/**
 * Business Analytics — composable for chart state, SVG rendering, and domain filtering.
 * SVG chart math extracted from /app/pages/index.vue dashboard charts.
 */
import { useLocalStorageRef } from '~/utils/useLocalStorageRef'
import {
  ANALYTICS_METRICS,
  ANALYTICS_KPI_SUMMARIES,
  type AnalyticsDomainId,
  type AnalyticsChartType,
  type AnalyticsTimePoint,
} from '~/data/mock-analytics'

export interface ChartSvgModel {
  lineD: string
  areaD: string
  points: { x: number; y: number; v: number }[]
  bars: { x: number; y: number; w: number; h: number }[]
  gridYs: number[]
  viewW: number
  viewH: number
  padX: number
  innerW: number
  bottomY: number
}

interface AnalyticsState {
  activeDomain: AnalyticsDomainId
  chartBuilderMetric: string
  chartBuilderType: AnalyticsChartType
  chartBuilderRange: '3m' | '6m' | '12m'
}

function buildDefaults(): AnalyticsState {
  return {
    activeDomain: 'production',
    chartBuilderMetric: 'gwp',
    chartBuilderType: 'area',
    chartBuilderRange: '6m',
  }
}

export function useAnalytics() {
  const state = useLocalStorageRef<AnalyticsState>('policy-ui-analytics-v1', buildDefaults)

  const allMetrics = ANALYTICS_METRICS
  const kpiSummaries = ANALYTICS_KPI_SUMMARIES

  const domainMetrics = computed(() =>
    allMetrics.filter(m => m.domain === state.value.activeDomain)
  )

  const chartBuilderMetricObj = computed(() =>
    allMetrics.find(m => m.id === state.value.chartBuilderMetric) ?? allMetrics[0]!
  )

  const chartBuilderData = computed(() => {
    const data = chartBuilderMetricObj.value.data12m.filter(d => d.m)
    const range = state.value.chartBuilderRange
    if (range === '3m') return data.slice(-3)
    if (range === '6m') return data.slice(-6)
    return data
  })

  // ── SVG chart model builder (extracted from dashboard index.vue) ──
  function buildSvgModel(data: AnalyticsTimePoint[], viewW = 400, viewH = 120): ChartSvgModel {
    const pts = data.map(d => d.v)
    const padX = 8; const padY = 14
    const innerW = viewW - padX * 2; const innerH = viewH - padY * 2
    const maxV = Math.max(...pts, 1); const minV = Math.min(...pts, 0)
    const span = maxV - minV || 1
    const points = pts.map((p, i) => ({
      x: padX + (i / Math.max(1, pts.length - 1)) * innerW,
      y: padY + (1 - (p - minV) / span) * innerH,
      v: p,
    }))
    const bottomY = padY + innerH
    const first = points[0]!; const last = points[points.length - 1]!

    // Line + area paths (smooth Bézier curves)
    let lineD = `M ${first.x},${first.y}`
    let areaD = `M ${first.x},${bottomY} L ${first.x},${first.y}`
    for (let i = 1; i < points.length; i++) {
      const p0 = points[i - 1]!; const p1 = points[i]!
      const cx = (p0.x + p1.x) / 2
      const seg = ` C ${cx},${p0.y} ${cx},${p1.y} ${p1.x},${p1.y}`
      lineD += seg; areaD += seg
    }
    areaD += ` L ${last.x},${bottomY} Z`

    // Bar geometry
    const barW = Math.min(innerW / pts.length * 0.6, 40)
    const bars = pts.map((p, i) => ({
      x: padX + (i / Math.max(1, pts.length - 1)) * innerW - barW / 2,
      y: padY + (1 - (p - minV) / span) * innerH,
      w: barW,
      h: ((p - minV) / span) * innerH,
    }))

    const gridYs = [0, 0.5, 1].map(t => padY + t * innerH)
    return { lineD, areaD, points, bars, gridYs, viewW, viewH, padX, innerW, bottomY }
  }

  // ── Sparkline helpers ──
  function sparklinePath(pts: number[], w = 112, h = 32, pad = 2): string {
    const max = Math.max(...pts); const min = Math.min(...pts); const r = max - min || 1
    const mapped = pts.map((p, i, arr) => ({
      x: pad + (i / Math.max(1, arr.length - 1)) * (w - pad * 2),
      y: pad + (1 - (p - min) / r) * (h - pad * 2),
    }))
    if (mapped.length < 2) return ''
    let d = `M ${mapped[0]!.x},${mapped[0]!.y}`
    for (let i = 0; i < mapped.length - 1; i++) {
      const p0 = mapped[i]!; const p1 = mapped[i + 1]!; const cx = (p0.x + p1.x) / 2
      d += ` C ${cx},${p0.y} ${cx},${p1.y} ${p1.x},${p1.y}`
    }
    return d
  }

  function sparklineArea(pts: number[], w = 112, h = 32, pad = 2): string {
    const path = sparklinePath(pts, w, h, pad)
    if (!path) return ''
    const max = Math.max(...pts); const min = Math.min(...pts); const r = max - min || 1
    const mapped = pts.map((p, i, arr) => ({
      x: pad + (i / Math.max(1, arr.length - 1)) * (w - pad * 2),
      y: pad + (1 - (p - min) / r) * (h - pad * 2),
    }))
    return `${path} L ${mapped[mapped.length - 1]!.x},${h} L ${mapped[0]!.x},${h} Z`
  }

  const chartBuilderSvgModel = computed(() =>
    buildSvgModel(chartBuilderData.value, 400, 180)
  )

  return {
    state,
    allMetrics,
    kpiSummaries,
    domainMetrics,
    chartBuilderMetricObj,
    chartBuilderData,
    chartBuilderSvgModel,
    buildSvgModel,
    sparklinePath,
    sparklineArea,
  }
}