function push_point(s, x, y, ax, ay, bx, by, thickness, r, g, b, stroke_id) {
    ser_f32(s, x);
    ser_f32(s, y);
    ser_f32(s, thickness);
    ser_f32(s, ax);
    ser_f32(s, ay);
    ser_f32(s, bx);
    ser_f32(s, by);
    ser_u8(s, r);
    ser_u8(s, g);
    ser_u8(s, b);
    ser_align(s, 4);
    ser_u32(s, stroke_id);
}

function push_quad(s, p1x, p1y, p2x, p2y, p3x, p3y, p4x, p4y, ax, ay, bx, by, thickness, r, g, b, stroke_id) {
    push_point(s, p1x, p1y, ax, ay, bx, by, thickness, r, g, b, stroke_id);
    push_point(s, p2x, p2y, ax, ay, bx, by, thickness, r, g, b, stroke_id);
    push_point(s, p3x, p3y, ax, ay, bx, by, thickness, r, g, b, stroke_id);
    push_point(s, p4x, p4y, ax, ay, bx, by, thickness, r, g, b, stroke_id);
}

function push_stroke(s, stroke, stroke_index) {
    const stroke_width = stroke.width;
    const points = stroke.points;
    const color_u32 = stroke.color;
    const radius = stroke_width / 2;

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

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

    for (let i = 0; i < points.length - 1; ++i) {
        const from = points[i];
        const to = points[i + 1];

        const dir_x = to.x - from.x;
        const dir_y = to.y - from.y;
        const len = Math.sqrt(dir_x * dir_x + dir_y * dir_y);

        const dir1_x = dir_x / len;
        const dir1_y = dir_y / len;

        const up_x =  dir_y / len;
        const up_y = -dir_x / len;

        let p1_x = from.x + (up_x - dir1_x) * radius;
        let p1_y = from.y + (up_y - dir1_y) * radius;

        let p2_x = to.x + (up_x + dir1_x) * radius;
        let p2_y = to.y + (up_y + dir1_y) * radius;

        let p3_x = from.x + (-up_x - dir1_x) * radius;
        let p3_y = from.y + (-up_y - dir1_y) * radius;

        let p4_x = to.x + (-up_x + dir1_x) * radius;
        let p4_y = to.y + (-up_y + dir1_y) * radius;

        push_quad(s,
            p1_x, p1_y, 
            p2_x, p2_y, 
            p3_x, p3_y, 
            p4_x, p4_y,
            from.x, from.y, 
            to.x, to.y, 
            stroke_width, 
            r, g, b,
            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_stroke(state, 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_add_stroke(state, context, stroke, stroke_index, skip_bvh = false) {
    if (!state.online || !stroke || stroke.points.length === 0) return;

    stroke.index = state.events.length;

    for (let i = 0; i < config.lod_levels; ++i) {
        // TODO: just pass zoom to process_stroke ?
        const saved_zoom = state.canvas.zoom;
        state.canvas.zoom = Math.pow(0.5, i);
        const points = (i > 0 ? process_stroke(state, stroke.points) : stroke.points);
        state.canvas.zoom = saved_zoom;

        const vertex_serializer = context.lods[i].vertices = ser_ensure_by(context.lods[i].vertices, points.length * 4 * config.bytes_per_point);
        /*  
        event.index = state.events.length;
        event.starting_index = state.starting_index;

        if (event.points.length > 1) {
            state.starting_index += (event.points.length - 1) * 4;
        }

        state.total_points += event.points.length;
        */

        let starting_index = 0;

        if (state.events.length > 0) {
            const last_stroke = state.events[stroke_index - 1].lods[i];
            starting_index = last_stroke.starting_index + (last_stroke.points.length - 1) * 4;
        }

        stroke.lods.push({
            'points': points,
            'starting_index': starting_index,
            'width': stroke.width,
            'color': stroke.color,
        });

        context.lods[i].total_points += points.length;

        push_stroke(vertex_serializer, stroke.lods[stroke.lods.length - 1], stroke_index);

        if (i === 0)  {
            stroke.bbox = stroke_bbox(stroke);
            stroke.area = (stroke.bbox.x2 - stroke.bbox.x1) * (stroke.bbox.y2 - stroke.bbox.y1);
        }
    }
    
    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 bytes_needed = 0;

    for (const player_id in state.players) {
        const player = state.players[player_id];
        if (player.points.length > 0) {
            bytes_needed += player.points.length * 6 * config.bytes_per_point;
        }
    }

    if (bytes_needed > context.dynamic_serializer.size) {
        context.dynamic_serializer = serializer_create(Math.ceil(bytes_needed * 1.62));
    } else {
        context.dynamic_serializer.offset = 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];
        if (player.points.length > 1) {
            push_stroke(context.dynamic_serializer, player, 0);
        }
    }

    context.need_dynamic_upload = true;
}

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);
    schedule_draw(state, context);
}

function add_image(context, image_id, bitmap, p) {
    return; // TODO

    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;
}