import { useEffect, useMemo, useRef } from "react";
import * as echarts from "echarts";
import {
  buildHearingSplineSeries,
  resolveHearingFreqLabels,
} from "@/lib/hearingCurve";

const LEFT_COLOR = "rgb(0, 255, 246)";
const RIGHT_COLOR = "#FF5A36";

type HearingCompensationChartProps = {
  left: number[];
  right: number[];
  leftLabel?: string;
  rightLabel?: string;
  className?: string;
};

export default function HearingCompensationChart({
  left,
  right,
  leftLabel = "Left",
  rightLabel = "Right",
  className,
}: HearingCompensationChartProps) {
  const containerRef = useRef<HTMLDivElement>(null);
  const chartRef = useRef<echarts.ECharts | null>(null);

  const leftSeries = useMemo(() => buildHearingSplineSeries(left), [left]);
  const rightSeries = useMemo(() => buildHearingSplineSeries(right), [right]);

  // X axis adapts to the control-point count: 7-band (legacy) or 10-band (adds 3k/5k/6k).
  const pointCount = Math.max(left.length, right.length);
  const freqLabels = useMemo(() => resolveHearingFreqLabels(pointCount), [pointCount]);
  const xMax = Math.max(0, pointCount - 1);

  useEffect(() => {
    const el = containerRef.current;
    if (!el) return;

    const option: echarts.EChartsOption = {
      animation: false,
      legend: {
        show: true,
        top: 8,
        data: [
          {
            name: leftLabel,
            icon: "circle",
            textStyle: { color: LEFT_COLOR },
            itemStyle: { color: LEFT_COLOR, borderColor: LEFT_COLOR },
          },
          {
            name: rightLabel,
            icon: "circle",
            textStyle: { color: RIGHT_COLOR },
            itemStyle: { color: RIGHT_COLOR, borderColor: RIGHT_COLOR },
          },
        ],
        textStyle: { fontSize: 13 },
      },
      grid: {
        left: 48,
        right: 36,
        top: 48,
        bottom: 28,
      },
      graphic: [
        {
          type: "text",
          right: 10,
          bottom: 6,
          style: {
            text: "Hz",
            fill: "#999",
            fontSize: 14,
          },
          z: 100,
        },
      ],
      xAxis: {
        type: "value",
        min: 0,
        max: xMax,
        interval: 1,
        axisLabel: {
          formatter: (value: number) => {
            const idx = Math.round(value);
            if (Math.abs(value - idx) > 1e-6) return "";
            return freqLabels[idx] ?? "";
          },
          fontSize: 14,
          color: "#999",
        },
        splitLine: {
          show: true,
          lineStyle: { type: "solid", color: "#3A4348" },
        },
        axisLine: {
          lineStyle: { color: "#3A4348" },
        },
      },
      yAxis: {
        type: "value",
        min: -80,
        // Top raised to +20 dB: levels above 70 map to positive dB and were
        // clipped at the old max of 0, leaving gaps at the top of the curve.
        max: 20,
        interval: 10,
        name: "dB",
        nameLocation: "end",
        nameGap: 8,
        nameTextStyle: {
          color: "#999",
          fontSize: 14,
          align: "right",
          padding: [0, 8, 0, 0],
        },
        axisLabel: {
          fontSize: 14,
          color: "#999",
        },
        splitLine: {
          show: true,
          lineStyle: { type: "solid", color: "#3A4348" },
        },
        axisLine: {
          lineStyle: { color: "#3A4348" },
        },
      },
      series: [
        {
          name: leftLabel,
          type: "line",
          data: leftSeries,
          showSymbol: false,
          smooth: false,
          lineStyle: { color: LEFT_COLOR, width: 2 },
          itemStyle: { color: LEFT_COLOR },
        },
        {
          name: rightLabel,
          type: "line",
          data: rightSeries,
          showSymbol: false,
          smooth: false,
          lineStyle: { color: RIGHT_COLOR, width: 2 },
          itemStyle: { color: RIGHT_COLOR },
        },
      ],
    };

    if (!chartRef.current) {
      chartRef.current = echarts.init(el, undefined, { renderer: "canvas" });
    }
    chartRef.current.setOption(option, true);

    const onResize = () => chartRef.current?.resize();
    const ro = new ResizeObserver(onResize);
    ro.observe(el);
    window.addEventListener("resize", onResize);

    return () => {
      ro.disconnect();
      window.removeEventListener("resize", onResize);
    };
  }, [leftSeries, rightSeries, leftLabel, rightLabel, freqLabels, xMax]);

  useEffect(() => {
    return () => {
      chartRef.current?.dispose();
      chartRef.current = null;
    };
  }, []);

  return (
    <div
      ref={containerRef}
      className={
        className
        ?? "w-full h-[min(52vw,240px)] min-h-[180px] md:h-[320px] lg:h-[380px] rounded-lg bg-black/30"
      }
      aria-hidden
    />
  );
}