function init_listeners() {
    document.querySelector('.main').addEventListener('dragover', cancel);
    document.querySelector('.main').addEventListener('drop', drop);
    document.querySelector('.main').addEventListener('click', debug);

    window.addEventListener('keydown', keydown);
    window.addEventListener('keyup', keyup);
}

function debug() {
    schedule_draw();
}

function cancel(e) {
    e.preventDefault();
    e.stopPropagation();
}

function keydown(e) {
    if (e.code === 'ArrowLeft') {
        offset.x += 10 / scale;
    } else if (e.code === 'ArrowRight') {
        offset.x -= 10 / scale;
    } else if (e.code === 'ArrowDown') {
        offset.y -= 10 / scale;
    } else if (e.code === 'ArrowUp') {
        offset.y += 10 / scale;
    } else if (e.code === 'PageUp') {
        scale *= 0.9;
    } else if (e.code === 'PageDown') {
        scale *= 1.1;
    }

    schedule_draw();
}

function keyup(e) {
}

function drop(e) {
    e.preventDefault();

    if (e.dataTransfer.files.length !== 1) {
        console.error('Only one file at once, please!');
        return false;
    }

    const file = e.dataTransfer.files[0];
    const fr = new FileReader();
    
    const upload_failed = () => {
        console.error('Upload failed');
    };

    const upload_started = () => {
        console.log('Upload started');
    };

    const upload_finished = () => {
        const text = fr.result;
        console.log('Finished. String length:', text.length);
        parse(text);        
    };

    const upload_progress = (e) => {
        if (e.lengthComputable) {
            const percent = Math.floor(e.loaded / e.total * 100);
            console.log(`Progress: ${percent}%`);
        } else {
            console.log('Progress: unknown');
        }
    };

    fr.addEventListener('abort', upload_failed);
    fr.addEventListener('error', upload_failed);
    fr.addEventListener('load', upload_finished);
    fr.addEventListener('loadstart', upload_started);
    fr.addEventListener('progress', upload_progress);

    fr.readAsText(file);
}