import {
  BadRequestException,
  Injectable,
  NotFoundException,
  UnauthorizedException,
} from '@nestjs/common';
import { MembershipStatus, Role, SyncOperation } from '@prisma/client';
import { randomBytes } from 'crypto';
import { PrismaClient } from '../prisma/prisma.module';
import { SyncService } from '../sync/sync.service';
import { TokenVerificationService } from '../auth/token-verification.service';
import { resolveOrProvisionAuthentikUser } from '../auth/provision-user';
import { AuthenticatedUser } from '../auth/authenticated-request';

/// Self-service onboarding for Gemeinde Verantwortliche, plus the
/// Leitungsteam-initiated shortcut that skips the approval step entirely.
@Injectable()
export class OnboardingService {
  constructor(
    private readonly prisma: PrismaClient,
    private readonly sync: SyncService,
    private readonly tokens: TokenVerificationService,
  ) {}

  /// Public: resolves an invite code to the KC name and its Gemeinden so the
  /// registrant can pick theirs. The code itself is the shared secret.
  async resolveInvite(inviteCode: string) {
    const trimmed = inviteCode.trim();
    const kc =
      (await this.prisma.kc.findFirst({
        where: { inviteCode: { equals: trimmed, mode: 'insensitive' } },
        include: {
          gemeinden: { select: { id: true, name: true }, orderBy: { name: 'asc' } },
        },
      })) ||
      (await this.prisma.kc.findUnique({
        where: { inviteCode: trimmed },
        include: {
          gemeinden: { select: { id: true, name: true }, orderBy: { name: 'asc' } },
        },
      }));
    if (!kc || !kc.isActive) {
      throw new NotFoundException('Unknown or inactive KC invite code');
    }
    return { kcId: kc.id, kcName: kc.name, gemeinden: kc.gemeinden };
  }

  async registerVerantwortliche(token: string | undefined, inviteCode: string, gemeindeId: string) {
    if (!token) {
      throw new UnauthorizedException('Missing Authentik bearer token');
    }
    const { isLeitungsteam, ...claims } = await this.tokens.verifyAuthentikClaims(token);

    const trimmed = inviteCode.trim();
    const kc =
      (await this.prisma.kc.findFirst({
        where: { inviteCode: { equals: trimmed, mode: 'insensitive' } },
      })) ||
      (await this.prisma.kc.findUnique({ where: { inviteCode: trimmed } }));
    if (!kc || !kc.isActive) {
      throw new NotFoundException('Unknown or inactive KC invite code');
    }
    const gemeinde = await this.prisma.gemeinde.findUnique({ where: { id: gemeindeId } });
    if (!gemeinde || gemeinde.kcId !== kc.id) {
      throw new BadRequestException('Gemeinde does not belong to this KC');
    }

    const user = await resolveOrProvisionAuthentikUser(
      this.prisma,
      this.sync,
      claims,
      isLeitungsteam,
    );

    const existing = await this.prisma.membership.findUnique({
      where: {
        userId_kcId_gemeindeId: { userId: user.id, kcId: kc.id, gemeindeId },
      },
    });
    if (existing) {
      return this.summary(existing.id, existing.status, kc.name, gemeinde.name);
    }

    const membership = await this.prisma.membership.create({
      data: {
        userId: user.id,
        kcId: kc.id,
        gemeindeId,
        role: Role.GEMEINDE_VERANTWORTLICHER,
        status: MembershipStatus.PENDING,
      },
    });
    await this.sync.capture('Membership', SyncOperation.CREATE, membership.id, membership);
    return this.summary(membership.id, membership.status, kc.name, gemeinde.name);
  }

  async listRequests(kcId: string) {
    return this.prisma.membership.findMany({
      where: {
        kcId,
        status: MembershipStatus.PENDING,
        role: Role.GEMEINDE_VERANTWORTLICHER,
      },
      include: {
        user: { select: { id: true, email: true, firstName: true, lastName: true } },
        gemeinde: { select: { id: true, name: true } },
      },
      orderBy: { createdAt: 'asc' },
    });
  }

  async approve(membershipId: string) {
    await this.getPendingOrThrow(membershipId);
    const membership = await this.prisma.membership.update({
      where: { id: membershipId },
      data: { status: MembershipStatus.ACTIVE },
    });
    await this.sync.capture('Membership', SyncOperation.UPDATE, membership.id, membership);
    return membership;
  }

  async reject(membershipId: string) {
    await this.getPendingOrThrow(membershipId);
    const membership = await this.prisma.membership.delete({ where: { id: membershipId } });
    await this.sync.capture('Membership', SyncOperation.DELETE, membership.id, { id: membership.id });
    return { id: membership.id };
  }

  private async getPendingOrThrow(membershipId: string) {
    const membership = await this.prisma.membership.findUnique({ where: { id: membershipId } });
    if (!membership) {
      throw new NotFoundException('Request not found');
    }
    if (membership.status !== MembershipStatus.PENDING) {
      throw new BadRequestException('Request is not pending');
    }
    return membership;
  }

  private summary(
    membershipId: string,
    status: MembershipStatus,
    kcName: string,
    gemeindeName: string,
  ) {
    return { membershipId, status, kcName, gemeindeName };
  }

  // --- Leitungsteam-issued Verantwortliche invites ---
  // Skips the PENDING approval step: an LT member vouching for someone
  // directly is enough, unlike self-registration which needs review.

  async createInvite(
    caller: AuthenticatedUser,
    gemeindeId: string,
    dto: { email?: string; maxUses?: number; expiresInHours?: number },
  ) {
    if (!caller.memberships.some((m) => m.role === Role.LEITUNGSTEAM)) {
      throw new UnauthorizedException('Only Leitungsteam can issue this invite');
    }
    const gemeinde = await this.prisma.gemeinde.findUnique({ where: { id: gemeindeId } });
    if (!gemeinde) {
      throw new NotFoundException('Gemeinde not found');
    }
    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.verantwortlicheInvite.create({
      data: {
        kcId: gemeinde.kcId,
        gemeindeId,
        token: randomBytes(24).toString('base64url'),
        email,
        maxUses,
        expiresAt,
        createdByUserId: caller.userId,
      },
    });
    await this.sync.capture('VerantwortlicheInvite', SyncOperation.CREATE, invite.id, invite);
    return invite;
  }

  async listInvites(caller: AuthenticatedUser, gemeindeId: string) {
    if (!caller.memberships.some((m) => m.role === Role.LEITUNGSTEAM)) {
      throw new UnauthorizedException('Only Leitungsteam can view this');
    }
    return this.prisma.verantwortlicheInvite.findMany({
      where: { gemeindeId },
      orderBy: { createdAt: 'desc' },
    });
  }

  async revokeInvite(caller: AuthenticatedUser, gemeindeId: string, inviteId: string) {
    if (!caller.memberships.some((m) => m.role === Role.LEITUNGSTEAM)) {
      throw new UnauthorizedException('Only Leitungsteam can revoke this');
    }
    const invite = await this.prisma.verantwortlicheInvite.findFirst({
      where: { id: inviteId, gemeindeId },
    });
    if (!invite) {
      throw new NotFoundException('Invite not found');
    }
    const updated = await this.prisma.verantwortlicheInvite.update({
      where: { id: inviteId },
      data: { revokedAt: new Date() },
    });
    await this.sync.capture('VerantwortlicheInvite', SyncOperation.UPDATE, updated.id, updated);
    return updated;
  }

  /// Redeems an LT-issued invite: provisions/updates the caller's Authentik
  /// User and grants an immediately-ACTIVE GEMEINDE_VERANTWORTLICHER
  /// membership (no approval step, unlike self-registration).
  async redeemInvite(token: string | undefined, inviteToken: string) {
    if (!token) {
      throw new UnauthorizedException('Missing Authentik bearer token');
    }
    const invite = await this.prisma.verantwortlicheInvite.findUnique({
      where: { token: inviteToken },
    });
    if (!invite || invite.revokedAt) {
      throw new NotFoundException('Unknown or revoked invite');
    }
    if (invite.expiresAt && invite.expiresAt.getTime() < Date.now()) {
      throw new BadRequestException('Invite has expired');
    }
    if (invite.maxUses !== null && invite.usedCount >= invite.maxUses) {
      throw new BadRequestException('Invite has already been used up');
    }

    const { isLeitungsteam, ...claims } = await this.tokens.verifyAuthentikClaims(token);
    if (invite.email && invite.email !== claims.email.toLowerCase()) {
      throw new BadRequestException('This invite is pinned to a different account');
    }

    const user = await resolveOrProvisionAuthentikUser(
      this.prisma,
      this.sync,
      claims,
      isLeitungsteam,
    );

    const existing = await this.prisma.membership.findUnique({
      where: {
        userId_kcId_gemeindeId: {
          userId: user.id,
          kcId: invite.kcId,
          gemeindeId: invite.gemeindeId,
        },
      },
    });
    const membership = existing
      ? await this.prisma.membership.update({
          where: { id: existing.id },
          data: { status: MembershipStatus.ACTIVE, role: Role.GEMEINDE_VERANTWORTLICHER },
        })
      : await this.prisma.membership.create({
          data: {
            userId: user.id,
            kcId: invite.kcId,
            gemeindeId: invite.gemeindeId,
            role: Role.GEMEINDE_VERANTWORTLICHER,
            status: MembershipStatus.ACTIVE,
          },
        });
    await this.sync.capture(
      'Membership',
      existing ? SyncOperation.UPDATE : SyncOperation.CREATE,
      membership.id,
      membership,
    );

    const updatedInvite = await this.prisma.verantwortlicheInvite.update({
      where: { id: invite.id },
      data: { usedCount: { increment: 1 } },
    });
    await this.sync.capture(
      'VerantwortlicheInvite',
      SyncOperation.UPDATE,
      updatedInvite.id,
      updatedInvite,
    );

    return { membershipId: membership.id, status: membership.status };
  }
}