//
//  RMMemoryCache.m
//
// Copyright (c) 2008-2009, Route-Me Contributors
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
//   list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

#import "RMMemoryCache.h"
#import "RMTileImage.h"

@implementation RMMemoryCache
{
    NSMutableDictionary *_memoryCache;
    dispatch_queue_t _memoryCacheQueue;
    NSUInteger _memoryCacheCapacity;
}

- (id)initWithCapacity:(NSUInteger)aCapacity
{
    if (!(self = [super init]))
        return nil;

    RMLog(@"initializing memory cache %@ with capacity %d", self, aCapacity);

    _memoryCache = [[NSMutableDictionary alloc] initWithCapacity:aCapacity];
    _memoryCacheQueue = dispatch_queue_create("routeme.memoryCacheQueue", DISPATCH_QUEUE_CONCURRENT);

    if (aCapacity < 1)
        aCapacity = 1;

    _memoryCacheCapacity = aCapacity;

    return self;
}

- (id)init
{
	return [self initWithCapacity:32];
}

- (void)dealloc
{
    dispatch_barrier_sync(_memoryCacheQueue, ^{
        [_memoryCache removeAllObjects];
        [_memoryCache release]; _memoryCache = nil;
    });

	[super dealloc];
}

- (void)didReceiveMemoryWarning
{
	LogMethod();

    dispatch_barrier_async(_memoryCacheQueue, ^{
        [_memoryCache removeAllObjects];
    });
}

- (void)removeTile:(RMTile)tile
{
    dispatch_barrier_async(_memoryCacheQueue, ^{
        [_memoryCache removeObjectForKey:[RMTileCache tileHash:tile]];
    });
}

- (UIImage *)cachedImage:(RMTile)tile withCacheKey:(NSString *)aCacheKey
{
//    RMLog(@"Memory cache check  tile %d %d %d (%@)", tile.x, tile.y, tile.zoom, [RMTileCache tileHash:tile]);

    __block RMCacheObject *cachedObject = nil;
    NSNumber *tileHash = [RMTileCache tileHash:tile];

    dispatch_sync(_memoryCacheQueue, ^{

        cachedObject = [[_memoryCache objectForKey:tileHash] retain];

        if (cachedObject)
        {
            if ([[cachedObject cacheKey] isEqualToString:aCacheKey])
            {
                [cachedObject touch];
            }
            else
            {
                dispatch_barrier_async(_memoryCacheQueue, ^{
                    [_memoryCache removeObjectForKey:tileHash];
                });

                [cachedObject release]; cachedObject = nil;
            }
        }

    });

//    RMLog(@"Memory cache hit    tile %d %d %d (%@)", tile.x, tile.y, tile.zoom, [RMTileCache tileHash:tile]);

    [cachedObject autorelease];

    return [cachedObject cachedObject];
}

/// Remove the least-recently used image from cache, if cache is at or over capacity. Removes only 1 image.
- (void)makeSpaceInCache
{
    dispatch_barrier_async(_memoryCacheQueue, ^{

        while ([_memoryCache count] >= _memoryCacheCapacity)
        {
            // Rather than scanning I would really like to be using a priority queue
            // backed by a heap here.

            // Maybe deleting one random element would work as well.

            NSEnumerator *enumerator = [_memoryCache objectEnumerator];
            RMCacheObject *image;

            NSDate *oldestDate = nil;
            RMCacheObject *oldestImage = nil;

            while ((image = (RMCacheObject *)[enumerator nextObject]))
            {
                if (oldestDate == nil || ([oldestDate timeIntervalSinceReferenceDate] > [[image timestamp] timeIntervalSinceReferenceDate]))
                {
                    oldestDate = [image timestamp];
                    oldestImage = image;
                }
            }

            if (oldestImage)
            {
                // RMLog(@"Memory cache delete tile %d %d %d (%@)", oldestImage.tile.x, oldestImage.tile.y, oldestImage.tile.zoom, [RMTileCache tileHash:oldestImage.tile]);
                [_memoryCache removeObjectForKey:[RMTileCache tileHash:oldestImage.tile]];
            }
        }

    });
}

- (void)addImage:(UIImage *)image forTile:(RMTile)tile withCacheKey:(NSString *)aCacheKey
{
//    RMLog(@"Memory cache insert tile %d %d %d (%@)", tile.x, tile.y, tile.zoom, [RMTileCache tileHash:tile]);

	[self makeSpaceInCache];

    dispatch_barrier_async(_memoryCacheQueue, ^{
        [_memoryCache setObject:[RMCacheObject cacheObject:image forTile:tile withCacheKey:aCacheKey] forKey:[RMTileCache tileHash:tile]];
    });
}

- (void)removeAllCachedImages
{
    LogMethod();

    dispatch_barrier_async(_memoryCacheQueue, ^{
        [_memoryCache removeAllObjects];
    });
}

@end