/**
 * @packageDocumentation
 * @module harmony-crypto
 * @hidden
 */

// this file is ported from https://github.com/ethers-io/ethers.js/blob/master/src.ts/utils/rlp.ts
// and done some fixes
import { arrayify, hexlify, Arrayish } from './bytes';

function arrayifyInteger(value: number): number[] {
  const result = [];
  while (value) {
    result.unshift(value & 0xff);
    value >>= 8;
  }
  return result;
}

function unarrayifyInteger(data: Uint8Array, offset: number, length: number): number {
  let result = 0;
  for (let i = 0; i < length; i++) {
    result = result * 256 + data[offset + i];
  }
  return result;
}

function _encode(object: any[] | string): number[] {
  if (Array.isArray(object)) {
    let payload: number[] = [];
    object.forEach((child) => {
      payload = payload.concat(_encode(child));
    });

    if (payload.length <= 55) {
      payload.unshift(0xc0 + payload.length);
      return payload;
    }

    // tslint:disable-next-line: no-shadowed-variable
    const length = arrayifyInteger(payload.length);
    length.unshift(0xf7 + length.length);

    return length.concat(payload);
  }

  const data: number[] = Array.prototype.slice.call(arrayify(object));

  if (data.length === 1 && data[0] <= 0x7f) {
    return data;
  } else if (data.length <= 55) {
    data.unshift(0x80 + data.length);
    return data;
  }

  const length = arrayifyInteger(data.length);
  length.unshift(0xb7 + length.length);

  return length.concat(data);
}

export function encode(object: any): string {
  return hexlify(_encode(object));
}

interface Decoded {
  result: any;
  consumed: number;
}

function _decodeChildren(
  data: Uint8Array,
  offset: number,
  childOffset: number,
  length: number,
): Decoded {
  const result = [];

  while (childOffset < offset + 1 + length) {
    const decoded = _decode(data, childOffset);

    result.push(decoded.result);

    childOffset += decoded.consumed;
    if (childOffset > offset + 1 + length) {
      throw new Error('invalid rlp');
    }
  }

  return { consumed: 1 + length, result };
}

// returns { consumed: number, result: Object }
function _decode(data: Uint8Array, offset: number): { consumed: number; result: any } {
  if (data.length === 0) {
    throw new Error('invalid rlp data');
  }

  // Array with extra length prefix
  if (data[offset] >= 0xf8) {
    const lengthLength = data[offset] - 0xf7;
    if (offset + 1 + lengthLength > data.length) {
      throw new Error('too short');
    }

    const length = unarrayifyInteger(data, offset + 1, lengthLength);
    if (offset + 1 + lengthLength + length > data.length) {
      throw new Error('to short');
    }

    return _decodeChildren(data, offset, offset + 1 + lengthLength, lengthLength + length);
  } else if (data[offset] >= 0xc0) {
    const length = data[offset] - 0xc0;
    if (offset + 1 + length > data.length) {
      throw new Error('invalid rlp data');
    }

    return _decodeChildren(data, offset, offset + 1, length);
  } else if (data[offset] >= 0xb8) {
    const lengthLength = data[offset] - 0xb7;
    if (offset + 1 + lengthLength > data.length) {
      throw new Error('invalid rlp data');
    }

    const length = unarrayifyInteger(data, offset + 1, lengthLength);
    if (offset + 1 + lengthLength + length > data.length) {
      throw new Error('invalid rlp data');
    }

    const result = hexlify(
      data.slice(offset + 1 + lengthLength, offset + 1 + lengthLength + length),
    );
    return { consumed: 1 + lengthLength + length, result };
  } else if (data[offset] >= 0x80) {
    const length = data[offset] - 0x80;
    if (offset + 1 + length > data.length) {
      throw new Error('invlaid rlp data');
    }

    const result = hexlify(data.slice(offset + 1, offset + 1 + length));
    return { consumed: 1 + length, result };
  }
  return { consumed: 1, result: hexlify(data[offset]) };
}

export function decode(data: Arrayish): any {
  const bytes = arrayify(data) || new Uint8Array();
  const decoded = _decode(bytes, 0);
  if (decoded.consumed !== bytes.length) {
    throw new Error('invalid rlp data');
  }
  return decoded.result;
}