function init_listeners(state, context) {
    window.addEventListener('keydown', (e) => keydown(e, state, context));
    window.addEventListener('keyup', (e) => keyup(e, state, context));
    window.addEventListener('paste', (e) => paste(e, state, context));

    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('mouseleave', (e) => mouseup(e, state, context));
    context.canvas.addEventListener('contextmenu', cancel);
    context.canvas.addEventListener('wheel', (e) => wheel(e, state, context));

    context.canvas.addEventListener('touchstart', (e) => touchstart(e, state, context));
    context.canvas.addEventListener('touchmove', (e) => touchmove(e, state, context));
    context.canvas.addEventListener('touchend', (e) => touchend(e, state, context));
    context.canvas.addEventListener('touchcancel', (e) => touchend(e, state, context));

    context.canvas.addEventListener('drop', (e) => on_drop(e, state, context));
    context.canvas.addEventListener('dragover', (e) => mousemove(e, state, context));

    debug_panel_init(state, context);
}

function debug_panel_init(state, context) {
    document.getElementById('debug-red').checked = state.debug.red;
    document.getElementById('debug-do-prepass').checked = state.debug.do_prepass;
    document.getElementById('debug-limit-from').checked = state.debug.limit_from;
    document.getElementById('debug-limit-to').checked = state.debug.limit_to;

    document.getElementById('debug-red').addEventListener('change', (e) => {
        state.debug.red = e.target.checked;
        schedule_draw(state, context);
    });

    document.getElementById('debug-do-prepass').addEventListener('change', (e) => {
        state.debug.do_prepass = e.target.checked;
        schedule_draw(state, context);
    });
    
    document.getElementById('debug-limit-from').addEventListener('change', (e) => {
        state.debug.limit_from = e.target.checked;
        schedule_draw(state, context);
    });
    
    document.getElementById('debug-limit-to').addEventListener('change', (e) => {
        state.debug.limit_to = e.target.checked;
        schedule_draw(state, context);
    });

    document.getElementById('debug-render-from').addEventListener('input', (e) => {
        state.debug.render_from = parseInt(e.target.value);
        schedule_draw(state, context);
    });
    
    document.getElementById('debug-render-to').addEventListener('input', (e) => {
        state.debug.render_to = parseInt(e.target.value);
        schedule_draw(state, context);
    });

    document.getElementById('debug-begin-benchmark').addEventListener('click', (e) => {
        state.canvas.zoom = config.benchmark.zoom;
        state.canvas.offset.x = config.benchmark.offset.x;
        state.canvas.offset.y = config.benchmark.offset.y;

        state.debug.benchmark_mode = true;

        const origin_x = state.canvas.offset.x;
        const origin_y = state.canvas.offset.y;
        const original_button_text = e.target.innerText;

        let frame = 0;

        state.debug.on_benchmark = () => {
            if (frame >= config.benchmark.frames) {
                state.debug.benchmark_mode = false;
                e.target.disabled = false;
                e.target.innerText = original_button_text;
                return false;
            }

            state.canvas.offset.x = origin_x + Math.round(100 * Math.cos(frame / 360));
            state.canvas.offset.y = origin_y + Math.round(100 * Math.sin(frame / 360));
            frame += 1;

            return true;
        }

        e.target.disabled = true;
        e.target.innerText = 'Benchmark in progress...';

        schedule_draw(state, context);
    });
}

function cancel(e) {
    e.preventDefault();
    return false;
}

function zenmode() {
    document.querySelector('.pallete-wrapper').classList.toggle('hidden');
    document.querySelector('.sizer-wrapper').classList.toggle('hidden');
}

async function paste(e, state, context) {
    const items = (e.clipboardData || e.originalEvent.clipboardData).items;
    for (const item of items) {
        if (item.kind === 'file') {
            const file = item.getAsFile();
            await insert_image(state, context, file);
        }
    }
}

function keydown(e, state, context) {
    if (e.code === 'Space' && !state.drawing) {
        state.spacedown = true;
        context.canvas.classList.add('movemode');
    } else if (e.code === 'Tab') {
        e.preventDefault();
        zenmode();
    } else if (e.code === 'KeyZ') {
        const topleft = screen_to_canvas(state, {'x': 0, 'y': 0});
        const bottomright = screen_to_canvas(state, {'x': context.canvas.width, 'y': context.canvas.height});

        for (let i = 0; i < state.events.length; ++i) {
            const event = state.events[i];

            if (event.type === EVENT.STROKE) {
                let on_screen = false;

                for (const p of event.points) {
                    if (topleft.x <= p.x && p.x <= bottomright.x && topleft.y <= p.y && p.y <= bottomright.y) {
                        on_screen = true;
                        break;
                    }
                }

                if (on_screen) {
                    console.log(i);
                }
            }
        }
    } else if (e.code === 'KeyD') {
        document.querySelector('.debug-window').classList.toggle('dhide');
    }
}

function keyup(e, state, context) {
    if (e.code === 'Space' && state.spacedown) {
        state.spacedown = false;
        state.moving = false;
        context.canvas.classList.remove('movemode');
    }
}

function mousedown(e, state, context) {
    const screenp = {'x': window.devicePixelRatio * e.clientX, 'y': window.devicePixelRatio * e.clientY};
    const canvasp = screen_to_canvas(state, screenp);

    if (e.button === 2) {
        // Right click on image to select it
        const image_event = image_at(state, canvasp.x, canvasp.y);

        if (image_event) {
            context.active_image = image_event.image_id;
        } else {
            context.active_image = null;
        }

        schedule_draw(state, context);

        return;
    }

    if (e.button !== 0) {
        return;
    }

    if (context.active_image) {
        // Move selected image with left click
        const image_event = image_at(state, canvasp.x, canvasp.y);
        if (image_event && image_event.image_id === context.active_image) {
            state.moving_image = image_event;
            return;        
        }
    }

    if (state.spacedown) {
        state.moving = true;
        context.canvas.classList.add('moving');
        return;
    }

    if (state.tools.active === 'pencil') {
        geometry_clear_player(state, context, state.me);
        geometry_add_point(state, context, state.me, canvasp);

        state.drawing = true;
        context.active_image = null;

        schedule_draw(state, context);
    } else if (state.tools.active === 'ruler') {

    } else if (state.tools.active === 'eraser') {
        state.erasing = true;
    }
}

function mousemove(e, state, context) {
    e.preventDefault();

    let do_draw = false;

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

    if (state.moving_image) {
        state.moving_image.x += e.movementX / state.canvas.zoom;
        state.moving_image.y += e.movementY / state.canvas.zoom;
        move_image(context, state.moving_image);
        do_draw = true;
    }

    const screenp = {'x': window.devicePixelRatio * e.clientX, 'y': window.devicePixelRatio * e.clientY};
    const canvasp = screen_to_canvas(state, screenp);

    if (state.drawing) {
        geometry_add_point(state, context, state.me, canvasp);
        fire_event(state, predraw_event(canvasp.x, canvasp.y));
        do_draw = true;
    }

    if (state.erasing) {
        const p1 = screen_to_canvas(state, state.cursor);
        const p2 = { 'x': canvasp.x, 'y': canvasp.y };
        const erased = strokes_intersect_line(state, p1, p2);

        for (const index of erased) {
            if (!state.events[index].deleted) {
                state.events[index].deleted = true;
                do_draw = true;
                geometry_delete_stroke(state, context, index);
            }
        }
    }

    if (do_draw) {
        schedule_draw(state, context);
    }

    state.cursor = screenp;

    return false;
}

function mouseup(e, state, context) {
    if (e.button !== 0) {
        return;
    }

    if (state.moving_image) {
        schedule_draw(state, context);
        queue_event(state, image_move_event(context.active_image, state.moving_image.x, state.moving_image.y));
        state.moving_image = null;
        return;
    }

    if (state.moving) {
        state.moving = false;
        context.canvas.classList.remove('moving');
        return;
    }

    if (state.drawing) {
        const stroke = geometry_prepare_stroke(state);

        if (stroke) {
            //geometry_add_stroke(state, context, stroke, 0); // TODO: stroke index?
            queue_event(state, stroke_event(state));
            //geometry_clear_player(state, context, state.me);
            schedule_draw(state, context);
        }

        state.drawing = false;

        return;
    }

    if (state.erasing) {
        state.erasing = false;
        return;
    }
}

function wheel(e, state, context) {
    const screenp = {'x': window.devicePixelRatio * e.clientX, 'y': window.devicePixelRatio * e.clientY};
    const canvasp = screen_to_canvas(state, screenp);

    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 > config.max_zoom) {
        state.canvas.zoom = old_zoom;
        return;
    }

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

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

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

    schedule_draw(state, context);
}

function start_move(e, state, context) {
    // two touch identifiers are expected to be pushed into state.touch.ids at this point

    geometry_clear_player(state, context, state.me); // Hide predraws of this stroke that is not means to be
    fire_event(state, clear_event(state)); // Tell others to hide predraws of this stroke

    for (const touch of e.touches) {
        const screenp = {'x': window.devicePixelRatio * touch.clientX, 'y': window.devicePixelRatio * touch.clientY};

        if (touch.identifier === state.touch.ids[0]) {
            state.touch.first_finger_position = screenp;
        } else if (touch.identifier === state.touch.ids[1]) {
            state.touch.second_finger_position = screenp;
        }
    }
}

function touchstart(e, state, context) {
    e.preventDefault();

    // First finger(s) down?
    if (state.touch.ids.length === 0) {
        if (e.changedTouches.length === 1) {

            // We give a bit of time to add a second finger
            state.touch.waiting_for_second_finger = true;
            state.touch.moves = 0;
            state.touch.buffered.length = 0;
            state.touch.ids.push(e.changedTouches[0].identifier);
            state.touch.drawing = true;

            setTimeout(() => {
                state.touch.waiting_for_second_finger = false;
            }, config.second_finger_timeout);
        } else {
            state.touch.ids.push(e.changedTouches[0].identifier);
            state.touch.ids.push(e.changedTouches[1].identifier);
            start_move(e, state, context);
        }

        return;
    }

    // There are touches already
    if (state.touch.waiting_for_second_finger) {
        if (e.changedTouches.length === 1) {
            state.touch.ids.push(e.changedTouches[0].identifier);
            start_move(e, state, context);
        }

        return;
    }
}

function touchmove(e, state, context) {
    if (state.touch.ids.length === 1) {
        const touch = find_touch(e.changedTouches, state.touch.ids[0]);

        if (!touch) {
            return;
        }

        const screenp = {'x': window.devicePixelRatio * touch.clientX, 'y': window.devicePixelRatio * touch.clientY};
        const canvasp = screen_to_canvas(state, screenp);

        if (state.touch.moving) {
            // Can happen if we have been panning the canvas and lifted one finger,
            // but not the second one
            return;
        }

        state.touch.moves += 1;

        if (state.touch.moves > config.buffer_first_touchmoves) {
            // At this point touch with second finger will NOT start a pan
            state.touch.waiting_for_second_finger = false;
        }

        geometry_add_point(state, context, state.me, canvasp);
        fire_event(state, predraw_event(canvasp.x, canvasp.y));

        schedule_draw(state, context);

        return;
    }

    if (state.touch.ids.length === 2) {
        state.touch.moving = true;

        let first_finger_position = null;
        let second_finger_position = null;

        // A separate loop because touches might be in different order ? (question mark)
        // IMPORTANT: e.touches, not e.changedTouches!
        for (const touch of e.touches) {
            const screenp = {'x': window.devicePixelRatio * touch.clientX, 'y': window.devicePixelRatio * touch.clientY};

            if (touch.identifier === state.touch.ids[0]) {
                first_finger_position = screenp;
            } else if (touch.identifier === state.touch.ids[1]) {
                second_finger_position = screenp;
            }
        }

        const old_finger_midpoint = mid_v2(state.touch.first_finger_position, state.touch.second_finger_position);
        const new_finger_midpoint = mid_v2(first_finger_position, second_finger_position);

        const new_finger_midpoint_canvas = mid_v2(
            screen_to_canvas(state, first_finger_position),
            screen_to_canvas(state, second_finger_position)
        );

        const old_finger_distance = dist_v2(state.touch.first_finger_position, state.touch.second_finger_position);
        const new_finger_distance = dist_v2(first_finger_position, second_finger_position);

        const dx = new_finger_midpoint.x - old_finger_midpoint.x;
        const dy = new_finger_midpoint.y - old_finger_midpoint.y;

        const old_zoom = state.canvas.zoom;

        state.canvas.offset.x += dx;
        state.canvas.offset.y += dy;

        // console.log(new_finger_distance, state.touch.finger_distance);

        const scale_by = new_finger_distance / old_finger_distance;
        const dz = state.canvas.zoom * (scale_by - 1.0);

        const zoom_offset_x = dz * new_finger_midpoint_canvas.x;
        const zoom_offset_y = dz * new_finger_midpoint_canvas.y;

        if (config.min_zoom <= state.canvas.zoom * scale_by && state.canvas.zoom * scale_by <= config.max_zoom) {
            state.canvas.zoom *= scale_by;
            state.canvas.offset.x -= zoom_offset_x;
            state.canvas.offset.y -= zoom_offset_y;
        }

        state.touch.first_finger_position = first_finger_position;
        state.touch.second_finger_position = second_finger_position;

        schedule_draw(state, context);

        return;
    }
}

function touchend(e, state, context) {
    for (const touch of e.changedTouches) {
        if (state.touch.drawing) {
            if (state.touch.ids[0] == touch.identifier) {
                // const event = stroke_event();
                // await queue_event(event);
                
                const stroke = geometry_prepare_stroke(state);

                if (false && stroke) { // TODO: FIX!
                    geometry_add_stroke(state, context, stroke, 0); // TODO: stroke index
                    queue_event(state, stroke_event(state));
                    geometry_clear_player(state, context, state.me);
                    schedule_draw(state, context);
                }

                state.touch.drawing = false;
            }
        }

        const index = state.touch.ids.indexOf(touch.identifier);

        if (index !== -1) {
            state.touch.ids.splice(index, 1);
        }
    }

    if (state.touch.ids.length === 0) {
        // Only allow drawing again when ALL fingers have been lifted
        state.touch.moving = false;
        waiting_for_second_finger = false;
    }
}

async function on_drop(e, state, context) {
    e.preventDefault();

    if (e.dataTransfer.files.length !== 1) {
        return;
    }

    const file = e.dataTransfer.files[0];
    await insert_image(state, context, file);

    schedule_draw(state, context);

    return false;
}