import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { PrismaService } from '../../../prisma/prisma.service';
import {
  appointmentWithinWorkingHours,
  blocksForDay,
  localDayOfWeekMondayZero,
  validateWorkingHoursBlocks,
  type WorkingHoursBlockInput,
} from '../../common/working-hours';
import { UpsertWorkingHoursDto } from './dto/upsert-working-hours.dto';

@Injectable()
export class StaffWorkingHoursService {
  constructor(private readonly prisma: PrismaService) {}

  async getWorkingHours(actorUserId: string, organizationId: string, membershipId: string) {
    await this.assertCanViewStaff(actorUserId, organizationId);

    const membership = await this.findMembership(membershipId, organizationId);
    const schedule = await this.prisma.staffWorkingHoursSchedule.findUnique({
      where: { membershipId: membership.id },
      include: {
        blocks: { orderBy: [{ dayOfWeek: 'asc' }, { sortOrder: 'asc' }, { startMinute: 'asc' }] },
      },
    });

    if (!schedule) {
      return {
        success: true,
        data: {
          autoRepeatWeekly: true,
          blocks: [],
          hasWorkingHours: false,
        },
      };
    }

    return {
      success: true,
      data: {
        autoRepeatWeekly: schedule.autoRepeatWeekly,
        blocks: schedule.blocks.map((b) => ({
          dayOfWeek: b.dayOfWeek,
          startMinute: b.startMinute,
          endMinute: b.endMinute,
          sortOrder: b.sortOrder,
        })),
        hasWorkingHours: schedule.blocks.length > 0,
      },
    };
  }

  async upsertWorkingHours(
    actorUserId: string,
    organizationId: string,
    membershipId: string,
    dto: UpsertWorkingHoursDto,
  ) {
    await this.assertCanEditStaff(actorUserId, organizationId);

    const membership = await this.findMembership(membershipId, organizationId);
    const validationError = validateWorkingHoursBlocks(dto.blocks);
    if (validationError) {
      throw new BadRequestException(validationError);
    }

    const normalizedBlocks = this.normalizeBlocks(dto.blocks);
    await this.assertNoConflictingAppointments(
      organizationId,
      membership.userId,
      normalizedBlocks,
    );

    await this.prisma.$transaction(async (tx) => {
      const schedule = await tx.staffWorkingHoursSchedule.upsert({
        where: { membershipId: membership.id },
        create: {
          membershipId: membership.id,
          autoRepeatWeekly: dto.autoRepeatWeekly,
        },
        update: {
          autoRepeatWeekly: dto.autoRepeatWeekly,
        },
      });

      await tx.staffWorkingHoursBlock.deleteMany({ where: { scheduleId: schedule.id } });

      if (normalizedBlocks.length > 0) {
        await tx.staffWorkingHoursBlock.createMany({
          data: normalizedBlocks.map((block, index) => ({
            scheduleId: schedule.id,
            dayOfWeek: block.dayOfWeek,
            startMinute: block.startMinute,
            endMinute: block.endMinute,
            sortOrder: block.sortOrder ?? index,
          })),
        });
      }
    });

    return {
      success: true,
      message: 'Working hours saved',
    };
  }

  async loadScheduleBlocksByMembershipIds(membershipIds: string[]) {
    if (membershipIds.length === 0) {
      return new Map<string, WorkingHoursBlockInput[]>();
    }

    const schedules = await this.prisma.staffWorkingHoursSchedule.findMany({
      where: { membershipId: { in: membershipIds } },
      include: {
        blocks: { orderBy: [{ dayOfWeek: 'asc' }, { sortOrder: 'asc' }, { startMinute: 'asc' }] },
      },
    });

    const map = new Map<string, WorkingHoursBlockInput[]>();
    for (const schedule of schedules) {
      map.set(
        schedule.membershipId,
        schedule.blocks.map((b) => ({
          dayOfWeek: b.dayOfWeek,
          startMinute: b.startMinute,
          endMinute: b.endMinute,
          sortOrder: b.sortOrder,
        })),
      );
    }
    return map;
  }

  dayBlocksFromMembershipBlocks(blocks: WorkingHoursBlockInput[], dayOfWeekMondayZero: number) {
    return blocksForDay(blocks, dayOfWeekMondayZero);
  }

  private normalizeBlocks(blocks: UpsertWorkingHoursDto['blocks']): WorkingHoursBlockInput[] {
    return blocks.map((block, index) => ({
      dayOfWeek: block.dayOfWeek,
      startMinute: block.startMinute,
      endMinute: block.endMinute,
      sortOrder: block.sortOrder ?? index,
    }));
  }

  private async assertNoConflictingAppointments(
    organizationId: string,
    providerUserId: string,
    blocks: WorkingHoursBlockInput[],
  ) {
    const now = new Date();
    const appointments = await this.prisma.appointment.findMany({
      where: {
        organizationId,
        providerUserId,
        endAt: { gt: now },
      },
      include: {
        patient: { select: { firstName: true, lastName: true } },
      },
      orderBy: { startAt: 'asc' },
    });

    const conflicts = appointments.filter((appointment) => {
      const startAt = new Date(appointment.startAt);
      const endAt = new Date(appointment.endAt);
      const dayOfWeek = localDayOfWeekMondayZero(startAt.getDay());
      const dayBlocks = blocksForDay(blocks, dayOfWeek);
      if (dayBlocks.length === 0) {
        return true;
      }
      return !appointmentWithinWorkingHours(startAt, endAt, dayBlocks);
    });

    if (conflicts.length === 0) {
      return;
    }

    const examples = conflicts.slice(0, 3).map((appointment) => {
      const startAt = new Date(appointment.startAt);
      const patientName = `${appointment.patient.firstName} ${appointment.patient.lastName}`;
      const when = startAt.toLocaleString(undefined, {
        weekday: 'short',
        month: 'short',
        day: 'numeric',
        hour: 'numeric',
        minute: '2-digit',
      });
      return `${patientName} (${when})`;
    });

    const extra =
      conflicts.length > examples.length
        ? ` and ${conflicts.length - examples.length} more`
        : '';

    throw new BadRequestException(
      `Cannot save working hours: ${conflicts.length} upcoming appointment${conflicts.length === 1 ? '' : 's'} fall outside the new schedule (${examples.join(', ')}${extra}). Reschedule or remove those appointments first.`,
    );
  }

  private async findMembership(membershipId: string, organizationId: string) {
    const membership = await this.prisma.membership.findFirst({
      where: { id: membershipId, organizationId },
      select: { id: true, isOwner: true, userId: true },
    });
    if (!membership) {
      throw new NotFoundException('Member not found');
    }
    if (membership.isOwner) {
      throw new BadRequestException('Working hours cannot be set for the organization owner');
    }
    return membership;
  }

  private async assertCanViewStaff(userId: string, organizationId: string) {
    const actor = await this.getActorMembership(userId, organizationId);
    if (!actor || !this.canViewStaff(actor)) {
      throw new ForbiddenException('You do not have access to staff management');
    }
  }

  private async assertCanEditStaff(userId: string, organizationId: string) {
    const actor = await this.getActorMembership(userId, organizationId);
    if (!actor || !this.canEditStaff(actor)) {
      throw new ForbiddenException('You cannot manage staff working hours');
    }
  }

  private async getActorMembership(userId: string, organizationId: string) {
    return this.prisma.membership.findFirst({
      where: { userId, organizationId },
      include: {
        permissions: { include: { permission: true } },
        organization: { select: { planId: true } },
      },
    });
  }

  private canViewStaff(m: {
    isOwner: boolean;
    permissions: { permission: { name: string } }[];
  }): boolean {
    if (m.isOwner) return true;
    return m.permissions.some(
      (p) => p.permission.name === 'TAB_STAFF_READ' || p.permission.name === 'TAB_STAFF_EDIT',
    );
  }

  private canEditStaff(m: {
    isOwner: boolean;
    organization?: { planId: string | null };
    permissions: { permission: { name: string } }[];
  }): boolean {
    if (m.isOwner) return Boolean(m.organization?.planId);
    return m.permissions.some((p) => p.permission.name === 'TAB_STAFF_EDIT');
  }
}