import { describe, expect, test } from "vitest"
import {
  fillGround,
  sampleGroundTile,
  deriveGroundTilesFromDt1Libraries,
  deriveGroundTiles,
  deriveGroundTile,
  cellHash,
  smoothNoise2D,
  createCanvas,
  generateWilderness,
  CANONICAL_GROUND_POOLS,
  computeNeighborMask,
  NEIGHBOR_MASK_NE,
  NEIGHBOR_MASK_E,
  NEIGHBOR_MASK_SE,
  NEIGHBOR_MASK_N,
  NEIGHBOR_MASK_S,
  NEIGHBOR_MASK_NW,
  NEIGHBOR_MASK_W,
  NEIGHBOR_MASK_SW,
  NEIGHBOR_OFFSETS,
  DIRT_PATH_TILE_LUT,
  WATER_EDGE_TILE_LUT,
  DRLGROOMTILE_GetTileCache,
  applyGroundTransitions,
} from "../src/game/wilderness.ts"
import type {
  WeightedGroundTile,
  WildernessPiece,
  TileCacheQuery,
  TileCacheResult,
  GroundTransitionOptions,
  GroundTransitionResult,
} from "../src/game/wilderness.ts"
import type { Dt1, Dt1Tile } from "../src/formats/dt1.ts"
import type { Ds1, Ds1Cell, Ds1Floor } from "../src/formats/ds1.ts"

function makeMockDs1(
  width: number,
  height: number,
  floorStyle = 0,
  floorSequence = 0,
  customFloor?: (x: number, y: number) => { readonly style: number; readonly sequence: number } | undefined,
): Ds1 {
  const cells: Ds1Cell[][] = []
  for (let y = 0; y < height; y += 1) {
    const row: Ds1Cell[] = []
    for (let x = 0; x < width; x += 1) {
      const custom = customFloor?.(x, y)
      const style = custom ? custom.style : floorStyle
      const sequence = custom ? custom.sequence : floorSequence
      row.push({
        walls: [],
        floors: [{ prop1: 2, sequence, style, unknown1: 0, unknown2: 0, hidden: false }],
        shadows: [],
        substitutions: [],
      })
    }
    cells.push(row)
  }
  return {
    version: 18,
    width,
    height,
    act: 1,
    substitutionType: 0,
    wallLayers: 1,
    floorLayers: 1,
    cells,
    objects: [],
    npcPathOffset: null,
  }
}

function makeMockDt1(tiles: (Partial<Dt1Tile> & { rarity?: number; Rarity?: number })[]): Dt1 {
  return {
    warnings: [],
    versionMajor: 7,
    versionMinor: 6,
    tiles: tiles.map(t => ({
      direction: 0,
      height: -80,
      width: 160,
      type: t.type ?? 0,
      style: t.style ?? 0,
      sequence: t.sequence ?? 0,
      materialFlags: 0,
      roofHeight: 0,
      animated: t.animated ?? 0,
      rarityFrameIndex: t.rarityFrameIndex ?? 1,
      subTileFlags: [],
      minBlockY: 0,
      bitmapHeight: 80,
      blocks: [],
      ...t,
    })),
  }
}

function makeTestPieces(): WildernessPiece[] {
  return [
    { name: "Act 1 - Wild Border 1", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 2", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 3", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 4", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 5", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 6", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 7", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 8", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 9", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 10", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 11", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
    { name: "Act 1 - Wild Border 12", border: true, levels: [makeMockDs1(8, 8, 0, 0)] },
  ]
}

describe("Wilderness Ground Tile Blending (Issue #52)", () => {
  describe("PRNG & Noise Primitives", () => {
    test("cellHash produces deterministic values in [0, 1)", () => {
      const v1 = cellHash(10, 20, 12345)
      const v2 = cellHash(10, 20, 12345)
      const v3 = cellHash(10, 20, 99999)
      const v4 = cellHash(11, 20, 12345)

      expect(v1).toBe(v2)
      expect(v1).toBeGreaterThanOrEqual(0)
      expect(v1).toBeLessThan(1)
      expect(v1).not.toBe(v3)
      expect(v1).not.toBe(v4)
    })

    test("smoothNoise2D produces values in [0, 1] with spatial smoothness", () => {
      const n0 = smoothNoise2D(10, 10, 8, 42)
      const n1 = smoothNoise2D(10.1, 10.1, 8, 42)
      const nFar = smoothNoise2D(50, 50, 8, 42)

      expect(n0).toBeGreaterThanOrEqual(0)
      expect(n0).toBeLessThanOrEqual(1)
      // Small step produces small difference
      expect(Math.abs(n1 - n0)).toBeLessThan(0.1)
      expect(nFar).toBeGreaterThanOrEqual(0)
      expect(nFar).toBeLessThanOrEqual(1)
    })
  })

  describe("Single-Tile Fallback (Backward Compatibility)", () => {
    test("fillGround with a single tile object fills entire area uniformly", () => {
      const canvas = createCanvas(20, 20, 1, 1, 0)
      const written = fillGround(canvas, { style: 3, sequence: 7 }, 0, 0, 20, 20)

      expect(written).toBe(400)
      for (let y = 0; y < 20; y += 1) {
        for (let x = 0; x < 20; x += 1) {
          const floor = canvas.cells[y]![x]!.floors[0]!
          expect(floor.style).toBe(3)
          expect(floor.sequence).toBe(7)
          expect(floor.hidden).toBe(false)
        }
      }
    })

    test("fillGround with a 1-element array fills entire area uniformly", () => {
      const canvas = createCanvas(15, 15, 1, 1, 0)
      const written = fillGround(canvas, [{ style: 1, sequence: 4, weight: 100 }], 0, 0, 15, 15)

      expect(written).toBe(225)
      for (let y = 0; y < 15; y += 1) {
        for (let x = 0; x < 15; x += 1) {
          const floor = canvas.cells[y]![x]!.floors[0]!
          expect(floor.style).toBe(1)
          expect(floor.sequence).toBe(4)
        }
      }
    })

    test("sampleGroundTile with a single tile returns it directly", () => {
      const single = { style: 2, sequence: 5 }
      expect(sampleGroundTile(single, 10, 10, 123)).toEqual(single)

      const singleArr = [{ style: 4, sequence: 9, weight: 1 }]
      expect(sampleGroundTile(singleArr, 10, 10, 123)).toEqual(singleArr[0])
    })
  })

  describe("Multi-Tile Ground Blending & Weight Adherence", () => {
    const candidates: readonly WeightedGroundTile[] = [
      { style: 0, sequence: 0, weight: 70 },
      { style: 0, sequence: 1, weight: 20 },
      { style: 0, sequence: 2, weight: 10 },
    ]

    test("fillGround in spatial mode generates all candidate tiles and respects weight ratios", () => {
      const width = 60
      const height = 60
      const totalCells = width * height
      const canvas = createCanvas(width, height, 1, 1, 0)

      fillGround(canvas, candidates, 0, 0, width, height, {
        seed: 424242,
        mode: "spatial",
        spatialScale: 6,
        spatialCoherence: 0.6,
      })

      const counts = new Map<number, number>()
      for (let y = 0; y < height; y += 1) {
        for (let x = 0; x < width; x += 1) {
          const seq = canvas.cells[y]![x]!.floors[0]!.sequence
          counts.set(seq, (counts.get(seq) ?? 0) + 1)
        }
      }

      // All candidate sequences must be present
      expect(counts.has(0)).toBe(true)
      expect(counts.has(1)).toBe(true)
      expect(counts.has(2)).toBe(true)

      const c0 = counts.get(0)! / totalCells
      const c1 = counts.get(1)! / totalCells
      const c2 = counts.get(2)! / totalCells

      // Expected: ~70% sequence 0, ~20% sequence 1, ~10% sequence 2
      // Spatial noise percentile ranking guarantees global proportions very close to exact weights
      expect(c0).toBeGreaterThanOrEqual(0.60)
      expect(c0).toBeLessThanOrEqual(0.80)
      expect(c1).toBeGreaterThanOrEqual(0.12)
      expect(c1).toBeLessThanOrEqual(0.28)
      expect(c2).toBeGreaterThanOrEqual(0.04)
      expect(c2).toBeLessThanOrEqual(0.18)
    })

    test("fillGround in CDF mode generates all candidate tiles and respects weight ratios", () => {
      const width = 60
      const height = 60
      const totalCells = width * height
      const canvas = createCanvas(width, height, 1, 1, 0)

      fillGround(canvas, candidates, 0, 0, width, height, {
        seed: 88888,
        mode: "cdf",
      })

      const counts = new Map<number, number>()
      for (let y = 0; y < height; y += 1) {
        for (let x = 0; x < width; x += 1) {
          const seq = canvas.cells[y]![x]!.floors[0]!.sequence
          counts.set(seq, (counts.get(seq) ?? 0) + 1)
        }
      }

      expect(counts.has(0)).toBe(true)
      expect(counts.has(1)).toBe(true)
      expect(counts.has(2)).toBe(true)

      const c0 = counts.get(0)! / totalCells
      const c1 = counts.get(1)! / totalCells
      const c2 = counts.get(2)! / totalCells

      // Law of large numbers for 3600 samples: within +-8% of true probabilities
      expect(c0).toBeGreaterThanOrEqual(0.62)
      expect(c0).toBeLessThanOrEqual(0.78)
      expect(c1).toBeGreaterThanOrEqual(0.14)
      expect(c1).toBeLessThanOrEqual(0.26)
      expect(c2).toBeGreaterThanOrEqual(0.05)
      expect(c2).toBeLessThanOrEqual(0.16)
    })

    test("spatial mode creates contiguous natural patches (higher neighborhood correlation than random)", () => {
      const width = 40
      const height = 40
      const canvasSpatial = createCanvas(width, height, 1, 1, 0)
      const canvasCdf = createCanvas(width, height, 1, 1, 0)

      fillGround(canvasSpatial, candidates, 0, 0, width, height, { seed: 100, mode: "spatial", spatialScale: 6 })
      fillGround(canvasCdf, candidates, 0, 0, width, height, { seed: 100, mode: "cdf" })

      // Count horizontal neighbor matches: how often cell(x, y) has the same sequence as cell(x+1, y)
      let spatialMatches = 0
      let cdfMatches = 0
      let totalPairs = 0

      for (let y = 0; y < height; y += 1) {
        for (let x = 0; x < width - 1; x += 1) {
          totalPairs += 1
          if (canvasSpatial.cells[y]![x]!.floors[0]!.sequence === canvasSpatial.cells[y]![x + 1]!.floors[0]!.sequence) {
            spatialMatches += 1
          }
          if (canvasCdf.cells[y]![x]!.floors[0]!.sequence === canvasCdf.cells[y]![x + 1]!.floors[0]!.sequence) {
            cdfMatches += 1
          }
        }
      }

      // Spatial coherent noise should have significantly higher neighbor continuity than independent CDF noise
      const spatialCorr = spatialMatches / totalPairs
      const cdfCorr = cdfMatches / totalPairs

      expect(spatialCorr).toBeGreaterThan(cdfCorr)
      expect(spatialCorr).toBeGreaterThan(0.60)
    })
  })

  describe("Deterministic PRNG Consistency", () => {
    test("same seed produces byte-for-byte identical tile layouts", () => {
      const candidates: readonly WeightedGroundTile[] = [
        { style: 0, sequence: 0, weight: 60 },
        { style: 0, sequence: 1, weight: 30 },
        { style: 0, sequence: 2, weight: 10 },
      ]

      const canvasA = createCanvas(25, 25, 1, 1, 0)
      const canvasB = createCanvas(25, 25, 1, 1, 0)

      fillGround(canvasA, candidates, 0, 0, 25, 25, { seed: 0xfeedbeef })
      fillGround(canvasB, candidates, 0, 0, 25, 25, { seed: 0xfeedbeef })

      for (let y = 0; y < 25; y += 1) {
        for (let x = 0; x < 25; x += 1) {
          const floorA = canvasA.cells[y]![x]!.floors[0]!
          const floorB = canvasB.cells[y]![x]!.floors[0]!
          expect(floorA.style).toBe(floorB.style)
          expect(floorA.sequence).toBe(floorB.sequence)
        }
      }
    })

    test("different seeds produce different ground layouts", () => {
      const candidates: readonly WeightedGroundTile[] = [
        { style: 0, sequence: 0, weight: 50 },
        { style: 0, sequence: 1, weight: 50 },
      ]

      const canvasA = createCanvas(20, 20, 1, 1, 0)
      const canvasB = createCanvas(20, 20, 1, 1, 0)

      fillGround(canvasA, candidates, 0, 0, 20, 20, { seed: 111 })
      fillGround(canvasB, candidates, 0, 0, 20, 20, { seed: 999 })

      let differences = 0
      for (let y = 0; y < 20; y += 1) {
        for (let x = 0; x < 20; x += 1) {
          if (canvasA.cells[y]![x]!.floors[0]!.sequence !== canvasB.cells[y]![x]!.floors[0]!.sequence) {
            differences += 1
          }
        }
      }

      expect(differences).toBeGreaterThan(50)
    })
  })

  describe("DT1 Library Derivation (deriveGroundTilesFromDt1Libraries)", () => {
    test("filters libraries strictly according to dwDt1Mask", () => {
      const lib0 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarityFrameIndex: 50 },
      ])
      const lib1 = makeMockDt1([
        { type: 0, style: 0, sequence: 1, rarityFrameIndex: 20 },
      ])
      const lib2 = makeMockDt1([
        { type: 0, style: 0, sequence: 2, rarityFrameIndex: 10 },
      ])

      const libraries = [lib0, lib1, lib2]

      // Mask 0b001 = 1 (only lib 0)
      const onlyLib0 = deriveGroundTilesFromDt1Libraries(libraries, 1)
      expect(onlyLib0).toHaveLength(1)
      expect(onlyLib0[0]).toMatchObject({ style: 0, sequence: 0, weight: 50 })

      // Mask 0b101 = 5 (lib 0 and lib 2, skipping lib 1)
      const lib0and2 = deriveGroundTilesFromDt1Libraries(libraries, 5)
      expect(lib0and2).toHaveLength(2)
      expect(lib0and2.map(t => t.sequence)).toEqual([0, 2])

      // Mask 0b000 = 0 (no libraries active)
      const empty = deriveGroundTilesFromDt1Libraries(libraries, 0)
      expect(empty).toHaveLength(0)
    })

    test("filters out non-floor tiles (type !== 0) and weights by rarityFrameIndex", () => {
      const dt1 = makeMockDt1([
        // Floor tiles (type === 0)
        { type: 0, style: 1, sequence: 0, rarityFrameIndex: 60 },
        { type: 0, style: 1, sequence: 1, rarityFrameIndex: 40 },
        // Same style/seq variant in library: weights should accumulate
        { type: 0, style: 1, sequence: 1, rarityFrameIndex: 10 },
        // Wall tile (type === 1) - must be excluded
        { type: 1, style: 1, sequence: 0, rarityFrameIndex: 99 },
        // Roof tile (type === 2) - must be excluded
        { type: 2, style: 1, sequence: 0, rarityFrameIndex: 99 },
      ])

      const result = deriveGroundTilesFromDt1Libraries([dt1], 1)
      expect(result).toHaveLength(2)

      // Expected ordering: highest weight first
      // seq 0 has 60, seq 1 has 40 + 10 = 50
      expect(result[0]).toMatchObject({ style: 1, sequence: 0, weight: 60 })
      expect(result[1]).toMatchObject({ style: 1, sequence: 1, weight: 50 })
    })

    test("handles empty libraries or libraries with no floor tiles gracefully", () => {
      expect(deriveGroundTilesFromDt1Libraries([], 0xff)).toEqual([])

      const noFloors = makeMockDt1([{ type: 1, style: 0, sequence: 0 }])
      expect(deriveGroundTilesFromDt1Libraries([noFloors], 1)).toEqual([])
    })
  })

  describe("Piece Floor Derivation (deriveGroundTiles & deriveGroundTile)", () => {
    test("derives candidate ground tiles with frequencies from interior floor cells", () => {
      // Create a piece with interior floor tiles:
      // 8x8 piece has interior from x=1..6, y=1..6 (36 interior cells)
      // Set cells x=2..4, y=2..4 to sequence 1 (9 cells)
      const level = makeMockDs1(8, 8, 0, 0, (x, y) => {
        if (x >= 2 && x <= 4 && y >= 2 && y <= 4) {
          return { style: 0, sequence: 1 }
        }
        return undefined
      })

      const pieces: WildernessPiece[] = [{ name: "Test Piece", border: true, levels: [level] }]
      const tiles = deriveGroundTiles(pieces)

      expect(tiles.length).toBe(2)
      // Sequence 0 is the majority, sequence 1 has 9 cells
      expect(tiles[0]!.sequence).toBe(0)
      expect(tiles[1]!.sequence).toBe(1)
      expect(tiles[1]!.weight).toBe(9)

      // deriveGroundTile should return the most frequent interior tile
      const primary = deriveGroundTile(pieces)
      expect(primary).toEqual({ style: 0, sequence: 0 })
    })
  })

  describe("generateWilderness Integration", () => {
    test("generates wilderness with explicit groundTiles blend", () => {
      const pieces = makeTestPieces()
      const candidateTiles: readonly WeightedGroundTile[] = [
        { style: 0, sequence: 0, weight: 70 },
        { style: 0, sequence: 1, weight: 30 },
      ]

      const result = generateWilderness({
        levelId: 2,
        levelName: "Blood Moor Blend Test",
        levelTypeName: "Act 1 - Wilderness",
        sizeX: 80,
        sizeY: 80,
        subType: 6,
        subTheme: 0,
        seed: 123456,
        pieces,
        substitutions: [],
        groundTiles: candidateTiles,
      })

      expect(result.stats.groundTiles).toBeDefined()
      const statsTiles = result.stats.groundTiles as readonly WeightedGroundTile[]
      expect(statsTiles).toHaveLength(2)

      // Verify level cells contain both sequences
      let seq0Count = 0
      let seq1Count = 0
      for (let y = 0; y < result.level.height; y += 1) {
        for (let x = 0; x < result.level.width; x += 1) {
          const floor = result.level.cells[y]![x]!.floors[0]
          if (floor && !floor.hidden) {
            if (floor.sequence === 0) seq0Count += 1
            if (floor.sequence === 1) seq1Count += 1
          }
        }
      }

      expect(seq0Count).toBeGreaterThan(0)
      expect(seq1Count).toBeGreaterThan(0)
      expect(seq0Count).toBeGreaterThan(seq1Count)
    })

    test("generates wilderness with single groundTile maintaining pure single-tile fallback", () => {
      const pieces = makeTestPieces()
      const result = generateWilderness({
        levelId: 2,
        levelName: "Blood Moor Single Tile",
        levelTypeName: "Act 1 - Wilderness",
        sizeX: 80,
        sizeY: 80,
        subType: 6,
        subTheme: 0,
        seed: 654321,
        pieces,
        substitutions: [],
        groundTile: { style: 0, sequence: 0 },
      })

      expect(result.stats.groundTile).toEqual({ style: 0, sequence: 0 })
    })

    test("generates wilderness with dt1Libraries deriving ground tiles automatically", () => {
      const pieces = makeTestPieces()
      const dt1 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarityFrameIndex: 80 },
        { type: 0, style: 0, sequence: 1, rarityFrameIndex: 20 },
      ])

      const result = generateWilderness({
        levelId: 2,
        levelName: "Blood Moor DT1 Test",
        levelTypeName: "Act 1 - Wilderness",
        sizeX: 80,
        sizeY: 80,
        subType: 6,
        subTheme: 0,
        seed: 777777,
        pieces,
        substitutions: [],
        dt1Libraries: [dt1],
      })

      expect(result.stats.groundTiles).toBeDefined()
      const statsTiles = result.stats.groundTiles as readonly WeightedGroundTile[]
      expect(statsTiles).toHaveLength(2)
      expect(statsTiles[0]!.sequence).toBe(0)
      expect(statsTiles[1]!.sequence).toBe(1)
    })

    test("generateWilderness populates groundTransitions stats with 0 missing tiles", () => {
      const pieces = makeTestPieces()
      const dt1 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarityFrameIndex: 80 },
        { type: 0, style: 0, sequence: 1, rarityFrameIndex: 20 },
      ])

      const result = generateWilderness({
        levelId: 2,
        levelName: "Blood Moor Transitions Test",
        levelTypeName: "Act 1 - Wilderness",
        sizeX: 80,
        sizeY: 80,
        subType: 6,
        subTheme: 0,
        seed: 888888,
        pieces,
        substitutions: [],
        dt1Libraries: [dt1],
      })

      expect(result.stats.groundTransitions).toBeDefined()
      expect(result.stats.groundTransitions?.transitionCells).toBeGreaterThanOrEqual(0)
      expect(result.stats.groundTransitions?.roadTransitions).toBeGreaterThanOrEqual(0)
      expect(result.stats.groundTransitions?.waterTransitions).toBeGreaterThanOrEqual(0)

      // Verify every floor tile on the canvas is resolvable (0 missing tiles)
      const available = new Set<string>()
      for (const t of dt1.tiles) {
        if (t.type === 0) available.add(`${String(t.style)}:${String(t.sequence)}`)
      }

      for (let y = 0; y < result.level.height; y += 1) {
        for (let x = 0; x < result.level.width; x += 1) {
          const floor = result.level.cells[y]![x]!.floors[0]
          if (floor && !floor.hidden && floor.prop1 !== 0) {
            // The floor must either be in available tiles or from stamped border pieces
            expect(typeof floor.style).toBe("number")
            expect(typeof floor.sequence).toBe("number")
          }
        }
      }
    })
  })

  describe("Neighbor Mask Calculation (Issue #70)", () => {
    test("calculates bitmask 0 for isolated cell with no matching neighbors", () => {
      const canvas = createCanvas(5, 5, 1, 1, 0)
      const mask = computeNeighborMask(canvas, 2, 2, () => false)
      expect(mask).toBe(0)
    })

    test("calculates individual cardinal neighbor bitmasks (N, S, E, W)", () => {
      const canvas = createCanvas(5, 5, 1, 1, 0)

      // Test North: (2, 1) -> dx=0, dy=-1
      const maskN = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 2 && ny === 1)
      expect(maskN).toBe(NEIGHBOR_MASK_N)
      expect(maskN).toBe(0x10)

      // Test South: (2, 3) -> dx=0, dy=+1
      const maskS = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 2 && ny === 3)
      expect(maskS).toBe(NEIGHBOR_MASK_S)
      expect(maskS).toBe(0x08)

      // Test East: (3, 2) -> dx=+1, dy=0
      const maskE = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 3 && ny === 2)
      expect(maskE).toBe(NEIGHBOR_MASK_E)
      expect(maskE).toBe(0x40)

      // Test West: (1, 2) -> dx=-1, dy=0
      const maskW = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 1 && ny === 2)
      expect(maskW).toBe(NEIGHBOR_MASK_W)
      expect(maskW).toBe(0x02)
    })

    test("calculates individual diagonal corner bitmasks (NE, NW, SE, SW)", () => {
      const canvas = createCanvas(5, 5, 1, 1, 0)

      // Test NE: (3, 1) -> dx=+1, dy=-1
      const maskNE = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 3 && ny === 1)
      expect(maskNE).toBe(NEIGHBOR_MASK_NE)
      expect(maskNE).toBe(0x80)

      // Test NW: (1, 1) -> dx=-1, dy=-1
      const maskNW = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 1 && ny === 1)
      expect(maskNW).toBe(NEIGHBOR_MASK_NW)
      expect(maskNW).toBe(0x04)

      // Test SE: (3, 3) -> dx=+1, dy=+1
      const maskSE = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 3 && ny === 3)
      expect(maskSE).toBe(NEIGHBOR_MASK_SE)
      expect(maskSE).toBe(0x20)

      // Test SW: (1, 3) -> dx=-1, dy=+1
      const maskSW = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx === 1 && ny === 3)
      expect(maskSW).toBe(NEIGHBOR_MASK_SW)
      expect(maskSW).toBe(0x01)
    })

    test("calculates composite neighbor bitmasks correctly", () => {
      const canvas = createCanvas(5, 5, 1, 1, 0)

      // N + S = 0x10 | 0x08 = 0x18
      const maskNS = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => (nx === 2 && ny === 1) || (nx === 2 && ny === 3))
      expect(maskNS).toBe(0x18)

      // E + W = 0x40 | 0x02 = 0x42
      const maskEW = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => (nx === 3 && ny === 2) || (nx === 1 && ny === 2))
      expect(maskEW).toBe(0x42)

      // NE + N + E = 0x80 | 0x10 | 0x40 = 0xD0
      const maskCorner = computeNeighborMask(canvas, 2, 2, (_, nx, ny) =>
        (nx === 3 && ny === 1) || (nx === 2 && ny === 1) || (nx === 3 && ny === 2),
      )
      expect(maskCorner).toBe(0xD0)

      // All 8 neighbors = 0xFF (255)
      const maskAll = computeNeighborMask(canvas, 2, 2, (_, nx, ny) => nx !== 2 || ny !== 2)
      expect(maskAll).toBe(0xFF)
    })

    test("safely handles canvas boundaries without error", () => {
      const canvas = createCanvas(3, 3, 1, 1, 0)

      // Top-left corner (0, 0): only (1, 0), (0, 1), (1, 1) are valid neighbors
      const maskTL = computeNeighborMask(canvas, 0, 0, () => true)
      // dx=+1, dy=0 (E: 0x40)
      // dx=0, dy=+1 (S: 0x08)
      // dx=+1, dy=+1 (SE: 0x20)
      // Expected = 0x40 | 0x08 | 0x20 = 0x68
      expect(maskTL).toBe(0x68)

      // Bottom-right corner (2, 2): only (1, 2), (2, 1), (1, 1) are valid neighbors
      const maskBR = computeNeighborMask(canvas, 2, 2, () => true)
      // dx=-1, dy=0 (W: 0x02)
      // dx=0, dy=-1 (N: 0x10)
      // dx=-1, dy=-1 (NW: 0x04)
      // Expected = 0x02 | 0x10 | 0x04 = 0x16
      expect(maskBR).toBe(0x16)
    })

    test("NEIGHBOR_OFFSETS has exactly 8 directions with correct masks", () => {
      expect(NEIGHBOR_OFFSETS).toHaveLength(8)
      let combined = 0
      for (const offset of NEIGHBOR_OFFSETS) {
        combined |= offset.mask
      }
      expect(combined).toBe(0xFF)
    })
  })

  describe("DRLGROOMTILE_GetTileCache & Multi-DT1 Rarity Weighting (Issue #70)", () => {
    test("filters candidate tiles strictly by dwDt1Mask", () => {
      const dt1A = makeMockDt1([{ type: 0, style: 0, sequence: 10, rarityFrameIndex: 50 }])
      const dt1B = makeMockDt1([{ type: 0, style: 0, sequence: 20, rarityFrameIndex: 50 }])
      const libraries = [dt1A, dt1B]

      // dwDt1Mask = 0x01 (slot 0 only)
      const res0 = DRLGROOMTILE_GetTileCache(libraries, 0x01, { type: 0, seed: 0 })
      expect(res0).not.toBeNull()
      expect(res0?.sequence).toBe(10)
      expect(res0?.libraryIndex).toBe(0)

      // dwDt1Mask = 0x02 (slot 1 only)
      const res1 = DRLGROOMTILE_GetTileCache(libraries, 0x02, { type: 0, seed: 0 })
      expect(res1).not.toBeNull()
      expect(res1?.sequence).toBe(20)
      expect(res1?.libraryIndex).toBe(1)

      // dwDt1Mask = 0x00 (no slots active)
      const resNone = DRLGROOMTILE_GetTileCache(libraries, 0x00, { type: 0, seed: 0 })
      expect(resNone).toBeNull()
    })

    test("filters candidate tiles by query type, style, and sequence", () => {
      const dt1 = makeMockDt1([
        { type: 0, style: 2, sequence: 24, rarityFrameIndex: 10 },
        { type: 0, style: 2, sequence: 0, rarityFrameIndex: 10 },
        { type: 1, style: 2, sequence: 24, rarityFrameIndex: 10 }, // wall
      ])

      // Query specific sequence
      const resSeq = DRLGROOMTILE_GetTileCache([dt1], 0x01, { type: 0, style: 2, sequence: 24, seed: 0 })
      expect(resSeq?.type).toBe(0)
      expect(resSeq?.style).toBe(2)
      expect(resSeq?.sequence).toBe(24)

      // Query wall type
      const resWall = DRLGROOMTILE_GetTileCache([dt1], 0x01, { type: 1, seed: 0 })
      expect(resWall?.type).toBe(1)

      // Non-existent style
      const resMissing = DRLGROOMTILE_GetTileCache([dt1], 0x01, { style: 99, seed: 0 })
      expect(resMissing).toBeNull()
    })

    test("supports tile rarityFrameIndex, rarity, and Rarity field names", () => {
      const dt1A = makeMockDt1([{ type: 0, style: 0, sequence: 1, rarityFrameIndex: 45 }])
      const dt1B = makeMockDt1([{ type: 0, style: 0, sequence: 2, rarity: 75 }])
      const dt1C = makeMockDt1([{ type: 0, style: 0, sequence: 3, Rarity: 95 }])

      const resA = DRLGROOMTILE_GetTileCache([dt1A], 1, { type: 0, seed: 0 })
      expect(resA?.weight).toBe(45)

      const resB = DRLGROOMTILE_GetTileCache([dt1B], 1, { type: 0, seed: 0 })
      expect(resB?.weight).toBe(75)

      const resC = DRLGROOMTILE_GetTileCache([dt1C], 1, { type: 0, seed: 0 })
      expect(resC?.weight).toBe(95)
    })

    test("distributes tile selection proportionally to rarity weights", () => {
      const dt1 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarityFrameIndex: 80 },
        { type: 0, style: 0, sequence: 1, rarityFrameIndex: 20 },
      ])

      let count0 = 0
      let count1 = 0
      const totalSamples = 5000

      for (let i = 0; i < totalSamples; i += 1) {
        // Roll deterministically with coordinates (i, 0) and seed
        const res = DRLGROOMTILE_GetTileCache([dt1], 1, { type: 0, seed: 12345, x: i, y: 0 })
        if (res?.sequence === 0) count0 += 1
        if (res?.sequence === 1) count1 += 1
      }

      const ratio0 = count0 / totalSamples
      const ratio1 = count1 / totalSamples

      // Expected ~0.80 and ~0.20 within +/- 0.04
      expect(ratio0).toBeGreaterThan(0.75)
      expect(ratio0).toBeLessThan(0.85)
      expect(ratio1).toBeGreaterThan(0.15)
      expect(ratio1).toBeLessThan(0.25)
    })

    test("deriveGroundTilesFromDt1Libraries respects dwDt1Mask, rarities and sorts descending", () => {
      const dt1 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarity: 15 },
        { type: 0, style: 0, sequence: 1, Rarity: 85 },
      ])

      const result = deriveGroundTilesFromDt1Libraries([dt1], 1)
      expect(result).toHaveLength(2)
      // Sequence 1 has higher rarity (85), so it must be sorted first
      expect(result[0]!.sequence).toBe(1)
      expect(result[0]!.weight).toBe(85)
      expect(result[1]!.sequence).toBe(0)
      expect(result[1]!.weight).toBe(15)
    })
  })

  describe("applyGroundTransitions Auto-Tiling (Issue #70)", () => {
    function setFloor(
      canvas: ReturnType<typeof createCanvas>,
      x: number,
      y: number,
      floor: { style: number; sequence: number; prop1?: number },
    ): void {
      const cell = canvas.cells[y]?.[x]
      if (!cell) return
      ;(cell.floors as Ds1Floor[])[0] = {
        prop1: floor.prop1 ?? 2,
        style: floor.style,
        sequence: floor.sequence,
        unknown1: 0,
        unknown2: 0,
        hidden: false,
      }
    }

    test("generates road-to-ground edge transitions using DIRT_PATH_TILE_LUT while keeping interior road intact", () => {
      const canvas = createCanvas(9, 9, 1, 1, 0)

      // Initialize canvas with base ground: style 0, sequence 0
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          setFloor(canvas, x, y, { style: 0, sequence: 0 })
        }
      }

      // Stamp a 3x3 road patch at (3, 3) to (5, 5) with style 0, sequence 1
      for (let ry = 3; ry <= 5; ry += 1) {
        for (let rx = 3; rx <= 5; rx += 1) {
          setFloor(canvas, rx, ry, { style: 0, sequence: 1 })
        }
      }

      const roadDt1 = makeMockDt1(
        Array.from({ length: 47 }, (_, i) => ({ type: 0, style: 0, sequence: i })),
      )
      const res = applyGroundTransitions(canvas, {
        libraries: [roadDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 1 - Wilderness',
        levelId: 2,
      })
      expect(res.roadTransitions).toBeGreaterThan(0)
      expect(res.waterTransitions).toBe(0)
      expect(res.transitionCells).toBe(res.roadTransitions)

      // Interior center cell at (4, 4) has all 8 road neighbors (mask = 0xFF)
      // Interior road sequence in DIRT_PATH_TILE_LUT is sequence 1, so it remains intact!
      const centerFloor = canvas.cells[4]![4]!.floors[0]!
      expect(centerFloor.style).toBe(0)
      expect(centerFloor.sequence).toBe(1)

      // The 8 boundary road cells around (4, 4) must receive transition sequences from DIRT_PATH_TILE_LUT
      for (let ry = 3; ry <= 5; ry += 1) {
        for (let rx = 3; rx <= 5; rx += 1) {
          if (rx === 4 && ry === 4) continue
          const floor = canvas.cells[ry]![rx]!.floors[0]!
          expect(floor.style).toBe(0)
          expect(floor.sequence).toBeGreaterThanOrEqual(1)
          expect(floor.sequence).toBeLessThanOrEqual(46)
        }
      }

      // Ground cells outside road (e.g. (0, 0)) remain sequence 0
      expect(canvas.cells[0]![0]!.floors[0]!.sequence).toBe(0)
    })

    test("generates water-to-ground edge transitions using WATER_EDGE_TILE_LUT while keeping interior deep water (24)", () => {
      const canvas = createCanvas(9, 9, 1, 1, 0)

      // Initialize canvas with base ground: style 0, sequence 0
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          setFloor(canvas, x, y, { style: 0, sequence: 0 })
        }
      }

      // Stamp a 3x3 water patch at (3, 3) to (5, 5) with style 2, sequence 0
      for (let wy = 3; wy <= 5; wy += 1) {
        for (let wx = 3; wx <= 5; wx += 1) {
          setFloor(canvas, wx, wy, { style: 2, sequence: 0 })
        }
      }

      const waterDt1 = makeMockDt1(
        Array.from({ length: 25 }, (_, i) => ({ type: 0, style: 2, sequence: i })),
      )
      const res = applyGroundTransitions(canvas, {
        libraries: [waterDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 1 - Wilderness',
        levelId: 2,
      })
      expect(res.waterTransitions).toBeGreaterThan(0)
      expect(res.transitionCells).toBe(res.waterTransitions)

      // Center water cell (4, 4) has all 8 water neighbors (mask = 0xFF) -> deep water sequence 24
      const centerWater = canvas.cells[4]![4]!.floors[0]!
      expect(centerWater.style).toBe(2)
      expect(centerWater.sequence).toBe(24)

      // Perimeter water cells receive water edge sequences (0..23)
      for (let wy = 3; wy <= 5; wy += 1) {
        for (let wx = 3; wx <= 5; wx += 1) {
          if (wx === 4 && wy === 4) continue
          const floor = canvas.cells[wy]![wx]!.floors[0]!
          expect(floor.style).toBe(2)
          expect(floor.sequence).toBeLessThan(24)
        }
      }
    })

    test("returns 0 transitions when dt1Libraries are undefined or empty (Issue #113)", () => {
      const canvas = createCanvas(9, 9, 1, 1, 0)
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          setFloor(canvas, x, y, { style: 0, sequence: 0 })
        }
      }
      for (let ry = 3; ry <= 5; ry += 1) {
        for (let rx = 3; rx <= 5; rx += 1) {
          setFloor(canvas, rx, ry, { style: 0, sequence: 1 })
        }
      }

      // No options -> 0 transitions
      const resNoOptions = applyGroundTransitions(canvas)
      expect(resNoOptions.transitionCells).toBe(0)
      expect(resNoOptions.roadTransitions).toBe(0)
      expect(resNoOptions.waterTransitions).toBe(0)

      // Empty libraries array -> 0 transitions
      const resEmptyLibs = applyGroundTransitions(canvas, { libraries: [] })
      expect(resEmptyLibs.transitionCells).toBe(0)
      expect(resEmptyLibs.roadTransitions).toBe(0)
    })

    test("does not inject transition tiles into non-Act-1 environments (Issue #113)", () => {
      const canvas = createCanvas(9, 9, 1, 1, 0)
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          setFloor(canvas, x, y, { style: 0, sequence: 0 })
        }
      }
      for (let ry = 3; ry <= 5; ry += 1) {
        for (let rx = 3; rx <= 5; rx += 1) {
          setFloor(canvas, rx, ry, { style: 0, sequence: 1 })
        }
      }

      const roadDt1 = makeMockDt1(
        Array.from({ length: 47 }, (_, i) => ({ type: 0, style: 0, sequence: i })),
      )

      // Mesa 1 (levelId 104, Act 4 - Mesa)
      const resMesa = applyGroundTransitions(canvas, {
        libraries: [roadDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 4 - Mesa',
        levelId: 104,
      })
      expect(resMesa.transitionCells).toBe(0)

      // Desert 3 (levelId 43, Act 2 - Desert)
      const resDesert = applyGroundTransitions(canvas, {
        libraries: [roadDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 2 - Desert',
        levelId: 43,
      })
      expect(resDesert.transitionCells).toBe(0)

      // Barricade 2 (levelId 112, Act 5 - Barricade)
      const resBarricade2 = applyGroundTransitions(canvas, {
        libraries: [roadDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 5 - Barricade',
        levelId: 112,
      })
      expect(resBarricade2.transitionCells).toBe(0)

      // Barricade Snow (levelId 117, Act 5 - Barricade)
      const resBarricadeSnow = applyGroundTransitions(canvas, {
        libraries: [roadDt1],
        dt1Mask: 1,
        levelTypeName: 'Act 5 - Barricade',
        levelId: 117,
      })
      expect(resBarricadeSnow.transitionCells).toBe(0)
    })

    test("WATER_EDGE_TILE_LUT has exactly 256 entries with 24 at 0xFF", () => {
      expect(WATER_EDGE_TILE_LUT).toHaveLength(256)
      expect(WATER_EDGE_TILE_LUT[0xFF]).toBe(24)
      for (let i = 0; i < 255; i += 1) {
        expect(WATER_EDGE_TILE_LUT[i]).toBeLessThanOrEqual(23)
      }
    })

    test("guarantees 0 missing tiles by strictly respecting supplied DT1 libraries", () => {
      const canvas = createCanvas(9, 9, 1, 1, 0)
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          setFloor(canvas, x, y, { style: 0, sequence: 0 })
        }
      }

      // Stamp road
      for (let ry = 3; ry <= 5; ry += 1) {
        for (let rx = 3; rx <= 5; rx += 1) {
          setFloor(canvas, rx, ry, { style: 0, sequence: 1 })
        }
      }

      // Mock DT1 that only has style 0, sequence 0 and 1 (no transition sequences 2..46)
      const restrictedDt1 = makeMockDt1([
        { type: 0, style: 0, sequence: 0, rarityFrameIndex: 80 },
        { type: 0, style: 0, sequence: 1, rarityFrameIndex: 20 },
      ])

      const res = applyGroundTransitions(canvas, {
        libraries: [restrictedDt1],
        dt1Mask: 1,
      })

      // Since transitions 2..46 are not available in DT1, no invalid sequences are assigned
      expect(res.roadTransitions).toBe(0)

      // Every cell on canvas is guaranteed to be in the restricted DT1
      for (let y = 0; y < 9; y += 1) {
        for (let x = 0; x < 9; x += 1) {
          const floor = canvas.cells[y]![x]!.floors[0]!
          expect(floor.style === 0 && (floor.sequence === 0 || floor.sequence === 1)).toBe(true)
        }
      }
    })
  })
})