/**
 * EPG Fetching Service
 * Fetches EPG data from multiple sources with fallback
 */

import { fetchAndParseXMLTV } from '../parsers/xmltv';
import type { EPGSource, EPGChannel, EPGProgram } from '../types';

/**
 * Default EPG Sources
 * iptv-org provides comprehensive international EPG with 30K+ channels
 * https://github.com/iptv-org/epg
 */
export const DEFAULT_EPG_SOURCES: EPGSource[] = [
  {
    id: 'iptv-org-global',
    name: 'IPTV-Org Global EPG',
    url: 'https://iptv-org.github.io/epg/guides/all.xml.gz',
    enabled: true,
    priority: 100, // Low priority - fallback after provider EPG
  },
];

/**
 * Fetch EPG data from a single source
 */
export async function fetchEPGFromSource(
  source: EPGSource,
  proxyUrl?: string
): Promise<{ channels: EPGChannel[]; programs: EPGProgram[] }> {
  try {
    const result = await fetchAndParseXMLTV(
      source.url,
      source.timezone,
      proxyUrl
    );
    
    // Update source with success info
    source.lastFetch = new Date().toISOString();
    delete source.lastError;
    
    return result;
  } catch (error) {
    // Update source with error info
    source.lastError = error instanceof Error ? error.message : String(error);
    throw new Error(`Failed to fetch EPG from ${source.name}: ${error}`);
  }
}

/**
 * Fetch EPG from multiple sources with fallback
 * Tries sources in priority order until one succeeds
 */
export async function fetchEPG(
  sources: EPGSource[] = DEFAULT_EPG_SOURCES,
  proxyUrl?: string
): Promise<{ channels: EPGChannel[]; programs: EPGProgram[]; source: EPGSource }> {
  const sortedSources = sources
    .filter((s) => s.enabled)
    .sort((a, b) => a.priority - b.priority);
  
  if (sortedSources.length === 0) {
    throw new Error('No enabled EPG sources available');
  }
  
  const errors: string[] = [];
  
  for (const source of sortedSources) {
    try {
      const result = await fetchEPGFromSource(source, proxyUrl);
      return {
        ...result,
        source,
      };
    } catch (error) {
      const errorMsg = error instanceof Error ? error.message : String(error);
      errors.push(`${source.name}: ${errorMsg}`);
      console.warn(`EPG source ${source.name} failed, trying next...`, error);
      continue;
    }
  }
  
  throw new Error(`All EPG sources failed:\n${errors.join('\n')}`);
}

/**
 * Fetch EPG for specific channels only (optimization)
 * This would require EPG sources that support filtering by channel IDs
 * For now, we fetch all and filter client-side
 */
export async function fetchEPGForChannels(
  _channelIds: string[],
  sources: EPGSource[] = DEFAULT_EPG_SOURCES,
  proxyUrl?: string
): Promise<{ channels: EPGChannel[]; programs: EPGProgram[]; source: EPGSource }> {
  // For now, fetch all EPG data
  // In the future, we could optimize by filtering at source level if supported
  return fetchEPG(sources, proxyUrl);
}