/**
 * hasselink/tiling/delta-pixels.ts
 * ------------------------------------------------------
 * Type-level constructors for Delta pixels.
 *
 * Delta pixels are intended to carry "semantic change" markers (logical deltas)
 * rather than absolute values.
 */

import type { BlockAssignment, PixelAssignment, TypedTiledPixel } from "./tiling.ts";

/**
 * A single delta pixel inside a Level-1 block.
 *
 * We intentionally keep geometry simple here:
 * - Level-1 is a 2x2 block, which is a convenient "ribs/metadata" scale.
 * - The precise position conventions belong to the strategy/impl.
 */
export type DeltaPixel<
  B extends BlockAssignment<1>,
  I extends 0 | 1,
  J extends 0 | 1
> =
  PixelAssignment<1> & {
    owner: B["owner"];
    level: 1;
    block: B["block"];
    role: B["role"];
    pixel: TypedTiledPixel<1> & {
      block: B["block"];
      index: { ix: I; iy: J };
      role: "Delta";
      channel: "Meta";
    };
  };

export type DeltaPixelsForBlock<B extends BlockAssignment<1>> = readonly [
  DeltaPixel<B, 0, 0>,
  DeltaPixel<B, 1, 0>,
  DeltaPixel<B, 0, 1>,
  DeltaPixel<B, 1, 1>
];