#version 330

// Input vertex attributes (from vertex shader)
in vec3 fragPosition;
in vec2 fragTexCoord;
in vec4 fragColor;
in vec3 fragNormal;
in vec3 worldPos;

// Input uniform values
uniform sampler2D texture0;
uniform vec4 colDiffuse;

// Custom uniforms for sky
uniform vec3 horizonColor;
uniform vec3 zenithColor;
uniform vec3 sunDirection;
uniform vec3 sunColor;
uniform float sunIntensity;
uniform vec3 moonDirection;
uniform vec3 moonColor;
uniform float moonIntensity;
uniform float moonPhase;
uniform float starsIntensity;
uniform float time;

// Output fragment color
out vec4 finalColor;

// Simple hash function for stars
float hash(vec2 p) {
    return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453);
}

// Noise function for clouds
float noise(vec2 p) {
    vec2 i = floor(p);
    vec2 f = fract(p);
    
    // Four corners in 2D of a tile
    float a = hash(i);
    float b = hash(i + vec2(1.0, 0.0));
    float c = hash(i + vec2(0.0, 1.0));
    float d = hash(i + vec2(1.0, 1.0));
    
    // Smooth interpolation
    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;
}

// Fractal brownian motion for cloud shapes
float fbm(vec2 p) {
    float value = 0.0;
    float amplitude = 0.5;
    float frequency = 2.0;
    
    for (int i = 0; i < 3; i++) {
        value += amplitude * noise(p * frequency);
        amplitude *= 0.5;
        frequency *= 2.0;
    }
    
    return value;
}



void main()
{
    // Normalize the world position to get direction from center
    vec3 direction = normalize(worldPos);
    
    // Calculate gradient based on Y component (height)
    float gradientFactor = smoothstep(-0.5, 1.0, direction.y);
    
    // Interpolate between horizon and zenith colors
    vec3 skyColor = mix(horizonColor, zenithColor, gradientFactor);
    
    // Simple cloud layer (only during day)
    if (direction.y > 0.1 && sunIntensity > 0.2) {
        // Map direction to 2D cloud coordinates
        vec2 cloudCoord = direction.xz / max(direction.y, 0.001) * 0.5;
        
        // Animate clouds
        cloudCoord += vec2(time * 0.02, time * 0.01);
        
        // Generate cloud pattern using multiple layers of noise
        float cloudNoise = 0.0;
        cloudNoise += fbm(cloudCoord * 2.0) * 0.5;
        cloudNoise += fbm(cloudCoord * 5.0) * 0.25;
        cloudNoise += fbm(cloudCoord * 11.0) * 0.125;
        
        // Shape the clouds
        float cloudDensity = smoothstep(0.4, 0.6, cloudNoise);
        
        // Fade clouds at horizon
        cloudDensity *= smoothstep(0.0, 0.3, direction.y);
        
        if (cloudDensity > 0.01) {
            // Simple cloud lighting
            float lightness = 0.7 + 0.3 * sunIntensity;
            
            // Make clouds slightly bluish in shadow, whiter in light
            vec3 cloudColor = mix(
                vec3(0.7, 0.75, 0.85),  // Shadow color
                vec3(1.0, 1.0, 1.0),     // Lit color
                lightness
            );
            
            // Mix clouds with sky
            skyColor = mix(skyColor, cloudColor, cloudDensity * 0.8);
        }
    }
    
    // Add stars (only visible at night)
    if (starsIntensity > 0.01 && direction.y > -0.1) { // Don't render stars below horizon
        // Create a simple star field using noise
        vec2 starCoord = direction.xz * 30.0; // Less dense grid
        
        // Two layers of stars for depth (reduced from 3)
        for (int i = 0; i < 2; i++) {
            vec2 gridPos = floor(starCoord * (1.0 + float(i) * 0.3));
            vec2 gridFract = fract(starCoord * (1.0 + float(i) * 0.3));
            
            float starRandom = hash(gridPos + vec2(float(i) * 13.0, float(i) * 17.0));
            
            // Much fewer stars (higher threshold)
            if (starRandom > 0.985 + float(i) * 0.005) {
                float starBrightness = hash(gridPos + vec2(37.0, 73.0));
                
                // Circular star points
                vec2 starCenter = vec2(0.5);
                float dist = length(gridFract - starCenter);
                
                if (dist < 0.05) { // Slightly larger star points
                    float starAlpha = pow(1.0 - dist / 0.05, 1.5) * starsIntensity;
                    starAlpha *= (0.4 + starBrightness * 0.6); // Vary brightness
                    skyColor = mix(skyColor, vec3(0.95, 0.95, 1.0), starAlpha);
                }
            }
        }
    }
    
    vec3 color = skyColor;
    
    // Calculate sun contribution
    vec3 sunDir = normalize(sunDirection);
    float sunDot = dot(direction, sunDir);
    
    // Only render sun if it's above horizon and has intensity
    if (sunDir.y > 0.0 && sunIntensity > 0.1) {
        // Sun disc with soft edges - much smaller
        float sunSize = 0.9985; // Much smaller sun (closer to 1.0 = smaller)
        float sunEdge = 0.997;
        
        if (sunDot > sunSize) {
            // Bright sun core
            color = mix(sunColor, vec3(1.0, 1.0, 0.95), 0.8);
        } else if (sunDot > sunEdge) {
            // Soft edge
            float edge = smoothstep(sunEdge, sunSize, sunDot);
            color = mix(color, sunColor, edge);
        }
        
        // Sun glow - tighter radius
        if (sunDot > 0.94) {
            float glow = pow(max(0.0, (sunDot - 0.94) / 0.06), 2.0) * sunIntensity;
            color = mix(color, sunColor, glow * 0.4);
        }
    }
    
    // Calculate moon contribution
    vec3 moonDir = normalize(moonDirection);
    float moonDot = dot(direction, moonDir);
    
    // Only render moon if it's above horizon
    if (moonDir.y > 0.0 && moonIntensity > 0.1) {
        // Moon disc - 15% smaller than before
        float moonSize = 0.9992; // Much smaller than sun (sun is 0.9985)
        float moonEdge = 0.999;
        
        if (moonDot > moonSize) {
            // Simple moon disc (simplified for smaller size)
            color = mix(color, moonColor, moonIntensity);
        } else if (moonDot > moonEdge) {
            // Soft moon edge
            float edge = smoothstep(moonEdge, moonSize, moonDot);
            color = mix(color, moonColor * 0.8, edge * moonIntensity);
        }
        
        // Subtle moon glow - even tighter for smaller moon
        if (moonDot > 0.98) {
            float glow = pow(max(0.0, (moonDot - 0.98) / 0.02), 2.0) * moonIntensity;
            color = mix(color, moonColor, glow * 0.1);
        }
    }
    
    finalColor = vec4(color, 1.0);
}