const fs = require("node:fs");
const path = require("node:path");
const { parse } = require("csv-parse/sync");
const { ChartJSNodeCanvas } = require("chartjs-node-canvas");
const { createCanvas, loadImage, registerFont } = require("canvas");

const CHART_WIDTH = 1400;
const CHART_HEIGHT = 540;
const CHINESE_FONT_PATH = "C:\\Windows\\Fonts\\msyh.ttc";

if (fs.existsSync(CHINESE_FONT_PATH)) {
  registerFont(CHINESE_FONT_PATH, { family: "Microsoft YaHei" });
}

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

async function renderTimeSeries(points, options) {
  return chartCanvas.renderToBuffer({
    type: "line",
    data: {
      datasets: [{
        data: points.map((row) => ({ x: row.t, y: row[options.column] })),
        borderColor: options.color,
        borderWidth: 2,
        pointRadius: 0,
        stepped: options.stepped,
        tension: 0,
        fill: false
      }]
    },
    options: {
      responsive: false,
      animation: false,
      parsing: false,
      layout: { padding: { top: 14, right: 34, bottom: 8, left: 24 } },
      plugins: {
        legend: { display: false },
        title: {
          display: true,
          text: options.title,
          color: "#222222",
          font: { family: "Microsoft YaHei", size: 21, weight: "normal" },
          padding: { bottom: 10 }
        }
      },
      scales: {
        x: {
          type: "linear",
          min: options.xMin,
          max: options.xMax,
          grid: { color: "#d8d8d8", lineWidth: 1 },
          border: { color: "#333333", width: 1.5 },
          ticks: { color: "#333333", font: { family: "Microsoft YaHei", size: 14 } },
          title: {
            display: true,
            text: "时间 (s)",
            color: "#333333",
            font: { family: "Microsoft YaHei", size: 17 }
          }
        },
        y: {
          min: 0,
          max: options.yMax,
          grid: { color: "#d8d8d8", lineWidth: 1 },
          border: { color: "#333333", width: 1.5 },
          ticks: { color: "#333333", font: { family: "Microsoft YaHei", size: 14 } },
          title: {
            display: true,
            text: options.yLabel,
            color: "#333333",
            font: { family: "Microsoft YaHei", size: 17 }
          }
        }
      }
    }
  });
}

async function renderCombinedPlot(points, outputPath) {
  const minimumTime = Math.min(...points.map((row) => row.t));
  const maximumTime = Math.max(...points.map((row) => row.t));
  const timeSpan = Math.max(maximumTime - minimumTime, 1);
  const xMin = Math.min(0, minimumTime);
  const xMax = Math.ceil((maximumTime + timeSpan * 0.05) / 10) * 10;
  const maximumPressure = Math.max(...points.map((row) => row.p));
  const pressureStep = maximumPressure <= 100 ? 20 : 50;
  const pressureMax = Math.ceil((maximumPressure * 1.1) / pressureStep) * pressureStep;

  const upperImage = await renderTimeSeries(points, {
    column: "u",
    color: "#304ffe",
    stepped: true,
    title: "阀门开度随时间变化",
    yLabel: "阀门开度 u (%)",
    xMin,
    xMax,
    yMax: 100
  });
  const lowerImage = await renderTimeSeries(points, {
    column: "p",
    color: "#f5222d",
    stepped: false,
    title: "压力随时间变化",
    yLabel: "压力 p (kPa)",
    xMin,
    xMax,
    yMax: pressureMax
  });

  const canvas = createCanvas(CHART_WIDTH, CHART_HEIGHT * 2);
  const context = canvas.getContext("2d");
  context.fillStyle = "white";
  context.fillRect(0, 0, canvas.width, canvas.height);
  context.drawImage(await loadImage(upperImage), 0, 0);
  context.drawImage(await loadImage(lowerImage), 0, CHART_HEIGHT);

  await fs.promises.writeFile(outputPath, canvas.toBuffer("image/png"));
  console.log(`[${new Date().toISOString()}] 已生成时序图: ${outputPath}`);
}

async function plotCsv(csvPath) {
  const content = await fs.promises.readFile(csvPath, "utf8");
  const rows = parse(content, {
    bom: true,
    columns: true,
    skip_empty_lines: true,
    trim: true
  });
  const requiredColumns = ["t", "u", "p"];
  const headers = rows.length > 0 ? Object.keys(rows[0]) : [];
  const missingColumns = requiredColumns.filter((column) => !headers.includes(column));
  if (missingColumns.length > 0) {
    throw new Error(`CSV 缺少列: ${missingColumns.join(", ")}`);
  }

  const points = rows
    .map((row) => ({ t: Number(row.t), u: Number(row.u), p: Number(row.p) }))
    .filter((row) => Number.isFinite(row.t) && Number.isFinite(row.u) && Number.isFinite(row.p));
  if (points.length === 0) {
    throw new Error("CSV 中没有可绘制的 t、u、p 数值行");
  }

  const parsedPath = path.parse(csvPath);
  const outputPath = path.join(parsedPath.dir, `${parsedPath.name}-u-p-t.png`);
  await renderCombinedPlot(points, outputPath);
  return outputPath;
}

module.exports = { plotCsv };