const express = require('express');
const bodyParser = require('body-parser');
const fs = require('fs');
const path = require('path');

const app = express();
const PORT = process.env.PORT || 3000;
const DATA_FILE_PATH = process.env.DATA_FILE_PATH || path.join(__dirname, 'data', 'weight-tracker-data.json'); // Default path for local dev, override in Docker

// Ensure data directory exists (especially for local dev, Docker volume handles it in container)
const dataDir = path.dirname(DATA_FILE_PATH);
if (!fs.existsSync(dataDir)) {
    fs.mkdirSync(dataDir, { recursive: true });
}

app.use(bodyParser.json({ limit: '10mb' })); // Generous limit for the data file

// Middleware to log requests
app.use((req, res, next) => {
    console.log(`${new Date().toISOString()} - ${req.method} ${req.originalUrl}`);
    next();
});

// GET endpoint to retrieve data
app.get('/', (req, res) => {
    fs.readFile(DATA_FILE_PATH, 'utf8', (err, data) => {
        if (err) {
            if (err.code === 'ENOENT') {
                console.log(`Data file not found at ${DATA_FILE_PATH}, returning empty object.`);
                return res.json({}); // If file doesn't exist, return empty JSON object
            }
            console.error('Error reading data file:', err);
            return res.status(500).send('Error reading data file');
        }
        // If file is empty or just whitespace, treat as empty object
        if (!data || data.trim() === '') {
            console.log(`Data file at ${DATA_FILE_PATH} is empty, returning empty object.`);
            return res.json({});
        }

        try {
            res.json(JSON.parse(data));
        } catch (parseErr) {
            console.error(`Error parsing data file content from ${DATA_FILE_PATH}:`, parseErr);
            return res.status(500).json({ message: 'Error parsing data file content. File may be corrupted.', error: parseErr.message });
        }
    });
});

// PUT endpoint to save data
app.put('/', (req, res) => {
    const dataToSave = JSON.stringify(req.body, null, 2); // Pretty print JSON
    fs.writeFile(DATA_FILE_PATH, dataToSave, 'utf8', (err) => {
        if (err) {
            console.error('Error writing data file:', err);
            return res.status(500).json({ message: 'Error writing data file', error: err.message || 'Unknown error' });
        }
        console.log(`Data saved successfully to ${DATA_FILE_PATH}`);
        res.status(200).json({ message: 'Data saved successfully' });
    });
});

app.listen(PORT, '0.0.0.0', () => {
    console.log(`Server API listening on port ${PORT}`);
    console.log(`Data file path: ${DATA_FILE_PATH}`);
});

// Basic error handler
app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('Something broke!');
});