//
//  HashMapHash.m
//  pithos-macos
//
// Copyright 2011 GRNET S.A. All rights reserved.
//
// Redistribution and use in source and binary forms, with or
// without modification, are permitted provided that the following
// conditions are met:
// 
//   1. Redistributions of source code must retain the above
//      copyright notice, this list of conditions and the following
//      disclaimer.
// 
//   2. 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 GRNET S.A. ``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 GRNET S.A 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.
// 
// The views and conclusions contained in the software and
// documentation are those of the authors and should not be
// interpreted as representing official policies, either expressed
// or implied, of GRNET S.A.

#import "HashMapHash.h"
#import <CommonCrypto/CommonHMAC.h>

@implementation HashMapHash

+ (NSString *)calculateHashMapHash:(NSArray *)hashes {
    const char padding[] = {
        '\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0',
        '\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0'};
    
    NSUInteger hashesCount = [hashes count];
    if (hashesCount == 0)
        return [self formatHash:[self calculateHash:[NSData data]]];
    if (hashesCount == 1)
        return [self formatHash:[hashes objectAtIndex:0]];
    
    NSUInteger s = 2;
    while (s < hashesCount)
        s = s * 2;
    
    NSMutableArray *h = [NSMutableArray arrayWithCapacity:s];
    for (NSUInteger i = 0; i < hashesCount; i++)
        [h addObject:[hashes objectAtIndex:i]];
    for (NSUInteger i = 0; i < s - hashesCount; i++)
        [h addObject:[NSMutableData dataWithBytes:padding length:32]];
    
    while ([h count] > 1) {
        for (NSUInteger i = 0; i < [h count]; i = i + 2) {
            NSMutableData *bytesData = [h objectAtIndex:i];
            [bytesData appendData:[h objectAtIndex:i + 1]];
            [h replaceObjectAtIndex:i withObject:[self calculateHash:bytesData]];
        }
        
        NSMutableIndexSet *indicesToRemove = [NSMutableIndexSet indexSet];
        for (int i = 0; i < [h count]; i = i + 2) 
            [indicesToRemove addIndex:i + 1]; 
        
        [h removeObjectsAtIndexes:indicesToRemove];
    }
    return [self formatHash:[h objectAtIndex:0]];
}

+ (NSData *)calculateHash:(NSData *)data {
    unsigned char hash[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256([data bytes], (unsigned int)[data length], hash);
    return [NSMutableData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];
}

+ (NSString *)formatHash:(NSData *)data {
    return [[[NSString stringWithFormat:@"%@", data] 
             stringByReplacingOccurrencesOfString:@" " withString:@""] 
            stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"<>"]];
}

// XXX hardcoded hash algorithm for now
+ (NSArray *)calculateObjectHashMap:(NSString *)filePath withBlockHash:(NSString *)blockHash andBlockSize:(NSUInteger)blockSize {
    NSFileHandle *fileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];
    if (!fileHandle) {
        NSLog(@"HashMapHash failed to open file: %@", filePath);
        return nil;
    }
    
    NSDictionary *attributes = [[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil];
    NSUInteger fileSize = [attributes fileSize];
    NSMutableArray *hashes = [NSMutableArray arrayWithCapacity:(fileSize/blockSize + 1)];
    
    BOOL done;
    while (!done) {
        NSAutoreleasePool * pool = [NSAutoreleasePool new];
        NSData *data = [fileHandle readDataOfLength:blockSize];
        done = ([data length] == 0);
        
        if (!done) {
            // Strip trailing slashes.
            const char *bytes = [data bytes];
            NSInteger i;
            for (i = [data length] - 1; i >= 0; i--) {
                if (bytes[i] != '\0')
                    break;
            }
            if (i != [data length] - 1) {
                if (i >= 0)
                    data = [data subdataWithRange:NSMakeRange(0, i + 1)];
                else
                    data = [NSData data];
            }
            
            unsigned char hash[CC_SHA256_DIGEST_LENGTH];
            if (CC_SHA256([data bytes], (unsigned int)[data length], hash))
                [hashes addObject:[NSMutableData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH]];
        }
        
        [pool drain];
    }
    [fileHandle closeFile];
    
    return [NSArray arrayWithArray:hashes];
}

+ (NSArray *)objectHashMapStrings:(NSString *)filePath withBlockHash:(NSString *)blockHash andBlockSize:(NSUInteger)blockSize {
    NSArray *hashHexes = [HashMapHash calculateObjectHashMap:filePath withBlockHash:blockHash andBlockSize:blockSize];
    if (!hashHexes)
        return nil;
    
    NSMutableArray *hashStrings = [NSMutableArray arrayWithCapacity:[hashHexes count]];
    for (NSData *hashHex in hashHexes) {
        [hashStrings addObject:[self formatHash:hashHex]];
    }
    return [NSArray arrayWithArray:hashStrings];
}

@end