import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import type { Freight } from '@edr/types';

import { FilesService } from '../files/files.service';
import type { FileRecord } from '../files/entities/file.entity';

/**
 * `files.resource` of the GL Ethiopia ↔ GL Djibouti document exchange. The
 * thread is keyed by the entity the two desks are working on — a booking id on
 * the per-booking clearance pages, a contract id on the pre-booking ones — so
 * both desks opening the same record see the same documents.
 */
export const GL_EXCHANGE_RESOURCE = 'gl_exchange';

export type GlExchangeSide = 'ET' | 'DJ';

export interface GlExchangeActor {
  userId: string;
  name?: string | null;
  side: GlExchangeSide;
}

export interface GlExchangeUploadInput {
  title: string;
  visibleToCustomer: boolean;
}

/**
 * Free-form document exchange between the two Global Logistics desks. Anything
 * either side needs the other to have (scans, correspondence, corrected forms)
 * lands here under a title they choose, instead of a fixed clearance slot.
 *
 * Rules, all enforced here rather than in the UI:
 *  - both desks read every document in a thread, whoever uploaded it;
 *  - only the uploader may retitle, replace or remove one;
 *  - the customer sees only what its uploader marked visible.
 */
@Injectable()
export class GlExchangeService {
  constructor(private readonly filesService: FilesService) {}

  /** Every document on one thread, newest first, from a GL desk's view. */
  async list(
    entityId: string,
    viewerId: string,
  ): Promise<Freight.GlExchangeDocument[]> {
    const records = await this.filesService.findByResource(
      entityId,
      GL_EXCHANGE_RESOURCE,
    );
    return this.sort(records.map((r) => this.toDto(r, viewerId)));
  }

  /**
   * The customer-facing slice across several threads (a booking and the
   * contract it belongs to). Never exposes internal documents, and never marks
   * anything editable — the customer is not a GL desk.
   */
  async listVisibleToCustomer(
    entityIds: string[],
  ): Promise<Freight.GlExchangeDocument[]> {
    const ids = [...new Set(entityIds.filter(Boolean))];
    if (ids.length === 0) return [];
    const grouped = await this.filesService.findByResourceIdsGrouped(
      ids,
      GL_EXCHANGE_RESOURCE,
    );
    const visible = [...grouped.values()]
      .flat()
      .filter((r) => r.visibleToCustomer);
    return this.sort(visible.map((r) => this.toDto(r, null)));
  }

  async upload(
    entityId: string,
    file: Express.Multer.File | undefined,
    input: GlExchangeUploadInput,
    actor: GlExchangeActor,
  ): Promise<Freight.GlExchangeDocument> {
    const title = input.title?.trim();
    if (!title) throw new BadRequestException('A document title is required.');
    if (!file) throw new BadRequestException('A file is required.');

    const record = await this.filesService.upload({
      resourceId: entityId,
      resource: GL_EXCHANGE_RESOURCE,
      // No fixed slot exists for these — `code` carries the uploading desk, so
      // a document's origin survives even if the uploader leaves the org.
      code: actor.side,
      file,
      title,
      visibleToCustomer: input.visibleToCustomer,
      uploadedByUserId: actor.userId,
      uploadedByName: actor.name ?? null,
    });
    return this.toDto(record, actor.userId);
  }

  /**
   * Retitle, re-share or replace a document. Uploader only — the other desk
   * reads it but never edits it. A replacement file supersedes the old record
   * (soft-deleted, bytes kept) and carries its metadata forward.
   */
  async update(
    documentId: string,
    patch: { title?: string; visibleToCustomer?: boolean },
    file: Express.Multer.File | undefined,
    actorId: string,
  ): Promise<Freight.GlExchangeDocument> {
    const record = await this.assertUploader(documentId, actorId);
    const title = patch.title?.trim();
    if (patch.title != null && !title) {
      throw new BadRequestException('A document title is required.');
    }

    if (file) {
      const replacement = await this.filesService.upload({
        resourceId: record.resourceId,
        resource: GL_EXCHANGE_RESOURCE,
        code: record.code,
        file,
        title: title ?? record.title,
        visibleToCustomer: patch.visibleToCustomer ?? record.visibleToCustomer,
        uploadedByUserId: record.uploadedByUserId,
        uploadedByName: record.uploadedByName,
      });
      await this.filesService.remove(record.id);
      return this.toDto(replacement, actorId);
    }

    const updated = await this.filesService.updateMeta(record.id, {
      ...(title ? { title } : {}),
      ...(patch.visibleToCustomer != null
        ? { visibleToCustomer: patch.visibleToCustomer }
        : {}),
    });
    return this.toDto(updated, actorId);
  }

  /** Uploader-only removal (soft delete — the stored bytes are kept). */
  async remove(documentId: string, actorId: string): Promise<void> {
    const record = await this.assertUploader(documentId, actorId);
    await this.filesService.remove(record.id);
  }

  private async assertUploader(
    documentId: string,
    actorId: string,
  ): Promise<FileRecord> {
    const record = await this.filesService.findById(documentId);
    if (record.resource !== GL_EXCHANGE_RESOURCE) {
      throw new NotFoundException(`Exchange document ${documentId} not found`);
    }
    if (record.uploadedByUserId !== actorId) {
      throw new ForbiddenException(
        'Only the person who uploaded this document can change it.',
      );
    }
    return record;
  }

  private sort(
    docs: Freight.GlExchangeDocument[],
  ): Freight.GlExchangeDocument[] {
    return docs.sort((a, b) => b.uploadedAt.localeCompare(a.uploadedAt));
  }

  private toDto(
    record: FileRecord,
    viewerId: string | null,
  ): Freight.GlExchangeDocument {
    return {
      id: record.id,
      entityId: record.resourceId,
      // Pre-title rows (none in practice) fall back to the filename so a list
      // never renders a blank row.
      title: record.title ?? record.name,
      side: record.code === 'DJ' ? 'DJ' : 'ET',
      visibleToCustomer: record.visibleToCustomer,
      uploadedById: record.uploadedByUserId,
      uploadedByName: record.uploadedByName,
      uploadedAt: record.createdAt.toISOString(),
      file: {
        id: record.id,
        name: record.name,
        url: record.url,
        size: record.size,
        mimeType: record.mimeType,
      },
      canEdit: viewerId != null && record.uploadedByUserId === viewerId,
    };
  }
}