// apps/edr-freight-api/src/modules/container-management/containers.service.ts
import { Injectable, NotFoundException, ConflictException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { DataSource, FindOptionsOrder, FindOptionsWhere, ILike, Repository } from 'typeorm';
import { CreateContainerDto } from './dto/create-container.dto';
import { UpdateContainerDto } from './dto/update-container.dto';
import { AssignContainerToWagonDto } from './dto/assign-container-to-wagon.dto';
import { Container } from './entities/container.entity';
import { Wagon } from '../wagons/entities/wagon.entity';
import { ContainerType } from '../rule-engine/entities/container-type.entity';

@Injectable()
export class ContainersService {
  constructor(
    @InjectRepository(Container)
    private readonly containerRepo: Repository<Container>,
    @InjectRepository(Wagon)
    private readonly wagonRepo: Repository<Wagon>,   // ✅ use raw repository
    @InjectRepository(ContainerType)
    private readonly containerTypeRepo: Repository<ContainerType>,
    private readonly dataSource: DataSource,
  ) {}

  async create(dto: CreateContainerDto): Promise<Container> {
    const existing = await this.containerRepo.findOne({
      where: { containerNumber: dto.containerNumber },
    });
    if (existing) {
      throw new ConflictException(`Container number "${dto.containerNumber}" already exists`);
    }

    const containerType = await this.containerTypeRepo.findOne({
      where: { id: dto.containerTypeId, isActive: true },
    });
    if (!containerType) {
      throw new NotFoundException(`Container type ${dto.containerTypeId} not found`);
    }

    if (dto.wagonId) {
      const wagon = await this.wagonRepo.findOne({ where: { id: dto.wagonId } });
      if (!wagon) throw new NotFoundException(`Wagon ${dto.wagonId} not found`);
    }

    const container = this.containerRepo.create(dto);
    if (dto.wagonId === undefined) container.wagonId = null;
    if (dto.position === undefined) container.position = null;
    return this.containerRepo.save(container);
  }

  async findAll(query: Record<string, string | undefined> = {}): Promise<Container[]> {
    const where: FindOptionsWhere<Container>[] | FindOptionsWhere<Container> = [];
    const search = query.search?.trim();
    const status = query.status?.trim();
    const wagonId = query.wagonId?.trim();

    if (search) {
      where.push({
        containerNumber: ILike(`%${search}%`),
        ...(status ? { status } : {}),
        ...(wagonId ? { wagonId } : {}),
      });
    }

    const sortBy = ['containerNumber', 'tareWeight', 'maxGrossWeight', 'status', 'position'].includes(query.sortBy ?? '')
      ? (query.sortBy as keyof Container)
      : 'containerNumber';
    const sortOrder = query.sortOrder?.toUpperCase() === 'DESC' ? 'DESC' : 'ASC';

    return this.containerRepo.find({
      where: search ? where : { ...(status ? { status } : {}), ...(wagonId ? { wagonId } : {}) },
      order: { [sortBy]: sortOrder } as FindOptionsOrder<Container>,
      skip: query.page && query.limit ? (Number(query.page) - 1) * Number(query.limit) : undefined,
      take: query.limit ? Number(query.limit) : undefined,
    });
  }

  async findById(id: string): Promise<Container> {
    const container = await this.containerRepo.findOne({ where: { id } });
    if (!container) throw new NotFoundException(`Container ${id} not found`);
    return container;
  }

  async update(id: string, dto: UpdateContainerDto): Promise<Container> {
    const container = await this.findById(id);
    if (dto.containerNumber && dto.containerNumber !== container.containerNumber) {
      const existing = await this.containerRepo.findOne({
        where: { containerNumber: dto.containerNumber },
      });
      if (existing) {
        throw new ConflictException(`Container number "${dto.containerNumber}" already exists`);
      }
    }
    if (dto.containerTypeId) {
      const containerType = await this.containerTypeRepo.findOne({
        where: { id: dto.containerTypeId, isActive: true },
      });
      if (!containerType) {
        throw new NotFoundException(`Container type ${dto.containerTypeId} not found`);
      }
    }
    if (dto.wagonId) {
      const wagon = await this.wagonRepo.findOne({ where: { id: dto.wagonId } });
      if (!wagon) throw new NotFoundException(`Wagon ${dto.wagonId} not found`);
    }
    Object.assign(container, dto);
    return this.containerRepo.save(container);
  }

  async remove(id: string): Promise<void> {
    const container = await this.findById(id);
    await this.containerRepo.remove(container);
  }

  async assignToWagon(containerId: string, dto: AssignContainerToWagonDto): Promise<Container> {
    const container = await this.findById(containerId);
    if (container.status === 'LOADED') {
      throw new ConflictException('Cannot reassign a loaded container');
    }
    // Reject a container that is already placed on a wagon — it must be
    // unassigned first, otherwise it would silently jump to another wagon.
    if (container.wagonId) {
      throw new ConflictException(
        `Container ${containerId} is already assigned to wagon ${container.wagonId}`,
      );
    }

    const wagon = await this.wagonRepo.findOne({ where: { id: dto.wagonId } });
    if (!wagon) throw new NotFoundException(`Wagon ${dto.wagonId} not found`);

    // The MAX(position)+1 allocation is check-then-act: two concurrent assigns can
    // read the same MAX and collide on the same position. Do the read + save inside
    // one transaction to narrow the race window.
    // TODO: add a unique (wagon_id, position) DB index so the database itself
    // rejects a colliding position even under concurrency.
    return this.dataSource.transaction(async (manager) => {
      const containerRepo = manager.getRepository(Container);

      let position: number | null = dto.position ?? null;
      if (position === null) {
        const maxPos = await containerRepo
          .createQueryBuilder('c')
          .select('MAX(c.position)', 'max')
          .where('c.wagonId = :wagonId', { wagonId: wagon.id })
          .getRawOne<{ max: number | null }>();
        position = (maxPos?.max ?? 0) + 1;
      }

      container.wagonId = wagon.id;
      container.position = position;
      // Placing a container on a wagon does not make it AVAILABLE. The status enum
      // (AVAILABLE, LOADED, IN_TRANSIT, MAINTENANCE, DAMAGED) has no ASSIGNED/ON_WAGON
      // state, so leave the existing status unchanged rather than forcing AVAILABLE.
      return containerRepo.save(container);
    });
  }

  async unassignFromWagon(containerId: string): Promise<Container> {
    const container = await this.findById(containerId);
    if (container.status === 'LOADED') {
      throw new ConflictException('Cannot unassign a loaded container');
    }
    container.wagonId = null;
    container.position = null;
    container.status = 'AVAILABLE';
    return this.containerRepo.save(container);
  }
}