import React, { useState, useEffect, useRef, useCallback } from 'react'
import {
  View, Text, TextInput, TouchableOpacity, FlatList,
  StyleSheet, KeyboardAvoidingView, Platform, Alert,
} from 'react-native'
import * as SecureStore from 'expo-secure-store'
import { COLORS, WS_BASE } from '../../constants/Config'
import { getSRChat, sendSRChat } from '../../services/api'

export default function SRChatRoomScreen() {
  const [srId, setSrId]     = useState('')
  const [joined, setJoined] = useState(false)
  const [msgs, setMsgs]     = useState<any[]>([])
  const [input, setInput]   = useState('')
  const [sending, setSending] = useState(false)
  const wsRef   = useRef<WebSocket | null>(null)
  const flatRef = useRef<FlatList>(null)

  const join = useCallback(async () => {
    const id = parseInt(srId, 10)
    if (!id) { Alert.alert('오류', 'SR 번호를 입력해주세요.'); return }
    try {
      const r = await getSRChat(id)
      setMsgs(r.data?.items ?? r.data ?? [])
      setJoined(true)
      // WebSocket 연결
      const token = await SecureStore.getItemAsync('grd_token')
      const ws = new WebSocket(`${WS_BASE}/ws/sr-chat/${id}?token=${token ?? ''}`)
      ws.onmessage = e => {
        try {
          const msg = JSON.parse(e.data)
          if (msg.content) setMsgs(prev => [...prev, msg])
        } catch {}
      }
      ws.onerror = () => {}
      wsRef.current = ws
    } catch { Alert.alert('오류', 'SR 채팅방을 열 수 없습니다.') }
  }, [srId])

  useEffect(() => () => { wsRef.current?.close() }, [])

  const send = async () => {
    if (!input.trim() || sending) return
    setSending(true)
    try {
      await sendSRChat(parseInt(srId, 10), input.trim())
      setMsgs(prev => [...prev, { id: Date.now(), content: input.trim(), sender: 'me', created_at: new Date().toISOString(), msg_type: 'text' }])
      setInput('')
      setTimeout(() => flatRef.current?.scrollToEnd(), 100)
    } catch {} finally { setSending(false) }
  }

  if (!joined) {
    return (
      <View style={s.joinContainer}>
        <Text style={s.joinTitle}>SR 채팅방</Text>
        <Text style={s.joinDesc}>SR 번호를 입력하면 해당 SR의 채팅방에 연결됩니다.</Text>
        <TextInput
          style={s.joinInput}
          value={srId}
          onChangeText={setSrId}
          placeholder="SR 번호 입력 (예: 42)"
          keyboardType="numeric"
          onSubmitEditing={join}
        />
        <TouchableOpacity style={s.joinBtn} onPress={join}>
          <Text style={s.joinBtnText}>채팅방 참여</Text>
        </TouchableOpacity>
      </View>
    )
  }

  return (
    <KeyboardAvoidingView style={{ flex: 1 }} behavior={Platform.OS === 'ios' ? 'padding' : undefined}>
      <View style={s.container}>
        <View style={s.header}>
          <Text style={s.headerTitle}>SR #{srId} 채팅</Text>
          <TouchableOpacity onPress={() => { setJoined(false); wsRef.current?.close() }}>
            <Text style={s.leave}>나가기</Text>
          </TouchableOpacity>
        </View>

        <FlatList
          ref={flatRef}
          data={msgs}
          keyExtractor={(_, i) => String(i)}
          contentContainerStyle={{ padding: 12 }}
          renderItem={({ item }) => {
            const isMe = item.sender === 'me' || item.sender_name === 'me'
            return (
              <View style={[s.msgWrap, isMe && s.msgWrapRight]}>
                {!isMe && <Text style={s.sender}>{item.sender_name ?? item.sender}</Text>}
                <View style={[s.bubble, isMe && s.bubbleRight]}>
                  <Text style={[s.msgText, isMe && s.msgTextRight]}>{item.content}</Text>
                </View>
                <Text style={s.msgTime}>{item.created_at?.slice(11, 16)}</Text>
              </View>
            )
          }}
        />

        <View style={s.inputRow}>
          <TextInput
            style={s.textInput}
            value={input}
            onChangeText={setInput}
            placeholder="메시지 입력..."
            multiline
          />
          <TouchableOpacity style={s.sendBtn} onPress={send} disabled={sending}>
            <Text style={s.sendBtnText}>전송</Text>
          </TouchableOpacity>
        </View>
      </View>
    </KeyboardAvoidingView>
  )
}

const s = StyleSheet.create({
  joinContainer: { flex: 1, backgroundColor: COLORS.bg, padding: 24, justifyContent: 'center' },
  joinTitle:     { fontSize: 22, fontWeight: '800', color: COLORS.text, marginBottom: 8 },
  joinDesc:      { fontSize: 14, color: COLORS.muted, marginBottom: 24, lineHeight: 22 },
  joinInput:     { backgroundColor: '#fff', borderRadius: 10, borderWidth: 1, borderColor: COLORS.border, padding: 14, fontSize: 15, marginBottom: 12 },
  joinBtn:       { backgroundColor: COLORS.accent, borderRadius: 10, padding: 14, alignItems: 'center' },
  joinBtnText:   { color: '#fff', fontWeight: '800', fontSize: 15 },
  container:     { flex: 1, backgroundColor: COLORS.bg },
  header:        { flexDirection: 'row', justifyContent: 'space-between', alignItems: 'center', backgroundColor: COLORS.gnbBg, padding: 14 },
  headerTitle:   { fontSize: 15, fontWeight: '700', color: '#fff' },
  leave:         { color: COLORS.accent, fontSize: 14 },
  msgWrap:       { marginBottom: 10, maxWidth: '80%' },
  msgWrapRight:  { alignSelf: 'flex-end' },
  sender:        { fontSize: 11, color: COLORS.muted, marginBottom: 2 },
  bubble:        { backgroundColor: '#fff', borderRadius: 12, padding: 10, elevation: 1 },
  bubbleRight:   { backgroundColor: COLORS.accent },
  msgText:       { fontSize: 14, color: COLORS.text },
  msgTextRight:  { color: '#fff' },
  msgTime:       { fontSize: 10, color: COLORS.muted, marginTop: 2 },
  inputRow:      { flexDirection: 'row', padding: 10, backgroundColor: '#fff', borderTopWidth: 1, borderTopColor: COLORS.border, gap: 8 },
  textInput:     { flex: 1, backgroundColor: COLORS.bg, borderRadius: 20, paddingHorizontal: 14, paddingVertical: 8, fontSize: 14, maxHeight: 100 },
  sendBtn:       { backgroundColor: COLORS.accent, borderRadius: 20, paddingHorizontal: 16, justifyContent: 'center' },
  sendBtnText:   { color: '#fff', fontWeight: '700' },
})