function init_listeners(state, context) {
    window.addEventListener('keydown', (e) => keydown(e, state));
    window.addEventListener('keyup', (e) => keyup(e, state));
    
    context.canvas.addEventListener('mousedown', (e) => mousedown(e, state, context));
    context.canvas.addEventListener('mousemove', (e) => mousemove(e, state, context));
    context.canvas.addEventListener('mouseup', (e) => mouseup(e, state, context));
    context.canvas.addEventListener('wheel', (e) => wheel(e, state, context));
}

function keydown(e, state) {
    if (e.code === 'Space') {
        state.spacedown = true;
    } else if (e.code === 'KeyD') {

    }
}

function keyup(e, state) {
    if (e.code === 'Space') {
        state.spacedown = false;
        state.moving = false;
    }
}

function mousedown(e, state, context) {
    if (state.spacedown) {
        state.moving = true;
        return;
    }

    const x = cursor_x = (e.clientX - state.canvas.offset.x) / state.canvas.zoom;
    const y = cursor_y = (e.clientY - state.canvas.offset.y) / state.canvas.zoom;
    
    clear_dynamic_stroke(state, context);
    update_dynamic_stroke(state, context, {'x': x, 'y': y});
    state.drawing = true;

    window.requestAnimationFrame(() => draw(state, context));
}

function mousemove(e, state, context) {
    let do_draw = false;

    if (state.moving) {
        state.canvas.offset.x += e.movementX;
        state.canvas.offset.y += e.movementY;
        do_draw = true;
    }

    if (state.drawing) {
        const x = cursor_x = (e.clientX - state.canvas.offset.x) / state.canvas.zoom;
        const y = cursor_y = (e.clientY - state.canvas.offset.y) / state.canvas.zoom;
        update_dynamic_stroke(state, context, {'x': x, 'y': y});
        do_draw = true;
    }

    if (do_draw) {
        window.requestAnimationFrame(() => draw(state, context));
    }
}

function mouseup(e, state, context) {
    if (state.spacedown) {
        state.moving = false;
        return;
    }

    if (state.drawing) {
        const stroke = {
            'color': Math.round(Math.random() * 4294967295),
            'points': process_stroke(state.current_stroke.points)
        };

        add_static_stroke(state, context, stroke);
        clear_dynamic_stroke(state, context);        
        state.drawing = false;

        window.requestAnimationFrame(() => draw(state, context));

        return;
    }
}

function wheel(e, state, context) {
    const x = Math.round((e.clientX - state.canvas.offset.x) / state.canvas.zoom);
    const y = Math.round((e.clientY - state.canvas.offset.y) / state.canvas.zoom);

    const dz = (e.deltaY < 0 ? 0.1 : -0.1);
    const old_zoom = state.canvas.zoom;

    state.canvas.zoom *= (1.0 + dz);

    if (state.canvas.zoom > 100.0) {
        state.canvas.zoom = old_zoom;
        return;
    }

    if (state.canvas.zoom < 0.2) {
        state.canvas.zoom = old_zoom;
        return;
    }

    const zoom_offset_x = Math.round((dz * old_zoom) * x);
    const zoom_offset_y = Math.round((dz * old_zoom) * y);

    state.canvas.offset.x -= zoom_offset_x;
    state.canvas.offset.y -= zoom_offset_y;

    window.requestAnimationFrame(() => draw(state, context));
}