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 rdp_find_max(state, zoom, stroke, start, end) {
    // Finds a point from the range [start, end) with the maximum distance from the line (start--end) that is also further than EPS
    const EPS = 1.0 / zoom;

    let result = -1;
    let max_dist = 0;

    const ax = state.coordinates.data[stroke.coords_from + start * 2 + 0];
    const ay = state.coordinates.data[stroke.coords_from + start * 2 + 1];
    const bx = state.coordinates.data[stroke.coords_from + end * 2 + 0];
    const by = state.coordinates.data[stroke.coords_from + end * 2 + 1];

    const dx = bx - ax;
    const dy = by - ay;

    const dist_ab = Math.sqrt(dx * dx + dy * dy);
    const dir_nx = dy / dist_ab;
    const dir_ny = -dx / dist_ab;

    for (let i = start + 1; i < end; ++i) {
        const px = state.coordinates.data[stroke.coords_from + i * 2 + 0];
        const py = state.coordinates.data[stroke.coords_from + i * 2 + 1];
        
        const apx = px - ax;
        const apy = py - ay;

        const dist = Math.abs(apx * dir_nx + apy * dir_ny);

        if (dist > EPS && dist > max_dist) {
            result = i;
            max_dist = dist;
        }
    }

    state.stats.rdp_max_count++;
    state.stats.rdp_segments += end - start - 1;

    return result;
}

function do_lod(state, context) {
    let stack = new Array(4096);

    for (let i = 0; i < context.clipped_indices.count; ++i) {
        const stroke_index = context.clipped_indices.data[i];
        const stroke = state.events[stroke_index];
        const point_count = (stroke.coords_to - stroke.coords_from) / 2;

        if (point_count > 4096) {
            stack = new Array(round_to_pow2(point_count, 4096));
        }

        // Basic CSR crap
        state.segments_from.data[i] = state.segments.count;

        if (state.canvas.zoom <= stroke.turns_into_straight_line_zoom) {
            state.segments.data[state.segments.count++] = 0;
            state.segments.data[state.segments.count++] = point_count - 1;
        } else {
            let segment_count = 2;

            state.segments.data[state.segments.count++] = 0;
            
            let head = 0;
            // Using stack.push() allocates even if the stack is pre-allocated!
            
            stack[head++] = 0;
            stack[head++] = 0;
            stack[head++] = point_count - 1;

            while (head > 0) {
                const end = stack[--head];
                const value = start = stack[--head];
                const type = stack[--head];

                if (type === 1) {
                    state.segments.data[state.segments.count++] = value;
                } else {
                    const max = rdp_find_max(state, state.canvas.zoom, stroke, start, end);
                    if (max !== -1) {
                        segment_count += 1;
                        
                        stack[head++] = 0;
                        stack[head++] = max;
                        stack[head++] = end;

                        stack[head++] = 1;
                        stack[head++] = max;
                        stack[head++] = -1;
                        
                        stack[head++] = 0;
                        stack[head++] = start;
                        stack[head++] = max;
                    }
                }
            }

            state.segments.data[state.segments.count++] = point_count - 1;

            if (segment_count === 2 && state.canvas.zoom > stroke.turns_into_straight_line_zoom) {
                stroke.turns_into_straight_line_zoom = state.canvas.zoom;
            }
        }
    }
}

function geometry_write_instances(state, context) {
    if (state.segments_from.cap < context.clipped_indices.count + 1) {
        state.segments_from.cap = round_to_pow2(context.clipped_indices.count + 1, 4096);
        state.segments_from.data = new Uint32Array(state.segments_from.cap);
    }

    if (state.segments.cap < state.coordinates.size / 2) {
        state.segments.cap = round_to_pow2(state.coordinates.size, 4096); 
        state.segments.data = new Uint32Array(state.segments.cap);
    }
    
    state.segments_from.count = 0;
    state.segments.count = 0;

    state.stats.rdp_max_count = 0;
    state.stats.rdp_segments = 0;

    do_lod(state, context);

    state.segments_from.data[context.clipped_indices.count] = state.segments.count;
    state.segments_from.count = context.clipped_indices.count + 1;
        
    context.instance_data_points = tv_ensure(context.instance_data_points, state.segments.count * 2);
    context.instance_data_ids = tv_ensure(context.instance_data_ids, state.segments.count);

    tv_clear(context.instance_data_points);
    tv_clear(context.instance_data_ids);

    for (let i = 0; i < state.segments_from.count - 1; ++i) {
        const stroke_index = context.clipped_indices.data[i];
        const stroke = state.events[stroke_index];
        const from = state.segments_from.data[i];
        const to = state.segments_from.data[i + 1];

        for (let j = from; j < to; ++j) {
            const base_this = state.segments.data[j];

            const ax = state.coordinates.data[stroke.coords_from + base_this * 2 + 0];
            const ay = state.coordinates.data[stroke.coords_from + base_this * 2 + 1];
           
            tv_add(context.instance_data_points, ax);
            tv_add(context.instance_data_points, ay);

            // Pack 1 into highest bit of stroke_index if we should not draw a segemtn from this
            // point to the next one
            if (j != to - 1) {
                tv_add(context.instance_data_ids, stroke_index);
            } else {
                tv_add(context.instance_data_ids, stroke_index | (1 << 31));
            }
        }
    }

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

    return state.segments.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);
    stroke.turns_into_straight_line_zoom = -1;

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

    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;
        }
    }

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