const express = require('express');
const cors = require('cors');
const bodyParser = require('body-parser');
const { exec } = require('child_process');
const fs = require('fs');
const path = require('path');
const { v4: uuidv4 } = require('uuid');

const app = express();
const port = process.env.PORT || 7860;

app.set('view engine', 'ejs');
app.set('views', path.join(__dirname, 'views'));

app.use(cors());
app.use(bodyParser.json());
app.use(express.static(__dirname));

app.get('/', (req, res) => {
    res.render('index');
});

app.get('/subject', (req, res) => {
    res.render('subject');
});

const TEMP_DIR = path.join(__dirname, 'temp');
if (!fs.existsSync(TEMP_DIR)) {
    fs.mkdirSync(TEMP_DIR);
}

app.post('/run', (req, res) => {
    const { code, language, input } = req.body;
    const id = uuidv4();
    let fileName, compileCmd, runCmd;

    switch (language) {
        case 'c':
            fileName = `main_${id}.c`;
            const exeName = `main_${id}.exe`;
            fs.writeFileSync(path.join(TEMP_DIR, fileName), code);
            compileCmd = `gcc ${path.join(TEMP_DIR, fileName)} -o ${path.join(TEMP_DIR, exeName)}`;
            runCmd = `${path.join(TEMP_DIR, exeName)}`;
            break;
        case 'python':
            fileName = `main_${id}.py`;
            fs.writeFileSync(path.join(TEMP_DIR, fileName), code);
            runCmd = `python3 ${path.join(TEMP_DIR, fileName)}`;
            break;
        case 'java':
            fileName = `Main_${id.replace(/-/g, '_')}.java`;
            // Note: Java requires class name to match file name
            const javaCode = code.replace(/public class \w+/, `public class Main_${id.replace(/-/g, '_')}`);
            fs.writeFileSync(path.join(TEMP_DIR, fileName), javaCode);
            compileCmd = `javac ${path.join(TEMP_DIR, fileName)}`;
            runCmd = `java -cp ${TEMP_DIR} Main_${id.replace(/-/g, '_')}`;
            break;
        default:
            return res.status(400).json({ error: 'Unsupported language' });
    }

    const execute = () => {
        const process = exec(runCmd, { timeout: 10000 }, (runErr, stdout, stderr) => {
            // Cleanup
            fs.readdirSync(TEMP_DIR).forEach(file => {
                if (file.includes(id) || file.includes(id.replace(/-/g, '_'))) {
                    try { fs.unlinkSync(path.join(TEMP_DIR, file)); } catch (e) {}
                }
            });

            if (runErr && runErr.killed) {
                return res.json({
                    stdout: stdout,
                    stderr: 'Error: Execution timed out (limit: 10s)',
                    exitCode: 124
                });
            }

            res.json({
                stdout: stdout,
                stderr: stderr || (runErr ? runErr.message : ''),
                exitCode: runErr ? runErr.code : 0
            });
        });

        if (input) {
            process.stdin.write(input);
            process.stdin.end();
        }
    };

    if (compileCmd) {
        exec(compileCmd, (compErr, stdout, stderr) => {
            if (compErr) {
                return res.json({
                    stdout: stdout,
                    stderr: stderr || compErr.message,
                    exitCode: compErr.code
                });
            }
            execute();
        });
    } else {
        execute();
    }
});

app.listen(port, "0.0.0.0", () => {
    console.log(`Server is running on port ${port}`);
});