import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
  UnauthorizedException,
} from '@nestjs/common';
import * as bcrypt from 'bcryptjs';
import * as crypto from 'node:crypto';
import * as fs from 'node:fs/promises';
import * as path from 'node:path';
import { PrismaService } from '../prisma/prisma.service';
import { AuditLogService } from '../audit/audit-log.service';
import { MfaService, MfaEnrollment } from '../auth/mfa/mfa.service';
import { PermissionResolverService } from '../auth/permissions/permission-resolver.service';
import { UsersService } from '../users/users.service';
import {
  ALLOWED_AVATAR_MIME_TYPES,
  MAX_AVATAR_SIZE_BYTES,
  mimeTypeForExtension,
} from './avatar-mime-types';
import { UpdateProfileDto } from './dto/update-profile.dto';

const BCRYPT_SALT_ROUNDS = 12;

export interface ProfileSummary {
  id: string;
  email: string;
  name: string;
}

function avatarStorageRoot(): string {
  return path.join(
    process.env.DOCUMENTS_STORAGE_PATH ?? './uploads',
    'avatars',
  );
}

@Injectable()
export class ProfileService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly auditLog: AuditLogService,
    private readonly mfaService: MfaService,
    private readonly permissionResolver: PermissionResolverService,
    private readonly usersService: UsersService,
  ) {}

  private async requireUser(userId: string) {
    const user = await this.prisma.user.findUnique({ where: { id: userId } });
    if (!user) {
      throw new NotFoundException('User not found');
    }
    return user;
  }

  async updateProfile(
    userId: string,
    dto: UpdateProfileDto,
  ): Promise<ProfileSummary> {
    const before = await this.requireUser(userId);
    if (dto.email && dto.email !== before.email) {
      const currentMatches =
        dto.currentPassword &&
        (await bcrypt.compare(dto.currentPassword, before.passwordHash));
      if (!currentMatches) {
        throw new UnauthorizedException(
          'Aktuelles Passwort erforderlich, um die E-Mail-Adresse zu ändern',
        );
      }
      const existing = await this.prisma.user.findUnique({
        where: { email: dto.email },
      });
      if (existing) {
        throw new ConflictException('Email already in use');
      }
    }
    const user = await this.prisma.user.update({
      where: { id: userId },
      data: { name: dto.name, email: dto.email },
    });
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'UPDATE',
      userId,
      beforeData: { name: before.name, email: before.email },
      afterData: { name: user.name, email: user.email },
    });
    return { id: user.id, email: user.email, name: user.name };
  }

  async changePassword(
    userId: string,
    currentPassword: string,
    newPassword: string,
  ): Promise<void> {
    const user = await this.requireUser(userId);
    const currentMatches = await bcrypt.compare(
      currentPassword,
      user.passwordHash,
    );
    if (!currentMatches) {
      throw new UnauthorizedException('Aktuelles Passwort ist falsch');
    }
    const passwordHash = await bcrypt.hash(newPassword, BCRYPT_SALT_ROUNDS);
    await this.prisma.user.update({
      where: { id: userId },
      data: { passwordHash, passwordChangedAt: new Date() },
    });
    // A changed password should invalidate any session issued before the
    // change, on this device or any other: refresh tokens are revoked
    // outright, and the permission cache is cleared so JwtAuthGuard picks
    // up the new passwordChangedAt within this request cycle instead of
    // waiting out the cache TTL - that's what makes a still-live access
    // token stop working immediately (see PermissionResolverService).
    await this.prisma.refreshToken.updateMany({
      where: { userId, revokedAt: null },
      data: { revokedAt: new Date() },
    });
    this.permissionResolver.invalidateUser(userId);
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'UPDATE',
      userId,
    });
  }

  async deactivateAccount(
    userId: string,
    currentPassword: string,
  ): Promise<void> {
    const user = await this.requireUser(userId);
    const currentMatches = await bcrypt.compare(
      currentPassword,
      user.passwordHash,
    );
    if (!currentMatches) {
      throw new UnauthorizedException('Aktuelles Passwort ist falsch');
    }
    await this.usersService.deactivate(userId, userId);
  }

  async uploadAvatar(userId: string, dataUrl: string): Promise<void> {
    const match = /^data:(image\/(?:jpeg|png|webp));base64,(.+)$/.exec(dataUrl);
    if (!match) {
      throw new BadRequestException('Ungültiges Bildformat');
    }
    const [, mimeType, base64] = match;
    if (!(mimeType in ALLOWED_AVATAR_MIME_TYPES)) {
      throw new BadRequestException('Nicht unterstützter Dateityp');
    }
    const buffer = Buffer.from(base64, 'base64');
    if (buffer.length > MAX_AVATAR_SIZE_BYTES) {
      throw new BadRequestException('Datei zu groß (max. 2 MB)');
    }
    const user = await this.requireUser(userId);
    const extension = ALLOWED_AVATAR_MIME_TYPES[mimeType];
    const directory = avatarStorageRoot();
    await fs.mkdir(directory, { recursive: true });
    const avatarPath = path.join(
      directory,
      `${crypto.randomUUID()}${extension}`,
    );
    await fs.writeFile(avatarPath, buffer);
    if (user.avatarPath) {
      await fs.unlink(user.avatarPath).catch(() => undefined);
    }
    await this.prisma.user.update({
      where: { id: userId },
      data: { avatarPath },
    });
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'UPDATE',
      userId,
    });
  }

  async deleteAvatar(userId: string): Promise<void> {
    const user = await this.requireUser(userId);
    if (!user.avatarPath) {
      return;
    }
    await fs.unlink(user.avatarPath).catch(() => undefined);
    await this.prisma.user.update({
      where: { id: userId },
      data: { avatarPath: null },
    });
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'UPDATE',
      userId,
    });
  }

  async getAvatar(
    userId: string,
  ): Promise<{ buffer: Buffer; mimeType: string }> {
    const user = await this.requireUser(userId);
    if (!user.avatarPath) {
      throw new NotFoundException('No avatar set');
    }
    const buffer = await fs.readFile(user.avatarPath);
    return {
      buffer,
      mimeType: mimeTypeForExtension(path.extname(user.avatarPath)),
    };
  }

  async enrollMfa(userId: string, email: string): Promise<MfaEnrollment> {
    const user = await this.requireUser(userId);
    if (user.mfaEnabled) {
      throw new ConflictException('MFA is already enabled');
    }
    return this.mfaService.startEnrollment(userId, email);
  }

  async confirmMfaEnrollment(
    userId: string,
    email: string,
    setupToken: string,
    code: string,
  ): Promise<void> {
    const { encryptedSecret } = await this.mfaService.confirmEnrollment(
      userId,
      setupToken,
      email,
      code,
    );
    await this.prisma.user.update({
      where: { id: userId },
      data: { mfaEnabled: true, mfaSecret: encryptedSecret },
    });
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'MFA_ENABLED',
      userId,
    });
  }

  async disableMfa(userId: string, currentPassword: string): Promise<void> {
    const user = await this.requireUser(userId);
    const currentMatches = await bcrypt.compare(
      currentPassword,
      user.passwordHash,
    );
    if (!currentMatches) {
      throw new UnauthorizedException('Aktuelles Passwort ist falsch');
    }
    await this.prisma.user.update({
      where: { id: userId },
      data: { mfaEnabled: false, mfaSecret: null },
    });
    await this.auditLog.record({
      entityType: 'User',
      entityId: userId,
      action: 'MFA_DISABLED',
      userId,
    });
  }
}