//
//  RMDatabaseCache.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 "RMDatabaseCache.h"
#import "FMDatabase.h"
#import "RMTileImage.h"
#import "RMTile.h"

#define kWriteQueueLimit 15

@interface RMDatabaseCache ()

- (NSUInteger)count;
- (NSUInteger)countTiles;
- (void)touchTile:(RMTile)tile withKey:(NSString *)cacheKey;
- (void)purgeTiles:(NSUInteger)count;

@end

#pragma mark -

@implementation RMDatabaseCache

@synthesize databasePath;

+ (NSString *)dbPathUsingCacheDir:(BOOL)useCacheDir
{
	NSArray *paths;

	if (useCacheDir) {
		paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
	} else {
		paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
	}

	if ([paths count] > 0) // Should only be one...
	{
		NSString *cachePath = [paths objectAtIndex:0];
		
		// check for existence of cache directory
		if ( ![[NSFileManager defaultManager] fileExistsAtPath: cachePath]) 
		{
			// create a new cache directory
			[[NSFileManager defaultManager] createDirectoryAtPath:cachePath withIntermediateDirectories:NO attributes:nil error:nil];
		}
		
		NSString *filename = [NSString stringWithFormat:@"RMTileCache.db"];
		return [cachePath stringByAppendingPathComponent:filename];
	}

	return nil;
}

- (void)configureDBForFirstUse
{
    [[db executeQuery:@"PRAGMA synchronous=OFF"] close];
    [[db executeQuery:@"PRAGMA journal_mode=OFF"] close];
    [[db executeQuery:@"PRAGMA cache-size=100"] close];
    [[db executeQuery:@"PRAGMA count_changes=OFF"] close];
    [db executeUpdate:@"CREATE TABLE IF NOT EXISTS ZCACHE (tile_hash INTEGER NOT NULL, cache_key VARCHAR(25) NOT NULL, last_used DOUBLE NOT NULL, data BLOB NOT NULL)"];
    [db executeUpdate:@"CREATE UNIQUE INDEX IF NOT EXISTS main_index ON ZCACHE(tile_hash, cache_key)"];
    [db executeUpdate:@"CREATE INDEX IF NOT EXISTS last_used_index ON ZCACHE(last_used)"];
}

- (id)initWithDatabase:(NSString *)path
{
	if (!(self = [super init]))
		return nil;

	self.databasePath = path;

    writeQueue = [NSOperationQueue new];
    [writeQueue setMaxConcurrentOperationCount:1];
    writeQueueLock = [NSRecursiveLock new];

	RMLog(@"Opening database at %@", path);

	db = [[FMDatabase alloc] initWithPath:path];
	if (![db open])
	{
		RMLog(@"Could not connect to database - %@", [db lastErrorMessage]);
        [[NSFileManager defaultManager] removeItemAtPath:path error:NULL];
        if (![db open]) {
            [self release];
            return nil;
        }
	}

	[db setCrashOnErrors:TRUE];
    [db setShouldCacheStatements:TRUE];

	[self configureDBForFirstUse];

    tileCount = [self countTiles];

	return self;	
}

- (id)initUsingCacheDir:(BOOL)useCacheDir
{
	return [self initWithDatabase:[RMDatabaseCache dbPathUsingCacheDir:useCacheDir]];
}

- (void)dealloc
{
    self.databasePath = nil;
    [writeQueueLock lock];
    [writeQueue release]; writeQueue = nil;
    [writeQueueLock unlock];
    [writeQueueLock release]; writeQueueLock = nil;
    [db close]; [db release]; db = nil;
	[super dealloc];
}

- (void)setPurgeStrategy:(RMCachePurgeStrategy)theStrategy
{
	purgeStrategy = theStrategy;
}

- (void)setCapacity:(NSUInteger)theCapacity
{
	capacity = theCapacity;
}

- (void)setMinimalPurge:(NSUInteger)theMinimalPurge
{
	minimalPurge = theMinimalPurge;
}

- (UIImage *)cachedImage:(RMTile)tile withCacheKey:(NSString *)aCacheKey
{
//	RMLog(@"DB cache check for tile %d %d %d", tile.x, tile.y, tile.zoom);

    [writeQueueLock lock];

	FMResultSet *results = [db executeQuery:@"SELECT data FROM ZCACHE WHERE tile_hash = ? AND cache_key = ?", [RMTileCache tileHash:tile], aCacheKey];

	if ([db hadError]) {
		RMLog(@"DB error while fetching tile data: %@", [db lastErrorMessage]);
		return nil;
	}

	NSData *data = nil;
    UIImage *cachedImage = nil;

	if ([results next]) {
		data = [results dataForColumnIndex:0];
        if (data) cachedImage = [UIImage imageWithData:data];
	}

	[results close];

    [writeQueueLock unlock];

    if (capacity != 0 && purgeStrategy == RMCachePurgeStrategyLRU) {
        [self touchTile:tile withKey:aCacheKey];
    }

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

	return cachedImage;
}

- (void)addImage:(UIImage *)image forTile:(RMTile)tile withCacheKey:(NSString *)aCacheKey
{
    // TODO: Converting the image here (again) is not so good...
	NSData *data = UIImagePNGRepresentation(image);

    if (capacity != 0)
    {
        NSUInteger tilesInDb = [self count];
        if (capacity <= tilesInDb) {
            [self purgeTiles:MAX(minimalPurge, 1+tilesInDb-capacity)];
        }

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

        // Don't add new images to the database while there are still more than kWriteQueueLimit
        // insert operations pending. This prevents some memory issues.
        BOOL skipThisTile = NO;
        [writeQueueLock lock];
        if ([writeQueue operationCount] > kWriteQueueLimit) skipThisTile = YES;
        [writeQueueLock unlock];

        if (skipThisTile) return;

        [writeQueue addOperationWithBlock:^{
            //        RMLog(@"addData\t%d", tileHash);

            [writeQueueLock lock];
            BOOL result = [db executeUpdate:@"INSERT OR IGNORE INTO ZCACHE (tile_hash, cache_key, last_used, data) VALUES (?, ?, ?, ?)", [RMTileCache tileHash:tile], aCacheKey, [NSDate date], data];
            [writeQueueLock unlock];

            if (result == NO)
            {
                RMLog(@"Error occured adding data");
            } else
                tileCount++;
        }];
	}
}

#pragma mark -

- (NSUInteger)count
{
    return tileCount;
}

- (NSUInteger)countTiles
{
    [writeQueueLock lock];

	NSUInteger count = 0;
    FMResultSet *results = [db executeQuery:@"SELECT COUNT(tile_hash) FROM ZCACHE"];
	if ([results next])
		count = [results intForColumnIndex:0];
	else
		RMLog(@"Unable to count columns");
	[results close];

    [writeQueueLock unlock];

	return count;
}

- (void)purgeTiles:(NSUInteger)count
{
    RMLog(@"purging %u old tiles from db cache", count);

    [writeQueueLock lock];
    BOOL result = [db executeUpdate:@"DELETE FROM ZCACHE WHERE tile_hash IN (SELECT tile_hash FROM ZCACHE ORDER BY last_used LIMIT ?)", [NSNumber numberWithUnsignedInt:count]];
    [db executeQuery:@"VACUUM"];
    tileCount = [self countTiles];
    [writeQueueLock unlock];

    if (result == NO) {
        RMLog(@"Error purging cache");
    }
}

- (void)removeAllCachedImages 
{
    [writeQueue addOperationWithBlock:^{
        [writeQueueLock lock];
        BOOL result = [db executeUpdate:@"DELETE FROM ZCACHE"];
        [db executeQuery:@"VACUUM"];
        [writeQueueLock unlock];

        if (result == NO) {
            RMLog(@"Error purging cache");
        }

        tileCount = [self countTiles];
    }];
}

- (void)touchTile:(RMTile)tile withKey:(NSString *)cacheKey
{
    [writeQueue addOperationWithBlock:^{
        [writeQueueLock lock];
        BOOL result = [db executeUpdate:@"UPDATE ZCACHE SET last_used = ? WHERE tile_hash = ? AND cache_key = ?", [NSDate date], [RMTileCache tileHash:tile], cacheKey];
        [writeQueueLock unlock];

        if (result == NO) {
            RMLog(@"Error touching tile");
        }
    }];
}

- (void)didReceiveMemoryWarning
{
    RMLog(@"Low memory in the database tilecache");
    [writeQueueLock lock];
    [writeQueue cancelAllOperations];
    [writeQueueLock unlock];
}

@end