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1/*
2 * Copyright (c) 2022 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 *     http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16import { EditStack } from './utils/EditStack';
17import { ImageFilterBase } from './base/ImageFilterBase';
18import { PixelMapWrapper } from './base/PixelMapWrapper';
19
20enum CacheDirection {
21    BACKWARD,
22    FORWARD
23}
24
25export class ImageFilterStack extends EditStack<ImageFilterBase> {
26    private static readonly CACHE_MAX: number = 20;
27    private cacheStart: number = 0;
28    private cacheEnd: number = 0;
29    private origin: PixelMapWrapper = undefined;
30
31    apply(pixelMap: PixelMapWrapper): PixelMapWrapper {
32        super.executeEach((filter: ImageFilterBase) => {
33            pixelMap = filter.render(pixelMap);
34        }, super.getLength());
35        return pixelMap;
36    }
37
38    push(filter: ImageFilterBase) {
39        super.push(filter);
40        this.updateCache(CacheDirection.FORWARD);
41    }
42
43    releaseAll() {
44        super.executeEach((filter: ImageFilterBase) => {
45            filter && filter.release();
46        }, super.getLength());
47        super.reset();
48        this.cacheStart = 0;
49        this.cacheEnd = 0;
50    }
51
52    setOriginPixelMap(origin: PixelMapWrapper) {
53        this.origin = origin;
54    }
55
56    doRedo(): PixelMapWrapper {
57        let position: number = super.redo();
58        this.updateCache(CacheDirection.FORWARD);
59        return super.at(position).getCache();
60    }
61
62    doUndo(): PixelMapWrapper {
63        let position: number = super.undo();
64        this.updateCache(CacheDirection.BACKWARD);
65        return super.at(position).getCache();
66    }
67
68    private shouldReleaseCache(): boolean {
69        return (this.cacheEnd - this.cacheStart >= ImageFilterStack.CACHE_MAX);
70    }
71
72    private updateCache(direction: CacheDirection) {
73        let position = super.getPosition();
74        let filter = super.at(position);
75        if (direction == CacheDirection.BACKWARD) {
76            if (!filter.isCached()) {
77                let pixelMap = this.origin;
78                filter.setCache(this.apply(pixelMap));
79                this.cacheStart--;
80            }
81
82            if (this.shouldReleaseCache()) {
83                super.at(this.cacheEnd).release();
84                this.cacheEnd--;
85            }
86        } else if (direction == CacheDirection.FORWARD) {
87            if (!filter.isCached()) {
88                let pixelMap = (position > 0) ? super.at(position - 1).getCache() : this.origin;
89                filter.setCache(filter.render(pixelMap));
90                this.cacheEnd++;
91            }
92
93            if (this.shouldReleaseCache()) {
94                super.at(this.cacheStart).release();
95                this.cacheStart++;
96            }
97        }
98    }
99}