const fs = require('fs');
const path = require('path');
const { createCanvas, ImageData } = require('canvas');
const sharp = require('sharp');

// 配置参数
const config = {
    outputDir: 'G:/tiles/cloud',   // 输出目录
    emptyValue: 9.999e+20,         // 空值标识
    minZoom: 0,                    // 最小缩放级别
    maxZoom: 5                     // 最大缩放级别
};

async function createCloudImageDeep(inputFile) {
    try {
        // 确保输出目录存在
        if (!fs.existsSync(inputFile)) {
            fs.mkdirSync(inputFile, { recursive: true });
        }

        // 解析数据文件
        const { grid, width, height } = parseDataFile(inputFile);

        // 生成各级别瓦片
        for (let zoom = config.minZoom; zoom <= config.maxZoom; zoom++) {
            await generateTiles(grid, width, height, zoom);
        }

        // 生成图例
        generateLegend();

        console.log('瓦片生成完成！');
        console.log(`输出目录: ${path.resolve(config.outputDir)}`);
    } catch (error) {
        console.error('处理过程中发生错误:', error);
    }
}

// 读取并解析数据文件
function parseDataFile(filePath) {
    console.log('正在读取数据文件...');
    const data = fs.readFileSync(filePath, 'utf8').split('\n');

    // 解析第一行获取尺寸信息
    const dimensions = data[0].split(' ').map(Number);
    const dataWidth = dimensions[0];
    const dataHeight = dimensions[1];

    console.log(`数据尺寸: ${dataWidth}x${dataHeight}`);

    // 解析数据值
    const grid = [];
    for (let i = 1; i < data.length; i++) {
        if (data[i].trim() === '') continue;

        const value = parseFloat(data[i]);
        // 处理空值
        grid.push(value === config.emptyValue ? NaN : value);
    }

    console.log(`已读取 ${grid.length} 个数据点`);
    return { grid, width: dataWidth, height: dataHeight };
}

// 将经纬度转换为瓦片坐标
function latLonToTileIndex(lat, lon, zoom) {
    const x = Math.floor((lon + 180) / 360 * Math.pow(2, zoom));
    const y = Math.floor((1 - Math.log(Math.tan(lat * Math.PI / 180) +
        1 / Math.cos(lat * Math.PI / 180)) / Math.PI) / 2 * Math.pow(2, zoom));
    return { x, y };
}

// 将瓦片坐标转换为经纬度范围
function tileToLatLon(x, y, zoom) {
    const n = Math.pow(2, zoom);
    const lon1 = x / n * 360 - 180;
    const lat1 = Math.atan(Math.sinh(Math.PI * (1 - 2 * y / n))) * 180 / Math.PI;
    const lon2 = (x + 1) / n * 360 - 180;
    const lat2 = Math.atan(Math.sinh(Math.PI * (1 - 2 * (y + 1) / n))) * 180 / Math.PI;

    return {
        west: lon1,
        east: lon2,
        south: lat2,
        north: lat1
    };
}

// 生成指定缩放级别的瓦片
async function generateTiles(data, dataWidth, dataHeight, zoom) {
    console.log(`正在生成第 ${zoom} 级瓦片...`);
    const tileSize = 256;
    const totalTiles = Math.pow(2, zoom);

    // 创建进度跟踪
    let processed = 0;
    const totalToProcess = totalTiles * totalTiles;

    for (let x = 0; x < totalTiles; x++) {
        for (let y = 0; y < totalTiles; y++) {
            const canvas = createCanvas(tileSize, tileSize);
            const ctx = canvas.getContext('2d');
            const imageData = ctx.createImageData(tileSize, tileSize);

            // 获取当前瓦片的经纬度范围
            const bounds = tileToLatLon(x, y, zoom);

            // 为瓦片中的每个像素计算数据值
            for (let py = 0; py < tileSize; py++) {
                for (let px = 0; px < tileSize; px++) {
                    // 计算当前像素的经纬度
                    const pixelLon = bounds.west + (px / tileSize) * (bounds.east - bounds.west);
                    const pixelLat = bounds.south + (py / tileSize) * (bounds.north - bounds.south);

                    // 将经纬度转换为数据网格索引
                    const dataX = Math.floor((pixelLon + 180) / 360 * dataWidth);
                    const dataY = Math.floor((90 - pixelLat) / 180 * dataHeight);

                    // 确保索引在有效范围内
                    const safeX = Math.max(0, Math.min(dataWidth - 1, dataX));
                    const safeY = Math.max(0, Math.min(dataHeight - 1, dataY));

                    const dataIndex = safeY * dataWidth + safeX;

                    // 获取数据值并处理空值
                    let value = data[dataIndex];
                    if (isNaN(value)) {
                        // 空值处理：设置为完全透明
                        setPixel(imageData, px, py, 0, 0, 0, 0);
                    } else {
                        // 将云量值(0-100)映射到颜色(蓝色到白色)
                        const intensity = Math.min(255, Math.max(0, Math.floor(value * 2.55)));
                        // 使用蓝色渐变表示云量
                        setPixel(imageData, px, py, intensity, intensity, 255, 180);
                    }
                }
            }

            ctx.putImageData(imageData, 0, 0);

            // 创建目录并保存瓦片
            const tileDir = path.join(config.outputDir, zoom.toString(), x.toString());
            if (!fs.existsSync(tileDir)) {
                fs.mkdirSync(tileDir, { recursive: true });
            }

            const tilePath = path.join(tileDir, `${y}.png`);
            const buffer = canvas.toBuffer('image/png');
            await sharp(buffer).png().toFile(tilePath);

            // 更新进度
            processed++;
            if (processed % 100 === 0) {
                console.log(`进度: ${Math.round(processed / totalToProcess * 100)}%`);
            }
        }
    }
}

// 设置像素颜色
function setPixel(imageData, x, y, r, g, b, a) {
    const index = (y * imageData.width + x) * 4;
    imageData.data[index] = r;
    imageData.data[index + 1] = g;
    imageData.data[index + 2] = b;
    imageData.data[index + 3] = a;
}

// 生成图例
function generateLegend() {
    const legend = `
    <!DOCTYPE html>
    <html>
    <head>
      <title>云量图例</title>
      <style>
        .legend {
          position: absolute;
          bottom: 20px;
          right: 20px;
          background: white;
          padding: 10px;
          border-radius: 5px;
          box-shadow: 0 0 10px rgba(0,0,0,0.2);
        }
        .color-bar {
          height: 20px;
          width: 200px;
          background: linear-gradient(to right, #0000ff, #ffffff);
          margin-bottom: 5px;
        }
        .labels {
          display: flex;
          justify-content: space-between;
        }
      </style>
    </head>
    <body>
      <div class="legend">
        <div>云量百分比</div>
        <div class="color-bar"></div>
        <div class="labels">
          <span>0%</span>
          <span>100%</span>
        </div>
      </div>
    </body>
    </html>
  `;

    fs.writeFileSync(path.join(config.outputDir, 'legend.html'), legend);
}

// 主函数
async function main() {
    try {
        // 确保输出目录存在
        if (!fs.existsSync(config.outputDir)) {
            fs.mkdirSync(config.outputDir, { recursive: true });
        }

        // 解析数据文件
        const { grid, width, height } = parseDataFile(config.inputFile);

        // 生成各级别瓦片
        for (let zoom = config.minZoom; zoom <= config.maxZoom; zoom++) {
            await generateTiles(grid, width, height, zoom);
        }

        // 生成图例
        generateLegend();

        console.log('瓦片生成完成！');
        console.log(`输出目录: ${path.resolve(config.outputDir)}`);
    } catch (error) {
        console.error('处理过程中发生错误:', error);
    }
}

module.exports = {
    createCloudImageDeep
};