/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.camera;

import android.graphics.Bitmap;

class BitmapCache implements ImageViewTouchBase.Recycler {
    public static class Entry {
        int mPos;
        Bitmap mBitmap;
        public Entry() {
            clear();
        }
        public void clear() {
            mPos = -1;
            mBitmap = null;
        }
    }

    private final Entry[] mCache;

    public BitmapCache(int size) {
        mCache = new Entry[size];
        for (int i = 0; i < mCache.length; i++) {
            mCache[i] = new Entry();
        }
    }

    // Given the position, find the associated entry. Returns null if there is
    // no such entry.
    private Entry findEntry(int pos) {
        for (Entry e : mCache) {
            if (pos == e.mPos) {
                return e;
            }
        }
        return null;
    }

    // Returns the thumb bitmap if we have it, otherwise return null.
    public synchronized Bitmap getBitmap(int pos) {
        Entry e = findEntry(pos);
        if (e != null) {
            return e.mBitmap;
        }
        return null;
    }

    public synchronized void put(int pos, Bitmap bitmap) {
        // First see if we already have this entry.
        if (findEntry(pos) != null) {
            return;
        }

        // Find the best entry we should replace.
        // See if there is any empty entry.
        // Otherwise assuming sequential access, kick out the entry with the
        // greatest distance.
        Entry best = null;
        int maxDist = -1;
        for (Entry e : mCache) {
            if (e.mPos == -1) {
                best = e;
                break;
            } else {
                int dist = Math.abs(pos - e.mPos);
                if (dist > maxDist) {
                    maxDist = dist;
                    best = e;
                }
            }
        }

        // Recycle the image being kicked out.
        // This only works because our current usage is sequential, so we
        // do not happen to recycle the image being displayed.
        if (best.mBitmap != null) {
            best.mBitmap.recycle();
        }

        best.mPos = pos;
        best.mBitmap = bitmap;
    }

    // Recycle all bitmaps in the cache and clear the cache.
    public synchronized void clear() {
        for (Entry e : mCache) {
            if (e.mBitmap != null) {
                e.mBitmap.recycle();
            }
            e.clear();
        }
    }

    // Returns whether the bitmap is in the cache.
    public synchronized boolean hasBitmap(int pos) {
        Entry e = findEntry(pos);
        return (e != null);
    }

    // Recycle the bitmap if it's not in the cache.
    // The input must be non-null.
    public synchronized void recycle(Bitmap b) {
        for (Entry e : mCache) {
            if (e.mPos != -1) {
                if (e.mBitmap == b) {
                    return;
                }
            }
        }
        b.recycle();
    }
}