import {
  BadRequestException,
  Body,
  Controller,
  Delete,
  ForbiddenException,
  Get,
  NotFoundException,
  Param,
  Patch,
  Post,
  Res,
  UploadedFile,
  UseGuards,
  UseInterceptors,
} from '@nestjs/common';
import { FileInterceptor } from '@nestjs/platform-express';
import { Role } from '@prisma/client';
import * as fs from 'fs';
import * as path from 'path';
import { Response } from 'express';
import { CurrentUser } from '../auth/decorators/current-user.decorator';
import { Roles } from '../auth/decorators/roles.decorator';
import { RolesGuard } from '../auth/guards/roles.guard';
import { PrismaService } from '../prisma/prisma.service';
import { CreateUserDto } from './dto/create-user.dto';
import { UpdateUserDto } from './dto/update-user.dto';
import { UserService } from './user.service';

/** Map accepted MIME types to file extensions (T-gbh-01). */
const AVATAR_MIME_TO_EXT: Record<string, string> = {
  'image/png': 'png',
  'image/jpeg': 'jpg',
  'image/webp': 'webp',
};

/** Resolve the avatars storage directory relative to the monorepo root.
 *  At runtime __dirname = apps/api/dist/user/ → go up 4 levels. */
function resolveAvatarsDir(): string {
  return path.resolve(__dirname, '..', '..', '..', '..', 'user-files', 'avatars');
}

@Controller('users')
@UseGuards(RolesGuard)
export class UserController {
  constructor(
    private readonly userService: UserService,
    private readonly prisma: PrismaService,
  ) {}

  /**
   * GET /users
   * ADMIN sees own-tenant users only. SUPER_ADMIN sees all users.
   * T-02-10: ADMIN filtered by tenant at controller level.
   */
  @Get()
  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
  async findAll(@CurrentUser() currentUser: any) {
    if (currentUser.role === Role.SUPER_ADMIN) {
      return this.prisma.user.findMany({
        select: {
          id: true,
          username: true,
          email: true,
          displayName: true,
          role: true,
          isActive: true,
          tenantId: true,
          createdAt: true,
          lastLoginAt: true,
        },
        orderBy: { username: 'asc' },
      });
    }

    // ADMIN: filter by own tenant
    return this.prisma.user.findMany({
      where: { tenantId: currentUser.tenantId },
      select: {
        id: true,
        username: true,
        email: true,
        displayName: true,
        role: true,
        isActive: true,
        tenantId: true,
        createdAt: true,
        lastLoginAt: true,
      },
      orderBy: { username: 'asc' },
    });
  }

  /**
   * GET /users/:id
   */
  @Get(':id')
  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
  async findOne(@Param('id') id: string, @CurrentUser() currentUser: any) {
    // 260910-das, Aufgabe 2: UserService.findById() bekommt einen
    // Pflicht-Mandanten (siehe user.service.ts). Nur die Signatur wird hier
    // nachgezogen, damit die Typpruefung sauber bleibt -- die Rollenlogik
    // (insbesondere die uebergreifende SUPER_ADMIN-Sicht ueber
    // findByIdForPlatformAdmin()) wird erst in Aufgabe 3 vollstaendig
    // verdrahtet.
    const user = await this.userService.findById(currentUser.tenantId, id);
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // ADMIN can only view users in own tenant
    if (
      currentUser.role !== Role.SUPER_ADMIN &&
      user.tenantId !== currentUser.tenantId
    ) {
      throw new ForbiddenException('Cannot access users from other tenants');
    }

    const { passwordHash, ...result } = user;
    return result;
  }

  /**
   * POST /users
   * T-02-08: ADMIN can only create users in own tenant; cannot set SUPER_ADMIN role.
   */
  @Post()
  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
  async create(@Body() dto: CreateUserDto, @CurrentUser() currentUser: any) {
    // ADMIN can only create users in own tenant
    const tenantId =
      currentUser.role === Role.SUPER_ADMIN && dto.tenantId
        ? dto.tenantId
        : currentUser.tenantId;

    // T-02-08: ADMIN cannot create SUPER_ADMIN users
    if (currentUser.role !== Role.SUPER_ADMIN && dto.role === Role.SUPER_ADMIN) {
      throw new ForbiddenException('Cannot assign SUPER_ADMIN role');
    }

    const user = await this.userService.create({
      username: dto.username,
      email: dto.email,
      password: dto.password,
      displayName: dto.displayName,
      role: dto.role ?? Role.USER,
      tenantId,
    });

    const { passwordHash, ...result } = user;
    return result;
  }

  /**
   * PATCH /users/:id
   * T-02-08: ADMIN cannot escalate to SUPER_ADMIN or modify other tenants' users.
   */
  @Patch(':id')
  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
  async update(
    @Param('id') id: string,
    @Body() dto: UpdateUserDto,
    @CurrentUser() currentUser: any,
  ) {
    // 260910-das, Aufgabe 2: siehe Kommentar in findOne() oben.
    const user = await this.userService.findById(currentUser.tenantId, id);
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // ADMIN can only update users in own tenant
    if (
      currentUser.role !== Role.SUPER_ADMIN &&
      user.tenantId !== currentUser.tenantId
    ) {
      throw new ForbiddenException('Cannot modify users from other tenants');
    }

    // T-02-08: ADMIN cannot set role to SUPER_ADMIN
    if (currentUser.role !== Role.SUPER_ADMIN && dto.role === Role.SUPER_ADMIN) {
      throw new ForbiddenException('Cannot assign SUPER_ADMIN role');
    }

    const updated = await this.userService.update(currentUser.tenantId, id, {
      username: dto.username,
      email: dto.email,
      password: dto.password,
      displayName: dto.displayName,
      role: dto.role,
      isActive: dto.isActive,
    });

    const { passwordHash, ...result } = updated;
    return result;
  }

  /**
   * DELETE /users/:id
   * ADMIN cannot delete self or users from other tenants.
   */
  @Delete(':id')
  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
  async remove(@Param('id') id: string, @CurrentUser() currentUser: any) {
    // 260910-das, Aufgabe 2: siehe Kommentar in findOne() oben.
    const user = await this.userService.findById(currentUser.tenantId, id);
    if (!user) {
      throw new NotFoundException('User not found');
    }

    // Cannot delete self
    if (user.id === currentUser.sub) {
      throw new ForbiddenException('Cannot delete your own account');
    }

    // ADMIN can only delete users in own tenant
    if (
      currentUser.role !== Role.SUPER_ADMIN &&
      user.tenantId !== currentUser.tenantId
    ) {
      throw new ForbiddenException('Cannot delete users from other tenants');
    }

    await this.userService.delete(currentUser.tenantId, id);
    return { message: 'User deleted' };
  }

  // ─── Self-service avatar endpoints (all authenticated roles) ───────────────
  // No @Roles() → RolesGuard.canActivate() returns true when requiredRoles is
  // empty (see guards/roles.guard.ts). Global JwtAuthGuard still enforces auth.

  /**
   * POST /users/me/avatar
   * Upload or replace the current user's profile picture.
   * T-gbh-01: 2 MB size limit + image-only MIME allowlist.
   * T-gbh-02: userId derived from @CurrentUser() only — never from request body.
   * T-gbh-04: filename = {userId}.{ext} derived from MIME — no path traversal.
   */
  @Post('me/avatar')
  @UseInterceptors(
    FileInterceptor('file', { limits: { fileSize: 2 * 1024 * 1024 } }),
  )
  async uploadAvatar(
    @UploadedFile() file: any,
    @CurrentUser() currentUser: any,
  ) {
    if (!file || !file.buffer) {
      throw new BadRequestException('No file provided');
    }

    const ext = AVATAR_MIME_TO_EXT[file.mimetype as string];
    if (!ext) {
      throw new BadRequestException(
        'Invalid file type. Allowed: image/png, image/jpeg, image/webp',
      );
    }

    const avatarsDir = resolveAvatarsDir();
    fs.mkdirSync(avatarsDir, { recursive: true });

    const filename = `${currentUser.id}.${ext}`;
    const filePath = path.join(avatarsDir, filename);

    // Remove any previous avatar files for this user (different extension)
    for (const existingExt of Object.values(AVATAR_MIME_TO_EXT)) {
      const candidate = path.join(avatarsDir, `${currentUser.id}.${existingExt}`);
      if (candidate !== filePath && fs.existsSync(candidate)) {
        fs.unlinkSync(candidate);
      }
    }

    fs.writeFileSync(filePath, file.buffer as Buffer);

    // Persist relative path (relative to monorepo root)
    const relativePath = path.join('user-files', 'avatars', filename);
    await this.prisma.user.update({
      where: { id: currentUser.id },
      data: { avatarPath: relativePath },
    });

    return { success: true };
  }

  /**
   * DELETE /users/me/avatar
   * Remove the current user's profile picture.
   */
  @Delete('me/avatar')
  async deleteAvatar(@CurrentUser() currentUser: any) {
    const user = await this.prisma.user.findUnique({
      where: { id: currentUser.id },
      select: { avatarPath: true },
    });

    if (user?.avatarPath) {
      const monorepoRoot = path.resolve(__dirname, '..', '..', '..', '..');
      const absolutePath = path.join(monorepoRoot, user.avatarPath);
      if (fs.existsSync(absolutePath)) {
        fs.unlinkSync(absolutePath);
      }
      await this.prisma.user.update({
        where: { id: currentUser.id },
        data: { avatarPath: null },
      });
    }

    return { success: true };
  }

  /**
   * PATCH /users/me/accent-color
   * Set or clear the current user's accent color.
   * T-acc-01: hex color validated server-side.
   */
  @Patch('me/accent-color')
  async updateAccentColor(
    @Body() body: { color: string | null },
    @CurrentUser() currentUser: any,
  ) {
    if (body.color !== null && body.color !== undefined && !/^#[0-9a-fA-F]{6}$/.test(body.color)) {
      throw new BadRequestException('Invalid color format. Use hex (#rrggbb).');
    }

    await this.prisma.user.update({
      where: { id: currentUser.id },
      data: { accentColor: body.color ?? null },
    });

    return { success: true };
  }

  /**
   * GET /users/me/avatar
   * Stream the current user's avatar image.
   * T-gbh-05: Only the authenticated user's own file is served here.
   */
  @Get('me/avatar')
  async getAvatar(
    @CurrentUser() currentUser: any,
    @Res() res: Response,
  ) {
    const user = await this.prisma.user.findUnique({
      where: { id: currentUser.id },
      select: { avatarPath: true },
    });

    if (!user?.avatarPath) {
      throw new NotFoundException('No avatar set');
    }

    // Resolve from monorepo root (same upward-walk pattern as DkvService)
    const monorepoRoot = path.resolve(__dirname, '..', '..', '..', '..');
    const absolutePath = path.join(monorepoRoot, user.avatarPath);

    if (!fs.existsSync(absolutePath)) {
      throw new NotFoundException('Avatar file not found');
    }

    const ext = path.extname(absolutePath).slice(1).toLowerCase();
    const mimeTypes: Record<string, string> = {
      png: 'image/png',
      jpg: 'image/jpeg',
      webp: 'image/webp',
    };
    const contentType = mimeTypes[ext] ?? 'application/octet-stream';

    const buffer = fs.readFileSync(absolutePath);
    res.setHeader('Content-Type', contentType);
    res.setHeader('Cache-Control', 'no-store');
    res.send(buffer);
  }
}