/*
	JSColors.js - Javascript Functions for color evaluation and changing
	2022 by mercury0x0d, Creative Commons Attribution 4.0 International License

	Revision history:
	2022-07-25 - Initial release
*/





function ColorAdjustText(element, classLight, classDark)
{
	/*
		Calls ColorEvaluate() on the background color of the specified element and sets its color attribute to contrast nicely against it.
		Based upon code found at https://awik.io/determine-color-bright-dark-using-javascript.

		Input:
			element		The element whose background color will be evaluated and whose color will be altered
			classLight	The name of the class to be applied if the element's background color is a "light" color
			classDark	The name of the class to be applied if the element's background color is a "dark" color

		Output:
			n/a
	*/


	// Get the element's background color
	var bgColor = window.getComputedStyle(element, null).getPropertyValue('background-color');

	// If the background color is dark, add the textLight class to it
	if(ColorEvaluate(bgColor) == 'dark')
	{
		element.classList.remove(classDark);
		element.classList.add(classLight);
	} else {
		element.classList.remove(classLight);
		element.classList.add(classDark);
	}
}





function ColorAlter(hexColor, magnitude)
{
	/*
		Alters a given color by a percentage of magnitude.
		Based upon code found at https://natclark.com/tutorials/javascript-lighten-darken-hex-color.

		Input:
			color		The color to be evaluated
			magnitude	The magnitude percentage by which to lighten or darken the color

		Output:
			n/a
	*/


	var hexColor = hexColor.replace(`#`, ``);
	if (hexColor.length === 6)
	{
		const decimalColor = parseInt(hexColor, 16);
		var r = (decimalColor >> 16) + magnitude;
		r > 255 && (r = 255);
		r < 0 && (r = 0);
		var g = (decimalColor & 0x0000ff) + magnitude;
		g > 255 && (g = 255);
		g < 0 && (g = 0);
		var b = ((decimalColor >> 8) & 0x00ff) + magnitude;
		b > 255 && (b = 255);
		b < 0 && (b = 0);
		return `#${(g | (b << 8) | (r << 16)).toString(16)}`;
	} else {
		return hexColor;
	}
}





function ColorEvaluate(color)
{
	/*
		Evaluates the given color to determine whether it is a "light" or "dark" color.
		Based upon code found at https://awik.io/determine-color-bright-dark-using-javascript.

		Input:
			color	The color to be evaluated

		Output:
			'light'		The color is classified as a "light" color
			'dark'		The color is classified as a "dark" color
	*/


	// Check the format of the color, HEX or RGB?
	if (color.match(/^rgb/))
	{
		// If HEX --> store the red, green, blue values in separate variables
		var color = color.match(/^rgba?\((\d+),\s*(\d+),\s*(\d+)(?:,\s*(\d+(?:\.\d+)?))?\)$/);

		var r = color[1];
		var g = color[2];
		var b = color[3];
	} else {
		// If RGB --> Convert it to HEX: http://gist.github.com/983661
		color = +("0x" + color.slice(1).replace( 
		color.length < 5 && /./g, '$&$&'
		)
		);

		r = color >> 16;
		g = color >> 8 & 255;
		b = color & 255;
	}

	// Use the Hue Saturation and Perceived Brightness equation from http://alienryderflex.com/hsp.html
	var hsp = Math.sqrt(0.299 * (r * r) + 0.587 * (g * g) + 0.114 * (b * b));

	// Using the HSP value, determine whether the color is light or dark
	if (hsp > 127.5)
	{
		return 'light';
	} else {
		return 'dark';
	}
}