const express = require('express');
const axios = require('axios');

const app = express();
const PORT = 3000;

app.use(express.static('public'));

// Функция для парсинга CSV-ответа от IEM API
function parseIEMData(csvData) {
    const lines = csvData.trim().split('\n');
    if (lines.length < 2) {
        return [];
    }

    const headerLine = lines.find(line => !line.startsWith('#'));
    if (!headerLine) return [];

    const headers = headerLine.split(',');

    const dataLines = lines.filter(line => !line.startsWith('#') && line !== headerLine);

    const jsonData = dataLines.map(line => {
        const values = line.split(',');
        const report = {};
        headers.forEach((header, index) => {
            const value = values[index];
            const numValue = (value === 'M' || value === '') ? null : parseFloat(value);
            if (['tmpf', 'dwpf', 'alti', 'sknt', 'drct'].includes(header)) {
                report[header] = numValue;
            } else {
                report[header] = values[index];
            }
        });
        return report;
    });

    return jsonData;
}


app.get('/api/metar', async (req, res) => {
    const { station, days } = req.query;

    if (!station) {
        return res.status(400).json({ error: 'Station code is required' });
    }

    const endDate = new Date();
    const startDate = new Date();
    startDate.setDate(endDate.getDate() - parseInt(days, 10));

    const iemApiUrl = `https://mesonet.agron.iastate.edu/cgi-bin/request/asos.py?` +
        `station=${station}&` +
        `data=metar&` +
        `data=tmpf&` +
        `data=dwpf&` +
        `data=alti&` +
        `data=sknt&` +
        `data=drct&` +
        `year1=${startDate.getUTCFullYear()}&month1=${startDate.getUTCMonth() + 1}&day1=${startDate.getUTCDate()}&` +
        `year2=${endDate.getUTCFullYear()}&month2=${endDate.getUTCMonth() + 1}&day2=${endDate.getUTCDate()}&` +
        `tz=Etc/UTC&` +
        `format=comma&` +
        `latlon=no&` +
        `missing=M`;

    try {
        console.log(`Fetching data from: ${iemApiUrl}`);
        const response = await axios.get(iemApiUrl);

        if (!response.data || response.data.trim() === '' || response.data.includes('No data found')) {
            return res.status(404).json({ error: 'No data found for the specified station or period.' });
        }

        const jsonData = parseIEMData(response.data);

        res.json({ data: jsonData });

    } catch (error) {
        console.error('Error fetching data from IEM API:', error.message);
        res.status(500).json({ error: 'Failed to fetch or process data from IEM API.' });
    }
});

app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});