import React, { createContext, useContext, useEffect, useRef, useState } from 'react';

const BackendContext = createContext(null);

export function useBackend() {
  return useContext(BackendContext);
}

export function BackendProvider({ children }) {
  const API_BASE = process.env.REACT_APP_API_BASE || '';
  const [backendOnline, setBackendOnline] = useState(false);
  const [checking, setChecking] = useState(true);
  const esRef = useRef(null);
  const eventTargetRef = useRef(new EventTarget());

  useEffect(() => {
    let mounted = true;
    const check = async () => {
      if (!mounted) return;
      setChecking(true);
      try {
        const resp = await fetch(`${API_BASE}/api/servers/health`);
        if (!mounted) return;
        setBackendOnline(!!(resp && resp.ok));
      } catch (e) {
        if (!mounted) return;
        setBackendOnline(false);
      } finally {
        if (mounted) setChecking(false);
      }
    };
    check();
    const iv = setInterval(check, 5000);
    return () => { mounted = false; clearInterval(iv); };
  }, [API_BASE]);

  // Single shared EventSource forwarded into a DOM EventTarget
  useEffect(() => {
    if (typeof window === 'undefined' || typeof EventSource === 'undefined') return;
    const url = `${API_BASE}/api/events`;
    let es = null;
    try {
      es = new EventSource(url);
      esRef.current = es;
    } catch (err) {
      // silently ignore
      return;
    }

    const forward = (type) => (e) => {
      try {
        const evt = new CustomEvent(type, { detail: e.data ? JSON.parse(e.data) : null });
        eventTargetRef.current.dispatchEvent(evt);
      } catch (err) {
        // ignore parse errors
      }
    };

    es.addEventListener('connected', forward('connected'));
    es.addEventListener('commandToggle', forward('commandToggle'));
    es.addEventListener('twitchUsersUpdate', forward('twitchUsersUpdate'));
    es.addEventListener('liveNotificationsUpdate', forward('liveNotificationsUpdate'));
    es.addEventListener('adminLogAdded', forward('adminLogAdded'));
    es.addEventListener('adminLogDeleted', forward('adminLogDeleted'));
    es.addEventListener('adminLogsCleared', forward('adminLogsCleared'));

    es.onerror = () => {
      // Let consumers react to backendOnline state changes instead of surfacing connection errors
    };

    return () => { try { es && es.close(); } catch (e) {} };
  }, []); // eslint-disable-line react-hooks/exhaustive-deps

  const forceCheck = async () => {
    const API_BASE2 = process.env.REACT_APP_API_BASE || '';
    try {
      setChecking(true);
      const resp = await fetch(`${API_BASE2}/api/servers/health`);
      setBackendOnline(!!(resp && resp.ok));
    } catch (e) {
      setBackendOnline(false);
    } finally {
      setChecking(false);
    }
  };

  const value = {
    backendOnline,
    checking,
    eventTarget: eventTargetRef.current,
    forceCheck,
  };

  return (
    <BackendContext.Provider value={value}>
      {children}
    </BackendContext.Provider>
  );
}

export default BackendContext;