#import "SecretChatKeyVisualization.h"

#import <objc/runtime.h>

#define UIColorRGB(rgb) ([[UIColor alloc] initWithRed:(((rgb >> 16) & 0xff) / 255.0f) green:(((rgb >> 8) & 0xff) / 255.0f) blue:(((rgb) & 0xff) / 255.0f) alpha:1.0f])

static int32_t get_bits(uint8_t const *bytes, unsigned int bitOffset, unsigned int numBits)
{
    uint8_t const *data = bytes;
    numBits = (unsigned int)pow(2, numBits) - 1; //this will only work up to 32 bits, of course
    data += bitOffset / 8;
    bitOffset %= 8;
    return (*((int*)data) >> bitOffset) & numBits;
}

UIImage *SecretChatKeyVisualization(NSData *data, NSData *additionalData, CGSize size) {
    uint8_t bits[128];
    memset(bits, 0, 128);
    
    uint8_t additionalBits[256 * 8];
    memset(additionalBits, 0, 256 * 8);
    
    [data getBytes:bits length:MIN((NSUInteger)128, data.length)];
    [additionalData getBytes:additionalBits length:MIN((NSUInteger)256, additionalData.length)];
    
    static CGColorRef colors[6];
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        static const int textColors[] =
        {
            0xffffff,
            0xd5e6f3,
            0x2d5775,
            0x2f99c9
        };
        
        for (int i = 0; i < 4; i++)
        {
            colors[i] = CGColorRetain(UIColorRGB(textColors[i]).CGColor);
        }
    });
    
    UIGraphicsBeginImageContextWithOptions(size, true, 0.0f);
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextSetFillColorWithColor(context, colors[0]);
    CGContextFillRect(context, CGRectMake(0.0f, 0.0f, size.width, size.height));
    
    if (additionalData == nil) {
        int bitPointer = 0;
        
        CGFloat rectSize = size.width / 8.0f;
        
        for (int iy = 0; iy < 8; iy++)
        {
            for (int ix = 0; ix < 8; ix++)
            {
                int32_t byteValue = get_bits(bits, bitPointer, 2);
                bitPointer += 2;
                int colorIndex = ABS(byteValue) % 4;
                
                CGContextSetFillColorWithColor(context, colors[colorIndex]);
                
                CGRect rect = CGRectMake(ix * rectSize, iy * rectSize, rectSize, rectSize);
                if (size.width > 200) {
                    rect.origin.x = ceil(rect.origin.x);
                    rect.origin.y = ceil(rect.origin.y);
                    rect.size.width = ceil(rect.size.width);
                    rect.size.height = ceil(rect.size.height);
                }
                CGContextFillRect(context, rect);
            }
        }
    } else {
        int bitPointer = 0;
        
        CGFloat rectSize = size.width / 12.0f;
        
        for (int iy = 0; iy < 12; iy++)
        {
            for (int ix = 0; ix < 12; ix++)
            {
                int32_t byteValue = 0;
                if (bitPointer < 128) {
                    byteValue = get_bits(bits, bitPointer, 2);
                } else {
                    byteValue = get_bits(additionalBits, bitPointer - 128, 2);
                }
                bitPointer += 2;
                int colorIndex = ABS(byteValue) % 4;
                
                CGContextSetFillColorWithColor(context, colors[colorIndex]);
                
                CGRect rect = CGRectMake(ix * rectSize, iy * rectSize, rectSize, rectSize);
                if (size.width > 200) {
                    rect.origin.x = ceil(rect.origin.x);
                    rect.origin.y = ceil(rect.origin.y);
                    rect.size.width = ceil(rect.size.width);
                    rect.size.height = ceil(rect.size.height);
                }
                CGContextFillRect(context, rect);
            }
        }
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;
}