import { Injectable, inject } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { BehaviorSubject, combineLatest, distinctUntilChanged, debounceTime, map, switchMap, filter, shareReplay, from, of } from 'rxjs';
import type { ProviderId } from '../core/providers/provider-registry';
import type { SuggestionItemV1, SearchResponseV1 } from './api.v1';
import { YtAdapter } from './adapters/yt';
import { DmAdapter } from './adapters/dm';
import { TwAdapter } from './adapters/tw';
import { PtAdapter } from './adapters/pt';
import { OdAdapter } from './adapters/od';
import { RuAdapter } from './adapters/ru';
import type { ProviderAdapter, ProviderSearchParams, SearchResult } from './models';
import { VideoItem } from 'src/app/shared/models/video-item.model';

export type SuggestionItem = SuggestionItemV1;
export type SearchResponse = SearchResponseV1;

type CacheKey = string;
interface CacheEntry<T> { t: number; data: SearchResult<T>; }

@Injectable({ providedIn: 'root' })
export class SearchService {
  private http = inject(HttpClient);

  // Subjects for params from UI/URL
  readonly q$ = new BehaviorSubject<string>('');
  readonly providers$ = new BehaviorSubject<ProviderId[] | 'all'>('all');
  readonly page$ = new BehaviorSubject<number>(1);
  readonly pageSize$ = new BehaviorSubject<number>(24);
  readonly sort$ = new BehaviorSubject<'relevance' | 'date' | 'views' | 'duration'>('relevance');

  // In-memory cache 60s per (provider, q, params)
  private cache = new Map<CacheKey, CacheEntry<VideoItem>>();
  private cacheTtlMs = 60_000;

  // Adapters registry
  private adapters: Record<ProviderId, ProviderAdapter<VideoItem>> = {
    yt: new YtAdapter(this.http),
    dm: new DmAdapter(this.http),
    tw: new TwAdapter(this.http),
    pt: new PtAdapter(this.http),
    od: new OdAdapter(this.http),
    ru: new RuAdapter(this.http)
  };

  readonly params$ = combineLatest([this.q$, this.providers$, this.page$, this.pageSize$, this.sort$]).pipe(
    debounceTime(120),
    distinctUntilChanged((a, b) => JSON.stringify(a) === JSON.stringify(b))
  );

  // Public request stream: aggregates groups by provider, runs adapters in parallel with timeout/abort/retry
  readonly request$ = this.params$.pipe(
    filter(([q]) => typeof q === 'string' && q.trim().length >= 2),
    switchMap(([q, prov, page, pageSize, sort]) => from(this.runAdapters({
      q: String(q),
      pageToken: String(page || 1),
      sort: (sort as any) || 'relevance',
      // global filter knobs could be added here: time/length/type in the future
    }, prov)))
  ,
    // Map provider results to the format expected by the UI
    map((byProvider) => {
      const groups = Object.entries(byProvider).reduce((acc, [pid, result]) => {
        acc[pid as ProviderId] = result.items;
        return acc;
      }, {} as Record<ProviderId, VideoItem[]>);

      const providers = Object.keys(byProvider) as ProviderId[];
      const resp: SearchResponse = { q: this.q$.value, providers, groups };
      return resp;
    }),
    shareReplay(1)
  );

  // Orchestrate all active providers in parallel with timeout(8s), retry(1) and abort on param change.
  private async runAdapters(params: ProviderSearchParams, prov: ProviderId[] | 'all'): Promise<Record<ProviderId, SearchResult<VideoItem>>> {
    const active: ProviderId[] = prov === 'all' ? ['yt','dm','tw','pt','od','ru'] : (Array.isArray(prov) ? prov : []);
    const controller = new AbortController();
    const signal = controller.signal;
    const tasks = active.map(async (pid) => {
      const adapter = this.adapters[pid];
      if (!adapter) return [pid, { items: [] } as SearchResult<VideoItem>] as const;
      const key: CacheKey = `${pid}|${params.q}|${params.pageToken}|${params.sort}`;
      const now = Date.now();
      const cached = this.cache.get(key);
      if (cached && (now - cached.t) < this.cacheTtlMs) {
        return [pid, cached.data] as const;
      }
      const perProviderTimeout = 8000;
      const withTimeout = <T>(p: Promise<T>): Promise<T> => new Promise((resolve, reject) => {
        const tid = setTimeout(() => reject(new Error('timeout')), perProviderTimeout);
        p.then(v => { clearTimeout(tid); resolve(v); }).catch(e => { clearTimeout(tid); reject(e); });
      });
      const attempt = async (): Promise<SearchResult<VideoItem>> => withTimeout(adapter.search(params, signal));
      try {
                const res: SearchResult<VideoItem> = await attempt().catch(async (e) => {
          // retry once on network-like errors
          if (e && (e.name === 'AbortError' || String(e.message || '').includes('abort'))) throw e;
          try { return await attempt(); } catch (err) { throw err; }
        });
        this.cache.set(key, { t: Date.now(), data: res });
        return [pid, res] as const;
      } catch {
        // Swallow errors per provider, return empty
        return [pid, { items: [] } as SearchResult<VideoItem>] as const;
      }
    });
    const results = await Promise.all(tasks);
    return Object.fromEntries(results) as Record<ProviderId, SearchResult<VideoItem>>;
  }

  // Convenience setter helpers
  setQuery(q: string) { this.q$.next(q || ''); }
  setProviders(list: ProviderId[] | 'all') { this.providers$.next(list && (Array.isArray(list) ? list : 'all')); }
  setPage(page: number) { this.page$.next(Math.max(1, Math.floor(page || 1))); }
  setPageSize(size: number) { this.pageSize$.next(Math.min(50, Math.max(1, Math.floor(size || 24)))); }
  setSort(sort: 'relevance' | 'date' | 'views' | 'duration') { this.sort$.next(sort || 'relevance'); }
}