import {BitTreeDecoder} from './BitTreeDecoder'
import {LZMA} from './LZMA'
import {RangeDecoder} from './RangeDecoder'
/**
 * LZMA Decoder
 * @author Nidin Vinayakan | nidinthb@gmail.com
 */

export class LenDecoder {
  private choice = new Uint16Array([LZMA.PROB_INIT_VAL, LZMA.PROB_INIT_VAL])
  private lowCoder: Array<BitTreeDecoder> // 3
  private midCoder: Array<BitTreeDecoder> // 3
  private highCoder: BitTreeDecoder // 8

  constructor() {
    this.lowCoder = BitTreeDecoder.constructArray(3, 1 << LZMA.kNumPosBitsMax )
    this.midCoder = BitTreeDecoder.constructArray(3, 1 << LZMA.kNumPosBitsMax )
    this.highCoder = new BitTreeDecoder(8)
  }

  public init(): void {
    this.highCoder.init()
    for (let i: number = 0; i < (1 << LZMA.kNumPosBitsMax); i++) {
      this.lowCoder[i].init()
      this.midCoder[i].init()
    }
  }
  public decode(rc: RangeDecoder, posState: number): number {
    if (rc.decodeBit(this.choice ,0) === 0) {
      return this.lowCoder[posState].decode(rc)
    }
    if (rc.decodeBit(this.choice ,1) === 0) {
      return 8 + this.midCoder[posState].decode(rc)
    }
    return 16 + this.highCoder.decode(rc)
  }
}