/* BTW: You can use ANY function as the noise/plasma function
 * It just needs to return a float in the range 0.0 - 17.0
 * But shouldn't return 0.0 or 17.0 (they're exclusive bounds).
 * View this shader on shadertoy: https://www.shadertoy.com/view/t3tSRj#
 */

// is highp wasteful for this shader?
#ifdef GL_ES
# ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
# else
precision mediump float;
# endif
#endif

uniform float uTime;
uniform vec2 uResolution;

/* ==== Text Colouring  ==== */
#define PHOSPHOR_COL vec4(196./255., 167./255., 231./255., 1.)
// #define BG_COL vec4(0.2, 0.0, 0.2, 0.5)
#define BG_COL vec4(14./255., 13./255., 20./255., 1.)
/* ======= Text Size ======= */
#define FONT_SIZE vec2(10.,20.)
#define ROWCOLS vec2(80., 24.)

// ===================================================================
// Library Functions
//
float rand (in vec2 _st) {
    return fract(sin(dot(_st.xy, vec2(12.9898,78.233))) * 43758.5453123);
}

float quantise(float val, float n) {
    return clamp(floor(val * n), 0.0, n) / n;
}

float roundSquare(vec2 p, vec2 b, float r) {
    return length(max(abs(p)-b,0.0))-r;
}


// ===================================================================
// VT220 Font Rendering
// Author/Source : https://www.shadertoy.com/view/llSXDV
//
#define l(y,a,b) roundLine(p, vec2(float(a), float(y)), vec2(float(b), float(y)))
float roundLine(vec2 p, vec2 a, vec2 b) {
    b -= a + vec2(1.0,0.);
    p -= a;
    float f = length(p-clamp(dot(p,b)/dot(b,b),0.0,1.0)*b);
    if (uResolution.y < 320.) // attempt to get rid of aliasing on small resolution
        return smoothstep(1.0, 0.9, f);    
    else if (uResolution.y < 720.)
        return smoothstep(0.75, 0.5, f);    
    else
        return smoothstep(1., 0., f);    
}

float vt220Font(vec2 p, float c) {
    if (c < 1.) return 0.;
    if (p.y > 16.) {
        if (c > 2.) return 0.0;
		if (c > 1.) return l(17,1,9);
    }
    if (p.y > 14.) {
		if (c > 16.) return l(15,3,8);
		if (c > 15.) return l(15,1,8);
		if (c > 14.) return l(15,1,3)+ l(15,7,9);
		if (c > 13.) return l(15,2,8);
		if (c > 12.) return l(15,1,9);
		if (c > 11.) return l(15,2,8);
		if (c > 10.) return l(15,1,3)+ l(15,6,8);
		if (c > 9.) return l(15,4,6);
    if (c > 8.) return l(15,2,4)+ l(15,5,7);
		if (c > 7.) return l(15,2,8);
		if (c > 6.) return l(15,2,8);
		if (c > 5.) return l(15,2,8);
		if (c > 4.) return l(15,2,9);
		if (c > 3.) return l(15,1,8);
		if (c > 2.) return l(15,2,9);
    }
    if (p.y > 12.) {
		if (c > 16.) return l(13,2,4)+ l(13,7,9);
		if (c > 15.) return l(13,2,4)+ l(13,7,9);
		if (c > 14.) return l(13,1,3)+ l(13,7,9);
		if (c > 13.) return l(13,1,3)+ l(13,7,9);
		if (c > 12.) return l(13,1,3);
		if (c > 11.) return l(13,4,6);
		if (c > 10.) return l(13,2,4)+ l(13,5,9);
		if (c > 9.) return l(13,2,8);
		if (c > 8.) return l(13,2,4)+ l(13,5,7);
		if (c > 7.) return l(13,1,3)+ l(13,7,9);
		if (c > 6.) return l(13,1,3)+ l(13,7,9);
		if (c > 5.) return l(13,1,3)+ l(13,7,9);
		if (c > 4.) return l(13,1,3)+ l(15,2,9);
		if (c > 3.) return l(13,1,4)+ l(13,7,9);
		if (c > 2.) return l(13,1,3)+ l(13,6,9);
    }
    if (p.y > 10.) {
		if (c > 16.) return l(11,1,3);
		if (c > 15.) return l(11,2,4)+ l(11,7,9);
		if (c > 14.) return l(11,1,9);
		if (c > 13.) return l(11,7,9);
		if (c > 12.) return l(11,2,5);
		if (c > 11.) return l(11,4,6);
		if (c > 10.) return l(11,3,5)+ l(11,6,8);
		if (c > 9.) return l(11,4,6)+ l(11,7,9);
		if (c > 8.) return l(11,1,8);
		if (c > 7.) return l(11,1,3)+ l(11,7,9);
		if (c > 6.) return l(11,1,3)+ l(11,7,9);
		if (c > 5.) return l(11,1,3)+ l(11,7,9);
		if (c > 4.) return l(11,1,3);
		if (c > 3.) return l(11,1,3)+ l(11,7,9);
		if (c > 2.) return l(11,2,9);
    }
    if (p.y > 8.) {
		if (c > 16.) return l(9,1,3);
		if (c > 15.) return l(9,2,8);
		if (c > 14.) return l(9,1,3)+ l(9,7,9);
		if (c > 13.) return l(9,4,8);
		if (c > 12.) return l(9,4,8);
		if (c > 11.) return l(9,4,6);
		if (c > 10.) return l(9,4,6);
		if (c > 9.) return l(9,2,8);
		if (c > 8.) return l(9,2,4)+ l(9,5,7);
		if (c > 7.) return l(9,1,3)+ l(9,7,9);
		if (c > 6.) return l(9,1,3)+ l(9,7,9);
		if (c > 5.) return l(9,1,3)+ l(9,7,9);
		if (c > 4.) return l(9,1,3)+ l(9,7,9);
		if (c > 3.) return l(9,1,4)+ l(9,7,9);
		if (c > 2.) return l(9,7,9);
    }
    if (p.y > 6.) {
		if (c > 16.) return l(7,1,3);
		if (c > 15.) return l(7,2,4)+ l(7,7,9);
		if (c > 14.) return l(7,2,4)+ l(7,6,8);
		if (c > 13.) return l(7,5,7);
		if (c > 12.) return l(7,7,9);
		if (c > 11.) return l(7,2,6);
		if (c > 10.) return l(7,2,4)+ l(7,5,7);
		if (c > 9.) return l(7,1,3)+ l(7,4,6);
		if (c > 8.) return l(7,1,8);
		if (c > 7.) return l(7,2,8);
		if (c > 6.) return l(7,2,8);
		if (c > 5.) return l(7,2,8);
		if (c > 4.) return l(7,2,8);
		if (c > 3.) return l(7,1,8);
		if (c > 2.) return l(7,2,8);
    }
    if (p.y > 4.) {
		if (c > 16.) return l(5,2,4)+ l(5,7,9);
		if (c > 15.) return l(5,2,4)+ l(5,7,9);
		if (c > 14.) return l(5,3,7);
		if (c > 13.) return l(5,6,8);
		if (c > 12.) return l(5,1,3)+ l(5,7,9);
		if (c > 11.) return l(5,3,6);
		if (c > 10.) return l(5,1,5)+ l(5,6,8);
		if (c > 9.) return l(5,2,8);
		if (c > 8.) return l(5,2,4)+ l(5,5,7);
		if (c > 7.) return 0.;
		if (c > 6.) return 0.;
		if (c > 5.) return 0.;
		if (c > 4.) return 0.;
		if (c > 3.) return l(5,1,3);
		if (c > 2.) return 0.;
    }
    if (p.y > 2.) {
		if (c > 16.) return l(3,3,8);
		if (c > 15.) return l(3,1,8);
		if (c > 14.) return l(3,4,6);
		if (c > 13.) return l(3,1,9);
		if (c > 12.) return l(3,2,8);
		if (c > 11.) return l(3,4,6);
		if (c > 10.) return l(3,2,4)+ l(3,7,9);
		if (c > 9.) return l(3,4,6);
		if (c > 8.) return l(3,2,4)+ l(3,5,7);
		if (c > 7.) return l(3,2,4)+ l(3,6,8);
		if (c > 6.) return l(3,1,3)+ l(3,4,7);
		if (c > 5.) return l(3,2,4)+ l(3,6,8);
		if (c > 4.) return 0.;
		if (c > 3.) return l(3,1,3);
		if (c > 2.) return 0.;
    }
    else {
		if (c > 7.) return 0.;
		if (c > 6.) return l(1,2,5)+ l(1,6,8);
    }
    return 0.0;      
}


// ===================================================================
// Text Effects
//     textLines(...) is for simulating the writing of random characters in line formats
//     https://www.shadertoy.com/view/llSXDV (same author as VT220 font rendering)
//
float textLines(vec2 uvG) {
    float wt = 5. * (uTime + 0.5*sin(uTime*1.4) + 0.2*sin(uTime*2.9)); // wobbly time
    vec2 uvGt = uvG + vec2(0., floor(wt));
    float ll = rand(vec2(uvGt.y, - 1.)) * ROWCOLS.x; // line length
    
    if (uvG.y > ROWCOLS.y - 2.){
        if (ceil(uvG.x) == floor(min(ll, fract(wt)*ROWCOLS.x)))
        	return 2.;
        if (ceil(uvG.x) > floor(min(ll, fract(wt)*ROWCOLS.x)))
        	return 0.;
    }
    if (uvGt.x > 5. && rand(uvGt) < .075)
        return 0.;
    if (max(5., uvGt.x) > ll)
        return 0.;
       
    return rand(uvGt)*15. + 2.;
}


// ===================================================================
// Noise Generation Algorithms
//     noise(...) is for the main noise generation algorithm (very tunable)
//     https://www.shadertoy.com/view/MsdGWn
//

// Based on Morgan McGuire @morgan3d
// https://www.shadertoy.com/view/4dS3Wd
float noise (in vec2 _st) {
    vec2 i = floor(_st);
    vec2 f = fract(_st);

    // Four corners in 2D of a tile
    float a = rand(i);
    float b = rand(i + vec2(1.0, 0.0));
    float c = rand(i + vec2(0.0, 1.0));
    float d = rand(i + vec2(1.0, 1.0));

    vec2 u = f * f * (3.0 - 2.0 * f);

    return mix(a, b, u.x) +
            (c - a)* u.y * (1.0 - u.x) +
            (d - b) * u.x * u.y;
}

#define NUM_OCTAVES 100
// Brightness (0.0 - 1.0)
#define BRIGHTNESS 0.55
#define LACUNARITY 2.0
#define GAIN 0.5
#define SHIFT 100.0

// VAR_THETA defines whether to compute
// sin/cos values at runtime or 
#define VAR_THETA 0
#define THETA 0.5
#if (VAR_THETA == 1)
#endif

float fbm( in vec2 _st) {
    float v = 0.0;
    float a = BRIGHTNESS;
    // Rotate to reduce axial bias
    mat2 T = LACUNARITY * mat2(cos(THETA), sin(THETA), 
                               -sin(THETA), cos(THETA));
    for (int i = 0; i < NUM_OCTAVES; ++i) {
        _st = T * _st + SHIFT;
        v += noise(_st) * a;
        a *= GAIN;
    }
    return v;
}


#define SCALE_UV 3.
#define SCALE_TIME 1.

// XXX: TODO: use two shaders, the first on a MUCH lower resolution (one pixel for each text character)
// XXX: TODO: then the second should map those pixel values to higher resolution text characters
void main() {       
    vec2 uv = gl_FragCoord.xy / uResolution;
    vec2 st = uv * SCALE;
        
    // // uvNoise = ceil(uvNoise * ROWCOLS) / ROWCOLS;
    // float val = noise(st);
    // // Noise is fed through a sigmoid function, then quantised to integer range 0-17
    // val = (exp(val) / 2.71828);  // increase contrast (normalised 0.0 - 1.0)
    // val = 1.0 / val;
    // val *= 1.0 / (1.0 + exp(-val)) - 0.5; // subtraction value is tunable (range 0.0 - 0.5)
    // val *= quantise(val, 17.0); // quantise by 17 then normalise back to 0.0 - 1.0
    // val = pow(18.0, val) - 1.0; // TODO: try changing 18.0 to 200.0 and you'll notice some pretty changes :)
      
    // // VT220 Font Rendering
    // vec2 base = uv;
    // base.y = 1 - base.y;    
   	// vec2 uvT = ROWCOLS * FONT_SIZE * base;
   	// vec2 uvG = floor(ROWCOLS * base;
    // gl_FragColor = vt220Font(uvT - uvG * FONT_SIZE, val) * PHOSPHOR_COL + BG_COL;

    vec2 q = vec2(
        fbm( st + 0.*uTime),
        fbm( st + vec2(1.0))
    );

    vec2 r = vec2(
        fbm( st + 1.0*q + vec2(1.7,9.2)+ 0.15*uTime ),
        fbm( st + 1.0*q + vec2(8.3,2.8)+ 0.126*uTime)
    );

    float f = fbm(st+r);

    vec3 color = mix(vec3(0.101961,0.619608,0.666667),
                vec3(0.666667,0.666667,0.498039),
                clamp((f*f)*4.0,0.0,1.0));

    color = mix(color,
                vec3(0,0,0.164706),
                clamp(length(q),0.0,1.0));

    color = mix(color,
                vec3(0.666667,1,1),
                clamp(length(r.x),0.0,1.0));

    gl_FragColor = vec4((f*f*f+.6*f*f+.5*f)*color,1.);
}