import { BufferGeometry, Group, MeshStandardNodeMaterial, UniformNode } from "three/webgpu";

export interface TerrainGeneratorParameters {
    seed: number;
    size: number;
    segments: number;
    heightScale: number;
    frequency: number;
    octaves: number;
    lacunarity: number;
    gain: number;
    erosion: number;
    warp: number;
    valleyBias: number;
    seaLevel: number;
    talus: number;
    talusPasses: number;
}

/**
 * Bakes a procedural mountain range into a single {@link THREE.BufferGeometry} and
 * returns a `THREE.Group` ready to add to a scene.
 *
 * The heightfield is a derivative-damped fractal sum ( Quilez's fake erosion ): each
 * octave is suppressed where the running slope is already steep, concentrating detail
 * into weathered ridgelines, and a low-frequency domain warp makes those ridges
 * meander. A few passes of thermal ( talus ) erosion then relax any slope past the
 * angle of repose, settling the fractal's needle-spikes into real crests.
 *
 * The grid is triangulated with alternating quad diagonals ( a diamond pattern ), so a
 * coarse mesh holds its silhouette without a one-way grain. The surface shades itself
 * from altitude and slope in TSL — grass, forest, rock, scree and snow, with detail
 * normals and aerial perspective — so no material or textures are needed.
 *
 * The baked height grid is exposed through {@link TerrainGenerator#sampleHeight} so a
 * scattered forest ( or anything else ) can sit exactly on the surface.
 *
 * ```js
 * const terrain = new TerrainGenerator( { seed: 1 } );
 * scene.add( terrain.build() );
 * ```
 */
export class TerrainGenerator {
    constructor(parameters?: Partial<TerrainGeneratorParameters>);

    parameters: TerrainGeneratorParameters;

    minHeight: UniformNode<"float", number>;
    maxHeight: UniformNode<"float", number>;

    material: MeshStandardNodeMaterial;
    geometry: BufferGeometry | null;
    group: Group | null;

    heights?: Float32Array;
    gridSize?: number;
    minY?: number;
    maxY?: number;

    build(): Group;

    sampleHeight(x: number, z: number): number;
    sampleSlope(x: number, z: number): number;
    dispose(): void;

    static defaults: TerrainGeneratorParameters;
}