let files = [];

let socket = null;
let fileIndex = 0;
let byteIndex = 0;

function sendMetadata() {
    const metadata = files.map((file) => ({
        name: file.name,
        size: file.size,
        modtime: file.lastModified,
    }));
    socket.send(JSON.stringify(metadata));
}

function finishSending() {
    if (socket.bufferedAmount > 0) {
        window.setTimeout(finishSending, 1000);
        return;
    }
    socket.close();
    alert("done");
}

function sendData() {
    if (fileIndex >= files.length) {
        finishSending();
    }
    const currentFile = files[fileIndex];
    if (byteIndex < currentFile.size) {
        const endpoint = Math.min(byteIndex+8192, currentFile.size);
        const data = currentFile.slice(byteIndex, endpoint);
        socket.send(data);
        byteIndex = endpoint;
    } else {
        fileIndex += 1;
        byteIndex = 0;
        sendData();
    }
}

const fileInput = document.getElementById('file_input');
const fileInputMessage = document.getElementById('file_input_message');
const fileList = document.getElementById('file_list');
const uploadButton = document.getElementById('upload');

function updateButtons() {
    if (files.length === 0) {
        uploadButton.disabled = true;
        fileInputMessage.textContent = 'Select files to upload...';
    } else {
        uploadButton.disabled = false;
        fileInputMessage.textContent = 'Select more files to upload...';
    }
}

updateButtons();

function addFile(newFile) {
    if (files.some((oldFile) => newFile.name === oldFile.name)) { return; }

    files.push(newFile);

    const listEntry = document.createElement('li');
    const deleteButton = document.createElement('button');
    deleteButton.textContent = 'x';
    deleteButton.addEventListener('click', () => {
        removeFile(newFile.name);
        listEntry.remove();
        updateButtons();
    });
    const entryName = document.createElement('span');
    entryName.textContent = newFile.name;
    listEntry.appendChild(deleteButton);
    listEntry.appendChild(entryName);

    fileList.appendChild(listEntry);
}

function removeFile(name) {
    files = files.filter((file) => file.name !== name);
}

fileInput.addEventListener('input', (e) => {
    for (const file of e.target.files) { addFile(file); }
    updateButtons();
    e.target.value = '';
});

uploadButton.addEventListener('click', (e) => {
    if (files.length === 0) { return; }

    fileInput.disabled = true;
    for (const button of document.getElementsByTagName('button')) {
        button.disabled = true;
    }

    socket = new WebSocket('ws://localhost:3000/upload');
    socket.addEventListener('open', sendMetadata);
    socket.addEventListener('message', (msg) => {
        if (msg.data === 'ack') {
            sendData();
        }
    });
})