import {
  ForbiddenException,
  HttpException,
  HttpStatus,
  Injectable,
  UnauthorizedException,
} from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { ConfigService } from '@nestjs/config';
import { createHash, randomBytes } from 'node:crypto';
import * as bcrypt from 'bcrypt';
import { PlatformPrismaService } from '../prisma/platform-prisma.service';
import { RedisService } from '../redis/redis.service';
import { TenantConnectionService } from '../tenancy/tenant-connection.service';
import { normalizeSlug } from '../tenancy/tenant-url';
import type { AuthUser, JwtPayload } from './auth.types';
import type { LoginDto } from './dto/login.dto';
import { permissionsFor, ROLE_LABEL } from './roles';

const LOGIN_WINDOW_SECONDS = 15 * 60;
const LOGIN_MAX_ATTEMPTS = 10;

@Injectable()
export class AuthService {
  constructor(
    private readonly platform: PlatformPrismaService,
    private readonly tenants: TenantConnectionService,
    private readonly jwt: JwtService,
    private readonly config: ConfigService,
    private readonly redis: RedisService,
  ) {}

  async login(dto: LoginDto, ip?: string) {
    await this.assertRateLimit(dto.email, ip);

    const slug = dto.tenantSlug?.trim();
    if (!slug || slug.toLowerCase() === 'platform') {
      return this.loginPlatform(dto.email, dto.password, ip);
    }

    return this.loginTenant(normalizeSlug(slug), dto.email, dto.password, ip);
  }

  async refresh(rawToken: string | undefined) {
    if (!rawToken) {
      throw new UnauthorizedException();
    }
    const hashed = hashToken(rawToken);
    const platformToken = await this.platform.platformRefreshToken.findFirst({
      where: { hashed, revokedAt: null, expiresAt: { gt: new Date() } },
      include: { user: true },
    });
    if (platformToken) {
      await this.platform.platformRefreshToken.update({
        where: { id: platformToken.id },
        data: { revokedAt: new Date() },
      });
      return this.issuePlatformSession(platformToken.user.id, platformToken.user.email, platformToken.user.name);
    }

    const tenants = await this.platform.tenant.findMany({ where: { status: 'ACTIVE' } });
    for (const tenant of tenants) {
      const db = this.tenants.getByDatabase(tenant.database);
      const token = await db.refreshToken.findFirst({
        where: { hashed, revokedAt: null, expiresAt: { gt: new Date() } },
        include: { user: true },
      });
      if (!token) {
        continue;
      }
      await db.refreshToken.update({
        where: { id: token.id },
        data: { revokedAt: new Date() },
      });
      return this.issueTenantSession(tenant.id, tenant.slug, token.user.id, token.user.email, token.user.name, token.user.role);
    }

    throw new UnauthorizedException();
  }

  async logout(rawToken: string | undefined, user: AuthUser) {
    if (!rawToken) {
      return;
    }
    const hashed = hashToken(rawToken);
    if (user.kind === 'platform') {
      await this.platform.platformRefreshToken.updateMany({
        where: { hashed, revokedAt: null },
        data: { revokedAt: new Date() },
      });
      return;
    }
    if (!user.tenantId) {
      return;
    }
    const db = await this.tenants.getByTenantId(user.tenantId);
    await db.refreshToken.updateMany({
      where: { hashed, revokedAt: null },
      data: { revokedAt: new Date() },
    });
  }

  profile(user: AuthUser) {
    return {
      id: user.sub,
      name: user.name,
      email: user.email,
      role: user.role,
      roleLabel: ROLE_LABEL[user.role],
      kind: user.kind,
      tenantId: user.tenantId ?? null,
      tenantSlug: user.tenantSlug ?? null,
      permissions: permissionsFor(user.role),
    };
  }

  private async loginPlatform(email: string, password: string, ip?: string) {
    const user = await this.platform.platformUser.findUnique({ where: { email } });
    if (!user || !(await bcrypt.compare(password, user.passwordHash))) {
      throw new UnauthorizedException('Credenciais inválidas.');
    }
    await this.platform.platformUser.update({
      where: { id: user.id },
      data: { lastLoginAt: new Date() },
    });
    await this.platform.platformAuditLog.create({
      data: { userId: user.id, action: 'login', ip, entity: 'PlatformUser', entityId: user.id },
    });
    return this.issuePlatformSession(user.id, user.email, user.name);
  }

  private async loginTenant(slug: string, email: string, password: string, ip?: string) {
    const tenant = await this.platform.tenant.findUnique({ where: { slug } });
    if (!tenant) {
      throw new UnauthorizedException('Credenciais inválidas.');
    }
    if (tenant.status !== 'ACTIVE') {
      throw new ForbiddenException('Empresa suspensa.');
    }
    const db = this.tenants.getByDatabase(tenant.database);
    const user = await db.user.findUnique({ where: { email } });
    if (!user || !(await bcrypt.compare(password, user.passwordHash))) {
      throw new UnauthorizedException('Credenciais inválidas.');
    }
    await db.user.update({
      where: { id: user.id },
      data: { lastLoginAt: new Date() },
    });
    await db.auditLog.create({
      data: { userId: user.id, action: 'login', ip, entity: 'User', entityId: user.id },
    });
    return this.issueTenantSession(tenant.id, tenant.slug, user.id, user.email, user.name, user.role);
  }

  private async issuePlatformSession(id: string, email: string, name: string) {
    const payload: JwtPayload = {
      sub: id,
      email,
      name,
      role: 'PLATFORM_ADMIN',
    };
    const accessToken = await this.jwt.signAsync(payload);
    const refreshToken = rawRefreshToken();
    await this.platform.platformRefreshToken.create({
      data: {
        userId: id,
        hashed: hashToken(refreshToken),
        expiresAt: refreshExpiry(),
      },
    });
    return { accessToken, refreshToken, user: this.profile({ ...payload, kind: 'platform' }) };
  }

  private async issueTenantSession(
    tenantId: string,
    tenantSlug: string,
    id: string,
    email: string,
    name: string,
    role: JwtPayload['role'],
  ) {
    const payload: JwtPayload = {
      sub: id,
      email,
      name,
      role,
      tenantId,
      tenantSlug,
    };
    const accessToken = await this.jwt.signAsync(payload);
    const refreshToken = rawRefreshToken();
    const db = await this.tenants.getByTenantId(tenantId);
    await db.refreshToken.create({
      data: {
        userId: id,
        hashed: hashToken(refreshToken),
        expiresAt: refreshExpiry(),
      },
    });
    return { accessToken, refreshToken, user: this.profile({ ...payload, kind: 'tenant' }) };
  }

  private async assertRateLimit(email: string, ip?: string) {
    const key = `login:${ip ?? 'unknown'}:${email.toLowerCase()}`;
    const count = await this.redis.increment(key, LOGIN_WINDOW_SECONDS);
    if (count !== null && count > LOGIN_MAX_ATTEMPTS) {
      throw new HttpException('Muitas tentativas. Aguarde alguns minutos.', HttpStatus.TOO_MANY_REQUESTS);
    }
  }
}

function rawRefreshToken(): string {
  return randomBytes(48).toString('hex');
}

function hashToken(token: string): string {
  return createHash('sha256').update(token).digest('hex');
}

function refreshExpiry(): Date {
  return new Date(Date.now() + 7 * 24 * 60 * 60 * 1000);
}