export const fireVertexShader = `
varying vec2 vUv;
void main() {
    vUv = uv;
    gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`;

export const fireFragmentShader = `
varying vec2 vUv;
uniform float u_time;

// 2D Random function
float random (vec2 st) {
    return fract(sin(dot(st.xy,
                         vec2(12.9898,78.233)))*
        43758.5453123);
}

// 2D Noise function
float noise (in vec2 st) {
    vec2 i = floor(st);
    vec2 f = fract(st);

    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(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;
}

// Fractional Brownian Motion to create more complex noise
float fbm(in vec2 st) {
    float value = 0.0;
    float amplitude = 0.5;
    float frequency = 0.0;

    for (int i = 0; i < 4; i++) {
        value += amplitude * noise(st);
        st *= 2.0;
        amplitude *= 0.5;
    }
    return value;
}

void main() {
    vec2 uv = vUv;
    float q = fbm(uv * 2.0 - vec2(0.0, u_time * 1.2));
    float r = fbm(uv * 2.0 + q + vec2(1.7, 9.2) + vec2(0.0, u_time * -0.3));

    float fireAmount = fbm(uv * 2.0 + r + vec2(0.0, u_time * 0.15));

    // Shape the fire to rise from the bottom
    fireAmount *= (1.0 - uv.y);

    vec3 fireColor = mix(vec3(0.9, 0.3, 0.1), vec3(1.0, 0.9, 0.3), fireAmount);
    gl_FragColor = vec4(fireColor, fireAmount * 2.0);
}
`;