import { Injectable, inject, signal } from '@angular/core';
import { HttpClient, HttpParams } from '@angular/common/http';
import { EMPTY, Observable, Subject, from, of, throwError } from 'rxjs';
import {
  catchError,
  concatMap,
  debounceTime,
  expand,
  groupBy,
  map,
  mergeMap,
  reduce,
  retry,
  toArray,
} from 'rxjs/operators';
import { Project, Category, Subcategory, Item, ItemsListResponse } from '../models';
import { ItemName } from '../models/item.model';
import { MockDataService } from './mock-data.service';
import { ToastService } from './toast.service';
import { environment } from '../../environments/environment';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  private http = inject(HttpClient);
  private mockService = inject(MockDataService);
  private toast = inject(ToastService);
  private readonly API_BASE = environment.apiUrl;

  /** Whether a debounced save is in-flight */
  saving = signal(false);

  // Debounced save queue
  private saveQueue$ = new Subject<SaveOperation>();
  
  constructor() {
    // Debounce per unique type+id+field so independent fields don't clobber each other
    this.saveQueue$
      .pipe(
        groupBy(op => `${op.type}:${op.id}:${op.field}`),
        mergeMap(group$ => group$.pipe(debounceTime(500)))
      )
      .subscribe(operation => {
        this.executeSave(operation);
      });
  }

  // ─── Normalizers ──────────────────────────────────────────

  /** Get text from an ItemName entry, handling the backend 'valuue' typo */
  private nameValue(entry: ItemName): string {
    return entry.value || entry.valuue || '';
  }

  /** Normalize an item from the backend — extracts itemDetails, names, photos */
  private normalizeItem(raw: any): Item {
    const item: Item = { ...raw };

    // Extract price/currency/remaining from itemDetails[0] if present
    const details = raw.itemDetails || raw.itemdetails;
    if (details && Array.isArray(details) && details.length > 0) {
      const d = details[0];
      item.itemDetails = details;
      if (item.price == null || item.price === 0) item.price = d.price ?? 0;
      if (!item.currency) item.currency = d.currency || 'RUB';
      if (!item.colour) item.colour = d.colour || d.color || '';
      if (!item.size) item.size = d.size || '';
      if (item.quantity == null && d.remaining != null) item.quantity = d.remaining;
    }

    // Build translations from names[]/descriptions[] if translations map is empty
    if (raw.names && Array.isArray(raw.names)) {
      item.translations = item.translations || {};
      for (const n of raw.names) {
        const lang = n.language?.toLowerCase();
        const val = this.nameValue(n);
        if (lang && val) {
          item.translations[lang] = item.translations[lang] || {};
          item.translations[lang].name = val;
        }
      }
    }
    if (raw.descriptions && Array.isArray(raw.descriptions)) {
      item.translations = item.translations || {};
      for (const d of raw.descriptions) {
        const lang = d.language?.toLowerCase();
        const val = d.value || d.valuue || '';
        if (lang && val) {
          item.translations[lang] = item.translations[lang] || {};
          item.translations[lang].simpleDescription = val;
        }
      }
    }

    // Build imgs[] from photos[] if imgs is empty
    if ((!item.imgs || item.imgs.length === 0) && raw.photos && Array.isArray(raw.photos)) {
      item.imgs = raw.photos.map((p: any) => p.url);
    }

    // Map callbacks → comments if comments is missing
    if ((!item.comments || item.comments.length === 0) && raw.callbacks && Array.isArray(raw.callbacks)) {
      item.comments = raw.callbacks.map((c: any) => ({
        id: c.userID || '',
        text: c.content || '',
        author: c.userID || '',
        stars: c.rating,
        createdAt: c.timestamp,
      }));
    }

    // Defaults
    item.name = item.name || '';
    item.price = item.price ?? 0;
    item.discount = item.discount ?? 0;
    item.quantity = item.quantity ?? 0;
    item.currency = item.currency || 'RUB';
    item.imgs = item.imgs || [];
    item.tags = item.tags || [];
    item.description = item.description || [];
    item.simpleDescription = item.simpleDescription || '';

    return item;
  }

  /** Normalize a category — merges names[] into translations, maps Go struct fields */
  private normalizeCategory(raw: any): Category {
    const cat: Category = { ...raw };

    if (raw.names && Array.isArray(raw.names)) {
      cat.translations = cat.translations || {};
      for (const n of raw.names) {
        const lang = n.language?.toLowerCase();
        const val = this.nameValue(n);
        if (lang && val) {
          cat.translations[lang] = cat.translations[lang] || {};
          cat.translations[lang].name = val;
        }
      }
    }

    // Map Go struct fields
    if (raw.icon && !cat.img) cat.img = raw.icon;
    if (raw.wideicon) cat.wideBanner = raw.wideicon;
    if (raw.ItemsCount != null) cat.itemCount = raw.ItemsCount;
    if (raw.CategoriesCount != null) cat.categoriesCount = raw.CategoriesCount;

    return cat;
  }

  // Projects
  getProjects(): Observable<Project[]> {
    if (environment.useMockData) return this.mockService.getProjects();
    return this.http.get<Project[]>(`${this.API_BASE}/projects`).pipe(
      retry(2),
      catchError(this.handleError)
    );
  }

  // Categories
  getCategories(projectId: string): Observable<Category[]> {
    if (environment.useMockData) return this.mockService.getCategories(projectId);
    return this.http.get<any[]>(`${this.API_BASE}/projects/${projectId}/categories`).pipe(
      retry(2),
      map(cats => cats.map(c => this.normalizeCategory(c))),
      catchError(this.handleError)
    );
  }

  getCategory(categoryId: string): Observable<Category> {
    if (environment.useMockData) return this.mockService.getCategory(categoryId);
    return this.http.get<any>(`${this.API_BASE}/categories/${categoryId}`).pipe(
      retry(2),
      map(c => this.normalizeCategory(c)),
      catchError(this.handleError)
    );
  }

  updateCategory(categoryId: string, data: Partial<Category>): Observable<Category> {
    if (environment.useMockData) return this.mockService.updateCategory(categoryId, data);
    return this.http.patch<Category>(`${this.API_BASE}/categories/${categoryId}`, data).pipe(
      retry(1),
      catchError(this.handleError)
    );
  }

  createCategory(projectId: string, data: Partial<Category>): Observable<Category> {
    if (environment.useMockData) return this.mockService.createCategory(projectId, data);
    return this.http.post<Category>(`${this.API_BASE}/projects/${projectId}/categories`, data).pipe(
      catchError(this.handleError)
    );
  }

  deleteCategory(categoryId: string): Observable<void> {
    if (environment.useMockData) return this.mockService.deleteCategory(categoryId);
    return this.http.delete<void>(`${this.API_BASE}/categories/${categoryId}`).pipe(
      catchError(this.handleError)
    );
  }

  // Subcategories
  getSubcategories(categoryId: string): Observable<Subcategory[]> {
    if (environment.useMockData) {
      return this.mockService.getCategory(categoryId).pipe(
        map(cat => cat.subcategories || [])
      );
    }
    return this.http.get<Subcategory[]>(`${this.API_BASE}/categories/${categoryId}/subcategories`).pipe(
      retry(2),
      catchError(this.handleError)
    );
  }

  getSubcategory(subcategoryId: string): Observable<Subcategory> {
    if (environment.useMockData) return this.mockService.getSubcategory(subcategoryId);
    return this.http.get<Subcategory>(`${this.API_BASE}/subcategories/${subcategoryId}`).pipe(
      retry(2),
      catchError(this.handleError)
    );
  }

  updateSubcategory(subcategoryId: string, data: Partial<Subcategory>): Observable<Subcategory> {
    if (environment.useMockData) return this.mockService.updateSubcategory(subcategoryId, data);
    return this.http.patch<Subcategory>(`${this.API_BASE}/subcategories/${subcategoryId}`, data).pipe(
      retry(1),
      catchError(this.handleError)
    );
  }

  createSubcategory(parentId: string, parentType: 'category' | 'subcategory', data: Partial<Subcategory>): Observable<Subcategory> {
    if (environment.useMockData) return this.mockService.createSubcategory(parentId, data);
    const endpoint = parentType === 'category'
      ? `${this.API_BASE}/categories/${parentId}/subcategories`
      : `${this.API_BASE}/subcategories/${parentId}/subcategories`;
    return this.http.post<Subcategory>(endpoint, data).pipe(
      catchError(this.handleError)
    );
  }

  deleteSubcategory(subcategoryId: string): Observable<void> {
    if (environment.useMockData) return this.mockService.deleteSubcategory(subcategoryId);
    return this.http.delete<void>(`${this.API_BASE}/subcategories/${subcategoryId}`).pipe(
      catchError(this.handleError)
    );
  }

  // Items
  getItems(subcategoryId: string, page = 1, limit = 20, search?: string, filters?: ItemFilters): Observable<ItemsListResponse> {
    if (environment.useMockData) return this.mockService.getItems(subcategoryId, page, limit, search, filters);
    
    let params = new HttpParams()
      .set('page', page.toString())
      .set('limit', limit.toString());
    
    if (search) {
      params = params.set('search', search);
    }
    
    if (filters?.visible !== undefined) {
      params = params.set('visible', filters.visible.toString());
    }
    
    if (filters?.tags?.length) {
      params = params.set('tags', filters.tags.join(','));
    }

    return this.http.get<any>(`${this.API_BASE}/subcategories/${subcategoryId}/items`, { params }).pipe(
      retry(2),
      map(resp => ({
        ...resp,
        items: (resp.items || []).map((i: any) => this.normalizeItem(i))
      })),
      catchError(this.handleError)
    );
  }

  getItem(itemId: string): Observable<Item> {
    if (environment.useMockData) return this.mockService.getItem(itemId);
    return this.http.get<any>(`${this.API_BASE}/items/${itemId}`).pipe(
      retry(2),
      map(raw => this.normalizeItem(raw)),
      catchError(this.handleError)
    );
  }

  updateItem(itemId: string, data: Partial<Item>): Observable<Item> {
    if (environment.useMockData) return this.mockService.updateItem(itemId, data);
    return this.http.patch<Item>(`${this.API_BASE}/items/${itemId}`, data).pipe(
      retry(1),
      catchError(this.handleError)
    );
  }

  createItem(subcategoryId: string, data: Partial<Item>): Observable<Item> {
    if (environment.useMockData) return this.mockService.createItem(subcategoryId, data);
    return this.http.post<Item>(`${this.API_BASE}/subcategories/${subcategoryId}/items`, data).pipe(
      catchError(this.handleError)
    );
  }

  deleteItem(itemId: string): Observable<void> {
    if (environment.useMockData) return this.mockService.deleteItem(itemId);
    return this.http.delete<void>(`${this.API_BASE}/items/${itemId}`).pipe(
      catchError(this.handleError)
    );
  }

  bulkUpdateItems(itemIds: string[], data: Partial<Item>): Observable<void> {
    if (environment.useMockData) return this.mockService.bulkUpdateItems(itemIds, data);
    return this.http.patch<void>(`${this.API_BASE}/items/bulk`, { itemIds, data }).pipe(
      retry(1),
      catchError(this.handleError)
    );
  }

  setProjectVisibility(categories: Category[], visible: boolean): Observable<void> {
    const { categoryIds, subcategoryIds } = this.collectVisibilityTargets(categories);
    const requests = [
      ...categoryIds.map(id => () => this.updateCategory(id, { visible })),
      ...subcategoryIds.map(id => () => this.updateSubcategory(id, { visible })),
      ...subcategoryIds.map(id => () => this.updateSubcategoryItemsVisibility(id, visible)),
    ];

    if (!requests.length) {
      return of(void 0);
    }

    return from(requests).pipe(
      concatMap(request => request()),
      toArray(),
      map(() => void 0)
    );
  }

  // Image upload
  uploadImage(file: File): Observable<{ url: string }> {
    if (environment.useMockData) return this.mockService.uploadImage(file);
    
    const formData = new FormData();
    formData.append('image', file);
    
    return this.http.post<{ url: string }>(`${this.API_BASE}/upload`, formData).pipe(
      retry(1),
      catchError(this.handleError)
    );
  }

  // Debounced auto-save
  queueSave(type: 'category' | 'subcategory' | 'item', id: string, field: string, value: unknown) {
    this.saving.set(true);
    this.saveQueue$.next({ type, id, field, value });
  }

  private executeSave(operation: SaveOperation) {
    const data = { [operation.field]: operation.value };
    
    let request: Observable<any>;
    switch (operation.type) {
      case 'category':
        request = this.updateCategory(operation.id, data);
        break;
      case 'subcategory':
        request = this.updateSubcategory(operation.id, data);
        break;
      case 'item':
        request = this.updateItem(operation.id, data);
        break;
    }

    request.subscribe({
      next: () => {
        this.saving.set(false);
        this.toast.success('Saved');
      },
      error: (err) => {
        this.saving.set(false);
        this.toast.error(err.message || 'Failed to save');
      }
    });
  }

  private updateSubcategoryItemsVisibility(subcategoryId: string, visible: boolean): Observable<void> {
    return this.getAllSubcategoryItemIds(subcategoryId).pipe(
      concatMap(itemIds => itemIds.length ? this.bulkUpdateItems(itemIds, { visible }) : of(void 0))
    );
  }

  private getAllSubcategoryItemIds(subcategoryId: string): Observable<string[]> {
    const pageSize = 100;

    return this.getItems(subcategoryId, 1, pageSize).pipe(
      expand(response =>
        response.hasMore ? this.getItems(subcategoryId, response.page + 1, pageSize) : EMPTY
      ),
      reduce((itemIds, response) => {
        itemIds.push(...response.items.map(item => item.id));
        return itemIds;
      }, [] as string[])
    );
  }

  private collectVisibilityTargets(categories: Category[]) {
    const categoryIds = categories.map(category => category.id);
    const subcategoryIds: string[] = [];

    const visitSubcategories = (subcategories: Subcategory[]) => {
      for (const subcategory of subcategories) {
        subcategoryIds.push(subcategory.id);

        if (subcategory.subcategories?.length) {
          visitSubcategories(subcategory.subcategories);
        }
      }
    };

    for (const category of categories) {
      visitSubcategories(category.subcategories || []);
    }

    return { categoryIds, subcategoryIds };
  }

  private handleError = (error: any): Observable<never> => {
    let errorMessage = 'An unexpected error occurred';
    
    if (error.error instanceof ErrorEvent) {
      // Client-side or network error
      errorMessage = `Network error: ${error.error.message}`;
    } else if (error.status) {
      // Backend returned an unsuccessful response code
      switch (error.status) {
        case 400:
          errorMessage = error.error?.message || 'Invalid request';
          break;
        case 401:
          errorMessage = 'Unauthorized. Please log in again.';
          break;
        case 403:
          errorMessage = 'You do not have permission to perform this action';
          break;
        case 404:
          errorMessage = 'Resource not found';
          break;
        case 409:
          errorMessage = error.error?.message || 'Conflict: Resource already exists or has conflicts';
          break;
        case 422:
          errorMessage = error.error?.message || 'Validation failed';
          break;
        case 500:
          errorMessage = 'Server error. Please try again later.';
          break;
        case 503:
          errorMessage = 'Service unavailable. Please try again later.';
          break;
        default:
          errorMessage = error.error?.message || `Error: ${error.status} - ${error.statusText}`;
      }
    }
    
    console.error('API Error:', {
      message: errorMessage,
      status: error.status,
      error: error.error,
      url: error.url
    });
    
    return throwError(() => ({ message: errorMessage, status: error.status, originalError: error }));
  };
}

interface SaveOperation {
  type: 'category' | 'subcategory' | 'item';
  id: string;
  field: string;
  value: unknown;
}

interface ItemFilters {
  visible?: boolean;
  tags?: string[];
}