/*
  Utility class for access and management of low-level sprite data

  Maintains a single Float32Array of sprite data, keeping track of empty slots
  to allow constant-time insertion and deletion

  Automatically resizes by copying to a new, larger Float32Array when necessary,
  or compacting into a smaller Float32Array when there's space to do so.
*/

import TxSprite from './tx-sprite'

export class FastVertexArray {
  length: number;
  count: number;
  stride: number;
  sprites: TxSprite[];
  data: Float32Array;
  freeSlots: number[];
  lastSlot: number;

  constructor (length, stride) {
    this.length = length
    this.count = 0
    this.stride = stride
    this.sprites = []
    this.data = new Float32Array(this.length * this.stride)
    this.freeSlots = []
    this.lastSlot = 0
  }

  insert (sprite: TxSprite): number {
    this.count++

    let position
    if (this.freeSlots.length) {
      position = this.freeSlots.shift()
    } else {
      position = this.lastSlot
      this.lastSlot++
      if (this.lastSlot > this.length) {
        this.expand()
      }
    }
    this.sprites[position] = sprite
    return position
  }

  remove (index: number): void {
    this.count--
    this.clearData(index)
    this.freeSlots.push(index)
    this.sprites[index] = null
    if (this.length > 2048 && this.count < (this.length * 0.4)) this.compact()
  }

  setData (index: number, dataChunk: number[]): void {
    this.data.set(dataChunk, (index * this.stride))
  }

  clearData (index: number): void {
    this.data.fill(0, (index * this.stride), ((index+1) * this.stride))
  }

  getData (index: number): Float32Array {
    return this.data.subarray(index, this.stride)
  }

  expand (): void {
    this.length *= 2
    const newData = new Float32Array(this.length * this.stride)
    newData.set(this.data)
    this.data = newData
  }

  compact (): void {
    // New array length is the smallest power of 2 larger than the sprite count (but no smaller than 512)
    const newLength = Math.max(512, Math.pow(2, Math.ceil(Math.log2(this.count))))
    if (newLength != this.length) {
      this.length = newLength
      this.data = new Float32Array(this.length * this.stride)
      let sprite
      const newSprites = []
      let i = 0
      for (var index in this.sprites) {
        sprite = this.sprites[index]
        if (sprite) {
          newSprites.push(sprite)
          sprite.moveVertexPointer(i)
          sprite.compile()
          i++
        }
      }
      this.sprites = newSprites
      this.freeSlots = []
      this.lastSlot = i
    }
  }

  getVertexData (): Float32Array {
    return this.data
  }
}