import { rotateScreenPoint, type ScreenPoint } from '../camera/camera'
import { type TileStore, type TileStoreEntry } from '../tile/tileStore'
import { TileLayer } from '../layer/tileLayer'
import { buildCamera, type MapScene } from './mapRenderer'

interface TextureRecord {
  key: string
  texture: any
}

function createShader(gl: any, type: number, source: string): any {
  const shader = gl.createShader(type)
  if (!shader) {
    throw new Error('WebGL shader 创建失败')
  }

  gl.shaderSource(shader, source)
  gl.compileShader(shader)
  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
    const message = gl.getShaderInfoLog(shader) || 'unknown shader error'
    gl.deleteShader(shader)
    throw new Error(message)
  }

  return shader
}

function createProgram(gl: any, vertexSource: string, fragmentSource: string): any {
  const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexSource)
  const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentSource)
  const program = gl.createProgram()
  if (!program) {
    throw new Error('WebGL program 创建失败')
  }

  gl.attachShader(program, vertexShader)
  gl.attachShader(program, fragmentShader)
  gl.linkProgram(program)
  gl.deleteShader(vertexShader)
  gl.deleteShader(fragmentShader)

  if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
    const message = gl.getProgramInfoLog(program) || 'unknown program error'
    gl.deleteProgram(program)
    throw new Error(message)
  }

  return program
}

export class WebGLTileRenderer {
  canvas: any
  gl: any
  tileLayer: TileLayer
  tileStore: TileStore
  dpr: number
  program: any
  positionBuffer: any
  texCoordBuffer: any
  positionLocation: number
  texCoordLocation: number
  textureCache: Map<string, TextureRecord>

  constructor(tileLayer: TileLayer, tileStore: TileStore) {
    this.canvas = null
    this.gl = null
    this.tileLayer = tileLayer
    this.tileStore = tileStore
    this.dpr = 1
    this.program = null
    this.positionBuffer = null
    this.texCoordBuffer = null
    this.positionLocation = -1
    this.texCoordLocation = -1
    this.textureCache = new Map<string, TextureRecord>()
  }

  attachCanvas(canvasNode: any, width: number, height: number, dpr: number): void {
    this.canvas = canvasNode
    this.dpr = dpr || 1
    canvasNode.width = Math.max(1, Math.floor(width * this.dpr))
    canvasNode.height = Math.max(1, Math.floor(height * this.dpr))

    const gl = canvasNode.getContext('webgl') || canvasNode.getContext('experimental-webgl')
    if (!gl) {
      throw new Error('当前环境不支持 WebGL')
    }

    this.gl = gl
    this.program = createProgram(
      gl,
      'attribute vec2 a_position; attribute vec2 a_texCoord; varying vec2 v_texCoord; void main() { gl_Position = vec4(a_position, 0.0, 1.0); v_texCoord = a_texCoord; }',
      'precision mediump float; varying vec2 v_texCoord; uniform sampler2D u_texture; void main() { gl_FragColor = texture2D(u_texture, v_texCoord); }',
    )
    this.positionBuffer = gl.createBuffer()
    this.texCoordBuffer = gl.createBuffer()
    this.positionLocation = gl.getAttribLocation(this.program, 'a_position')
    this.texCoordLocation = gl.getAttribLocation(this.program, 'a_texCoord')

    gl.viewport(0, 0, canvasNode.width, canvasNode.height)
    gl.disable(gl.DEPTH_TEST)
    gl.enable(gl.BLEND)
    gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)

    this.tileStore.attachCanvas(canvasNode)
  }

  destroy(): void {
    if (this.gl) {
      this.textureCache.forEach((record) => {
        this.gl && this.gl.deleteTexture(record.texture)
      })
      if (this.program) {
        this.gl.deleteProgram(this.program)
      }
      if (this.positionBuffer) {
        this.gl.deleteBuffer(this.positionBuffer)
      }
      if (this.texCoordBuffer) {
        this.gl.deleteBuffer(this.texCoordBuffer)
      }
    }

    this.textureCache.clear()
    this.program = null
    this.positionBuffer = null
    this.texCoordBuffer = null
    this.gl = null
    this.canvas = null
  }

  render(scene: MapScene): void {
    if (!this.gl || !this.program || !this.positionBuffer || !this.texCoordBuffer) {
      return
    }

    const gl = this.gl
    const camera = buildCamera(scene)
    const tiles = this.tileLayer.prepareTiles(scene, camera, this.tileStore)

    gl.viewport(0, 0, this.canvas.width, this.canvas.height)
    gl.clearColor(0.8588, 0.9333, 0.8314, 1)
    gl.clear(gl.COLOR_BUFFER_BIT)
    gl.useProgram(this.program)

    for (const tile of tiles) {
      const readyEntry = this.tileStore.getEntry(tile.url)

      if (readyEntry && readyEntry.status === 'ready' && readyEntry.image) {
        this.drawEntry(readyEntry, tile.url, 0, 0, readyEntry.image.width || 256, readyEntry.image.height || 256, tile.leftPx, tile.topPx, tile.sizePx, tile.sizePx, scene)
        this.tileLayer.lastReadyTileCount += 1
        continue
      }

      const parentFallback = this.tileStore.getParentFallbackSlice(tile, scene)
      if (parentFallback) {
        this.drawEntry(
          parentFallback.entry,
          tile.url + '|parent',
          parentFallback.sourceX,
          parentFallback.sourceY,
          parentFallback.sourceWidth,
          parentFallback.sourceHeight,
          tile.leftPx,
          tile.topPx,
          tile.sizePx,
          tile.sizePx,
          scene,
        )
      }

      const childFallback = this.tileStore.getChildFallback(tile, scene)
      if (!childFallback) {
        continue
      }

      const cellWidth = tile.sizePx / childFallback.division
      const cellHeight = tile.sizePx / childFallback.division
      for (const child of childFallback.children) {
        this.drawEntry(
          child.entry,
          tile.url + '|child|' + child.offsetX + '|' + child.offsetY,
          0,
          0,
          child.entry.image.width || 256,
          child.entry.image.height || 256,
          tile.leftPx + child.offsetX * cellWidth,
          tile.topPx + child.offsetY * cellHeight,
          cellWidth,
          cellHeight,
          scene,
        )
      }
    }
  }

  drawEntry(
    entry: TileStoreEntry,
    cacheKey: string,
    sourceX: number,
    sourceY: number,
    sourceWidth: number,
    sourceHeight: number,
    drawLeft: number,
    drawTop: number,
    drawWidth: number,
    drawHeight: number,
    scene: MapScene,
  ): void {
    if (!this.gl || !entry.image) {
      return
    }

    const texture = this.getTexture(cacheKey, entry)
    if (!texture) {
      return
    }

    const gl = this.gl
    const imageWidth = entry.image.width || 256
    const imageHeight = entry.image.height || 256
    const texLeft = sourceX / imageWidth
    const texTop = sourceY / imageHeight
    const texRight = (sourceX + sourceWidth) / imageWidth
    const texBottom = (sourceY + sourceHeight) / imageHeight

    const topLeft = this.transformToClip(drawLeft, drawTop, scene)
    const topRight = this.transformToClip(drawLeft + drawWidth, drawTop, scene)
    const bottomLeft = this.transformToClip(drawLeft, drawTop + drawHeight, scene)
    const bottomRight = this.transformToClip(drawLeft + drawWidth, drawTop + drawHeight, scene)

    const positions = new Float32Array([
      topLeft.x, topLeft.y,
      topRight.x, topRight.y,
      bottomLeft.x, bottomLeft.y,
      bottomLeft.x, bottomLeft.y,
      topRight.x, topRight.y,
      bottomRight.x, bottomRight.y,
    ])
    const texCoords = new Float32Array([
      texLeft, texTop,
      texRight, texTop,
      texLeft, texBottom,
      texLeft, texBottom,
      texRight, texTop,
      texRight, texBottom,
    ])

    gl.bindTexture(gl.TEXTURE_2D, texture.texture)
    gl.bindBuffer(gl.ARRAY_BUFFER, this.positionBuffer)
    gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STREAM_DRAW)
    gl.enableVertexAttribArray(this.positionLocation)
    gl.vertexAttribPointer(this.positionLocation, 2, gl.FLOAT, false, 0, 0)

    gl.bindBuffer(gl.ARRAY_BUFFER, this.texCoordBuffer)
    gl.bufferData(gl.ARRAY_BUFFER, texCoords, gl.STREAM_DRAW)
    gl.enableVertexAttribArray(this.texCoordLocation)
    gl.vertexAttribPointer(this.texCoordLocation, 2, gl.FLOAT, false, 0, 0)

    gl.drawArrays(gl.TRIANGLES, 0, 6)
  }

  getTexture(cacheKey: string, entry: TileStoreEntry): TextureRecord | null {
    if (!this.gl || !entry.image) {
      return null
    }

    const key = cacheKey + '|' + entry.sourcePath
    const existing = this.textureCache.get(key)
    if (existing) {
      return existing
    }

    const texture = this.gl.createTexture()
    if (!texture) {
      return null
    }

    this.gl.bindTexture(this.gl.TEXTURE_2D, texture)
    this.gl.texParameteri(this.gl.TEXTURE_2D, this.gl.TEXTURE_WRAP_S, this.gl.CLAMP_TO_EDGE)
    this.gl.texParameteri(this.gl.TEXTURE_2D, this.gl.TEXTURE_WRAP_T, this.gl.CLAMP_TO_EDGE)
    this.gl.texParameteri(this.gl.TEXTURE_2D, this.gl.TEXTURE_MIN_FILTER, this.gl.LINEAR)
    this.gl.texParameteri(this.gl.TEXTURE_2D, this.gl.TEXTURE_MAG_FILTER, this.gl.LINEAR)
    this.gl.pixelStorei(this.gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, 1)
    this.gl.texImage2D(this.gl.TEXTURE_2D, 0, this.gl.RGBA, this.gl.RGBA, this.gl.UNSIGNED_BYTE, entry.image)

    const record = { key, texture }
    this.textureCache.set(key, record)
    return record
  }

  transformToClip(x: number, y: number, scene: MapScene): ScreenPoint {
    const rotated = rotateScreenPoint(
      { x, y },
      scene.viewportWidth / 2,
      scene.viewportHeight / 2,
      scene.rotationRad || 0,
    )
    const translated = {
      x: rotated.x + scene.translateX,
      y: rotated.y + scene.translateY,
    }
    const previewed = this.applyPreview(translated.x, translated.y, scene)

    return {
      x: this.toClipX(previewed.x, scene.viewportWidth),
      y: this.toClipY(previewed.y, scene.viewportHeight),
    }
  }

  applyPreview(x: number, y: number, scene: MapScene): { x: number; y: number } {
    const scale = scene.previewScale || 1
    const originX = scene.previewOriginX || scene.viewportWidth / 2
    const originY = scene.previewOriginY || scene.viewportHeight / 2

    return {
      x: originX + (x - originX) * scale,
      y: originY + (y - originY) * scale,
    }
  }

  toClipX(x: number, width: number): number {
    return x / width * 2 - 1
  }

  toClipY(y: number, height: number): number {
    return 1 - y / height * 2
  }
}