import {
  ConflictException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { randomBytes } from 'crypto';
import { Role, SyncOperation } from '@prisma/client';
import * as bcrypt from 'bcryptjs';
import { PrismaClient } from '../prisma/prisma.module';
import { SyncService } from '../sync/sync.service';
import { MailService } from '../mail/mail.service';
import { AuthenticatedUser } from '../auth/authenticated-request';
import { CreateTeamerInviteDto } from './dto/create-teamer-invite.dto';

const BCRYPT_ROUNDS = 10;

type PublicUser = {
  id: string;
  email: string;
  firstName: string;
  lastName: string;
  createdAt: Date;
};

/// Management of local Gemeinde Teamer accounts and their invites. Callable by
/// the Leitungsteam (any Gemeinde) or by a Gemeinde Verantwortliche/r for
/// their own Gemeinde only.
@Injectable()
export class TeamerService {
  constructor(
    private readonly prisma: PrismaClient,
    private readonly sync: SyncService,
    private readonly mail: MailService,
  ) {}

  async createTeamer(
    caller: AuthenticatedUser,
    gemeindeId: string,
    input: { firstName: string; lastName: string; email: string; password: string },
  ): Promise<PublicUser> {
    const gemeinde = await this.assertCanManage(caller, gemeindeId);
    const email = input.email.toLowerCase();
    if (await this.prisma.user.findUnique({ where: { email } })) {
      throw new ConflictException('An account with this email already exists');
    }

    const passwordHash = await bcrypt.hash(input.password, BCRYPT_ROUNDS);
    const user = await this.prisma.user.create({
      data: {
        email,
        firstName: input.firstName,
        lastName: input.lastName,
        passwordHash,
        kcId: gemeinde.kcId,
      },
    });
    const membership = await this.prisma.membership.create({
      data: {
        userId: user.id,
        kcId: gemeinde.kcId,
        gemeindeId,
        role: Role.GEMEINDE_TEAMER,
      },
    });
    await this.sync.capture('User', SyncOperation.CREATE, user.id, user);
    await this.sync.capture('Membership', SyncOperation.CREATE, membership.id, membership);
    return toPublicUser(user);
  }

  async listTeamer(caller: AuthenticatedUser, gemeindeId: string): Promise<PublicUser[]> {
    await this.assertCanManage(caller, gemeindeId);
    const memberships = await this.prisma.membership.findMany({
      where: { gemeindeId, role: Role.GEMEINDE_TEAMER },
      include: { user: true },
      orderBy: { user: { lastName: 'asc' } },
    });
    return memberships.map((m) => toPublicUser(m.user));
  }

  async removeTeamer(
    caller: AuthenticatedUser,
    gemeindeId: string,
    userId: string,
  ): Promise<{ id: string }> {
    await this.assertCanManage(caller, gemeindeId);
    const membership = await this.prisma.membership.findFirst({
      where: { userId, gemeindeId, role: Role.GEMEINDE_TEAMER },
      include: { user: true },
    });
    if (!membership || !membership.user.passwordHash) {
      throw new NotFoundException('No local Teamer account for this Gemeinde');
    }
    await this.prisma.user.delete({ where: { id: userId } });
    await this.sync.capture('User', SyncOperation.DELETE, userId, { id: userId });
    return { id: userId };
  }

  async createInvite(
    caller: AuthenticatedUser,
    gemeindeId: string,
    dto: CreateTeamerInviteDto,
  ) {
    const gemeinde = await this.assertCanManage(caller, gemeindeId);
    const email = dto.email?.toLowerCase() ?? null;
    const maxUses = dto.maxUses ?? (email ? 1 : null);
    const expiresAt = dto.expiresInHours
      ? new Date(Date.now() + dto.expiresInHours * 3600_000)
      : null;

    const invite = await this.prisma.teamerInvite.create({
      data: {
        kcId: gemeinde.kcId,
        gemeindeId,
        token: randomBytes(24).toString('base64url'),
        email,
        maxUses,
        expiresAt,
        createdByUserId: caller.userId,
      },
    });
    await this.sync.capture('TeamerInvite', SyncOperation.CREATE, invite.id, invite);

    // Personal invites go out by email (best-effort); group links are shared
    // by the Verantwortliche/r directly.
    let emailSent = false;
    if (email) {
      const kc = await this.prisma.kc.findUnique({
        where: { id: gemeinde.kcId },
        select: { name: true },
      });
      emailSent = await this.mail.sendTeamerInvite({
        to: email,
        kcName: kc?.name ?? '',
        gemeindeName: gemeinde.name,
        token: invite.token,
        expiresAt: invite.expiresAt,
      });
    }
    return { ...invite, emailSent };
  }

  async listInvites(caller: AuthenticatedUser, gemeindeId: string) {
    await this.assertCanManage(caller, gemeindeId);
    return this.prisma.teamerInvite.findMany({
      where: { gemeindeId },
      orderBy: { createdAt: 'desc' },
    });
  }

  async revokeInvite(caller: AuthenticatedUser, gemeindeId: string, inviteId: string) {
    await this.assertCanManage(caller, gemeindeId);
    const invite = await this.prisma.teamerInvite.findFirst({
      where: { id: inviteId, gemeindeId },
    });
    if (!invite) {
      throw new NotFoundException('Invite not found');
    }
    const updated = await this.prisma.teamerInvite.update({
      where: { id: inviteId },
      data: { revokedAt: new Date() },
    });
    await this.sync.capture('TeamerInvite', SyncOperation.UPDATE, updated.id, updated);
    return updated;
  }

  /// LT may manage every Gemeinde; a Verantwortliche/r only the one they hold
  /// that role for. Returns the Gemeinde (for its kcId) on success.
  private async assertCanManage(caller: AuthenticatedUser, gemeindeId: string) {
    const gemeinde = await this.prisma.gemeinde.findUnique({ where: { id: gemeindeId } });
    if (!gemeinde) {
      throw new NotFoundException('Gemeinde not found');
    }
    const isLeitungsteam = caller.memberships.some(
      (m) => m.role === Role.LEITUNGSTEAM,
    );
    const isVerantwortlich = caller.memberships.some(
      (m) => m.role === Role.GEMEINDE_VERANTWORTLICHER && m.gemeindeId === gemeindeId,
    );
    if (!isLeitungsteam && !isVerantwortlich) {
      throw new ForbiddenException('Not responsible for this Gemeinde');
    }
    return gemeinde;
  }
}

function toPublicUser(user: {
  id: string;
  email: string;
  firstName: string;
  lastName: string;
  createdAt: Date;
}): PublicUser {
  return {
    id: user.id,
    email: user.email,
    firstName: user.firstName,
    lastName: user.lastName,
    createdAt: user.createdAt,
  };
}