const fs = require("node:fs");
const path = require("node:path");
const { ChartJSNodeCanvas } = require("chartjs-node-canvas");

const chartCanvas = new ChartJSNodeCanvas({
  width: 1400,
  height: 720,
  backgroundColour: "white"
});

function normalizeJsonSeries(data) {
  if (Array.isArray(data)) {
    if (data.every(Number.isFinite)) {
      return { labels: data.map((_, index) => index), series: [{ label: "value", data }] };
    }
    if (data.every((item) => item && typeof item === "object" && !Array.isArray(item))) {
      const numericFields = [...new Set(data.flatMap(Object.keys))]
        .filter((field) => data.some((item) => Number.isFinite(item[field])));
      const xField = ["t", "time", "x", "timestamp", "index", "distance"]
        .find((field) => numericFields.includes(field));
      const valueFields = numericFields.filter((field) => field !== xField);
      const isTravelStability = xField === "distance" && valueFields.length === 1 && valueFields[0] === "pressure";
      return {
        labels: data.map((item, index) => xField ? item[xField] : index),
        series: valueFields.map((field) => ({
          label: field,
          data: isTravelStability
            ? data.filter((item) => Number.isFinite(item.distance) && Number.isFinite(item[field]))
              .map((item) => ({ x: item.distance, y: item[field] }))
            : data.map((item) => Number.isFinite(item[field]) ? item[field] : null)
        })),
        chartKind: isTravelStability ? "travel-stability" : "line",
        xLabel: xField === "distance" ? "行程" : "采样点 / 时间",
        yLabel: isTravelStability
          ? "稳态压力 (kPa)"
          : "数值"
      };
    }
  }

  if (data && typeof data === "object") {
    const arrays = Object.entries(data).filter(([, value]) => Array.isArray(value));
    if (arrays.length === 1) return normalizeJsonSeries(arrays[0][1]);

    const numericArrays = arrays.filter(([, values]) =>
      values.length > 0 && values.every(Number.isFinite)
    );
    if (numericArrays.length > 0) {
      const xEntry = numericArrays.find(([field]) =>
        ["t", "time", "x", "timestamp", "index"].includes(field)
      );
      const seriesEntries = numericArrays.filter(([field]) => !xEntry || field !== xEntry[0]);
      const pointCount = Math.max(...numericArrays.map(([, values]) => values.length));
      return {
        labels: xEntry ? xEntry[1] : Array.from({ length: pointCount }, (_, index) => index),
        series: seriesEntries.map(([label, values]) => ({ label, data: values }))
      };
    }
  }

  throw new Error("JSON 必须包含数字数组、数值对象数组或多个数值数组字段");
}

const travelPointLabels = {
  id: "travelPointLabels",
  afterDatasetsDraw(chart) {
    if (chart.options.plugins.travelPointLabels !== true) return;
    const { ctx } = chart;
    ctx.save();
    ctx.fillStyle = "#15251f";
    ctx.font = "12px sans-serif";
    ctx.textAlign = "left";
    ctx.textBaseline = "bottom";
    for (const meta of chart.getSortedVisibleDatasetMetas()) {
      meta.data.forEach((element, index) => {
        const point = chart.data.datasets[meta.index].data[index];
        ctx.fillText(`(${point.x}, ${Number(point.y).toFixed(2)})`, element.x + 7, element.y - 7);
      });
    }
    ctx.restore();
  }
};

function buildChartConfiguration(normalized, title) {
  const isTravelStability = normalized.chartKind === "travel-stability";
  const colors = ["#d62828", "#0077b6", "#2a9d8f", "#f77f00", "#6a4c93", "#495057"];
  return {
    type: isTravelStability ? "scatter" : "line",
    data: {
      labels: isTravelStability ? undefined : normalized.labels,
      datasets: normalized.series.map((item, index) => ({
        ...item,
        borderColor: colors[index % colors.length],
        borderWidth: 2,
        pointRadius: isTravelStability ? 4 : 0,
        pointHoverRadius: isTravelStability ? 7 : 3,
        showLine: isTravelStability,
        tension: 0,
        fill: false
      }))
    },
    options: {
      responsive: false,
      animation: false,
      layout: isTravelStability ? { padding: { top: 24, right: 92 } } : undefined,
      plugins: {
        title: { display: true, text: title },
        legend: { display: true },
        travelPointLabels: isTravelStability
      },
      scales: {
        x: isTravelStability
          ? { type: "linear", min: 0, max: 1000, title: { display: true, text: normalized.xLabel } }
          : { title: { display: true, text: normalized.xLabel } },
        y: { title: { display: true, text: normalized.yLabel } }
      }
    },
    plugins: isTravelStability ? [travelPointLabels] : []
  };
}

async function plotJson(jsonPath) {
  const content = await fs.promises.readFile(jsonPath, "utf8");
  const normalized = normalizeJsonSeries(JSON.parse(content));
  if (normalized.series.length === 0) throw new Error("JSON 数组中没有可绘制的数值字段");
  const image = await chartCanvas.renderToBuffer(buildChartConfiguration(normalized, path.basename(jsonPath)));

  const parsedPath = path.parse(jsonPath);
  const outputPath = path.join(parsedPath.dir, `${parsedPath.name}-line.png`);
  await fs.promises.writeFile(outputPath, image);
  console.log(`[${new Date().toISOString()}] 已生成 JSON 折线图: ${outputPath}`);
  return outputPath;
}

module.exports = { buildChartConfiguration, normalizeJsonSeries, plotJson };