const fs = require('fs');
const path = require('path');
const spawn = require('child_process').spawn;

function copyToTemp(texDocument, callback) {
    fs.mkdtemp('/tmp/pdfer-', (err, tmpPath) => {
        if (err) {
            callback(err);
            return;
        }

        const docPath = path.join(tmpPath, 'doc.tex');
        fs.writeFile(docPath, texDocument, (err) => {
            if (err) {
                callback(err);
            }
            callback(null, docPath);
        });
    });
}

function generateDoc(docPath, callback) {
    const pdflatex = spawn('pdflatex', [docPath, '-halt-on-error'], {cwd: path.dirname(docPath)});
    pdflatex.stderr.on('data', (data) => {
        console.error('onData', data);
    });

    pdflatex.on('close', (code) => {
        if (code > 0) {
            callback(`pdflatex returned with code ${code}`);
            return;
        }
        console.log('PDF generated');
        const pdfFilePath = docPath.replace('.tex', '.pdf');
        fs.readFile(pdfFilePath, (err, data) => {
            if (err) {
                callback(err);
                return;
            }
            callback(null, data);
        });
    });
}

module.exports = (texDocument, callback) => {
    copyToTemp(texDocument, (err, docPath) => {
        generateDoc(docPath, callback);
    });
};