function push_point(s, x, y, u, v, r, g, b, type) {
    ser_f32(s, x);
    ser_f32(s, y);
    ser_f32(s, u);
    ser_f32(s, v);
    ser_u8(s, r);
    ser_u8(s, g);
    ser_u8(s, b);
    ser_u8(s, type);
}

function push_circle(s, cx, cy, radius, r, g, b) {
    push_point(s, cx - radius, cy - radius, 0, 0, r, g, b, 1);
    push_point(s, cx - radius, cy + radius, 0, 1, r, g, b, 1);
    push_point(s, cx + radius, cy - radius, 1, 0, r, g, b, 1);

    push_point(s, cx + radius, cy + radius, 1, 1, r, g, b, 1);
    push_point(s, cx + radius, cy - radius, 1, 0, r, g, b, 1);
    push_point(s, cx - radius, cy + radius, 0, 1, r, g, b, 1);
}

function push_quad(s, p1x, p1y, p2x, p2y, p3x, p3y, p4x, p4y, r, g, b) {
    push_point(s, p1x, p1y, 0, 0, r, g, b, 0);
    push_point(s, p2x, p2y, 0, 1, r, g, b, 0);
    push_point(s, p3x, p3y, 1, 0, r, g, b, 0);

    push_point(s, p4x, p4y, 1, 1, r, g, b, 0);
    push_point(s, p3x, p3y, 1, 0, r, g, b, 0);
    push_point(s, p2x, p2y, 0, 1, r, g, b, 0);
}

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

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

    if (points.length === 0) {
        return;
    }

    if (points.length === 1) {
        push_circle(s, points[0].x, points[0].y, stroke_width / 2, r, g, b);
        return;
    }

    for (let i = 0; i < points.length - 1; ++i) {
        const px = points[i].x;
        const py = points[i].y;

        const nextpx = points[i + 1].x;
        const nextpy = points[i + 1].y;

        const d1x = nextpx - px;
        const d1y = nextpy - py;

        // Perpendicular to (d1x, d1y), points to the LEFT
        let perp1x = -d1y;
        let perp1y = d1x;

        const perpnorm1 = Math.sqrt(perp1x * perp1x + perp1y * perp1y);

        perp1x /= perpnorm1;
        perp1y /= perpnorm1;

        const s1x = px + perp1x * stroke_width / 2;
        const s1y = py + perp1y * stroke_width / 2;
        const s2x = px - perp1x * stroke_width / 2;
        const s2y = py - perp1y * stroke_width / 2;

        const s3x = nextpx + perp1x * stroke_width / 2;
        const s3y = nextpy + perp1y * stroke_width / 2;
        const s4x = nextpx - perp1x * stroke_width / 2;
        const s4y = nextpy - perp1y * stroke_width / 2;

        push_quad(s, s2x, s2y, s1x, s1y, s4x, s4y, s3x, s3y, r, g, b);
        push_circle(s, px, py, stroke_width / 2, r, g, b);
    }

    const lastp = points[points.length - 1];

    push_circle(s, lastp.x, lastp.y, stroke_width / 2, r, g, b);
}

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

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

function geometry_add_stroke(state, context, stroke) {
    if (!state.online || !stroke) return;

    const bytes_left = context.static_stroke_serializer.size - context.static_stroke_serializer.offset;
    const bytes_needed = (stroke.points.length * 12 + 6) * config.bytes_per_point;

    if (bytes_left < bytes_needed) {
        const old_view   = context.static_stroke_serializer.strview;
        const old_offset = context.static_stroke_serializer.offset;

        const new_size = Math.ceil((context.static_stroke_serializer.size + bytes_needed) * 1.62);

        context.static_stroke_serializer = serializer_create(new_size);
        context.static_stroke_serializer.strview.set(old_view);
        context.static_stroke_serializer.offset = old_offset;
    }

    push_stroke(context.static_stroke_serializer, stroke);
}

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 * 12 + 6) * config.bytes_per_point;
        }
    }

    if (bytes_needed > context.dynamic_stroke_serializer.size) {
        context.dynamic_stroke_serializer = serializer_create(Math.ceil(bytes_needed * 1.62));
    } else {
        context.dynamic_stroke_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 > 0) {
            push_stroke(context.dynamic_stroke_serializer, player);
        }
    }
}

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).length;

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

    gl.bindTexture(gl.TEXTURE_2D, context.textures[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).length;

    for (let id = 0; id < count; ++id) {
        const image = context.textures[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;
}