessionVersion)) return null;
  return {
    id: Buffer.from(match[1], "base64url").toString("utf8"),
    sessionVersion,
  };
}
const tokenSchema = z.string().regex(/^[a-f0-9]{64}$/i);
export const passwordResetMessage =
  "Wenn für diese E-Mail-Adresse ein aktiviertes Konto besteht, erhältst du einen Link für ein neues Passwort. Prüfe auch deinen Spamordner.";
const newPasswordSchema = z
  .object({ password: passwordSchema, confirmation: z.string() })
  .refine((input) => input.password === input.confirmation, {
    message: "Die neuen Passwörter stimmen nicht überein.",
    path: ["confirmation"],
  });
const resetSchema = newPasswordSchema.and(z.object({ token: tokenSchema }));
const invalidLink = () =>
  new UserFacingError(
    "Dieser Link ist ungültig, abgelaufen oder wurde bereits verwendet. Bitte fordere einen neuen Link an.",
  );

function siteOrigin() {
  const base =
    process.env.NEXT_PUBLIC_SITE_URL ||
    process.env.AUTH_URL ||
    process.env.NEXTAUTH_URL;
  if (!base && process.env.NODE_ENV !== "development")
    throw new Error("App-Adresse fehlt.");
  const url = new URL(base || "http://localhost:3000");
  if (
    !["http:", "https:"].includes(url.protocol) ||
    url.username ||
    url.password
  )
    throw new Error("Ungültige App-Adresse.");
  return url.origin;
}

export async function requestPasswordReset(email: string, send = sendAppEmail) {
  const parsed = z
    .string()
    .trim()
    .max(254)
    .email()
    .toLowerCase()
    .safeParse(email);
  if (!parsed.success) return;
  const resetToken = newToken();
  const tokenHash = hashToken(resetToken);
  const job = await serializableTransaction(async (tx) => {
    const user = await tx.user.findUnique({ where: { email: parsed.data } });
    if (!user || user.disabledAt || !user.emailVerifiedAt || !user.passwordHash)
      return null;
    await tx.$queryRaw`SELECT id FROM users WHERE id = ${user.id} FOR UPDATE`;
    const fresh = await tx.user.findUniqueOrThrow({ where: { id: user.id } });
    if (
      fresh.email !== parsed.data ||
      fresh.disabledAt ||
      !fresh.emailVerifiedAt ||
      !fresh.passwordHash
    )
      return null;
    const identifier = resetScope(user.id) + fresh.sessionVersion;
    await tx.verificationToken.deleteMany({
      where: { identifier: { startsWith: resetScope(user.id) } },
    });
    await tx.verificationToken.create({
      data: {
        identifier,
        token: tokenHash,
        expires: new Date(Date.now() + 30 * 60_000),
      },
    });
    return {
      id: user.id,
      email: fresh.email,
      name: fresh.firstName,
      identifier,
    };
  });
  if (!job) return;
  try {
    const result = await send({
      to: job.email,
      subject: "Kita-Planer: Neues Passwort festlegen",
      react: createElement(PasswordResetEmail, {
        name: job.name,
        resetLink: `${siteOrigin()}/neues-passwort/${resetToken}`,
      }),
      idempotencyKey: `password-reset/${tokenHash}`,
    });
    if (result.success) return;
  } catch {
    /* Return the same public response, including transport failure. */
  }
  await prisma.verificationToken.deleteMany({
    where: { identifier: job.identifier, token: tokenHash },
  });
}

export async function isPasswordResetValid(token: string) {
  if (!tokenSchema.safeParse(token).success) return false;
  const entry = await prisma.verificationToken.findUnique({
    where: { token: hashToken(token) },
  });
  if (!entry || !resetIdentity(entry.identifier) || entry.expires <= new Date())
    return false;
  return !!(await prisma.user.findFirst({
    where: {
      ...resetIdentity(entry.identifier)!,
      disabledAt: null,
      emailVerifiedAt: { not: null },
      passwordHash: { not: "" },
    },
    select: { id: true },
  }));
}

export async function resetPassword(raw: unknown) {
  const input = resetSchema.safeParse(raw);
  if (!input.success)
    throw new UserFacingError(
      input.error.issues[0]?.message ?? "Bitte die Eingaben prüfen.",
    );
  if (!(await isPasswordResetValid(input.data.token))) throw invalidLink();
  const passwordHash = await hash(input.data.password, 12);
  await serializableTransaction(async (tx) => {
    const tokenHash = hashToken(input.data.token);
    const entry = await tx.verificationToken.findUnique({
      where: { token: tokenHash },
    });
    if (
      !entry ||
      !resetIdentity(entry.identifier) ||
      entry.expires <= new Date()
    )
      throw invalidLink();
    const identity = resetIdentity(entry.identifier)!;
    const userId = identity.id;
    await tx.$queryRaw`SELECT id FROM users WHERE id = ${userId} FOR UPDATE`;
    const user = await tx.user.findFirst({
      where: {
        ...identity,
        disabledAt: null,
        emailVerifiedAt: { not: null },
        passwordHash: { not: "" },
      },
    });
    if (!user) throw invalidLink();
    const consumed = await tx.verificationToken.deleteMany({
      where: {
        identifier: entry.identifier,
        token: tokenHash,
        expires: { gt: new Date() },
      },
    });
    if (consumed.count !== 1) throw invalidLink();
    await tx.user.update({
      where: { id: userId },
      data: {
        passwordHash,
        sessionVersion: { increment: 1 },
        failedLoginAttempts: 0,
        lockedUntil: null,
      },
    });
    await tx.verificationToken.deleteMany({
      where: {
        OR: [
          { identifier: userId },
          { identifier: { startsWith: resetScope(userId) } },
        ],
      },
    });
  });
}

export async function changeOwnPassword(
  actor: { id: string; sessionVersion: number },
  raw: unknown,
) {
  const schema = newPasswordSchema.and(
    z.object({
      currentPassword: z
        .string()
        .min(1)
        .refine(
          (value) => Buffer.byteLength(value, "utf8") <= 72,
          "Aktuelles Passwort ist ungültig.",
        ),
    }),
  );
  const input = schema.safeParse(raw);
  if (!input.success)
    throw new UserFacingError(
      input.error.issues[0]?.message ?? "Bitte die Eingaben prüfen.",
    );
  const user = await prisma.user.findFirst({
    where: {
      id: actor.id,
      sessionVersion: actor.sessionVersion,
      disabledAt: null,
      emailVerifiedAt: { not: null },
    },
  });
  if (!user || !(await compare(input.data.currentPassword, user.passwordHash)))
    throw new UserFacingError(
      "Das aktuelle Passwort ist nicht korrekt. Bitte melde dich bei Bedarf erneut an.",
    );
  if (await compare(input.data.password, user.passwordHash))
    throw new UserFacingError("Bitte wähle ein anderes neues Passwort.");
  const passwordHash = await hash(input.data.password, 12);
  await serializableTransaction(async (tx) => {
    const changed = await tx.user.updateMany({
      where: {
        id: user.id,
        passwordHash: user.passwordHash,
        sessionVersion: actor.sessionVersion,
        disabledAt: null,
        emailVerifiedAt: { not: null },
      },
      data: {
        passwordHash,
        sessionVersion: { increment: 1 },
        failedLoginAttempts: 0,
        lockedUntil: null,
      },
    });
    if (changed.count !== 1)
      throw new UserFacingError(
        "Das Konto wurde inzwischen geändert. Bitte melde dich erneut an.",
      );
    await tx.verificationToken.deleteMany({
      where: {
        OR: [
          { identifier: user.id },
          { identifier: { startsWith: resetScope(user.id) } },
        ],
      },
    });
  });
}