import type { UserRepository } from "../../db/repositories/user.repository.js";
import { hashPassword, verifyPassword } from "../../server/auth/password.js";
import type { UserRole } from "../../shared/constants/user-roles.js";
import type { AuthConfig } from "../../server/auth/auth-config.js";
import { createLogger } from "../../shared/logging/logger.js";

const logger = createLogger("user-service");

export class InvalidCredentialsError extends Error {
  constructor() {
    super("Anmeldung fehlgeschlagen.");
  }
}

export class UsernameTakenError extends Error {
  constructor() {
    super("Dieser Anmeldename ist bereits vergeben.");
  }
}

export class WrongPasswordError extends Error {
  constructor() {
    super("Das aktuelle Passwort ist falsch.");
  }
}

export class UserService {
  constructor(
    private readonly repository: UserRepository,
    private readonly authConfig: AuthConfig
  ) {}

  /**
   * Creates the bootstrap admin from env vars, but only while the users
   * table is still completely empty. After the first account exists, every
   * further account is created through Config -> Benutzer, and the bootstrap
   * env vars are ignored - that's the whole point of them being a one-time
   * escape hatch instead of a standing backdoor.
   */
  async ensureBootstrapAdmin(): Promise<void> {
    if (!this.authConfig.bootstrap) return;
    const existingCount = await this.repository.count();
    if (existingCount > 0) return;
    const passwordHash = await hashPassword(this.authConfig.bootstrap.password);
    await this.repository.create({
      username: this.authConfig.bootstrap.username,
      name: "Administrator",
      role: "admin",
      passwordHash,
    });
    logger.info("bootstrap admin created", {
      username: this.authConfig.bootstrap.username,
    });
  }

  async authenticate(username: string, password: string) {
    const user = await this.repository.findByUsername(username);
    // Always hash something, even for an unknown user: otherwise the
    // response time would leak which usernames exist.
    const passwordHash = user?.passwordHash ?? (await hashPassword("placeholder"));
    const passwordMatches = await verifyPassword(password, passwordHash);
    if (!user || !user.active || !passwordMatches) {
      throw new InvalidCredentialsError();
    }
    return user;
  }

  async createUser(input: {
    username: string;
    name: string;
    role: UserRole;
    initialPassword: string;
  }) {
    const existing = await this.repository.findByUsername(input.username);
    if (existing) throw new UsernameTakenError();
    const passwordHash = await hashPassword(input.initialPassword);
    return this.repository.create({
      username: input.username,
      name: input.name,
      role: input.role,
      passwordHash,
    });
  }

  async updateRoleAndActive(userId: string, patch: { role?: UserRole; active?: boolean }) {
    return this.repository.updateRoleAndActive(userId, patch);
  }

  /** Admin-triggered reset with a new start password; forces a change on next login. */
  async resetPassword(userId: string, newPassword: string) {
    const passwordHash = await hashPassword(newPassword);
    return this.repository.setPassword(userId, passwordHash, true);
  }

  /** Self-service change by the signed-in user; clears mustChangePassword. */
  async changeOwnPassword(userId: string, currentPassword: string, newPassword: string) {
    const user = await this.repository.findById(userId);
    if (!user) throw new WrongPasswordError();
    const currentMatches = await verifyPassword(currentPassword, user.passwordHash);
    if (!currentMatches) throw new WrongPasswordError();
    const passwordHash = await hashPassword(newPassword);
    return this.repository.setPassword(userId, passwordHash, false);
  }
}