// CRTPipeline – PostFX pipeline that simulates a classic CRT monitor:
//   - Barrel distortion (curved screen edges)
//   - Scanlines (every other row darkened)
//   - Vignette (edge darkening)

const fragShader = `
    precision mediump float;

    uniform sampler2D uMainSampler;
    uniform vec2      uResolution;

    varying vec2 outTexCoord;

    void main (void) {
        // --- Screen curvature (barrel distortion) ---
        // Remap UV from [0,1] to centred [-0.5,0.5], distort, remap back
        vec2 uv = outTexCoord;
        vec2 dc = uv - 0.5;
        float strength = 0.18;
        uv = uv + dc * dot(dc, dc) * strength;

        // Pixels pushed outside [0,1] become black (the CRT bezel)
        if (uv.x < 0.0 || uv.x > 1.0 || uv.y < 0.0 || uv.y > 1.0) {
            gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
            return;
        }

        // --- Base colour ---
        vec4 color = texture2D(uMainSampler, uv);

        // --- Scanlines ---
        // Every other screen-pixel row is darkened by ~28%
        float lineY   = uv.y * uResolution.y;
        float scanline = mod(floor(lineY), 2.0);
        color.rgb *= mix(1.0, 0.72, scanline);

        // --- Vignette ---
        float vig = 1.4 - dot(dc * 1.8, dc * 1.8);
        vig = clamp(vig, 0.0, 1.0);
        vig = pow(vig, 0.45);
        color.rgb *= vig;

        gl_FragColor = color;
    }
`;

export default class CRTPipeline extends Phaser.Renderer.WebGL.Pipelines.PostFXPipeline {
    constructor(game) {
        super({ game, name: 'CRTPipeline', fragShader });
    }

    onPreRender() {
        this.set2f('uResolution', this.game.scale.width, this.game.scale.height);
    }
}