/**
 * Dimension Terrain Generators — Nether & End
 *
 * NetherGenerator:
 *  - Lava seas at y=32
 *  - Netherrack terrain with caves
 *  - Soul sand valleys, Crimson/Warped forests, Basalt deltas
 *  - Glowstone clusters, ores, bedrock borders
 *  - Height range: 0-128
 *
 * EndGenerator:
 *  - Central island (end stone, ~50 block radius)
 *  - Obsidian pillars of varying heights
 *  - Void below, flat top at y=64
 *  - Only terrain within ~100 blocks of origin
 */

import { createNoise2D, createNoise3D } from 'simplex-noise'
import {
  CHUNK_WIDTH,
  BLOCK_AIR,
  BLOCK_BEDROCK,
  BLOCK_NETHERRACK,
  BLOCK_LAVA,
  BLOCK_SOUL_SAND,
  BLOCK_SOUL_SOIL,
  BLOCK_BASALT,
  BLOCK_BLACKSTONE,
  BLOCK_GLOWSTONE,
  BLOCK_NETHER_QUARTZ_ORE,
  BLOCK_NETHER_GOLD_ORE,
  BLOCK_CRIMSON_NYLIUM,
  BLOCK_WARPED_NYLIUM,
  BLOCK_CRIMSON_STEM,
  BLOCK_WARPED_STEM,
  BLOCK_CRIMSON_FUNGUS,
  BLOCK_WARPED_FUNGUS,
  BLOCK_CRIMSON_PLANKS,
  BLOCK_WARPED_PLANKS,
  BLOCK_NETHER_WART_BLOCK,
  BLOCK_WARPED_WART_BLOCK,
  BLOCK_SHROOMLIGHT,
  BLOCK_MAGMA_BLOCK,
  BLOCK_END_STONE,
  BLOCK_OBSIDIAN,
  BLOCK_GRAVEL,
} from '../constants'
import type { ChunkData } from '@/types'

// ═══════════════════════════════════════════════════════════════
// CONSTANTS
// ═══════════════════════════════════════════════════════════════

const NETHER_HEIGHT = 128
const NETHER_LAVA_LEVEL = 32
const NETHER_CEILING = 128
const NETHER_FLOOR = 0

const END_HEIGHT = 128
const END_ISLAND_Y = 64
const END_ISLAND_RADIUS = 50
const END_TERRAIN_RADIUS = 100

// ═══════════════════════════════════════════════════════════════
// SEEDED RNG
// ═══════════════════════════════════════════════════════════════

function seededRandom(seed: number): () => number {
  let s = seed | 0
  return () => {
    s = (s * 1664525 + 1013904223) | 0
    return (s >>> 0) / 4294967296
  }
}

/** Deterministic hash from world coords → float in [0,1) */
function hashCoord(x: number, y: number, z: number, seed: number): number {
  let h = (seed | 0) ^ 0x5bd1e995
  h = ((h ^ (x * 0x5bd1e995)) * 0x27d4eb2d) | 0
  h = ((h ^ (y * 0x5bd1e995)) * 0x27d4eb2d) | 0
  h = ((h ^ (z * 0x5bd1e995)) * 0x27d4eb2d) | 0
  h ^= h >>> 16
  return (h >>> 0) / 4294967296
}

function hashCoord2(x: number, z: number, seed: number): number {
  let h = (seed | 0) ^ 0x5bd1e995
  h = ((h ^ (x * 0x5bd1e995)) * 0x27d4eb2d) | 0
  h = ((h ^ (z * 0x5bd1e995)) * 0x27d4eb2d) | 0
  h ^= h >>> 16
  return (h >>> 0) / 4294967296
}

// ═══════════════════════════════════════════════════════════════
// NETHER BIOME TYPES
// ═══════════════════════════════════════════════════════════════

enum NetherBiome {
  NetherWastes,
  SoulSandValley,
  CrimsonForest,
  WarpedForest,
  BasaltDeltas,
}

// ═══════════════════════════════════════════════════════════════
// NETHER GENERATOR
// ═══════════════════════════════════════════════════════════════

export class NetherGenerator {
  private seed: number

  // Noise instances
  private noiseTerrain: ReturnType<typeof createNoise3D>
  private noiseTerrain2: ReturnType<typeof createNoise3D>
  private noiseCave: ReturnType<typeof createNoise3D>
  private noiseCave2: ReturnType<typeof createNoise3D>
  private noiseBiome1: ReturnType<typeof createNoise2D>
  private noiseBiome2: ReturnType<typeof createNoise2D>
  private noiseBiome3: ReturnType<typeof createNoise2D>
  private noiseOre: ReturnType<typeof createNoise3D>
  private noiseGlowstone: ReturnType<typeof createNoise3D>
  private noiseDetail: ReturnType<typeof createNoise2D>
  private noisePillar: ReturnType<typeof createNoise2D>

  constructor(seed: number) {
    this.seed = seed
    const rng = seededRandom(seed ^ 0xDEADBEEF)

    this.noiseTerrain = createNoise3D(rng)
    this.noiseTerrain2 = createNoise3D(rng)
    this.noiseCave = createNoise3D(rng)
    this.noiseCave2 = createNoise3D(rng)
    this.noiseBiome1 = createNoise2D(rng)
    this.noiseBiome2 = createNoise2D(rng)
    this.noiseBiome3 = createNoise2D(rng)
    this.noiseOre = createNoise3D(rng)
    this.noiseGlowstone = createNoise3D(rng)
    this.noiseDetail = createNoise2D(rng)
    this.noisePillar = createNoise2D(rng)
  }

  generateChunk(cx: number, cz: number): ChunkData {
    const blocks = new Uint8Array(CHUNK_WIDTH * NETHER_HEIGHT * CHUNK_WIDTH)
    const heightMap = new Uint16Array(CHUNK_WIDTH * CHUNK_WIDTH)

    // Phase 1: Compute biome and height map
    const biomeCache = new Array<NetherBiome>(CHUNK_WIDTH * CHUNK_WIDTH)
    for (let lx = 0; lx < CHUNK_WIDTH; lx++) {
      for (let lz = 0; lz < CHUNK_WIDTH; lz++) {
        const wx = cx * CHUNK_WIDTH + lx
        const wz = cz * CHUNK_WIDTH + lz
        const biomeIdx = lx + lz * CHUNK_WIDTH
        biomeCache[biomeIdx] = this.getBiome(wx, wz)

        // Height map = highest non-air block
        heightMap[biomeIdx] = 0
      }
    }

    // Phase 2: Fill blocks
    for (let lx = 0; lx < CHUNK_WIDTH; lx++) {
      for (let lz = 0; lz < CHUNK_WIDTH; lz++) {
        const wx = cx * CHUNK_WIDTH + lx
        const wz = cz * CHUNK_WIDTH + lz
        const biomeIdx = lx + lz * CHUNK_WIDTH
        const biome = biomeCache[biomeIdx]

        for (let ly = 0; ly < NETHER_HEIGHT; ly++) {
          const blockId = this.getBlockAt(wx, ly, wz, biome)
          const idx = lx + lz * CHUNK_WIDTH + ly * CHUNK_WIDTH * CHUNK_WIDTH
          if (blockId !== BLOCK_AIR) {
            blocks[idx] = blockId
            heightMap[biomeIdx] = ly + 1
          }
        }
      }
    }

    // Phase 3: Place glowstone clusters
    this.placeGlowstone(cx, cz, blocks, heightMap, biomeCache)

    // Phase 4: Place crimson/warped vegetation
    this.placeNetherVegetation(cx, cz, blocks, heightMap, biomeCache)

    // Phase 5: Place basalt columns in basalt deltas
    this.placeBasaltColumns(cx, cz, blocks, heightMap, biomeCache)

    return {
      position: { x: cx, z: cz },
      blocks,
      heightMap,
      dirty: true,
      meshVersion: 0,
    }
  }

  // ─── Biome Determination ───────────────────────────────────

  private getBiome(wx: number, wz: number): NetherBiome {
    const s = 0.004 // biome scale
    const v1 = this.noiseBiome1(wx * s, wz * s)
    const v2 = this.noiseBiome2(wx * s, wz * s)
    const v3 = this.noiseBiome3(wx * s * 1.5, wz * s * 1.5)

    // Classify into 5 biomes based on noise
    if (v1 < -0.3) {
      return NetherBiome.SoulSandValley
    }
    if (v1 > 0.3 && v2 > 0.1) {
      return NetherBiome.CrimsonForest
    }
    if (v1 > 0.3 && v2 <= 0.1) {
      return NetherBiome.WarpedForest
    }
    if (v3 > 0.4) {
      return NetherBiome.BasaltDeltas
    }
    return NetherBiome.NetherWastes
  }

  // ─── Block Placement ───────────────────────────────────────

  private getBlockAt(wx: number, ly: number, wz: number, biome: NetherBiome): number {
    // Bedrock floor (y=0) and ceiling (y=127)
    if (ly <= 1) return BLOCK_BEDROCK
    if (ly >= NETHER_HEIGHT - 2) return BLOCK_BEDROCK

    // Random bedrock patches at floor/ceiling
    if (ly <= 4 && hashCoord(wx, ly, wz, this.seed) < (5 - ly) * 0.15) return BLOCK_BEDROCK
    if (ly >= NETHER_HEIGHT - 5 && hashCoord(wx, ly, wz, this.seed ^ 0xABCD) < (ly - (NETHER_HEIGHT - 5) + 1) * 0.15) return BLOCK_BEDROCK

    // Compute terrain density using 3D noise
    const density = this.computeDensity(wx, ly, wz, biome)

    // If density is below threshold, it's air (or lava)
    if (density < 0) {
      // Fill with lava below lava sea level
      if (ly <= NETHER_LAVA_LEVEL) {
        return BLOCK_LAVA
      }
      return BLOCK_AIR
    }

    // Solid terrain — determine block type based on biome and position
    return this.getBlockType(wx, ly, wz, biome)
  }

  private computeDensity(wx: number, ly: number, wz: number, biome: NetherBiome): number {
    // Base terrain shape
    const s = 0.02
    const n1 = this.noiseTerrain(wx * s, ly * s * 0.8, wz * s)
    const n2 = this.noiseTerrain2(wx * s * 2, ly * s * 1.6, wz * s * 2) * 0.5

    let density = n1 + n2

    // Add larger-scale shape variation
    const largeScale = this.noiseDetail(wx * 0.005, wz * 0.005) * 0.3
    density += largeScale

    // Carve caves
    const caveS = 0.04
    const cave1 = this.noiseCave(wx * caveS, ly * caveS * 0.6, wz * caveS)
    const cave2 = this.noiseCave2(wx * caveS * 1.5, ly * caveS * 0.9, wz * caveS * 1.5)

    // Spaghetti caves: thin winding tunnels
    const spaghettiThreshold = 0.05
    if (Math.abs(cave1) < spaghettiThreshold && Math.abs(cave2) < spaghettiThreshold * 1.5) {
      return -1 // carve out
    }

    // Cheese caves: larger spherical cavities
    if (cave1 * cave1 + cave2 * cave2 < 0.02) {
      return -1
    }

    // Biome-specific density modifiers
    switch (biome) {
      case NetherBiome.SoulSandValley:
        // Slightly more open terrain
        density -= 0.08
        break
      case NetherBiome.BasaltDeltas:
        // More jagged, denser terrain
        density += this.noisePillar(wx * 0.1, wz * 0.1) * 0.2
        break
      case NetherBiome.CrimsonForest:
      case NetherBiome.WarpedForest:
        // Moderate openness
        density -= 0.03
        break
    }

    // Height-based density: thin out near the floor ceiling and floor
    const floorFade = Math.min(1, ly / 10)
    const ceilingFade = Math.min(1, (NETHER_HEIGHT - ly) / 10)
    density *= floorFade * ceilingFade

    return density
  }

  private getBlockType(wx: number, ly: number, wz: number, biome: NetherBiome): number {
    // Check for ores first
    const oreVal = this.noiseOre(wx * 0.15, ly * 0.15, wz * 0.15)
    if (oreVal > 0.75) return BLOCK_NETHER_QUARTZ_ORE
    if (oreVal > 0.7) return BLOCK_NETHER_GOLD_ORE

    // Check if this is a surface block (has air above)
    // We'll check this via a simple heuristic
    const surfNoise = this.noiseTerrain(wx * 0.05, (ly + 1) * 0.05, wz * 0.05)
    const isNearSurface = surfNoise < 0.1

    switch (biome) {
      case NetherBiome.SoulSandValley:
        // Surface: soul sand/soil, interior: soul sand/soil
        if (isNearSurface) {
          return hashCoord(wx, ly, wz, this.seed ^ 0x1234) < 0.5 ? BLOCK_SOUL_SAND : BLOCK_SOUL_SOIL
        }
        return hashCoord(wx, ly, wz, this.seed ^ 0x5678) < 0.3 ? BLOCK_SOUL_SAND : BLOCK_NETHERRACK

      case NetherBiome.CrimsonForest:
        // Surface: crimson nylium, interior: netherrack
        if (isNearSurface && ly > NETHER_LAVA_LEVEL) {
          return BLOCK_CRIMSON_NYLIUM
        }
        return BLOCK_NETHERRACK

      case NetherBiome.WarpedForest:
        // Surface: warped nylium, interior: netherrack
        if (isNearSurface && ly > NETHER_LAVA_LEVEL) {
          return BLOCK_WARPED_NYLIUM
        }
        return BLOCK_NETHERRACK

      case NetherBiome.BasaltDeltas:
        // Basalt and blackstone terrain
        if (isNearSurface) {
          return hashCoord(wx, ly, wz, this.seed ^ 0xBEEF) < 0.4 ? BLOCK_BLACKSTONE : BLOCK_BASALT
        }
        return hashCoord(wx, ly, wz, this.seed ^ 0xCAFE) < 0.3 ? BLOCK_BLACKSTONE : BLOCK_BASALT

      case NetherBiome.NetherWastes:
      default:
        // Standard netherrack with occasional gravel and magma
        if (isNearSurface && ly <= NETHER_LAVA_LEVEL + 2) {
          // Magma near lava
          if (hashCoord(wx, ly, wz, this.seed ^ 0xF1E0) < 0.1) {
            return BLOCK_MAGMA_BLOCK
          }
        }
        if (hashCoord(wx, ly, wz, this.seed ^ 0x6AA0) < 0.02) {
          return BLOCK_GRAVEL
        }
        return BLOCK_NETHERRACK
    }
  }

  // ─── Glowstone Clusters ────────────────────────────────────

  private placeGlowstone(
    cx: number, cz: number,
    blocks: Uint8Array, heightMap: Uint16Array,
    _biomeCache: NetherBiome[]
  ): void {
    // Try to place glowstone clusters hanging from ceiling
    const rng = seededRandom((cx * 3419 + cz * 7919) ^ this.seed)

    for (let attempt = 0; attempt < 4; attempt++) {
      if (rng() > 0.4) continue

      const lx = Math.floor(rng() * 14) + 1
      const lz = Math.floor(rng() * 14) + 1
      const startHeight = NETHER_HEIGHT - 5 - Math.floor(rng() * 10)

      // Grow a cluster downward
      this.growGlowstone(blocks, lx, startHeight, lz, rng)
    }
  }

  private growGlowstone(
    blocks: Uint8Array, lx: number, ly: number, lz: number,
    rng: () => number, depth: number = 0
  ): void {
    if (depth > 8 || ly < 5 || lx < 0 || lx >= CHUNK_WIDTH || lz < 0 || lz >= CHUNK_WIDTH) return

    const idx = lx + lz * CHUNK_WIDTH + ly * CHUNK_WIDTH * CHUNK_WIDTH
    if (blocks[idx] !== BLOCK_AIR && blocks[idx] !== 0) return

    blocks[idx] = BLOCK_GLOWSTONE

    // Continue growing downward and sometimes sideways
    const dir = rng()
    if (dir < 0.5) {
      this.growGlowstone(blocks, lx, ly - 1, lz, rng, depth + 1)
    } else if (dir < 0.65) {
      this.growGlowstone(blocks, lx + 1, ly - 1, lz, rng, depth + 1)
    } else if (dir < 0.8) {
      this.growGlowstone(blocks, lx - 1, ly - 1, lz, rng, depth + 1)
    } else if (dir < 0.9) {
      this.growGlowstone(blocks, lx, ly - 1, lz + 1, rng, depth + 1)
    } else {
      this.growGlowstone(blocks, lx, ly - 1, lz - 1, rng, depth + 1)
    }

    // Sometimes branch
    if (rng() < 0.3 && depth < 5) {
      const sideX = lx + (rng() < 0.5 ? 1 : -1)
      const sideZ = lz + (rng() < 0.5 ? 1 : -1)
      this.growGlowstone(blocks, sideX, ly, sideZ, rng, depth + 2)
    }
  }

  // ─── Nether Vegetation ─────────────────────────────────────

  private placeNetherVegetation(
    cx: number, cz: number,
    blocks: Uint8Array, heightMap: Uint16Array,
    biomeCache: NetherBiome[]
  ): void {
    for (let lx = 0; lx < CHUNK_WIDTH; lx++) {
      for (let lz = 0; lz < CHUNK_WIDTH; lz++) {
        const biomeIdx = lx + lz * CHUNK_WIDTH
        const biome = biomeCache[biomeIdx]
        const wx = cx * CHUNK_WIDTH + lx
        const wz = cz * CHUNK_WIDTH + lz

        // Find the surface (first air from top down)
        let surfaceY = -1
        for (let ly = NETHER_HEIGHT - 3; ly > 0; ly--) {
          const idx = lx + lz * CHUNK_WIDTH + ly * CHUNK_WIDTH * CHUNK_WIDTH
          if (blocks[idx] !== BLOCK_AIR && blocks[idx] !== 0 && blocks[idx] !== BLOCK_LAVA) {
            surfaceY = ly
            break
          }
        }

        if (surfaceY < 0 || surfaceY >= NETHER_HEIGHT - 2) continue
        const aboveIdx = lx + lz * CHUNK_WIDTH + (surfaceY + 1) * CHUNK_WIDTH * CHUNK_WIDTH
        if (blocks[aboveIdx] !== BLOCK_AIR && blocks[aboveIdx] !== 0) continue

        const surfaceBlock = blocks[lx + lz * CHUNK_WIDTH + surfaceY * CHUNK_WIDTH * CHUNK_WIDTH]
        const h = hashCoord2(wx, wz, this.seed ^ 0x7E60)

        switch (biome) {
          case NetherBiome.CrimsonForest:
            if (surfaceBlock === BLOCK_CRIMSON_NYLIUM) {
              if (h < 0.04) {
                // Crimson fungus
                blocks[aboveIdx] = BLOCK_CRIMSON_FUNGUS
              } else if (h < 0.06) {
                // Crimson stem (small tree)
                this.placeCrimsonStem(blocks, lx, surfaceY + 1, lz)
              }
            }
            break

          case NetherBiome.WarpedForest:
            if (surfaceBlock === BLOCK_WARPED_NYLIUM) {
              if (h < 0.04) {
                // Warped fungus
                blocks[aboveIdx] = BLOCK_WARPED_FUNGUS
              } else if (h < 0.06) {
                // Warped stem (small tree)
                this.placeWarpedStem(blocks, lx, surfaceY + 1, lz)
              }
            }
            break

          case NetherBiome.NetherWastes:
            // Occasional crimson/warped in nether wastes
            if (h < 0.005) {
              blocks[aboveIdx] = BLOCK_CRIMSON_FUNGUS
            } else if (h < 0.01) {
              blocks[aboveIdx] = BLOCK_WARPED_FUNGUS
            }
            break
        }
      }
    }
  }

  private placeCrimsonStem(blocks: Uint8Array, lx: number, baseY: number, lz: number): void {
    const height = 3 + Math.floor(hashCoord(lx, baseY, lz, this.seed ^ 0xC1230) * 4)
    for (let dy = 0; dy < height && baseY + dy < NETHER_HEIGHT - 2; dy++) {
      const idx = lx + lz * CHUNK_WIDTH + (baseY + dy) * CHUNK_WIDTH * CHUNK_WIDTH
      blocks[idx] = BLOCK_CRIMSON_STEM
    }
    // Wart block on top
    const topY = baseY + height - 1
    if (topY < NETHER_HEIGHT - 2) {
      const topIdx = lx + lz * CHUNK_WIDTH + topY * CHUNK_WIDTH * CHUNK_WIDTH
      blocks[topIdx] = BLOCK_NETHER_WART_BLOCK
      // Shroomlight
      if (topY + 1 < NETHER_HEIGHT - 2) {
        const shroomIdx = lx + lz * CHUNK_WIDTH + (topY + 1) * CHUNK_WIDTH * CHUNK_WIDTH
        if (blocks[shroomIdx] === BLOCK_AIR || blocks[shroomIdx] === 0) {
          blocks[shroomIdx] = BLOCK_SHROOMLIGHT
        }
      }
    }
  }

  private placeWarpedStem(blocks: Uint8Array, lx: number, baseY: number, lz: number): void {
    const height = 3 + Math.floor(hashCoord(lx, baseY, lz, this.seed ^ 0xA4560) * 4)
    for (let dy = 0; dy < height && baseY + dy < NETHER_HEIGHT - 2; dy++) {
      const idx = lx + lz * CHUNK_WIDTH + (baseY + dy) * CHUNK_WIDTH * CHUNK_WIDTH
      blocks[idx] = BLOCK_WARPED_STEM
    }
    // Warped wart block on top
    const topY = baseY + height - 1
    if (topY < NETHER_HEIGHT - 2) {
      const topIdx = lx + lz * CHUNK_WIDTH + topY * CHUNK_WIDTH * CHUNK_WIDTH
      blocks[topIdx] = BLOCK_WARPED_WART_BLOCK
      // Shroomlight
      if (topY + 1 < NETHER_HEIGHT - 2) {
        const shroomIdx = lx + lz * CHUNK_WIDTH + (topY + 1) * CHUNK_WIDTH * CHUNK_WIDTH
        if (blocks[shroomIdx] === BLOCK_AIR || blocks[shroomIdx] === 0) {
          blocks[shroomIdx] = BLOCK_SHROOMLIGHT
        }
      }
    }
  }

  // ─── Basalt Columns ────────────────────────────────────────

  private placeBasaltColumns(
    cx: number, cz: number,
    blocks: Uint8Array, heightMap: Uint16Array,
    biomeCache: NetherBiome[]
  ): void {
    for (let lx = 0; lx < CHUNK_WIDTH; lx++) {
      for (let lz = 0; lz < CHUNK_WIDTH; lz++) {
        const biomeIdx = lx + lz * CHUNK_WIDTH
        const biome = biomeCache[biomeIdx]
        if (biome !== NetherBiome.BasaltDeltas) continue

        const wx = cx * CHUNK_WIDTH + lx
        const wz = cz * CHUNK_WIDTH + lz
        const h = hashCoord2(wx, wz, this.seed ^ 0xB4A40)

        // Occasionally add basalt columns/pillars
        if (h < 0.08) {
          const columnHeight = 5 + Math.floor(hashCoord(wx, 32, wz, this.seed ^ 0xC0A0) * 20)
          for (let ly = NETHER_LAVA_LEVEL + 1; ly < NETHER_LAVA_LEVEL + 1 + columnHeight && ly < NETHER_HEIGHT - 3; ly++) {
            const idx = lx + lz * CHUNK_WIDTH + ly * CHUNK_WIDTH * CHUNK_WIDTH
            if (blocks[idx] === BLOCK_AIR || blocks[idx] === 0) {
              blocks[idx] = BLOCK_BASALT
            }
          }
        }
      }
    }
  }
}

// ═══════════════════════════════════════════════════════════════
// END GENERATOR
// ═══════════════════════════════════════════════════════════════

export class EndGenerator {
  private seed: number

  // Noise instances
  private noiseTerrain: ReturnType<typeof createNoise2D>
  private noiseDetail: ReturnType<typeof createNoise2D>
  private noiseIsland: ReturnType<typeof createNoise2D>

  constructor(seed: number) {
    this.seed = seed
    const rng = seededRandom(seed ^ 0xEDEDD00)

    this.noiseTerrain = createNoise2D(rng)
    this.noiseDetail = createNoise2D(rng)
    this.noiseIsland = createNoise2D(rng)
  }

  generateChunk(cx: number, cz: number): ChunkData {
    const blocks = new Uint8Array(CHUNK_WIDTH * END_HEIGHT * CHUNK_WIDTH)
    const heightMap = new Uint16Array(CHUNK_WIDTH * CHUNK_WIDTH)

    // Calculate world coordinates for chunk origin
    const chunkOriginX = cx * CHUNK_WIDTH
    const chunkOriginZ = cz * CHUNK_WIDTH

    // Check if any part of this chunk is within the island radius
    const minDist = this.minDistToOrigin(chunkOriginX, chunkOriginZ, CHUNK_WIDTH)

    if (minDist > END_TERRAIN_RADIUS + 20) {
      // Entirely outside the island — return empty chunk
      return {
        position: { x: cx, z: cz },
        blocks,
        heightMap,
        dirty: true,
        meshVersion: 0,
      }
    }

    // Phase 1: Generate terrain
    for (let lx = 0; lx < CHUNK_WIDTH; lx++) {
      for (let lz = 0; lz < CHUNK_WIDTH; lz++) {
        const wx = chunkOriginX + lx
        const wz = chunkOriginZ + lz
        const biomeIdx = lx + lz * CHUNK_WIDTH
        const distFromOrigin = Math.sqrt(wx * wx + wz * wz)

        // Only generate terrain within the island radius
        if (distFromOrigin > END_TERRAIN_RADIUS) {
          heightMap[biomeIdx] = 0
          continue
        }

        // Compute island height
        const islandHeight = this.computeIslandHeight(wx, wz, distFromOrigin)

        for (let ly = 0; ly < END_HEIGHT; ly++) {
          const idx = lx + lz * CHUNK_WIDTH + ly * CHUNK_WIDTH * CHUNK_WIDTH
          const blockId = this.getBlockAt(wx, ly, wz, distFromOrigin, islandHeight)
          if (blockId !== BLOCK_AIR) {
            blocks[idx] = blockId
            heightMap[biomeIdx] = ly + 1
          }
        }
      }
    }

    // Phase 2: Place obsidian pillars
    this.placeObsidianPillars(cx, cz, blocks, heightMap)

    return {
      position: { x: cx, z: cz },
      blocks,
      heightMap,
      dirty: true,
      meshVersion: 0,
    }
  }

  // ─── Island Height ─────────────────────────────────────────

  private computeIslandHeight(wx: number, wz: number, distFromOrigin: number): number {
    // Main island is a flat disc at y=64 with some noise variation
    const baseY = END_ISLAND_Y

    // Taper the edges
    if (distFromOrigin > END_ISLAND_RADIUS) {
      // Edge falloff
      const edgeDist = (distFromOrigin - END_ISLAND_RADIUS) / (END_TERRAIN_RADIUS - END_ISLAND_RADIUS)
      if (edgeDist >= 1) return 0
      return baseY * (1 - edgeDist * edgeDist)
    }

    // Add some subtle height variation on the island surface
    const noise = this.noiseTerrain(wx * 0.02, wz * 0.02) * 4
    const detail = this.noiseDetail(wx * 0.05, wz * 0.05) * 2

    return baseY + noise + detail
  }

  // ─── Block Placement ───────────────────────────────────────

  private getBlockAt(
    wx: number, ly: number, wz: number,
    distFromOrigin: number, islandHeight: number
  ): number {
    if (islandHeight <= 0) return BLOCK_AIR

    // The island is a solid mass of end stone from y=0 up to the island height
    // Only the top few layers are end stone; below is also end stone but with
    // some variation for visual interest

    if (ly > Math.floor(islandHeight)) return BLOCK_AIR

    // Top surface is end stone
    // Interior is also end stone, with slight variation
    // Bottom surface gets some subtle shape

    // Check if near the bottom of the island
    const bottomY = Math.max(0, END_ISLAND_Y - 8 - Math.floor(this.noiseIsland(wx * 0.03, wz * 0.03) * 4))

    if (ly < bottomY) return BLOCK_AIR

    // Edge tapering
    if (distFromOrigin > END_ISLAND_RADIUS) {
      const edgeFactor = 1 - (distFromOrigin - END_ISLAND_RADIUS) / (END_TERRAIN_RADIUS - END_ISLAND_RADIUS)
      const effectiveTop = bottomY + (islandHeight - bottomY) * edgeFactor
      if (ly > Math.floor(effectiveTop)) return BLOCK_AIR
    }

    return BLOCK_END_STONE
  }

  // ─── Obsidian Pillars ──────────────────────────────────────

  private placeObsidianPillars(
    cx: number, cz: number,
    blocks: Uint8Array, heightMap: Uint16Array
  ): void {
    // Deterministic pillar positions based on seed
    // Pillars are scattered within ~40 blocks of origin
    const pillarSeed = this.seed ^ 0x71AA400
    const rng = seededRandom(pillarSeed)

    // Generate ~10 pillar positions
    const pillarCount = 10
    for (let i = 0; i < pillarCount; i++) {
      const pillarX = Math.floor(rng() * 80) - 40
      const pillarZ = Math.floor(rng() * 80) - 40
      const pillarRadius = Math.floor(rng() * 2) + 2 // 2-3 block radius
      const pillarHeight = Math.floor(rng() * 10) + 5 // 5-15 blocks tall

      // Check if this pillar intersects with this chunk
      const chunkMinX = cx * CHUNK_WIDTH
      const chunkMaxX = chunkMinX + CHUNK_WIDTH - 1
      const chunkMinZ = cz * CHUNK_WIDTH
      const chunkMaxZ = chunkMinZ + CHUNK_WIDTH - 1

      // Quick bounds check
      if (pillarX + pillarRadius < chunkMinX || pillarX - pillarRadius > chunkMaxX) continue
      if (pillarZ + pillarRadius < chunkMinZ || pillarZ - pillarRadius > chunkMaxZ) continue

      // Find the surface height at the pillar center
      const centerLX = pillarX - chunkMinX
      const centerLZ = pillarZ - chunkMinZ

      // Only place if we can find the surface
      let surfaceY = 0
      if (centerLX >= 0 && centerLX < CHUNK_WIDTH && centerLZ >= 0 && centerLZ < CHUNK_WIDTH) {
        surfaceY = heightMap[centerLX + centerLZ * CHUNK_WIDTH]
      } else {
        // Compute surface height for the pillar center
        surfaceY = Math.floor(this.computeIslandHeight(pillarX, pillarZ, Math.sqrt(pillarX * pillarX + pillarZ * pillarZ)))
      }

      if (surfaceY <= 0) continue

      // Place the pillar
      for (let dx = -pillarRadius; dx <= pillarRadius; dx++) {
        for (let dz = -pillarRadius; dz <= pillarRadius; dz++) {
          if (dx * dx + dz * dz > pillarRadius * pillarRadius) continue

          const lx = pillarX + dx - chunkMinX
          const lz = pillarZ + dz - chunkMinZ
          if (lx < 0 || lx >= CHUNK_WIDTH || lz < 0 || lz >= CHUNK_WIDTH) continue

          for (let dy = 0; dy < pillarHeight; dy++) {
            const y = surfaceY + dy
            if (y >= END_HEIGHT) break
            const idx = lx + lz * CHUNK_WIDTH + y * CHUNK_WIDTH * CHUNK_WIDTH
            blocks[idx] = BLOCK_OBSIDIAN
            if (y + 1 > heightMap[lx + lz * CHUNK_WIDTH]) {
              heightMap[lx + lz * CHUNK_WIDTH] = y + 1
            }
          }
        }
      }
    }
  }

  // ─── Utility ───────────────────────────────────────────────

  private minDistToOrigin(chunkMinX: number, chunkMinZ: number, chunkSize: number): number {
    // Find the minimum distance from origin to any point in the chunk
    const nearestX = Math.max(chunkMinX, Math.min(0, chunkMinX + chunkSize - 1))
    const nearestZ = Math.max(chunkMinZ, Math.min(0, chunkMinZ + chunkSize - 1))
    return Math.sqrt(nearestX * nearestX + nearestZ * nearestZ)
  }
}