package xmobilebackend

import (
	"golang.org/x/mobile/gl"
)

var unifiedVS = `
attribute vec2 vertex, texCoord;

uniform vec2 canvasSize;
uniform mat3 matrix;

varying vec2 v_cp, v_tc;

void main() {
	v_tc = texCoord;
	vec3 v = matrix * vec3(vertex.xy, 1.0);
	vec2 tf = v.xy / v.z;
	v_cp = tf;
	vec2 glp = tf * 2.0 / canvasSize - 1.0;
    gl_Position = vec4(glp.x, -glp.y, 0.0, 1.0);
}
`
var unifiedFS = `
#ifdef GL_ES
precision mediump float;
#endif

varying vec2 v_cp, v_tc;

uniform int func;

uniform vec4 color;
uniform float globalAlpha;

uniform sampler2D gradient;
uniform vec2 from, dir, to;
uniform float len, radFrom, radTo;

uniform vec2 imageSize;
uniform sampler2D image;
uniform mat3 imageTransform;
uniform vec2 repeat;

uniform bool useAlphaTex;
uniform sampler2D alphaTex;

uniform int boxSize;
uniform bool boxVertical;
uniform float boxScale;
uniform float boxOffset;

bool isNaN(float v) {
  return v < 0.0 || 0.0 < v || v == 0.0 ? false : true;
}

void main() {
	vec4 col = color;

	if (func == 5) {
		vec4 sum = vec4(0.0);
		if (boxVertical) {
			vec2 start = v_tc - vec2(0.0, (float(boxSize) * 0.5 + boxOffset) * boxScale);
			for (int i=0; i <= boxSize; i++) {
				sum += texture2D(image, start + vec2(0.0, float(i) * boxScale));
			}
		} else {
			vec2 start = v_tc - vec2((float(boxSize) * 0.5 + boxOffset) * boxScale, 0.0);
			for (int i=0; i <= boxSize; i++) {
				sum += texture2D(image, start + vec2(float(i) * boxScale, 0.0));
			}
		}
		gl_FragColor = sum / float(boxSize+1);
		return;
	}

	if (func == 1) {
		vec2 v = v_cp - from;
		float r = dot(v, dir) / len;
		r = clamp(r, 0.0, 1.0);
		col = texture2D(gradient, vec2(r, 0.0));
	} else if (func == 2) {
		float o_a = 0.5 * sqrt(
			pow(-2.0*from.x*from.x+2.0*from.x*to.x+2.0*from.x*v_cp.x-2.0*to.x*v_cp.x-2.0*from.y*from.y+2.0*from.y*to.y+2.0*from.y*v_cp.y-2.0*to.y*v_cp.y+2.0*radFrom*radFrom-2.0*radFrom*radTo, 2.0)
			-4.0*(from.x*from.x-2.0*from.x*v_cp.x+v_cp.x*v_cp.x+from.y*from.y-2.0*from.y*v_cp.y+v_cp.y*v_cp.y-radFrom*radFrom)
			*(from.x*from.x-2.0*from.x*to.x+to.x*to.x+from.y*from.y-2.0*from.y*to.y+to.y*to.y-radFrom*radFrom+2.0*radFrom*radTo-radTo*radTo)
		);
		float o_b = (from.x*from.x-from.x*to.x-from.x*v_cp.x+to.x*v_cp.x+from.y*from.y-from.y*to.y-from.y*v_cp.y+to.y*v_cp.y-radFrom*radFrom+radFrom*radTo);
		float o_c = (from.x*from.x-2.0*from.x*to.x+to.x*to.x+from.y*from.y-2.0*from.y*to.y+to.y*to.y-radFrom*radFrom+2.0*radFrom*radTo-radTo*radTo);
		float o1 = (-o_a + o_b) / o_c;
		float o2 = (o_a + o_b) / o_c;
		if (isNaN(o1) && isNaN(o2)) {
			gl_FragColor = vec4(0.0, 0.0, 0.0, 0.0);
			return;
		}
		float o = max(o1, o2);
		o = clamp(o, 0.0, 1.0);
		col = texture2D(gradient, vec2(o, 0.0));
	} else if (func == 3) {
		vec3 tfpt = vec3(v_cp, 1.0) * imageTransform;
		vec2 imgpt = tfpt.xy / imageSize;
		col = texture2D(image, mod(imgpt, 1.0));
		if (imgpt.x < 0.0 || imgpt.x > 1.0) {
			col *= repeat.x;
		}
		if (imgpt.y < 0.0 || imgpt.y > 1.0) {
			col *= repeat.y;
		}
	} else if (func == 4) {
		col = texture2D(image, v_tc);
	}

	if (useAlphaTex) {
		col.a *= texture2D(alphaTex, v_tc).a * globalAlpha;
	} else {
		col.a *= globalAlpha;
	}

    gl_FragColor = col;
}
`

const (
	shdFuncSolid int = iota
	shdFuncLinearGradient
	shdFuncRadialGradient
	shdFuncImagePattern
	shdFuncImage
	shdFuncBoxBlur
)

type unifiedShader struct {
	shaderProgram

	Vertex   gl.Attrib
	TexCoord gl.Attrib

	CanvasSize  gl.Uniform
	Matrix      gl.Uniform
	Color       gl.Uniform
	GlobalAlpha gl.Uniform

	Func gl.Uniform

	UseAlphaTex gl.Uniform
	AlphaTex    gl.Uniform

	Gradient       gl.Uniform
	From, To, Dir  gl.Uniform
	Len            gl.Uniform
	RadFrom, RadTo gl.Uniform

	ImageSize      gl.Uniform
	Image          gl.Uniform
	ImageTransform gl.Uniform
	Repeat         gl.Uniform

	BoxSize     gl.Uniform
	BoxVertical gl.Uniform
	BoxScale    gl.Uniform
	BoxOffset   gl.Uniform
}