import * as THREE from 'three';
import type { EnvironmentChapter } from '@/journey/types';
import type { RenderQualitySettings } from '@/scene/render-quality';
import type { SceneResourceBag } from '@/scene/resources';
import { CHAPTER_PALETTES } from '@/scene/world/palette';

export interface TerrainWorld {
  group: WorldGroup;
  update(
    distance: number,
    speed: number,
    chapter: EnvironmentChapter,
    routeProgress: number,
  ): void;
}

interface WorldGroup {
  add(...objects: unknown[]): void;
  getObjectByName(name: string): unknown;
}

const TERRAIN_WIDTH = 160;
const TERRAIN_DEPTH = 300;
const NEAR_Z = 14;
const ROAD_CLEAR_HALF_WIDTH = 11.4;
const RIDGE_START = 24;

export function createTerrain(
  resources: SceneResourceBag,
  quality: RenderQualitySettings,
): TerrainWorld {
  const group = new THREE.Group();
  group.name = 'terrain-world';
  const geometry = resources.own('geometry', createIndexedTerrainGeometry(quality.terrainSegments));
  const initialPalette = CHAPTER_PALETTES['deep-night'];
  const lowColor = new THREE.Color(initialPalette.terrainLow);
  const highColor = new THREE.Color(initialPalette.terrainHigh);
  const uniforms = {
    uDistance: { value: 0 },
    uSpeed: { value: 0 },
    uRouteProgress: { value: 0 },
    uTerrainEnergy: { value: initialPalette.terrainEnergy },
    uOctaves: { value: quality.terrainOctaves },
    uLowColor: { value: lowColor },
    uHighColor: { value: highColor },
  };
  const material = resources.own('material', new THREE.ShaderMaterial({
    uniforms,
    vertexShader: `
      attribute float roadMask;
      uniform float uDistance;
      uniform float uSpeed;
      uniform float uRouteProgress;
      uniform float uTerrainEnergy;
      uniform float uOctaves;
      varying float vHeight;
      varying float vRoadMask;
      varying float vDepthFade;
      varying float vFlow;

      float hash21(vec2 point) {
        point = fract(point * vec2(123.34, 456.21));
        point += dot(point, point + 45.32);
        return fract(point.x * point.y);
      }

      float valueNoise(vec2 point) {
        vec2 cell = floor(point);
        vec2 local = fract(point);
        local = local * local * (3.0 - 2.0 * local);
        return mix(
          mix(hash21(cell), hash21(cell + vec2(1.0, 0.0)), local.x),
          mix(hash21(cell + vec2(0.0, 1.0)), hash21(cell + vec2(1.0)), local.x),
          local.y
        );
      }

      float multiOctaveNoise(vec2 point) {
        float result = valueNoise(point) * 0.58;
        if (uOctaves > 1.5) result += valueNoise(point * 2.03 + 17.2) * 0.28;
        if (uOctaves > 2.5) result += valueNoise(point * 4.07 - 9.4) * 0.14;
        return result;
      }

      void main() {
        vec3 displaced = position;
        float wrappedPhase = mod(uDistance * (0.18 + uSpeed * 0.06), 96.0);
        float ridgeNoise = multiOctaveNoise(vec2(position.x * 0.038, (position.z - wrappedPhase) * 0.028));
        float macroRidge = multiOctaveNoise(vec2(position.x * 0.014 + 31.0, position.z * 0.012));
        float edgeGrowth = mix(0.6, 1.0, smoothstep(0.0, 72.0, abs(position.x)));
        float height = roadMask * (0.25 + ridgeNoise * ridgeNoise * 8.8 + macroRidge * 2.4);
        height *= edgeGrowth * uTerrainEnergy;
        displaced.y += height - 0.22;

        vHeight = clamp(height / 10.0, 0.0, 1.0);
        vRoadMask = roadMask;
        vDepthFade = smoothstep(-286.0, -205.0, position.z) * (1.0 - smoothstep(7.0, 14.0, position.z));
        vFlow = fract((-position.z + uDistance * (0.9 + uSpeed * 0.25)) / 11.0);
        gl_Position = projectionMatrix * modelViewMatrix * vec4(displaced, 1.0);
      }
    `,
    fragmentShader: `
      uniform vec3 uLowColor;
      uniform vec3 uHighColor;
      uniform float uRouteProgress;
      varying float vHeight;
      varying float vRoadMask;
      varying float vDepthFade;
      varying float vFlow;

      void main() {
        float ridgeMix = smoothstep(0.16, 0.78, vHeight);
        vec3 color = mix(uLowColor, uHighColor, ridgeMix);
        float pulse = 0.78 + 0.22 * smoothstep(0.18, 0.52, vFlow);
        float routeCalm = mix(1.0, 0.9, smoothstep(0.82, 1.0, uRouteProgress));
        float alpha = vRoadMask * vDepthFade * pulse * routeCalm * mix(0.34, 0.66, ridgeMix);
        gl_FragColor = vec4(color, alpha);
      }
    `,
    transparent: true,
    depthWrite: false,
    depthTest: true,
    blending: THREE.AdditiveBlending,
    toneMapped: true,
  }));

  const lines = new THREE.LineSegments(geometry, material);
  lines.name = 'terrain-lines';
  lines.frustumCulled = false;
  group.add(lines);

  return {
    group,
    update(distance, speed, chapter, routeProgress) {
      const palette = CHAPTER_PALETTES[chapter];
      uniforms.uDistance.value = finiteOrZero(distance);
      uniforms.uSpeed.value = clamp01(speed);
      uniforms.uRouteProgress.value = clamp01(routeProgress);
      uniforms.uTerrainEnergy.value = palette.terrainEnergy;
      lowColor.setHex(palette.terrainLow);
      highColor.setHex(palette.terrainHigh);
    },
  };
}

function createIndexedTerrainGeometry(segments: number) {
  const zSegments = Math.max(16, Math.floor(segments));
  const xSegments = Math.max(24, Math.floor(zSegments * 0.75 / 2) * 2);
  const columnCount = xSegments + 1;
  const rowCount = zSegments + 1;
  const positions = new Float32Array(columnCount * rowCount * 3);
  const roadMasks = new Float32Array(columnCount * rowCount);
  let vertexOffset = 0;
  let maskOffset = 0;

  for (let row = 0; row < rowCount; row += 1) {
    const z = NEAR_Z - (row / zSegments) * TERRAIN_DEPTH;
    for (let column = 0; column < columnCount; column += 1) {
      const x = -TERRAIN_WIDTH / 2 + (column / xSegments) * TERRAIN_WIDTH;
      positions[vertexOffset] = x;
      positions[vertexOffset + 1] = 0;
      positions[vertexOffset + 2] = z;
      vertexOffset += 3;
      roadMasks[maskOffset] = smoothstep(ROAD_CLEAR_HALF_WIDTH, RIDGE_START, Math.abs(x));
      maskOffset += 1;
    }
  }

  const indices: number[] = [];
  const vertexIndex = (column: number, row: number): number => row * columnCount + column;
  for (let row = 0; row < rowCount; row += 1) {
    for (let column = 0; column < columnCount; column += 1) {
      const x = -TERRAIN_WIDTH / 2 + (column / xSegments) * TERRAIN_WIDTH;
      if (row < zSegments && Math.abs(x) > ROAD_CLEAR_HALF_WIDTH) {
        indices.push(vertexIndex(column, row), vertexIndex(column, row + 1));
      }
      if (column < xSegments) {
        const nextX = -TERRAIN_WIDTH / 2 + ((column + 1) / xSegments) * TERRAIN_WIDTH;
        const midpoint = (x + nextX) * 0.5;
        if (Math.abs(midpoint) > ROAD_CLEAR_HALF_WIDTH) {
          indices.push(vertexIndex(column, row), vertexIndex(column + 1, row));
        }
      }
    }
  }

  const geometry = new THREE.BufferGeometry();
  geometry.setAttribute('position', new THREE.BufferAttribute(positions, 3));
  geometry.setAttribute('roadMask', new THREE.BufferAttribute(roadMasks, 1));
  geometry.setIndex(indices);
  geometry.computeBoundingSphere();
  return geometry;
}

function smoothstep(edge0: number, edge1: number, value: number): number {
  const progress = THREE.MathUtils.clamp((value - edge0) / (edge1 - edge0), 0, 1);
  return progress * progress * (3 - 2 * progress);
}

function finiteOrZero(value: number): number {
  return Number.isFinite(value) ? value : 0;
}

function clamp01(value: number): number {
  return THREE.MathUtils.clamp(finiteOrZero(value), 0, 1);
}