function ui_offline() {
    document.body.classList.add('offline');
    document.querySelector('.offline-toast').classList.remove('hidden');
}

function ui_online() {
    document.body.classList.remove('offline');
    document.querySelector('.offline-toast').classList.add('hidden');
}

async function insert_image(state, context, file) {
    const bitmap = await createImageBitmap(file);

    const p = { 'x': state.cursor.x, 'y': state.cursor.y };
    const canvasp = screen_to_canvas(state, p);

    canvasp.x -= bitmap.width / 2;
    canvasp.y -= bitmap.height / 2;

    const form_data = new FormData();
    form_data.append('file', file);

    const resp = await fetch(`/api/image?deskId=${state.desk_id}`, {
        method: 'post',
        body: form_data,
    })

    if (resp.ok) {
        const image_id = await resp.text();
        const event = image_event(image_id, canvasp.x, canvasp.y);
        await queue_event(state, event);
    }
}

function event_size(event) {
    let size = 4; // type

    switch (event.type) {
        case EVENT.PREDRAW:
        case EVENT.MOVE_CURSOR: {
            size += 4 * 2;
            break;
        }
   
        case EVENT.MOVE_CANVAS: {
            size += 4 * 2 + 4;
            break;
        }

        case EVENT.USER_JOINED:
        case EVENT.LEAVE:
        case EVENT.CLEAR: {
            break;
        }

        case EVENT.SET_COLOR: {
            size += 4;
            break;
        }

        case EVENT.SET_WIDTH: {
            size += 2;
            break;
        }

        case EVENT.STROKE: {
            // u32 stroke id + u16 (count) + u16 (width) + u32 (color) + count * (f32, f32) points + count (u8) pressures
            size += 4 + 2 + 2 + 4 + event.points.length * 4 * 2 + round_to_pow2(event.points.length, 4);
            break;
        }

        case EVENT.UNDO:
        case EVENT.REDO: {
            break;
        }

        case EVENT.IMAGE:
        case EVENT.IMAGE_MOVE: {
            size += 4 + 4 + 4; // file id + x + y
            break;
        }

        case EVENT.ERASER: {
            size += 4; // stroke id
            break;
        }

        default: {
            console.error('fuck');
        }
    }

    return size;
}

function find_touch(touchlist, id) {
    for (const touch of touchlist) {
        if (touch.identifier === id) {
            return touch;
        }
    }

    return null;
}

function find_image(state, image_id) {
    for (let i = state.events.length - 1; i >= 0; --i) {
        const event = state.events[i];
        if (event.type === EVENT.IMAGE && !event.deleted && event.image_id === image_id) {
            return event;
        }
    }
}

// TODO: move these to a file? TypedVector
function tv_create(class_name, capacity) {
    return {
        'class_name': class_name,
        'data': new class_name(capacity),
        'capacity': capacity,
        'size': 0, 
    };
}

function tv_create_on(class_name, capacity, buffer, offset) {
    return {
        'class_name': class_name,
        'data': new class_name(buffer, offset, capacity),
        'capacity': capacity,
        'size': 0,
    };
}

function tv_data(tv) {
    return tv.data.subarray(0, tv.size);
}

function tv_bytes(tv) {
    return new Uint8Array(tv.data.buffer, 0, tv.size * tv.data.BYTES_PER_ELEMENT);
}

function tv_ensure(tv, capacity) {
    if (tv.capacity < capacity) {
        const new_data = new tv.class_name(capacity);
        new_data.set(tv_data(tv));
        tv.capacity = capacity;
        tv.data = new_data;
    }
}

function tv_ensure_by(tv, by) {
    tv_ensure(tv, round_to_pow2(tv.size + by, 4096));
}

function tv_add(tv, item) {
    tv.data[tv.size++] = item;
}

function tv_pop(tv) {
    const result = tv.data[tv.size - 1];
    tv.size--;
    return result;
}

function tv_append(tv, typedarray) {
    tv.data.set(typedarray, tv.size);
    tv.size += typedarray.length;
}

function tv_clear(tv) {
    tv.size = 0;
}

function HTML(html) {
    const template = document.createElement('template');
    template.innerHTML = html.trim();
    return template.content.firstChild;
}

function toggle_follow_player(state, player_id) {
    document.querySelectorAll('.player-list .player').forEach(p => p.classList.remove('following'));

    if (state.following_player === null) {
        state.following_player = player_id;
    } else {
        if (player_id === state.following_player) {
            state.following_player = null;
        } else {
            state.following_player = player_id;
        }
    }

    const player_element = document.querySelector(`.player-list .player[data-player-id="${state.following_player}"]`);
    if (player_element) player_element.classList.add('following');

    send_follow(state.following_player);
}

function insert_player_cursor(state, player_id) {
    const color = random_bright_color_from_seed(parseInt(player_id));
    const path_copy = state.cursor_path.cloneNode();
    
    path_copy.style.fill = color;

    const cursor = HTML(`<svg viewBox="0 0 28 28" xmlns="http://www.w3.org/2000/svg" class="player-cursor" data-player-id="${player_id}">${path_copy.outerHTML}</svg>`);
    const player = HTML(`<div class="player" data-player-id="${player_id}"><img src="icons/player.svg"></div>`);

    player.style.background = color;

    player.addEventListener('click', () => {
        toggle_follow_player(state, player_id);
    });

    document.querySelector('.html-hud').appendChild(cursor);
    document.querySelector('.player-list').appendChild(player);

    document.querySelector('.player-list').classList.remove('vhide');

    return cursor;
}

async function load_player_cursor_template(state) {
    const resp = await fetch('icons/player-cursor.svg');
    const text = await resp.text();
    const parser = new DOMParser();
    const parsed_xml = parser.parseFromString(text, 'image/svg+xml');
    const path = parsed_xml.querySelector('path');

    state.cursor_path = path;
}