import { describe, expect, test } from "vitest"
import {
  fillGround,
  sampleGroundTile,
  deriveGroundTilesFromDt1Libraries,
  deriveGroundTiles,
  deriveGroundTile,
  cellHash,
  smoothNoise2D,
  createCanvas,
  generateWilderness,
  CANONICAL_GROUND_POOLS,
} from "../src/game/wilderness.ts"
import type {
  WeightedGroundTile,
  WildernessPiece,
} from "../src/game/wilderness.ts"
import type { Dt1, Dt1Tile } from "../src/formats/dt1.ts"
import type { Ds1, Ds1Cell } 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>[]): 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)
    })
  })
})