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#version 330

//uniform sampler2D cubemap[1];
uniform sampler2D cubemap0;
uniform sampler2D cubemap1;

in vec3 R; // vector from eye to object reflected in the normal direction
in vec2 outTexCoord;
out vec4 FragColor;

// Given methods to create homogeneous matrices
mat3 Translate(vec2 t) { return mat3(vec3(1,0,0),vec3(0,1,0),vec3(t.x,t.y,1)); }
mat3 Scale(vec2 s) { return mat3(vec3(s.x,0,0),vec3(0,s.y,0),vec3(0,0,1)); }
mat3 Mat(vec2 v0, vec2 v1, vec2 t) { return mat3(vec3(v0,0),vec3(v1,0),vec3(t,1)); }

void main( void )
{	vec2 uv;        // coodinates in [-1,1] on side of cube
    vec2 st0, st1;  // images after transformation of uv axis (1,0) and uv=(0,1), respectively.
    			    // refer to figure in assignment text
	vec2 offset;    // offset to center of square in cube map in [0,8]x[0,6]
		
	// TODO: Depending on the value of R.x, R.y, R.z
	// compute st0, st1 and offset.
	// Assign boolean expressions for all case and subcase
	// variables, such that you cover all combinations (correspoonding to cube faces) for 
	// R.x, R.y, R.z
	// NOTE: this can be done by 2 cases and 3 subcases (see below)
	// but additional cases may be added (full points may not be given in this case)
	
	
	// 3d vector h represents the cartesian coordnates 
	// of the intersection with a unit cube face 	
	// TODO: compute h in each case and then compute uv using h
	// HINT: look at preparatory exercise in the assignment text	        | total of 4 points
	
	//bool case1,case2;
	//bool subcase1, subcase2, subcase3;

	// Determine which face of the cube the reflection vector R intersects
	// Based on the largest absolute component of R
	vec3 absR = abs(R);
	float maxComponent = max(max(absR.x, absR.y), absR.z);
	
	// Cases based on which axis has the largest component
	bool case1 = (absR.x == maxComponent);  // X-dominant (left/right faces)
	bool case2 = (absR.y == maxComponent);  // Y-dominant (top/bottom faces)
	// case3 is Z-dominant (front/back faces)
	
	// Subcases for positive/negative directions
	bool subcase1 = (case1 && R.x > 0.0);  // +X face (right)
	bool subcase2 = (case2 && R.y > 0.0);  // +Y face (top)
	bool subcase3 = (!case1 && !case2 && R.z > 0.0);  // +Z face (front)
	
	// Compute intersection point h with the unit cube face
	// and map to uv coordinates on that face
	
	if (case1) {
		vec3 h;
		if (subcase1) {
			// +X face (right): x = +1
			float t = 1.0 / R.x;
			h = R * t;
			uv = vec2(h.z, h.y);  // Map z,y to u,v for right face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(5, 3);  // Right face position
		} else {
			// -X face (left): x = -1
			float t = -1.0 / R.x;
			h = R * t;
			uv = vec2(-h.z, h.y);   // Map z,y to u,v for left face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(1, 3);  // Left face position
		}
	} else if (case2) {
		vec3 h;
		if (subcase2) {
			// +Y face (top): y = +1
			float t = 1.0 / R.y;
			h = R * t;
			uv = vec2(h.x, h.z);  // Map x,z to u,v for top face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(3, 5);  // Top face position
		} else {
			// -Y face (bottom): y = -1
			float t = -1.0 / R.y;
			h = R * t;
			uv = vec2(h.x, -h.z);   // Map x,z to u,v for bottom face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(3, 1);  // Bottom face position
		}
	} else {
		vec3 h;
		if (subcase3) {
			// +Z face (front): z = +1
			float t = 1.0 / R.z;
			h = R * t;
			uv = vec2(-h.x, h.y);   // Map x,y to u,v for front face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(7, 3);  // Front face position
		} else {
			// -Z face (back): z = -1
			float t = -1.0 / R.z;
			h = R * t;
			uv = vec2(h.x, h.y);  // Map x,y to u,v for back face
			st0 = vec2(1, 0); st1 = vec2(0, 1); offset = vec2(3, 3);  // Back face position
		}
	}

    // TODO: Create a 3x3 matrix m0, using Mat() function
    // and st0, st1, offset which now represent column vectors in m0.; see below
    // The matrix maps locations on a face of the cube from [-1,1]x[-1,1]
    // to the appropriate cube map patch assuming coordinates range in [0,8]x[0,6] | total 3 points

   	// m0 transforms from face coordinates to cube map coordinates
    mat3 m0 = Mat(st0, st1, offset);							
	
    // TODO: Create a 3x3 scaling matrix m1, using Scale() function,
    // such that coordinates are scaled to [1,0]x[0,1]; see below          | total 1 point

    mat3 m1 = Scale(vec2(1.0/8.0, 1.0/6.0));

    // Finally, compute etxture coordinates
    vec3 st = m1*m0*vec3(uv,1);

    FragColor = texture(cubemap1, st.xy/st.z);
}