const http = require('http');
const fs = require('fs');
const path = require('path');

const PORT = 3000;
const DATA_DIR = process.env.DATA_DIR || '.';

const MIME_TYPES = {
    '.html': 'text/html',
    '.css': 'text/css',
    '.js': 'text/javascript',
    '.json': 'application/json',
    '.csv': 'text/csv',
};

const server = http.createServer((req, res) => {
    // API endpoint to list available months
    if (req.url === '/api/months') {
        fs.readdir(DATA_DIR, (err, files) => {
            if (err) {
                res.writeHead(500, { 'Content-Type': 'application/json' });
                res.end(JSON.stringify({ error: 'Failed to read directory' }));
                return;
            }

            // Find CSV files matching altcats-YYYY-MM.csv pattern
            const monthPattern = /^altcats-(\d{4}-\d{2})\.csv$/;
            const months = files
                .map(file => {
                    const match = file.match(monthPattern);
                    return match ? match[1] : null;
                })
                .filter(Boolean)
                .sort();

            res.writeHead(200, { 'Content-Type': 'application/json' });
            res.end(JSON.stringify(months));
        });
        return;
    }

    // Handle URL
    let filePath = '.' + req.url;
    if (filePath === './') {
        filePath = './index.html';
    } else if (filePath.endsWith('.csv')) {
        filePath = path.join(DATA_DIR, path.basename(filePath));
    }

    const extname = path.extname(filePath);
    const contentType = MIME_TYPES[extname] || 'application/octet-stream';

    fs.readFile(filePath, (err, data) => {
        if (err) {
            if (err.code === 'ENOENT') {
                res.writeHead(404);
                res.end('File not found');
            } else {
                res.writeHead(500);
                res.end('Server error: ' + err.code);
            }
            return;
        }

        res.writeHead(200, { 'Content-Type': contentType });
        res.end(data);
    });
});

server.listen(PORT, () => {
    console.log(`Server running at http://localhost:${PORT}/`);
    console.log(`Visualizing spending data with ECharts...`);
});