/**
 * MetricGraph (#47) — 실시간 메트릭 꺾은선 그래프
 *
 * react-native-svg가 설치되어 있지 않은 폐쇄망 호환 환경이므로
 * SVG 대신 View + StyleSheet로 꺾은선(세그먼트 회전)을 직접 렌더링한다.
 * 각 데이터 포인트 사이를 회전된 얇은 View(선분)로 연결.
 *
 * 범례: CPU(파랑) / MEM(초록) / DISK(주황)
 * X축: 시간, Y축: 0~100%
 */
import { View, Text, StyleSheet, LayoutChangeEvent } from 'react-native'
import { useState } from 'react'

export interface MetricPoint {
  timestamp: string
  cpu: number
  memory: number
  disk: number
}

interface SeriesDef { key: keyof Omit<MetricPoint, 'timestamp'>; label: string; color: string }

const SERIES: SeriesDef[] = [
  { key: 'cpu',    label: 'CPU', color: '#3b82f6' },
  { key: 'memory', label: 'MEM', color: '#22c55e' },
  { key: 'disk',   label: 'DISK', color: '#f59e0b' },
]

const CHART_H = 160
const PAD_BOTTOM = 22 // X축 라벨 영역

/** 두 점을 잇는 선분(회전 View) 생성 */
function Segment({
  x1, y1, x2, y2, color,
}: { x1: number; y1: number; x2: number; y2: number; color: string }) {
  const dx = x2 - x1
  const dy = y2 - y1
  const length = Math.sqrt(dx * dx + dy * dy)
  const angle = Math.atan2(dy, dx) * (180 / Math.PI)
  return (
    <View
      style={{
        position: 'absolute',
        left: x1,
        top: y1 - 1,
        width: length,
        height: 2,
        backgroundColor: color,
        transform: [{ translateX: 0 }, { rotate: `${angle}deg` }],
        transformOrigin: 'left center',
      }}
    />
  )
}

export default function MetricGraph({
  data,
  title,
}: { data: MetricPoint[]; title?: string }) {
  const [width, setWidth] = useState(0)
  const onLayout = (e: LayoutChangeEvent) => setWidth(e.nativeEvent.layout.width)

  const plotH = CHART_H - PAD_BOTTOM
  const n = data.length

  // y(0~100%) -> 화면 좌표 (0% 하단, 100% 상단)
  const toY = (v: number) => plotH - (Math.max(0, Math.min(100, v)) / 100) * plotH
  const toX = (i: number) => (n <= 1 ? 0 : (i / (n - 1)) * width)

  const xLabels = (() => {
    if (n === 0) return []
    const fmt = (ts: string) => {
      const d = new Date(ts)
      if (isNaN(d.getTime())) return ts
      return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`
    }
    const first = data[0], last = data[n - 1], mid = data[Math.floor(n / 2)]
    return [fmt(first.timestamp), n > 2 ? fmt(mid.timestamp) : '', fmt(last.timestamp)]
  })()

  return (
    <View style={s.wrap}>
      {title && <Text style={s.title}>{title}</Text>}

      {/* 범례 */}
      <View style={s.legend}>
        {SERIES.map(se => (
          <View key={se.key} style={s.legendItem}>
            <View style={[s.legendDot, { backgroundColor: se.color }]} />
            <Text style={s.legendTxt}>{se.label}</Text>
          </View>
        ))}
      </View>

      <View style={s.chartRow}>
        {/* Y축 라벨 */}
        <View style={s.yAxis}>
          {[100, 75, 50, 25, 0].map(v => (
            <Text key={v} style={s.yLabel}>{v}</Text>
          ))}
        </View>

        {/* 차트 영역 */}
        <View style={s.plot} onLayout={onLayout}>
          {/* 가로 격자선 */}
          {[0, 0.25, 0.5, 0.75, 1].map(g => (
            <View key={g} style={[s.grid, { top: g * plotH }]} />
          ))}

          {width > 0 && n >= 1 && SERIES.map(se =>
            data.map((p, i) => {
              if (i === n - 1) return null
              return (
                <Segment
                  key={`${se.key}-${i}`}
                  x1={toX(i)} y1={toY(p[se.key])}
                  x2={toX(i + 1)} y2={toY(data[i + 1][se.key])}
                  color={se.color}
                />
              )
            })
          )}

          {/* 데이터 포인트 점 */}
          {width > 0 && SERIES.map(se =>
            data.map((p, i) => (
              <View
                key={`pt-${se.key}-${i}`}
                style={{
                  position: 'absolute',
                  left: toX(i) - 2,
                  top: toY(p[se.key]) - 2,
                  width: 4, height: 4, borderRadius: 2,
                  backgroundColor: se.color,
                }}
              />
            ))
          )}

          {n === 0 && (
            <View style={s.empty}><Text style={s.emptyTxt}>데이터 없음</Text></View>
          )}
        </View>
      </View>

      {/* X축 라벨 */}
      <View style={s.xAxis}>
        {xLabels.map((l, i) => (
          <Text key={i} style={s.xLabel}>{l}</Text>
        ))}
      </View>
    </View>
  )
}

const s = StyleSheet.create({
  wrap:       { backgroundColor: '#fff', borderRadius: 12, padding: 14 },
  title:      { fontSize: 13, fontWeight: '700', color: '#1e293b', marginBottom: 8 },
  legend:     { flexDirection: 'row', gap: 14, marginBottom: 10 },
  legendItem: { flexDirection: 'row', alignItems: 'center', gap: 5 },
  legendDot:  { width: 10, height: 10, borderRadius: 5 },
  legendTxt:  { fontSize: 11, color: '#64748b', fontWeight: '600' },
  chartRow:   { flexDirection: 'row' },
  yAxis:      { width: 26, height: CHART_H - PAD_BOTTOM, justifyContent: 'space-between', alignItems: 'flex-end', paddingRight: 4 },
  yLabel:     { fontSize: 9, color: '#cbd5e1' },
  plot:       { flex: 1, height: CHART_H - PAD_BOTTOM, position: 'relative', overflow: 'hidden' },
  grid:       { position: 'absolute', left: 0, right: 0, height: 1, backgroundColor: '#f1f5f9' },
  xAxis:      { flexDirection: 'row', justifyContent: 'space-between', marginLeft: 26, marginTop: 4 },
  xLabel:     { fontSize: 9, color: '#94a3b8' },
  empty:      { flex: 1, alignItems: 'center', justifyContent: 'center' },
  emptyTxt:   { color: '#cbd5e1', fontSize: 12 },
})