const fs = require('fs');
const path = require('path');
const { parse } = require('csv-parse');
const readline = require('readline');
const { leftlon, rightlon, toplat, bottomlat } = require("./region");

// 仅导出中国区域数据
const JUST_EXPORT_CHINADATA = true;

// 配置参数
const config = {
    outputDir: path.join(__dirname, `../model`), // 输出目录
    sampleRate: 0.1, // 抽样率 (0.1 = 10%的数据)
    testMode: false, // 测试模式，只处理少量数据
    testLimit: 1000, // 测试模式下的最大行数

    outputDir: path.join(__dirname, `../model`),
    outputFile: 'windGridData.json',

    knownGridParams: {
        minLon: -179,
        maxLon: 180,
        minLat: -90,
        maxLat: 90,
        dx: 1.0, // 假设1度分辨率
        dy: 1.0, // 假设1度分辨率
        nx: 361, // 经度点数: 180*2 + 1
        ny: 181  // 纬度点数: 90*2 + 1
    }
};

async function createWindData(uFile, vFile) {
    try {
        console.log('开始转换为网格JSON格式...');

        // 并行解析U和V的CSV文件
        const [uData, vData] = await Promise.all([
            parseCSVFile(uFile, 'U'),
            parseCSVFile(vFile, 'V')
        ]);

        // 检查数据是否有效
        if (uData.length === 0 || vData.length === 0) {
            throw new Error('U或V数据为空');
        }

        // 使用已知的全球网格参数
        const gridParams = config.knownGridParams;

        // 为U和V数据创建网格结构
        const uGrid = createGridData(uData, gridParams, 'U');
        const vGrid = createGridData(vData, gridParams, 'V');

        if (!uGrid || !vGrid) {
            throw new Error('网格创建失败');
        }

        // 组合成风场库需要的数组格式
        const outputData = [uGrid, vGrid];

        // 写入输出文件
        const outputPath = path.join(config.outputDir, config.outputFile);
        fs.writeFileSync(outputPath, JSON.stringify(outputData));
        console.log(`转换成功! 网格JSON已保存到: ${outputPath}`);

        console.log(`U网格信息: nx=${uGrid.header.nx}, ny=${uGrid.header.ny}`);
        console.log(`V网格信息: nx=${vGrid.header.nx}, ny=${vGrid.header.ny}`);

    } catch (error) {
        console.error('转换过程中出错:', error);
    }
}

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

// 解析CSV文件的函数
async function parseCSVFile(filePath, component) {
    return new Promise((resolve, reject) => {
        const results = [];
        let lineCount = 0;

        const rl = readline.createInterface({
            input: fs.createReadStream(filePath),
            crlfDelay: Infinity
        });

        rl.on('line', (line) => {
            if (!line.trim()) return;

            try {
                const cleanedLine = line.replace(/"/g, '');
                const parts = cleanedLine.split(',');
                if (parts.length < 7) return;

                const lon = parseFloat(parts[4]);
                const lat = parseFloat(parts[5]);
                const value = parseFloat(parts[6]);

                if (!isNaN(lon) && !isNaN(lat) && !isNaN(value)) {
                    results.push({ lon, lat, value });
                }
            } catch (e) {
                console.error('解析行时出错:', line, e);
            }

            lineCount++;
        });

        rl.on('close', () => {
            console.log(`从 ${filePath} 解析了 ${results.length} 条 ${component} 记录`);
            resolve(results);
        });

        rl.on('error', reject);
    });
}

// 创建网格数据 - 使用已知的全球网格参数
function createGridData(parsedData, gridParams, component) {
    console.log(`开始创建 ${component} 网格数据...`);

    const { minLon, maxLon, minLat, maxLat, dx, dy, nx, ny } = gridParams;

    // 创建空网格（用null填充）
    const gridData = new Array(nx * ny).fill(null);

    // 将解析的数据填充到网格中
    let filledCount = 0;
    let missingCount = 0;

    parsedData.forEach(point => {
        // 计算网格索引
        const i = Math.round((point.lon - minLon) / dx);
        const j = Math.round((maxLat - point.lat) / dy); // 注意纬度是从上到下递减

        const index = j * nx + i;

        if (index >= 0 && index < gridData.length) {
            gridData[index] = point.value;
            filledCount++;
        } else {
            missingCount++;
            console.warn(`点超出网格范围: (${point.lon}, ${point.lat}) -> 索引: ${index}`);
        }
    });

    console.log(`${component} 网格填充了 ${filledCount} 个数据点，缺失 ${missingCount} 个点`);
    console.log(`${component} 数据非空比例: ${(filledCount / gridData.length * 100).toFixed(2)}%`);

    if (filledCount === 0) {
        console.error(`错误: ${component} 网格没有有效数据`);
        return null;
    }

    return {
        header: {
            parameterCategory: 2,
            parameterCategoryName: "Momentum",
            parameterNumber: component === 'U' ? 2 : 3,
            parameterNumberName: component === 'U' ? "U-component_of_wind" : "V-component_of_wind",
            nx: nx,
            ny: ny,
            lo1: minLon,
            la1: maxLat,
            dx: dx,
            dy: dy,
            numberPoints: nx * ny,
            refTime: "2025-09-10T00:00:00Z"
        },
        data: gridData
    };
}

async function main() {
    try {
        console.log('开始转换为网格JSON格式...');

        // 并行解析U和V的CSV文件
        const [uData, vData] = await Promise.all([
            parseCSVFile(config.uCsvFile, 'U'),
            parseCSVFile(config.vCsvFile, 'V')
        ]);

        // 检查数据是否有效
        if (uData.length === 0 || vData.length === 0) {
            throw new Error('U或V数据为空');
        }

        // 使用已知的全球网格参数
        const gridParams = config.knownGridParams;

        // 为U和V数据创建网格结构
        const uGrid = createGridData(uData, gridParams, 'U');
        const vGrid = createGridData(vData, gridParams, 'V');

        if (!uGrid || !vGrid) {
            throw new Error('网格创建失败');
        }

        // 组合成风场库需要的数组格式
        const outputData = [uGrid, vGrid];

        // 写入输出文件
        const outputPath = path.join(config.outputDir, config.outputFile);
        fs.writeFileSync(outputPath, JSON.stringify(outputData));
        console.log(`转换成功! 网格JSON已保存到: ${outputPath}`);

        console.log(`U网格信息: nx=${uGrid.header.nx}, ny=${uGrid.header.ny}`);
        console.log(`V网格信息: nx=${vGrid.header.nx}, ny=${vGrid.header.ny}`);

    } catch (error) {
        console.error('转换过程中出错:', error);
    }
}

module.exports = {
    createWindData
};