import * as THREE from 'three';

/**
 * Per-card UV transform injected into a `MeshStandardMaterial` shader.
 *
 * Cards share one texture (the deck's sprite sheet, cached by drei) and one
 * geometry, but each card samples a different sprite cell. Rather than cloning
 * the texture per card (which re-uploads the sheet on every GPU bind), the
 * repeat/offset is pushed into the material as a uniform. The shader source is
 * identical across cards, so three.js still compiles a single shared program.
 *
 * We inject our own uniform instead of setting `texture.repeat`/`offset`
 * because three r185 derives the map UVs from a `mapTransform` matrix that is
 * refreshed from `map.matrix` every frame, overwriting any per-material
 * transform we set on the shared texture.
 */
// Uniforms added via `onBeforeCompile` are not auto-declared by three.js, so
// they must be declared in the GLSL explicitly (the built-in `mapTransform` is
// declared in `uv_pars_vertex.glsl.js`).
const UNIFORM_DECLS = /* glsl */ `
	uniform vec2 uMapRepeat;
	uniform vec2 uMapOffset;
`;

const VERTEX_INJECT = /* glsl */ `
	#include <uv_vertex>
	vMapUv = uv * uMapRepeat + uMapOffset;
`;

/**
 * Apply a repeat/offset to a card material's map sampling. Call once per
 * material (the transform is baked into the shader). `repeat`/`offset` are
 * copied, so the caller may reuse the vectors.
 */
export function applyMapTransform(
  material: THREE.MeshStandardMaterial,
  repeat: THREE.Vector2,
  offset: THREE.Vector2,
): void {
  // Clone eagerly so later mutation of the caller's vectors can't leak into
  // the uniform once the material is compiled.
  const r = repeat.clone();
  const o = offset.clone();
  material.onBeforeCompile = (shader) => {
    shader.uniforms.uMapRepeat = { value: r };
    shader.uniforms.uMapOffset = { value: o };
    shader.vertexShader =
      UNIFORM_DECLS +
      shader.vertexShader.replace('#include <uv_vertex>', VERTEX_INJECT);
  };
}