//
//  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'};
    
    if ([hashes count] == 0)
        return [HashMapHash formatHash:[HashMapHash calculateHash:[NSData dataWithBytes:padding length:0]]];
    if ([hashes count] == 1)
        return [HashMapHash formatHash:[hashes objectAtIndex:0]];
    
    int s = 2;
    while (s < [hashes count])
        s = s * 2;
    
    NSMutableArray *h = [NSMutableArray array];
    for (int i = 0; i < [hashes count]; i++)
        [h addObject:[hashes objectAtIndex:i]];
    for (int i = 0; i < s - [hashes count]; i++)
        [h addObject:[NSMutableData dataWithBytes:padding length:32]];
    
    while ([h count] > 1) {
        for (int i = 0; i < [h count]; i = i + 2) {
            NSMutableData *bytesData = [h objectAtIndex:i];
            [bytesData appendData:[h objectAtIndex:i + 1]];
            [h replaceObjectAtIndex:i withObject:[HashMapHash calculateHash:bytesData]];
        }
        
        NSMutableIndexSet *indicesToRemove = [NSMutableIndexSet indexSet];
        for (int i = 0; i < [h count]; i = i + 2) 
            [indicesToRemove addIndex:i + 1]; 
        
        [h removeObjectsAtIndexes:indicesToRemove];
    }
    return [HashMapHash 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 {
    NSString *hashString;
    hashString = [NSString stringWithFormat:@"%@", data];
    hashString = [hashString stringByReplacingOccurrencesOfString:@" " withString:@""];
    hashString = [hashString stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"<>"]];
    return hashString;
}

// XXX hardcoded hash algorithm for now
+ (NSArray *)calculateObjectHashMap:(NSString *)filePath withBlockHash:(NSString *)blockHash andBlockSize:(NSUInteger)blockSize {
    NSFileHandle *fh = [NSFileHandle fileHandleForReadingAtPath:filePath];
    if (fh == nil) {
        NSLog(@"failed to open file: %@", filePath);
        return nil;
    }
    
    NSFileManager *fm = [NSFileManager defaultManager];
    NSDictionary *attributes = [fm attributesOfItemAtPath:filePath error:nil];
    NSUInteger endOfFile = [attributes fileSize];
    
    NSUInteger fileOffset = 0;
    [fh seekToFileOffset:fileOffset];
    
    NSMutableArray *hashes = [[[NSMutableArray alloc] init] autorelease];
    
    while(fileOffset < endOfFile){
        NSData *data = [fh readDataOfLength:blockSize];
        
        // 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) ) {
            NSData *sha256 = [NSMutableData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];
            [hashes addObject:sha256];
        }
        
        fileOffset += blockSize;
        [fh seekToFileOffset:fileOffset];
    }
    
    [fh closeFile];
    
    NSArray *hashMap = [NSArray arrayWithArray:hashes];
    
    return hashMap;
}

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

@end