/**
 * @module net
 */
/**
 * A wrapper class which provides methods
 * for writing data to a buffer.
 */
export class Writer {

  /**
   * The current index of the buffer.
   */
  index: number;
  /**
   * The wrapped buffer.
   */
  buffer: Buffer;

  private size: number;

  /**
   * Creates a new `Writer` and initalizes the
   * wrapped buffer to the default size of 8.
   */
  constructor() {
    this.size = 8;
    this.index = 0;
    this.buffer = Buffer.alloc(this.size);
  }

  /**
   * Writes a packet header to the first 5 bytes of this writer's buffer.
   * @param id The id to write to the header.
   */
  writeHeader(id: number): void {
    this.buffer.writeInt32BE(this.index, 0);
    this.buffer.writeInt8(id, 4);
  }

  /**
   * Writes a 4 byte integer to the buffer.
   * @param value The value to write.
   */
  writeInt32(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(4);
    this.index = this.buffer.writeInt32BE(value, this.index);
  }

  /**
   * Writes a 4 byte unsigned integer to the buffer.
   * @param value The value to write.
   */
  writeUInt32(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(4);
    this.index = this.buffer.writeUInt32BE(value, this.index);
  }

  /**
   * Writes a 2 byte integer to the buffer.
   * @param value The value to write.
   */
  writeShort(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(2);
    this.index = this.buffer.writeInt16BE(value, this.index);
  }

  /**
   * Writes a 2 byte unsigned integer to the buffer.
   * @param value The value to write.
   */
  writeUnsignedShort(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(2);
    this.index = this.buffer.writeUInt16BE(value, this.index);
  }

  /**
   * Writes a 1 byte integer to the buffer.
   * @param value The value to write.
   */
  writeByte(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(1);
    this.index = this.buffer.writeInt8(value, this.index);
  }

  /**
   * Writes a 1 byte unsigned integer to the buffer.
   * @param value The value to write.
   */
  writeUnsignedByte(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(1);
    this.index = this.buffer.writeUInt8(value, this.index);
  }

  /**
   * Writes a single byte to the buffer. Writes `1` if the value is `true` and `0` otherwise.
   * @param value The value to write.
   */
  writeBoolean(value: boolean): void {
    if (typeof value !== 'boolean') {
      value = false;
    }
    const byteValue = value ? 1 : 0;
    this.writeByte(byteValue);
  }

  /**
   * Writes a 4 byte floating point value to the buffer.
   * @param value The value to write.
   */
  writeFloat(value: number): void {
    if (isNaN(value)) {
      value = 0;
    }
    this.checkCapacity(4);
    this.index = this.buffer.writeFloatBE(value, this.index);
  }

  /**
   * Writes the length of the array as a 2 byte integer, then writes `length` bytes to the buffer.
   * @param value The value to write.
   */
  writeByteArray(value: number[]): void {
    if (!Array.isArray(value)) {
      this.writeShort(0);
      return;
    }
    this.writeShort(value.length);
    this.checkCapacity(value.length);
    for (const byte of value) {
      this.buffer[this.index++] = byte;
    }
  }

  /**
   * Writes the length of the string as a 2 byte integer, then writes the string to the buffer.
   * @param value The value to write.
   */
  writeString(value: string): void {
    if (typeof value !== 'string') {
      this.writeShort(0);
      return;
    }
    this.writeShort(value.length);
    this.checkCapacity(value.length);
    this.index += this.buffer.write(value, this.index, value.length, 'utf8');
  }

  /**
   * The same as `writeString()`, but writes 4 bytes for the length.
   * @param value The value to write.
   */
  writeStringUTF32(value: string): void {
    if (typeof value !== 'string') {
      this.writeInt32(0);
      return;
    }
    this.writeInt32(value.length);
    this.checkCapacity(value.length);
    this.index += this.buffer.write(value, this.index, value.length, 'utf8');
  }

  /**
   * Ensures there is enough capacity in the current buffer to store `addedBytes` more bytes.
   * @param addedBytes The number of bytes which need to be added.
   */
  private checkCapacity(addedBytes: number): void {
    while (this.index + addedBytes > this.buffer.length) {
      this.buffer = Buffer.concat([this.buffer, Buffer.alloc(this.size)], this.size * 2);
      this.size *= 2;
    }
  }
}