// Copyright 2017-2021 @polkadot/types authors & contributors
// SPDX-License-Identifier: Apache-2.0

import type { AnyU8a, Registry } from '../types';

import { assert, compactAddLength, compactFromU8a, compactToU8a, isString, isU8a, u8aToU8a } from '@polkadot/util';

import { Raw } from '../codec/Raw';

// Bytes are used for things like on-chain code, so it has a healthy limit
const MAX_LENGTH = 10 * 1024 * 1024;

/** @internal */
function decodeBytesU8a (value: Uint8Array): Uint8Array {
  if (!value.length) {
    return new Uint8Array();
  }

  // handle all other Uint8Array inputs, these do have a length prefix
  const [offset, length] = compactFromU8a(value);
  const total = offset + length.toNumber();

  assert(length.lten(MAX_LENGTH), `Bytes length ${length.toString()} exceeds ${MAX_LENGTH}`);
  assert(total <= value.length, `Bytes: required length less than remainder, expected at least ${total}, found ${value.length}`);

  return value.subarray(offset, total);
}

/** @internal */
function decodeBytes (value?: AnyU8a): Uint8Array | undefined {
  if (Array.isArray(value) || isString(value)) {
    return u8aToU8a(value);
  } else if (!(value instanceof Raw) && isU8a(value)) {
    // We are ensuring we are not a Raw instance. In the case of a Raw we already have gotten
    // rid of the length, i.e. new Bytes(new Bytes(...)) will work as expected
    return decodeBytesU8a(value);
  }

  return value;
}

/**
 * @name Bytes
 * @description
 * A Bytes wrapper for Vec<u8>. The significant difference between this and a normal Uint8Array
 * is that this version allows for length-encoding. (i.e. it is a variable-item codec, the same
 * as what is found in [[Text]] and [[Vec]])
 */
export class Bytes extends Raw {
  constructor (registry: Registry, value?: AnyU8a) {
    super(registry, decodeBytes(value));
  }

  /**
   * @description The length of the value when encoded as a Uint8Array
   */
  public get encodedLength (): number {
    return this.length + compactToU8a(this.length).length;
  }

  /**
   * @description Returns the base runtime type name for this instance
   */
  public toRawType (): string {
    return 'Bytes';
  }

  /**
   * @description Encodes the value as a Uint8Array as per the SCALE specifications
   * @param isBare true when the value has none of the type-specific prefixes (internal)
   */
  public toU8a (isBare?: boolean): Uint8Array {
    return isBare
      ? super.toU8a(isBare)
      : compactAddLength(this);
  }
}