//
//  CTGradient.m
//
//  Created by Chad Weider on 2/14/07.
//  Copyright (c) 2007 Chad Weider.
//  Some rights reserved: <http://creativecommons.org/licenses/by/2.5/>
//
//  Version: 1.6

#import "CTGradient.h"

//C Fuctions for color blending
static void linearEvaluation (void *info, const float *in, float *out);

@implementation CTGradient

- (id)init {
	if(self = [super init]) {
		CGFunctionCallbacks evaluationCallbackInfo = {0 , &linearEvaluation, 0};
		static const float input_value_range[2] = { 0, 1 };
		static const float output_value_ranges[8] = { 0, 1, 0, 1, 0, 1, 0, 1 };
		gradientFunction = CGFunctionCreate(&elementList, 1, input_value_range,	4, output_value_ranges, &evaluationCallbackInfo);
	}
	return self;
}

- (void)dealloc {
	CGFunctionRelease(gradientFunction);
	free(elementList->nextElement);
	free(elementToRemove);
	[super dealloc];
}

+ (id)gradientWithBeginningColor:(NSColor *)begin endingColor:(NSColor *)end {
	id newInstance = [[[self class] alloc] init];

	CTGradientElement color1, color2;

	[[begin colorUsingColorSpaceName:NSCalibratedRGBColorSpace]
							  getRed:&color1.red
							   green:&color1.green
							    blue:&color1.blue
							   alpha:&color1.alpha];
	[[end colorUsingColorSpaceName:NSCalibratedRGBColorSpace]
							getRed:&color2.red
							 green:&color2.green
							  blue:&color2.blue
							 alpha:&color2.alpha];

	[newInstance addElement:&color1];
	[newInstance addElement:&color2];
	return [newInstance autorelease];
}

- (void)fillRect:(NSRect)rect {
	//First Calculate where the beginning and ending points should be
	CGPoint startPoint;
	CGPoint endPoint;
	
	startPoint = CGPointMake(NSMinX(rect), NSMinY(rect));
	endPoint = CGPointMake(NSMinX(rect), NSMaxY(rect));
  
  //Calls to CoreGraphics
	CGContextRef currentContext = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
	CGContextSaveGState(currentContext);
	#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
		CGColorSpaceRef colorspace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
	#else
		CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
	#endif
	CGShadingRef myCGShading = CGShadingCreateAxial(colorspace, startPoint, endPoint, gradientFunction, false, false);

	CGContextClipToRect (currentContext, *(CGRect *)&rect);
	//This is where the action happens
	CGContextDrawShading(currentContext, myCGShading);

	CGShadingRelease(myCGShading);
	CGColorSpaceRelease(colorspace );
	CGContextRestoreGState(currentContext);
}

- (void)addElement:(CTGradientElement *)newElement {
	if(elementList) {
		//inserting somewhere inside list
		elementList->nextElement = malloc(sizeof(CTGradientElement));
		*(elementList->nextElement) = *newElement;
		elementList->nextElement->nextElement = 0;
	} else {
		//inserting at beginning of list
		elementList = malloc(sizeof(CTGradientElement));
		*elementList = *newElement;
		elementList->nextElement = 0;
	}
}

void linearEvaluation (void *info, const float *in, float *out) {
	float position = *in;

	CTGradientElement *color1 = *(CTGradientElement **)info;
	CTGradientElement *color2 = color1->nextElement;

	out[0] = (color2->red - color1->red)*position + color1->red; 
	out[1] = (color2->green - color1->green)*position + color1->green;
	out[2] = (color2->blue - color1->blue)*position + color1->blue;
	out[3] = (color2->alpha - color1->alpha)*position + color1->alpha;
}

@end