function push_stroke(s, stroke, stroke_index) {
    const points = stroke.points;

    if (points.length < 2) {
        return;
    }

    for (let i = 0; i < points.length - 1; ++i) {
        const from = points[i];
        const to = points[i + 1];
        
        ser_f32(s, from.x);
        ser_f32(s, from.y);
        ser_f32(s, to.x);
        ser_f32(s, to.y);
        ser_u32(s, stroke_index);
    }
}

function geometry_prepare_stroke(state) {
    if (!state.online) {
        return null;
    }

    if (state.players[state.me].points.length === 0) {
        return null;
    }    

    const points = process_stroke2(state.players[state.me].points); 

    return {
        'color': state.players[state.me].color,
        'width': state.players[state.me].width,
        'points': points,
        'user_id': state.me,
    };
}


function geometry_write_instances(state, context) {
    state.stats.rdp_max_count = 0;
    state.stats.rdp_segments = 0;

    const segment_count = do_lod(state, context);

    if (config.debug_print) console.debug('instances:', state.segments.count, 'rdp max:', state.stats.rdp_max_count, 'rdp segments:', state.stats.rdp_segments);

    return segment_count;
}

function geometry_add_stroke(state, context, stroke, stroke_index, skip_bvh = false) {
    if (!state.online || !stroke || stroke.coords_to - stroke.coords_from === 0) return;

    stroke.bbox = stroke_bbox(state, stroke);
    stroke.area = box_area(stroke.bbox);

    context.stroke_data = ser_ensure_by(context.stroke_data, config.bytes_per_stroke);

    tv_add(state.wasm.buffers['line_threshold'].tv, -1);
    state.wasm.buffers['line_threshold'].used += 4;

    const color_u32 = stroke.color;
    const r = (color_u32 >> 16) & 0xFF;
    const g = (color_u32 >> 8) & 0xFF;
    const b = color_u32 & 0xFF;

    ser_u16(context.stroke_data, r);
    ser_u16(context.stroke_data, g);
    ser_u16(context.stroke_data, b);
    ser_u16(context.stroke_data, stroke.width);

    if (!skip_bvh) bvh_add_stroke(state.bvh, stroke_index, stroke);
}

function geometry_delete_stroke(state, context, stroke_index) {
    // NEXT: deleted wrong stroke
    let offset = 0;

    for (let i = 0; i < stroke_index; ++i) {
        const event = state.events[i];
        
        if (event.type === EVENT.STROKE) {
            offset += (event.points.length * 12 + 6) * config.bytes_per_point;
        }   
    }

    const stroke = state.events[stroke_index];

    for (let i = 0; i < stroke.points.length * 12 + 6; ++i) {
        context.static_stroke_serializer.view.setUint8(offset + config.bytes_per_point - 1, 125);
        offset += config.bytes_per_point;
    }
}

function recompute_dynamic_data(state, context) {
    let total_points = 0;
    let total_strokes = 0;

    for (const player_id in state.players) {
        const player = state.players[player_id];
        if (player.points.length > 0) {
            total_points += player.points.length;
            total_strokes += 1;
        }
    }

    tv_ensure(context.dynamic_instance_points, round_to_pow2(total_points * 2, 4096));
    tv_ensure(context.dynamic_instance_ids, round_to_pow2(total_points, 4096));

    tv_clear(context.dynamic_instance_points);
    tv_clear(context.dynamic_instance_ids);
    
    context.dynamic_stroke_data = ser_ensure(context.dynamic_stroke_data, config.bytes_per_stroke * total_strokes);
    ser_clear(context.dynamic_stroke_data);

    let stroke_index = 0;

    for (const player_id in state.players) {
        // player has the same data as their current stroke: points, color, width
        const player = state.players[player_id];
    
        for (let i = 0; i < player.points.length; ++i) {
            const p = player.points[i];

            tv_add(context.dynamic_instance_points, p.x);
            tv_add(context.dynamic_instance_points, p.y);

            if (i !== player.points.length - 1) {
                tv_add(context.dynamic_instance_ids, stroke_index);
            } else {
                tv_add(context.dynamic_instance_ids, stroke_index | (1 << 31));
            }
        }
        
        if (player.points.length > 0) {
            const color_u32 = player.color;
            const r = (color_u32 >> 16) & 0xFF;
            const g = (color_u32 >> 8) & 0xFF;
            const b = color_u32 & 0xFF;

            ser_u16(context.dynamic_stroke_data, r);
            ser_u16(context.dynamic_stroke_data, g);
            ser_u16(context.dynamic_stroke_data, b);
            ser_u16(context.dynamic_stroke_data, player.width);

            stroke_index += 1; // TODO: proper player Z order
        }
    }

    context.dynamic_segment_count = total_points;
    context.dynamic_stroke_count = total_strokes;
}

function geometry_add_point(state, context, player_id, point) {
    if (!state.online) return;
    state.players[player_id].points.push(point);
    recompute_dynamic_data(state, context);
}

function geometry_clear_player(state, context, player_id) {
    if (!state.online) return;
    state.players[player_id].points.length = 0;
    recompute_dynamic_data(state, context);
}

function add_image(context, image_id, bitmap, p) {
    const x = p.x;
    const y = p.y;
    const gl = context.gl;
    const id = Object.keys(context.textures['image']).length;

    context.textures['image'][id] = {
        'texture': gl.createTexture(),
        'image_id': image_id
    };

    gl.bindTexture(gl.TEXTURE_2D, context.textures['image'][id].texture);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, bitmap);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

    context.quad_positions.push(...[
        x,                 y,
        x,                 y + bitmap.height,
        x + bitmap.width,  y + bitmap.height,

        x + bitmap.width,  y,
        x,                 y,
        x + bitmap.width,  y + bitmap.height,
    ]);

    context.quad_texcoords.push(...[
        0, 0,
        0, 1,
        1, 1,
        1, 0,
        0, 0,
        1, 1,
    ]);

    context.quad_positions_f32 = new Float32Array(context.quad_positions);
    context.quad_texcoords_f32 = new Float32Array(context.quad_texcoords);
}

function move_image(context, image_event) {
    const x = image_event.x;
    const y = image_event.y;

    const count = Object.keys(context.textures['image']).length;

    for (let id = 0; id < count; ++id) {
        const image = context.textures['image'][id];
        if (image.image_id === image_event.image_id) {
            context.quad_positions[id * 12 + 0] = x;
            context.quad_positions[id * 12 + 1] = y;
            context.quad_positions[id * 12 + 2] = x;
            context.quad_positions[id * 12 + 3] = y + image_event.height;
            context.quad_positions[id * 12 + 4] = x + image_event.width;
            context.quad_positions[id * 12 + 5] = y + image_event.height;

            context.quad_positions[id * 12 + 6] = x + image_event.width;
            context.quad_positions[id * 12 + 7] = y;
            context.quad_positions[id * 12 + 8] = x;
            context.quad_positions[id * 12 + 9] = y;
            context.quad_positions[id * 12 + 10] = x + image_event.width;
            context.quad_positions[id * 12 + 11] = y + image_event.height;

            context.quad_positions_f32 = new Float32Array(context.quad_positions);

            break;
        }
    }
}

function image_at(state, x, y) {
    for (let i = state.events.length - 1; i >= 0; --i) {
        const event = state.events[i];
        if (event.type === EVENT.IMAGE && !event.deleted) {
            if ('height' in event && 'width' in event) {
                if (event.x <= x && x <= event.x + event.width && event.y <= y && y <= event.y + event.height) {
                    return event;
                }
            }
        }
    }

    return null;
}