import {
  BadRequestException,
  Injectable,
  NotFoundException,
  ServiceUnavailableException,
} from '@nestjs/common';
import { EquipmentStatus, Prisma } from '@prisma/client';
import type { Equipment } from '@prisma/client';
import { Response } from 'express';
import type { Express } from 'express';
import { decodeUtf8FilenameFromMultipart } from '../../common/multipart-filename';
import { setListHeaders } from '../../common/http';
import { PrismaService } from '../../prisma/prisma.service';
import type { StoredAttachmentMeta } from '../../storage/storage.service';
import { StorageService } from '../../storage/storage.service';
import { CreateEquipmentDto } from './dto/create-equipment.dto';
import { UpdateEquipmentDto } from './dto/update-equipment.dto';
import { isEquipmentAttachmentStored } from './attachment.types';

@Injectable()
export class EquipmentService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly storage: StorageService,
  ) {}

  async findAll(query: Record<string, unknown>, response: Response) {
    const start = Number(query._start ?? 0);
    const end = Number(query._end ?? start + 25);
    const take = Math.max(end - start, 0);
    const sortField = typeof query._sort === 'string' ? query._sort : 'id';
    const sortOrder = query._order === 'DESC' ? 'desc' : 'asc';
    const q = typeof query.q === 'string' ? query.q.trim() : '';
    const rawStatus = query.status;
    const statuses = Array.isArray(rawStatus)
      ? rawStatus.filter((value): value is EquipmentStatus => typeof value === 'string')
      : typeof rawStatus === 'string'
        ? [rawStatus as EquipmentStatus]
        : [];

    const where: Prisma.EquipmentWhereInput = {};

    if (q) {
      where.OR = [
        { name: { contains: q, mode: 'insensitive' } },
        { serialNumber: { contains: q, mode: 'insensitive' } },
      ];
    }

    if (statuses.length === 1) {
      where.status = statuses[0];
    } else if (statuses.length > 1) {
      where.status = { in: statuses };
    }

    const orderByField = sortField === 'id' ? 'id' : sortField;
    const [total, items] = await this.prisma.$transaction([
      this.prisma.equipment.count({ where }),
      this.prisma.equipment.findMany({
        where,
        skip: start,
        take,
        orderBy: { [orderByField]: sortOrder },
      }),
    ]);

    setListHeaders(response, total, start, end);
    return Promise.all(items.map((item) => this.toRecord(item)));
  }

  async findOne(id: string) {
    const item = await this.prisma.equipment.findUnique({ where: { id } });
    if (!item) {
      throw new NotFoundException(`Equipment ${id} not found`);
    }

    return this.toRecord(item);
  }

  async create(dto: CreateEquipmentDto) {
    const created = await this.prisma.equipment.create({
      data: {
        name: dto.name,
        serialNumber: dto.serialNumber,
        dateOfInspection: dto.dateOfInspection ? new Date(dto.dateOfInspection) : undefined,
        commissionedAt: dto.commissionedAt ? new Date(dto.commissionedAt) : undefined,
        status: dto.status,
      },
    });

    return this.toRecord(created);
  }

  async update(id: string, dto: UpdateEquipmentDto) {
    await this.findOne(id);

    const { id: _id, ...payload } = dto as UpdateEquipmentDto & { id?: string };
    const updated = await this.prisma.equipment.update({
      where: { id },
      data: {
        ...payload,
        dateOfInspection: dto.dateOfInspection ? new Date(dto.dateOfInspection) : undefined,
        commissionedAt: dto.commissionedAt ? new Date(dto.commissionedAt) : undefined,
      },
    });

    return this.toRecord(updated);
  }

  async remove(id: string) {
    const item = await this.prisma.equipment.findUnique({ where: { id } });
    if (!item) {
      throw new NotFoundException(`Equipment ${id} not found`);
    }
    await this.deleteStoredAttachmentIfAny(item);
    const deleted = await this.prisma.equipment.delete({ where: { id } });
    return this.toRecord(deleted);
  }

  async uploadAttachment(id: string, file: Express.Multer.File | undefined) {
    if (!file?.buffer?.length) {
      throw new BadRequestException('File is required (multipart field "file").');
    }
    if (!this.storage.isConfigured()) {
      throw new ServiceUnavailableException(
        'Object storage is not configured (set S3_* environment variables).',
      );
    }

    const item = await this.prisma.equipment.findUnique({ where: { id } });
    if (!item) {
      throw new NotFoundException(`Equipment ${id} not found`);
    }

    await this.deleteStoredAttachmentIfAny(item);

    const decodedOriginalName = decodeUtf8FilenameFromMultipart(file.originalname);
    const objectKey = this.storage.buildEquipmentObjectKey(id, decodedOriginalName);
    const meta: StoredAttachmentMeta = {
      objectKey,
      originalFileName: decodedOriginalName,
      contentType: file.mimetype || 'application/octet-stream',
      sizeBytes: file.size,
    };

    await this.storage.putObject(objectKey, file.buffer, meta.contentType);

    const updated = await this.prisma.equipment.update({
      where: { id },
      data: { attachment: meta as unknown as Prisma.InputJsonValue },
    });

    return this.toRecord(updated);
  }

  async removeAttachment(id: string) {
    if (!this.storage.isConfigured()) {
      throw new ServiceUnavailableException(
        'Object storage is not configured (set S3_* environment variables).',
      );
    }

    const item = await this.prisma.equipment.findUnique({ where: { id } });
    if (!item) {
      throw new NotFoundException(`Equipment ${id} not found`);
    }

    await this.deleteStoredAttachmentIfAny(item);

    const updated = await this.prisma.equipment.update({
      where: { id },
      data: { attachment: Prisma.JsonNull },
    });

    return this.toRecord(updated);
  }

  private async deleteStoredAttachmentIfAny(item: Equipment) {
    const raw = item.attachment;
    if (!isEquipmentAttachmentStored(raw)) {
      return;
    }
    if (!this.storage.isConfigured()) {
      return;
    }
    try {
      await this.storage.deleteObject(raw.objectKey);
    } catch {
      // best-effort: DB will still clear / overwrite
    }
  }

  private async toRecord(item: Equipment) {
    return {
      id: item.id,
      name: item.name,
      serialNumber: item.serialNumber,
      dateOfInspection: item.dateOfInspection?.toISOString() ?? null,
      commissionedAt: item.commissionedAt?.toISOString() ?? null,
      status: item.status,
      attachment: await this.serializeAttachment(item.attachment),
    };
  }

  private async serializeAttachment(raw: Prisma.JsonValue | null) {
    if (raw === null || raw === undefined) {
      return null;
    }
    if (!isEquipmentAttachmentStored(raw)) {
      return null;
    }
    let downloadUrl: string | null = null;
    if (this.storage.isConfigured()) {
      try {
        downloadUrl = await this.storage.getDownloadUrl(raw.objectKey);
      } catch {
        downloadUrl = null;
      }
    }
    return {
      objectKey: raw.objectKey,
      originalFileName: decodeUtf8FilenameFromMultipart(raw.originalFileName),
      contentType: raw.contentType,
      sizeBytes: raw.sizeBytes,
      downloadUrl,
    };
  }
}