/** Faction tint in the shader instead of on canvas.
 *
 * The stock node-image fragment shader lets opaque avatar pixels fully cover
 * the node color (`mix(v_color, texel, texel.a)`). Scaling that blend factor
 * down makes every avatar pixel a TINT_ALPHA mix with the node (faction)
 * color — the same 50% wash we previously baked into per-node canvases, but
 * with one atlas image per avatar instead of one per avatar×color×theme, and
 * free re-tinting on theme switches (the color rides the node attribute).
 *
 * NOTE: this module touches WebGL at import time via @sigma/node-image, so
 * it must only ever be imported dynamically (see GraphView).
 */
import { createNodeImageProgram } from "@sigma/node-image";

const TINT_ALPHA = 0.5; // opacity of the faction color over the avatar

const ORIGINAL_MIX = "mix(v_color, texel, texel.a)";
const TINTED_MIX = `mix(v_color, texel, texel.a * ${(1 - TINT_ALPHA).toFixed(3)})`;

type ImageProgramOptions = NonNullable<Parameters<typeof createNodeImageProgram>[0]>;

export function createTintedNodeImageProgram(
  options: ImageProgramOptions,
): ReturnType<typeof createNodeImageProgram> {
  const Base = createNodeImageProgram(options) as any;
  return class TintedNodeImageProgram extends Base {
    getDefinition() {
      const def = super.getDefinition();
      const src = def.FRAGMENT_SHADER_SOURCE.replace(ORIGINAL_MIX, TINTED_MIX);
      if (src === def.FRAGMENT_SHADER_SOURCE)
        console.warn("fray: @sigma/node-image shader changed shape; avatars will render untinted");
      return { ...def, FRAGMENT_SHADER_SOURCE: src };
    }
  } as unknown as ReturnType<typeof createNodeImageProgram>;
}