const FILE_CHUNK_SIZE = 16384;
const MAX_FILES = 256;
const SAMPLE_WINDOW = 100;
const STALL_THRESHOLD = 1000;

let files = [];

let socket;
let fileIndex = 0;
let byteIndex = 0;
let bytesSent = 0;
let totalBytes = 0;
let timestamps = [];

let maxSize = null;

let uploadPassword;

let messageBox;
let fileInput;
let fileList;
let uploadButton;
let lifetimeInput;
let downloadCode;

let progressPercentage;
let progressSize;
let progressRate;
let progressEta;
let progressBar;

window.addEventListener('beforeunload', (event) => {
    if (socket && socket.readyState !== 3) {
        event.returnValue = "Upload is still in progress!";
    }
});

document.addEventListener('DOMContentLoaded', () => {
    document.body.className = 'landing';

    messageBox = document.getElementById('message');
    fileInput = document.getElementById('file_input');
    fileList = document.getElementById('file_list');
    uploadButton = document.getElementById('upload_button');
    lifetimeInput = document.getElementById('lifetime');
    downloadCode = document.getElementById('download_code');
    progressPercentage = document.getElementById('progress_percentage');
    progressSize = document.getElementById('progress_size');
    progressRate = document.getElementById('progress_rate');
    progressEta = document.getElementById('progress_eta');
    progressBar = document.getElementById('progress_bar');

    fetch('/upload/limits.json')
        .then((res) => res.json())
        .then((limits) => {
            if (limits.open === false) {
                document.body.className = 'uploads_closed landing';
                return;
            }
            maxSize = limits.max_size;
            updateMaxLifetime(limits.max_lifetime);
        });

    const uploadPasswordInput = document.getElementById('upload_password');
    const uploadPasswordForm = document.getElementById('upload_password_form');
    uploadPasswordForm.addEventListener('submit', (e) => {
        e.preventDefault();
        uploadPassword = uploadPasswordInput.value;
        fetch('/upload/check_password', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ password: uploadPassword }),
        }).then((res) => {
            if (res.ok) {
                updateFiles();
            } else {
                messageBox.textContent = (res.status === 403) ? 'Incorrect password' : 'An error occurred';
                uploadPasswordInput.value = '';
                document.body.className = 'error landing';
            }
        });
    });

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

    uploadButton.addEventListener('click', beginUpload);

    const downloadCodeContainer = document.getElementById('download_code_container');
    downloadCodeContainer.addEventListener('click', () => {
        const downloadUrl = new URL(`download?code=${downloadCode.textContent}`, window.location);
        navigator.clipboard.writeText(downloadUrl.href);
        downloadCodeContainer.className = 'copied';
    });
    downloadCodeContainer.addEventListener('mouseleave', () => {
        downloadCodeContainer.className = '';
    });
});

function updateFiles() {
    const fileInputMessage = document.getElementById('file_input_message');

    totalBytes = files.reduce((acc, file) => acc + file.size, 0);

    fileInput.disabled = (files.length >= MAX_FILES || (maxSize !== null && totalBytes >= maxSize));

    let extraClasses = '';
    if (maxSize !== null && totalBytes > maxSize) {
        uploadButton.disabled = true;
        displayError(`The maximum size for uploads is ${displaySize(maxSize)}`);
        extraClasses = ' error';
    } else {
        uploadButton.disabled = false;
    }

    if (files.length === 0) {
        fileInputMessage.textContent = 'Select files to upload...';
        document.body.className = 'no_files selecting' + extraClasses;
    } else {
        fileInputMessage.textContent = 'Select more files to upload...';
        uploadButton.textContent = `Upload ${files.length} file${files.length > 1 ? 's' : ''} (${displaySize(totalBytes)})`;
        document.body.className = 'selecting' + extraClasses;
    }
}

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

    files.push(newFile);

    addListEntry(newFile);
}

function addListEntry(file) {
    const listEntry = document.createElement('tr');

    const deleteButtonCell = document.createElement('td');
    deleteButtonCell.className = 'delete_button';
    deleteButtonCell.addEventListener('click', () => {
        removeFile(file.name);
        listEntry.remove();
        updateFiles();
    });

    const sizeCell = document.createElement('td');
    sizeCell.className = 'file_size';
    sizeCell.textContent = displaySize(file.size);

    const nameCell = document.createElement('td');
    nameCell.className = 'file_name';
    nameCell.textContent = file.name;

    listEntry.appendChild(deleteButtonCell);
    listEntry.appendChild(sizeCell);
    listEntry.appendChild(nameCell);

    fileList.appendChild(listEntry);
}

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

function beginUpload() {
    if (files.length === 0 || files.length > MAX_FILES) { return; }
    if (socket && socket.readyState !== 3) { return; }

    fileIndex = 0;
    byteIndex = 0;
    bytesSent = 0;
    timestamps = [];

    let websocketUrl = new URL('upload', window.location);
    websocketUrl.protocol = (window.location.protocol === 'http:') ? 'ws:' : 'wss:';
    socket = new WebSocket(websocketUrl);
    socket.addEventListener('open', sendManifest);
    socket.addEventListener('message', handleMessage);
    socket.addEventListener('close', handleClose);
}

function sendManifest() {
    const lifetime = parseInt(lifetimeInput.value);
    const fileMetadata = files.map((file) => ({
        name: file.name,
        size: file.size,
        modtime: file.lastModified,
    }));
    socket.send(JSON.stringify({
        files: fileMetadata,
        lifetime,
        password: uploadPassword,
    }));
}

function handleMessage(msg) {
    if (bytesSent === 0) {
        let reply;
        try {
            reply = JSON.parse(msg.data);
        } catch (error) {
            socket.close();
            displayError('Received an invalid response from the server');
            console.error(error);
            return;
        }
        if (reply.type === 'ready') {
            downloadCode.textContent = reply.code;
            updateProgress();
            document.body.className = 'uploading';
            sendData();
            return;
        }

        // we're going to display a more useful error message
        socket.removeEventListener('close', handleClose);
        socket.close();
        if (reply.type === 'too_big') {
            maxSize = reply.max_size;
            updateFiles();
        } else if (reply.type === 'too_long') {
            updateMaxLifetime(reply.max_lifetime);
            displayError(`The maximum retention time for uploads is ${reply.max_lifetime} days`);
        } else if (reply.type === 'incorrect_password') {
            messageBox.textContent = ('Incorrect password');
            document.body.className = 'error landing';
        } else if (reply.type === 'error') {
            displayError(reply.details);
        }
    } else {
        if (msg.data === 'ack') {
            sendData();
        } else {
            console.error('Received unexpected message from server instead of ack', msg.data);
            displayError();
            socket.close();
        }
    }
}

function updateMaxLifetime(lifetime) {
    let options = Array.from(lifetimeInput.options);
    options.reverse();
    for (const option of options) {
        if (option.value > lifetime) {
            option.disabled = true;
        } else {
            option.selected = true;
            break;
        }
    }
}

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

        // It's ok if the monotonically increasing fields like
        // percentage are updating super quickly, but it's awkward for
        // rate and ETA
        const now = Date.now() / 1000;
        if (timestamps.length === 0 || now - timestamps.at(-1)[0] > 1) {
            timestamps.push([now, bytesSent]);
            if (timestamps.length > SAMPLE_WINDOW) { timestamps.shift(); }
        }

        updateProgress();
    } else {
        fileIndex += 1;
        byteIndex = 0;
        sendData();
    }
}

function updateProgress() {
    let percentage;
    if (totalBytes === 0) {
        percentage = "0%";
    } else {
        percentage = `${(bytesSent*100/totalBytes).toFixed(1)}%`;
    }
    progressPercentage.textContent = percentage;

    progressSize.textContent = `${displaySize(bytesSent)}/${displaySize(totalBytes)}`;

    if (timestamps.length >= 2) {
        const start = timestamps.at(0);
        const end = timestamps.at(-1);
        const rate = (end[1] - start[1])/(end[0] - start[0]);
        progressRate.textContent = `${displaySize(rate)}/s`;

        if (rate > STALL_THRESHOLD) {
            // Use the value from timestamps rather than bytesSent to avoid awkward UI thrashing
            const remaining = (totalBytes - end[1]) / rate;
            progressEta.textContent = `${displayTime(remaining)} remaining`;
        } else {
            progressEta.textContent = "stalled";
        }
    } else {
        progressRate.textContent = "???B/s";
        progressEta.textContent = "??? remaining";
    }

    progressBar.style.backgroundSize = percentage;

    const fileEntries = Array.from(fileList.children);
    for (entry of fileEntries.slice(0, fileIndex)) {
        entry.style.backgroundSize = "100%";
    }
    if (fileIndex < files.length) {
        const currentFile = files[fileIndex];
        if (currentFile.size > 0) {
            fileEntries[fileIndex].style.backgroundSize = `${(byteIndex*100/currentFile.size)}%`;
        }
    }
}

function handleClose(e) {
    console.log('Websocket closed', e);
    if (fileIndex >= files.length) {
        displayCompletion();
    } else {
        let error;
        if (e.code === 1011) {
            if (e.reason) {
                error = `Server error: ${e.reason}`;
            } else {
                error = "A server error has occurred."
            }
        } else if (e.reason) {
            error = e.reason;
        }
        displayError(error);
    }
}

function finishSending() {
    if (socket.bufferedAmount > 0) {
        setTimeout(finishSending, 1000);
        return;
    }
    socket.close();
    displayCompletion();
}

function displayCompletion() {
    messageBox.textContent = 'Upload complete!';
    document.body.className = 'completed';
    removePerFileProgressBars(); // completed file backgrounds are handled in CSS
}

function displayError(error) {
    messageBox.textContent = error || 'An error has occurred.';
    document.body.className = 'selecting error';
    removePerFileProgressBars();
}

function removePerFileProgressBars() {
    const fileEntries = Array.from(fileList.children);
    for (entry of fileEntries) {
        entry.style.backgroundSize = "0%";
    }
}