enum GRADIENT_INTER {
	smooth,
	none,
	hue
}

function gradientKey(time, value) constructor {
	self.time  = time;
	self.value = value;
	
	static clone = function() { return new gradientKey(time, value); }
	
	static serialize = function() {
		var m = ds_map_create();
		m[? "time"]  = time;
		m[? "value"] = value;
		return m;
	}
}

function gradientObject(color = c_black) constructor {
	if(is_array(color))
		keys = [ new gradientKey(0, color[0]), new gradientKey(1, color[1]) ];
	else
		keys = [ new gradientKey(0, color) ];
	type = GRADIENT_INTER.smooth;
	
	static clone = function() {
		var g = new gradientObject();
		for( var i = 0; i < array_length(keys); i++ ) {
			g.keys[i] = keys[i].clone();
		}
		g.type = type;
		
		return g;
	}
	
	static add = function(_addkey, _deleteDup = true) {
		if(array_length(keys) == 0) {
			array_push(keys, _addkey);
			return;
		}
		
		for(var i = 0; i < array_length(keys); i++) {
			var _key = keys[i];
		
			if(_key.time == _addkey.time) {
				if(_deleteDup)
					_key.value = _addkey.value;
				return;
			} else if(_key.time > _addkey.time) {
				array_insert(keys, i, _addkey);
				return;
			}
		}
		
		array_push(keys, _addkey);
	}
	
	static eval = function(position) {
		if(array_length(keys) == 0) return c_black;
		if(array_length(keys) == 1) return keys[0].value;
	
		for(var i = 0; i < array_length(keys); i++) {
			var _key = keys[i];
			if(_key.time < position) continue;
			if(_key.time == position) return keys[i].value;
		
			if(i == 0) //before first color
				return keys[0].value;
		
			var c0 = keys[i - 1].value;
			if(type == GRADIENT_INTER.smooth) {
				var rat = (position - keys[i - 1].time) / (keys[i].time - keys[i - 1].time);
				var c1 = keys[i].value;
				return merge_color(c0, c1, rat);
			} else if(type == GRADIENT_INTER.none) {
				return c0;
			}
		}
	
		return keys[array_length(keys) - 1].value; //after last color
	}
	
	static draw = function(_x, _y, _w, _h) {
		static RES = 48;
		var _step  = _w / RES;
		var _ox, _oc;
	
		var uniform_grad_blend	= shader_get_uniform(sh_gradient_display, "gradient_blend");
		var uniform_grad		= shader_get_uniform(sh_gradient_display, "gradient_color");
		var uniform_grad_time	= shader_get_uniform(sh_gradient_display, "gradient_time");
		var uniform_grad_key	= shader_get_uniform(sh_gradient_display, "gradient_keys");
	
		var _grad_color = [];
		var _grad_time  = [];
	
		for(var i = 0; i < array_length(keys); i++) {
			if(keys[i].value == undefined) return;
		
			_grad_color[i * 4 + 0] = color_get_red(keys[i].value) / 255;
			_grad_color[i * 4 + 1] = color_get_green(keys[i].value) / 255;
			_grad_color[i * 4 + 2] = color_get_blue(keys[i].value) / 255;
			_grad_color[i * 4 + 3] = 1;
			_grad_time[i]  = keys[i].time;
		}
	
		if(array_length(keys) == 0) {
			draw_sprite_stretched(s_fx_pixel, 0, _x, _y, _w, _h)
		} else {
			shader_set(sh_gradient_display);
			shader_set_uniform_i(uniform_grad_blend, type);
			shader_set_uniform_f_array_safe(uniform_grad, _grad_color);
			shader_set_uniform_f_array_safe(uniform_grad_time, _grad_time);
			shader_set_uniform_i(uniform_grad_key, array_length(keys));
			
			draw_sprite_stretched(s_fx_pixel, 0, _x, _y, _w, _h)
			shader_reset();
		}
	}
	
	static toArray = function() {
		var _grad_color = [], _grad_time = []; 
	
		for(var i = 0; i < array_length(keys); i++) {
			if(is_undefined(keys[i].value)) continue;
		
			_grad_color[i * 4 + 0] = color_get_red(keys[i].value) / 255;
			_grad_color[i * 4 + 1] = color_get_green(keys[i].value) / 255;
			_grad_color[i * 4 + 2] = color_get_blue(keys[i].value) / 255;
			_grad_color[i * 4 + 3] = 1;
			_grad_time[i]  = keys[i].time;
		}
	
		return [ _grad_color, _grad_time ];
	}
	
	static serialize = function() {
		return json_stringify(self);
	}
	
	static deserialize = function(str) {
		var s = json_try_parse(str);
		type = s.type;
		keys = [];
		for( var i = 0; i < array_length(s.keys); i++ )
			keys[i] = new gradientKey(s.keys[i].time, s.keys[i].value); 
		
		return self;
	}
}