//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;

#define GRADIENT_LIMIT 128

uniform vec2  position;
uniform vec2  dimension;
uniform vec2  scale;
uniform float angle;
uniform float width;
uniform float shift;
uniform float seed;
uniform int shiftAxis;

uniform int mode;

uniform vec4 gapCol;
uniform int gradient_use;
uniform int gradient_blend;
uniform vec4 gradient_color[GRADIENT_LIMIT];
uniform float gradient_time[GRADIENT_LIMIT];
uniform int gradient_keys;

float random (in vec2 st) { return fract(sin(dot(st.xy + vec2(85.456034, 64.54065), vec2(12.9898, 78.233))) * (43758.5453123 + seed) ); }

vec3 rgb2hsv(vec3 c) {
	vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
    vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
    vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));

    float d = q.x - min(q.w, q.y);
    float e = 0.0000000001;
    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
 }

vec3 hsv2rgb(vec3 c) {
    vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
    vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
    return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}

float hueDist(float a0, float a1, float t) {
	float da = fract(a1 - a0);
    float ds = fract(2. * da) - da;
    return a0 + ds * t;
}

vec3 hsvMix(vec3 c1, vec3 c2, float t) {
	vec3 h1 = rgb2hsv(c1);
	vec3 h2 = rgb2hsv(c2);
	
	vec3 h = vec3(0.);
	h.x = h.x + hueDist(h1.x, h2.x, t);
	h.y = mix(h1.y, h2.y, t);
	h.z = mix(h1.z, h2.z, t);
	
	return hsv2rgb(h);
}

vec4 gradientEval(in float prog) {
	vec4 col = vec4(0.);
	
	for(int i = 0; i < GRADIENT_LIMIT; i++) {
		if(gradient_time[i] == prog) {
			col = gradient_color[i];
			break;
		} else if(gradient_time[i] > prog) {
			if(i == 0) 
				col = gradient_color[i];
			else {
				float t = (prog - gradient_time[i - 1]) / (gradient_time[i] - gradient_time[i - 1]);
				if(gradient_blend == 0)
					col = mix(gradient_color[i - 1], gradient_color[i], t);
				else if(gradient_blend == 1)
					col = gradient_color[i - 1];
				else if(gradient_blend == 2)
					col = vec4(hsvMix(gradient_color[i - 1].rgb, gradient_color[i].rgb, t), 1.);
			}
			break;
		}
		if(i >= gradient_keys - 1) {
			col = gradient_color[gradient_keys - 1];
			break;
		}
	}
	
	return col;
}

void main() {
	vec2 pos = v_vTexcoord - position, _pos;
	float ratio = dimension.x / dimension.y;
	_pos.x = pos.x * ratio * cos(angle) - pos.y * sin(angle);
	_pos.y = pos.x * ratio * sin(angle) + pos.y * cos(angle);
	
	if(shiftAxis == 0) {
		float cellY = floor(_pos.y * scale.y);
		float shiftX = mod(cellY, 2.) * shift;
	
		_pos.x += shiftX;
	} else {
		float cellX = floor(_pos.x * scale.x);
		float shiftY = mod(cellX, 2.) * shift;
	
		_pos.y += shiftY;
	}
	
	vec2 sqSt = floor(_pos * scale) / scale;
	vec2 dist = _pos - sqSt;
	float ww = width / 2.;
	bool isGap = dist != clamp(dist, vec2(ww), vec2(1. / scale - ww));
	
	if(mode == 0) {
		gl_FragColor = isGap? gapCol : vec4(gradientEval(random(sqSt)).rgb, 1.); 
	} else if(mode == 1) {
		vec2 nPos = abs(dist * scale - vec2(0.5)) * 2.; //distance in x, y axis
		float d = 1. - max(nPos.x, nPos.y);
		gl_FragColor = vec4(vec3(d), 1.);
	} else if(mode == 2) {
		vec2 uv = fract(_pos * scale);
		gl_FragColor = isGap? gapCol : texture2D( gm_BaseTexture, uv );
	} else if(mode == 3) {
		vec2 uv = fract(sqSt);
		gl_FragColor = isGap? gapCol : texture2D( gm_BaseTexture, uv );
	}
}