const path = require('path');
const fs = require('fs');
const axios = require('axios');
const { outputProgress, formatElapsedTime, estimateRemaining, calculateRate } = require('./metrics/utils/progress');

// Change working directory to script directory
process.chdir(path.dirname(__filename));

require('dotenv').config({ path: path.resolve(__dirname, '..', '.env') });

const FILES = [
    {
        name: '39f2x83-products.csv',
        url: process.env.PRODUCTS_CSV_URL
    },
    {
        name: '39f2x83-orders.csv',
        url: process.env.ORDERS_CSV_URL
    },
    {
        name: '39f2x83-purchase_orders.csv',
        url: process.env.PURCHASE_ORDERS_CSV_URL
    }
];

let isCancelled = false;

function cancelUpdate() {
    isCancelled = true;
    outputProgress({
        status: 'cancelled',
        operation: 'CSV update cancelled',
        current: 0,
        total: FILES.length,
        elapsed: null,
        remaining: null,
        rate: 0
    });
}

async function downloadFile(file, index, startTime) {
    if (isCancelled) return;

    const csvDir = path.join(__dirname, '../csv');
    if (!fs.existsSync(csvDir)) {
        fs.mkdirSync(csvDir, { recursive: true });
    }

    const writer = fs.createWriteStream(path.join(csvDir, file.name));
    
    try {
        const response = await axios({
            url: file.url,
            method: 'GET',
            responseType: 'stream'
        });

        const totalLength = response.headers['content-length'];
        let downloadedLength = 0;
        let lastProgressUpdate = Date.now();
        const PROGRESS_INTERVAL = 1000; // Update progress every second

        response.data.on('data', (chunk) => {
            if (isCancelled) {
                writer.end();
                return;
            }

            downloadedLength += chunk.length;
            
            // Update progress based on time interval
            const now = Date.now();
            if (now - lastProgressUpdate >= PROGRESS_INTERVAL) {
                const progress = (downloadedLength / totalLength) * 100;
                outputProgress({
                    status: 'running',
                    operation: `Downloading ${file.name}`,
                    current: index + (downloadedLength / totalLength),
                    total: FILES.length,
                    elapsed: formatElapsedTime(startTime),
                    remaining: estimateRemaining(startTime, index + (downloadedLength / totalLength), FILES.length),
                    rate: calculateRate(startTime, index + (downloadedLength / totalLength)),
                    percentage: progress.toFixed(1),
                    file_progress: {
                        name: file.name,
                        downloaded: downloadedLength,
                        total: totalLength,
                        percentage: progress.toFixed(1)
                    }
                });
                lastProgressUpdate = now;
            }
        });

        response.data.pipe(writer);

        return new Promise((resolve, reject) => {
            writer.on('finish', resolve);
            writer.on('error', reject);
        });
    } catch (error) {
        fs.unlinkSync(path.join(csvDir, file.name));
        throw error;
    }
}

// Main function to update all files
async function updateFiles() {
    const startTime = Date.now();
    
    outputProgress({
        status: 'running',
        operation: 'Starting CSV update',
        current: 0,
        total: FILES.length,
        elapsed: '0s',
        remaining: null,
        rate: 0,
        percentage: '0'
    });

    try {
        for (let i = 0; i < FILES.length; i++) {
            if (isCancelled) {
                return;
            }

            const file = FILES[i];
            await downloadFile(file, i, startTime);

            outputProgress({
                status: 'running',
                operation: 'CSV update in progress',
                current: i + 1,
                total: FILES.length,
                elapsed: formatElapsedTime(startTime),
                remaining: estimateRemaining(startTime, i + 1, FILES.length),
                rate: calculateRate(startTime, i + 1),
                percentage: (((i + 1) / FILES.length) * 100).toFixed(1)
            });
        }

        outputProgress({
            status: 'complete',
            operation: 'CSV update complete',
            current: FILES.length,
            total: FILES.length,
            elapsed: formatElapsedTime(startTime),
            remaining: '0s',
            rate: calculateRate(startTime, FILES.length),
            percentage: '100'
        });
    } catch (error) {
        outputProgress({
            status: 'error',
            operation: 'CSV update failed',
            error: error.message,
            current: 0,
            total: FILES.length,
            elapsed: formatElapsedTime(startTime),
            remaining: null,
            rate: 0
        });
        throw error;
    }
}

// Run the update only if this is the main module
if (require.main === module) {
    updateFiles().catch((error) => {
        console.error('Error updating CSV files:', error);
        process.exit(1);
    });
}

// Export the functions needed by the route
module.exports = {
    updateFiles,
    cancelUpdate
};