import { Injectable, inject } from '@angular/core';
import { HttpClient, HttpParams } from '@angular/common/http';
import { Observable, forkJoin, of } from 'rxjs';
import { switchMap, map } from 'rxjs/operators';
import { environment } from '../../../environments/environment';
import { ApiResponse, PaginatedResponse } from '../models/api.model';
import {
  PurchaseGrn,
  CreatePurchaseGrn,
  UpdatePurchaseGrn,
} from '../models/purchase-grn.model';

@Injectable({ providedIn: 'root' })
export class PurchaseGrnService {
  private http = inject(HttpClient);
  private apiUrl = `${environment.apiUrl}/purchases/grns`;

  private buildParams(filters?: Record<string, any>): HttpParams {
    let params = new HttpParams();
    if (filters) {
      Object.entries(filters).forEach(([key, value]) => {
        if (value != null && value !== '') {
          params = params.set(key, String(value));
        }
      });
    }
    return params;
  }

  list(
    page = 1,
    perPage = 100,
    filters?: Record<string, any>
  ): Observable<PaginatedResponse<PurchaseGrn>> {
    let params = this.buildParams(filters).set('page', page).set('per_page', perPage);
    return this.http.get<PaginatedResponse<PurchaseGrn>>(this.apiUrl, { params });
  }

  /** Fetch ALL pages in parallel and return combined result */
  listAll(): Observable<PaginatedResponse<PurchaseGrn>> {
    return this.list(1, 200).pipe(
      switchMap((firstPage) => {
        const lastPage = firstPage.meta.last_page;
        if (lastPage <= 1) {
          return of(firstPage);
        }
        const requests: Observable<PaginatedResponse<PurchaseGrn>>[] = [];
        for (let p = 2; p <= lastPage; p++) {
          requests.push(this.list(p, 200));
        }
        return forkJoin(requests).pipe(
          map((responses) => {
            const allData = [...firstPage.data, ...responses.flatMap((r) => r.data)];
            return {
              data: allData,
              links: firstPage.links,
              meta: {
                ...firstPage.meta,
                current_page: 1,
                last_page: 1,
                per_page: allData.length,
                to: allData.length,
                total: allData.length,
              },
            } as PaginatedResponse<PurchaseGrn>;
          })
        );
      })
    );
  }

  getById(id: number): Observable<ApiResponse<PurchaseGrn>> {
    return this.http.get<ApiResponse<PurchaseGrn>>(`${this.apiUrl}/${id}`);
  }

  create(data: CreatePurchaseGrn): Observable<ApiResponse<PurchaseGrn>> {
    return this.http.post<ApiResponse<PurchaseGrn>>(this.apiUrl, data);
  }

  update(id: number, data: UpdatePurchaseGrn): Observable<ApiResponse<PurchaseGrn>> {
    return this.http.put<ApiResponse<PurchaseGrn>>(`${this.apiUrl}/${id}`, data);
  }

  delete(id: number): Observable<{ message: string }> {
    return this.http.delete<{ message: string }>(`${this.apiUrl}/${id}`);
  }

  /** GRN uses /approve (not /confirm) — approve auto-receives stock */
  approve(id: number): Observable<ApiResponse<PurchaseGrn>> {
    return this.http.post<ApiResponse<PurchaseGrn>>(`${this.apiUrl}/${id}/approve`, {});
  }

  cancel(id: number): Observable<ApiResponse<PurchaseGrn>> {
    return this.http.post<ApiResponse<PurchaseGrn>>(`${this.apiUrl}/${id}/cancel`, {});
  }
}
