import {
  Box3,
  Box3Helper,
  BufferAttribute,
  BufferGeometry,
  Color,
  DoubleSide,
  Group,
  LineBasicMaterial,
  LineSegments,
  Mesh,
  MeshBasicMaterial,
  PlaneGeometry
} from 'three'

import type { CSM } from './CSM'

class CSMHelper extends Group {
  private readonly csm: CSM
  public displayFrustum = true
  public displayPlanes = true
  public displayShadowBounds = true
  private frustumLines: LineSegments<BufferGeometry, LineBasicMaterial>
  private cascadeLines: Box3Helper[] = []
  private cascadePlanes: Mesh[] = []
  private shadowLines: Group[] = []

  public constructor(csm: CSM) {
    super()
    this.csm = csm

    const indices = new Uint16Array([0, 1, 1, 2, 2, 3, 3, 0, 4, 5, 5, 6, 6, 7, 7, 4, 0, 4, 1, 5, 2, 6, 3, 7])
    const positions = new Float32Array(24)
    const frustumGeometry = new BufferGeometry()
    frustumGeometry.setIndex(new BufferAttribute(indices, 1))
    frustumGeometry.setAttribute('position', new BufferAttribute(positions, 3, false))
    const frustumLines = new LineSegments(frustumGeometry, new LineBasicMaterial())
    this.add(frustumLines)

    this.frustumLines = frustumLines
  }

  public updateVisibility() {
    const displayFrustum = this.displayFrustum
    const displayPlanes = this.displayPlanes
    const displayShadowBounds = this.displayShadowBounds

    const frustumLines = this.frustumLines
    const cascadeLines = this.cascadeLines
    const cascadePlanes = this.cascadePlanes
    const shadowLines = this.shadowLines
    for (let i = 0, l = cascadeLines.length; i < l; i++) {
      const cascadeLine = cascadeLines[i]
      const cascadePlane = cascadePlanes[i]
      const shadowLineGroup = shadowLines[i]

      cascadeLine.visible = displayFrustum
      cascadePlane.visible = displayFrustum && displayPlanes
      shadowLineGroup.visible = displayShadowBounds
    }

    frustumLines.visible = displayFrustum
  }

  public update() {
    const csm = this.csm
    const camera = csm.camera
    const cascades = csm.cascades
    const mainFrustum = csm.mainFrustum
    const frustums = csm.frustums
    const lights = csm.lights

    const frustumLines = this.frustumLines
    const frustumLinePositions = frustumLines.geometry.getAttribute('position')
    const cascadeLines = this.cascadeLines
    const cascadePlanes = this.cascadePlanes
    const shadowLines = this.shadowLines

    this.position.copy(camera.position)
    this.quaternion.copy(camera.quaternion)
    this.scale.copy(camera.scale)
    this.updateMatrixWorld(true)

    while (cascadeLines.length > cascades) {
      this.remove(cascadeLines.pop() as any)
      this.remove(cascadePlanes.pop() as any)
      this.remove(shadowLines.pop() as any)
    }

    while (cascadeLines.length < cascades) {
      const cascadeLine = new Box3Helper(new Box3(), new Color(0xffffff))
      const planeMat = new MeshBasicMaterial({ transparent: true, opacity: 0.1, depthWrite: false, side: DoubleSide })
      const cascadePlane = new Mesh(new PlaneGeometry(), planeMat)
      const shadowLineGroup = new Group()
      const shadowLine = new Box3Helper(new Box3(), new Color(0xffff00))
      shadowLineGroup.add(shadowLine)

      this.add(cascadeLine)
      this.add(cascadePlane)
      this.add(shadowLineGroup)

      cascadeLines.push(cascadeLine)
      cascadePlanes.push(cascadePlane)
      shadowLines.push(shadowLineGroup)
    }

    for (let i = 0; i < cascades; i++) {
      const frustum = frustums[i]
      const light = lights[i]
      const shadowCam = light.shadow.camera
      const farVerts = frustum.vertices.far

      const cascadeLine = cascadeLines[i]
      const cascadePlane = cascadePlanes[i]
      const shadowLineGroup = shadowLines[i]
      const shadowLine = shadowLineGroup.children[0] as Box3Helper

      cascadeLine.box.min.copy(farVerts[2])
      cascadeLine.box.max.copy(farVerts[0])
      cascadeLine.box.max.z += 1e-4

      cascadePlane.position.addVectors(farVerts[0], farVerts[2])
      cascadePlane.position.multiplyScalar(0.5)
      cascadePlane.scale.subVectors(farVerts[0], farVerts[2])
      cascadePlane.scale.z = 1e-4

      this.remove(shadowLineGroup)
      shadowLineGroup.position.copy(shadowCam.position)
      shadowLineGroup.quaternion.copy(shadowCam.quaternion)
      shadowLineGroup.scale.copy(shadowCam.scale)
      shadowLineGroup.updateMatrixWorld(true)
      this.attach(shadowLineGroup)

      shadowLine.box.min.set(shadowCam.bottom, shadowCam.left, -shadowCam.far)
      shadowLine.box.max.set(shadowCam.top, shadowCam.right, -shadowCam.near)
    }

    const nearVerts = mainFrustum.vertices.near
    const farVerts = mainFrustum.vertices.far
    frustumLinePositions.setXYZ(0, farVerts[0].x, farVerts[0].y, farVerts[0].z)
    frustumLinePositions.setXYZ(1, farVerts[3].x, farVerts[3].y, farVerts[3].z)
    frustumLinePositions.setXYZ(2, farVerts[2].x, farVerts[2].y, farVerts[2].z)
    frustumLinePositions.setXYZ(3, farVerts[1].x, farVerts[1].y, farVerts[1].z)

    frustumLinePositions.setXYZ(4, nearVerts[0].x, nearVerts[0].y, nearVerts[0].z)
    frustumLinePositions.setXYZ(5, nearVerts[3].x, nearVerts[3].y, nearVerts[3].z)
    frustumLinePositions.setXYZ(6, nearVerts[2].x, nearVerts[2].y, nearVerts[2].z)
    frustumLinePositions.setXYZ(7, nearVerts[1].x, nearVerts[1].y, nearVerts[1].z)
    frustumLinePositions.needsUpdate = true
  }
}

export default CSMHelper