export interface WriterProperties {
  bufs?: Buffer[];
}

export default class BufferWriter {
  bufs: Buffer[];
  bufLen: number;

  constructor(obj?: WriterProperties) {
    this.bufLen = 0;
    if (obj) {
      const { bufs, bufLen } = this.set(obj);

      // Re-assign in constructor to appease TS
      this.bufs = bufs;
      this.bufLen = bufLen;
    } else {
      this.bufs = [];
    }
  }

  set(obj: WriterProperties) {
    this.bufs = obj.bufs || this.bufs || [];
    this.bufLen = this.bufs.reduce(function (prev, buf) {
      return prev + buf.length;
    }, 0);
    return this;
  }

  toBuffer() {
    return this.concat();
  }

  concat() {
    return Buffer.concat(this.bufs, this.bufLen);
  }

  write(buf: Buffer) {
    this.bufs.push(buf);
    this.bufLen += buf.length;
    return this;
  }

  writeReverse(buf: Buffer) {
    this.write(Buffer.from(buf).reverse());
    return this;
  }

  writeUInt8(n: number) {
    const buf = Buffer.alloc(1);
    buf.writeUInt8(n);
    this.write(buf);
    return this;
  }

  writeUInt16BE(n: number) {
    const buf = Buffer.alloc(2);
    buf.writeUInt16BE(n);
    this.write(buf);
    return this;
  }

  writeUInt16LE(n: number) {
    const buf = Buffer.alloc(2);
    buf.writeUInt16LE(n);
    this.write(buf);
    return this;
  }

  writeUInt32BE(n: number) {
    const buf = Buffer.alloc(4);
    buf.writeUInt32BE(n);
    this.write(buf);
    return this;
  }

  writeInt32LE(n: number) {
    const buf = Buffer.alloc(4);
    buf.writeInt32LE(n);
    this.write(buf);
    return this;
  }

  writeUInt32LE(n: number) {
    const buf = Buffer.alloc(4);
    buf.writeUInt32LE(n);
    this.write(buf);
    return this;
  }

  writeUInt64BE(bn: bigint) {
    const buf = Buffer.alloc(8);
    buf.writeBigUInt64BE(BigInt(bn));
    this.write(buf);
    return this;
  }

  writeUInt64LE(bn: bigint) {
    const buf = Buffer.alloc(8);
    buf.writeBigUInt64LE(BigInt(bn));
    this.write(buf);
    return this;
  }

  writeVarintNum(n: number) {
    const buf = BufferWriter.varintBufNum(n);
    this.write(buf);
    return this;
  }

  writeVarLengthBuffer(buf: Buffer) {
    const len = BufferWriter.varintBufNum(buf.length);
    this.write(len);
    this.write(buf);
    return this;
  }

  static varintBufNum(n: number) {
    let buf;
    if (n < 253) {
      buf = Buffer.alloc(1);
      buf.writeUInt8(n, 0);
    } else if (n < 0x10000) {
      buf = Buffer.alloc(1 + 2);
      buf.writeUInt8(253, 0);
      buf.writeUInt16LE(n, 1);
    } else if (n < 0x100000000) {
      buf = Buffer.alloc(1 + 4);
      buf.writeUInt8(254, 0);
      buf.writeUInt32LE(n, 1);
    } else {
      buf = Buffer.alloc(1 + 8);
      buf.writeUInt8(255, 0);
      buf.writeInt32LE(n & -1, 1);
      buf.writeUInt32LE(Math.floor(n / 0x100000000), 5);
    }
    return buf;
  }
}