import React, { useState, useCallback } from 'react'
import { View, Text, ScrollView, StyleSheet, RefreshControl } from 'react-native'
import { useFocusEffect } from 'expo-router'
import { COLORS } from '../../constants/Config'
import client from '../../services/api'

const HOURS  = Array.from({ length: 24 }, (_, i) => i)
const DAYS   = ['월', '화', '수', '목', '금', '토', '일']

export default function SRHeatmapScreen() {
  const [matrix, setMatrix] = useState<number[][]>([])
  const [maxVal, setMaxVal] = useState(1)
  const [loading, setLoading] = useState(false)

  const load = useCallback(async () => {
    setLoading(true)
    try {
      const r = await client.get('/api/mobile2/hourly-pattern')
      const m = r.data?.matrix ?? r.data ?? []
      setMatrix(m)
      setMaxVal(Math.max(1, ...m.flat().filter(Number.isFinite)))
    } catch { setMatrix([]) } finally { setLoading(false) }
  }, [])

  useFocusEffect(useCallback(() => { load() }, [load]))

  const cellColor = (v: number) => {
    const alpha = Math.round((v / maxVal) * 255).toString(16).padStart(2, '0')
    return `${COLORS.accent}${alpha}`
  }

  return (
    <ScrollView style={s.container} refreshControl={<RefreshControl refreshing={loading} onRefresh={load} />}>
      <Text style={s.title}>SR 발생 히트맵 (요일×시간)</Text>

      <ScrollView horizontal showsHorizontalScrollIndicator={false} style={{ paddingLeft: 32 }}>
        <View>
          <View style={s.hourRow}>
            {HOURS.filter(h => h % 3 === 0).map(h => (
              <Text key={h} style={[s.hourLabel, { width: 36 * 3 }]}>{h}시</Text>
            ))}
          </View>
          {matrix.map((row, di) => (
            <View key={di} style={s.dayRow}>
              {row.map((v, hi) => (
                <View key={hi} style={[s.cell, { backgroundColor: cellColor(v) }]}>
                  {v > 0 && <Text style={s.cellVal}>{v}</Text>}
                </View>
              ))}
            </View>
          ))}
        </View>
      </ScrollView>

      <View style={s.legend}>
        {DAYS.slice(0, matrix.length).map((d, i) => <Text key={i} style={s.dayLabel}>{d}</Text>)}
      </View>
      <Text style={s.note}>셀 색이 진할수록 SR 발생량이 많습니다.</Text>
    </ScrollView>
  )
}

const s = StyleSheet.create({
  container: { flex: 1, backgroundColor: COLORS.bg, padding: 12 },
  title:     { fontSize: 16, fontWeight: '800', color: COLORS.text, marginBottom: 12 },
  hourRow:   { flexDirection: 'row', marginBottom: 4 },
  hourLabel: { fontSize: 9, color: COLORS.muted, textAlign: 'center' },
  dayRow:    { flexDirection: 'row', marginBottom: 2 },
  cell:      { width: 34, height: 34, borderRadius: 4, marginRight: 2, alignItems: 'center', justifyContent: 'center' },
  cellVal:   { fontSize: 9, color: '#fff', fontWeight: '700' },
  legend:    { flexDirection: 'row', flexWrap: 'wrap', gap: 8, marginTop: 12 },
  dayLabel:  { fontSize: 12, color: COLORS.muted },
  note:      { fontSize: 11, color: COLORS.muted, marginTop: 8 },
})