//
//  ZeroingData.m
//  TunnelKit
//
//  Created by Davide De Rosa on 4/28/17.
//  Copyright © 2018 London Trust Media. All rights reserved.
//

#import "ZeroingData.h"
#import "Allocation.h"

@interface ZeroingData () {
    uint8_t *_bytes;
}

@end

@implementation ZeroingData

- (instancetype)init
{
    return [self initWithBytes:NULL count:0];
}

- (instancetype)initWithCount:(NSInteger)count
{
    if ((self = [super init])) {
        _count = count;
        _bytes = allocate_safely(count);
    }
    return self;
}

- (instancetype)initWithBytes:(const uint8_t *)bytes count:(NSInteger)count
{
//    NSParameterAssert(bytes);

    if ((self = [super init])) {
        _count = count;
        _bytes = allocate_safely(count);
        memcpy(_bytes, bytes, count);
    }
    return self;
}

- (instancetype)initWithBytesNoCopy:(uint8_t *)bytes count:(NSInteger)count
{
    NSParameterAssert(bytes);

    if ((self = [super init])) {
        _count = count;
        _bytes = bytes;
    }
    return self;
}

- (instancetype)initWithUInt8:(uint8_t)uint8
{
    if ((self = [super init])) {
        _count = 1;
        _bytes = allocate_safely(_count);
        _bytes[0] = uint8;
    }
    return self;
}

- (instancetype)initWithUInt16:(uint16_t)uint16
{
    if ((self = [super init])) {
        _count = 2;
        _bytes = allocate_safely(_count);
        _bytes[0] = (uint16 & 0xff);
        _bytes[1] = (uint16 >> 8);
    }
    return self;
}

- (instancetype)initWithData:(NSData *)data
{
    return [self initWithData:data offset:0 count:data.length];
}

- (instancetype)initWithData:(NSData *)data offset:(NSInteger)offset count:(NSInteger)count
{
    NSParameterAssert(data);
//    NSParameterAssert(offset <= data.length);
    NSParameterAssert(offset + count <= data.length);

    if ((self = [super init])) {
        _count = count;
        _bytes = allocate_safely(count);
        memcpy(_bytes, data.bytes + offset, count);
    }
    return self;
}

- (instancetype)initWithString:(NSString *)string nullTerminated:(BOOL)nullTerminated
{
    NSParameterAssert(string);

    if ((self = [super init])) {
        const char *stringBytes = [string cStringUsingEncoding:NSASCIIStringEncoding];
        const int stringLength = (int)string.length;
        
        _count = stringLength + (nullTerminated ? 1 : 0);
        _bytes = allocate_safely(_count);
        memcpy(_bytes, stringBytes, stringLength);
        if (nullTerminated) {
            _bytes[stringLength] = '\0';
        }
    }
    return self;
}

- (void)dealloc
{
    bzero(_bytes, _count);
    free(_bytes);
}

- (const uint8_t *)bytes
{
    return _bytes;
}

- (uint8_t *)mutableBytes
{
    return _bytes;
}

- (void)appendData:(ZeroingData *)other
{
    NSParameterAssert(other);

    const NSInteger newCount = _count + other.count;
    uint8_t *newBytes = allocate_safely(newCount);
    memcpy(newBytes, _bytes, _count);
    memcpy(newBytes + _count, other.bytes, other.count);
    
    bzero(_bytes, _count);
    free(_bytes);
    
    _bytes = newBytes;
    _count = newCount;
}

- (void)truncateToSize:(NSInteger)size
{
    NSParameterAssert(size <= _count);
    
    uint8_t *newBytes = allocate_safely(size);
    memcpy(newBytes, _bytes, size);

    bzero(_bytes, _count);
    free(_bytes);
    
    _bytes = newBytes;
    _count = size;
}

- (void)removeUntilOffset:(NSInteger)until
{
    NSParameterAssert(until <= _count);
    
    const NSInteger newCount = _count - until;
    uint8_t *newBytes = allocate_safely(newCount);
    memcpy(newBytes, _bytes + until, newCount);
    
    bzero(_bytes, _count);
    free(_bytes);
    
    _bytes = newBytes;
    _count = newCount;
}

- (void)zero
{
    bzero(_bytes, _count);
}

- (ZeroingData *)appendingData:(ZeroingData *)other
{
    NSParameterAssert(other);

    const NSInteger newCount = _count + other.count;
    uint8_t *newBytes = allocate_safely(newCount);
    memcpy(newBytes, _bytes, _count);
    memcpy(newBytes + _count, other.bytes, other.count);
    
    return [[ZeroingData alloc] initWithBytesNoCopy:newBytes count:newCount];
}

- (ZeroingData *)withOffset:(NSInteger)offset count:(NSInteger)count
{
//    NSParameterAssert(offset <= _count);
    NSParameterAssert(offset + count <= _count);

    uint8_t *newBytes = allocate_safely(count);
    memcpy(newBytes, _bytes + offset, count);
    
    return [[ZeroingData alloc] initWithBytesNoCopy:newBytes count:count];
}

- (uint16_t)UInt16ValueFromOffset:(NSInteger)from
{
    NSParameterAssert(from + 2 <= _count);

    uint16_t value = 0;
    value |= _bytes[from];
    value |= _bytes[from + 1] << 8;
    return value;
}

- (uint16_t)networkUInt16ValueFromOffset:(NSInteger)from
{
    NSParameterAssert(from + 2 <= _count);
    
    uint16_t value = 0;
    value |= _bytes[from];
    value |= _bytes[from + 1] << 8;
    return CFSwapInt16BigToHost(value);
}

- (NSString *)nullTerminatedStringFromOffset:(NSInteger)from
{
    NSParameterAssert(from <= _count);

    NSInteger nullOffset = NSNotFound;
    for (NSInteger i = from; i < _count; ++i) {
        if (_bytes[i] == 0) {
            nullOffset = i;
            break;
        }
    }
    if (nullOffset == NSNotFound) {
        return nil;
    }
    const NSInteger stringLength = nullOffset - from;
    return [[NSString alloc] initWithBytes:_bytes length:stringLength encoding:NSASCIIStringEncoding];
}

- (BOOL)isEqualToData:(NSData *)data
{
    NSParameterAssert(data);
    NSParameterAssert(data.length <= _count);

    return !memcmp(_bytes, data.bytes, _count);
}

- (NSString *)toHex
{
    const NSUInteger capacity = _count * 2;
    NSMutableString *hexString = [[NSMutableString alloc] initWithCapacity:capacity];
    for (int i = 0; i < _count; ++i) {
        [hexString appendFormat:@"%02x", _bytes[i]];
    }
    return hexString;
}

@end