import BN from 'bn.js';
import bs58 from 'bs58';
import { Buffer } from 'buffer';
import { sha256 } from '@noble/hashes/sha256';

/**
 * Maximum length of derived pubkey seed
 */
export const MAX_SEED_LENGTH = 32;

/**
 * Size of public key in bytes
 */
export const PUBLIC_KEY_LENGTH = 32;

/**
 * Value to be converted into public key
 */
export type PublicKeyInitData =
  | number
  | string
  | Uint8Array
  | Array<number>
  | PublicKeyData;

/**
 * JSON object representation of PublicKey class
 */
export type PublicKeyData = {
  /** @internal */
  _bn: BN;
};

function isPublicKeyData(value: PublicKeyInitData): value is PublicKeyData {
  return (value as PublicKeyData)._bn !== undefined;
}

// local counter used by PublicKey.unique()
let uniquePublicKeyCounter = 1;

/**
 * A public key
 */
export class PublicKey {
  /** @internal */
  _bn: BN;

  /**
   * Create a new PublicKey object
   * @param value ed25519 public key as buffer or base-58 encoded string
   */
  constructor(value: PublicKeyInitData) {

    if (isPublicKeyData(value)) {
      this._bn = value._bn;
    } else {
      if (typeof value === 'string') {
        // assume base 58 encoding by default
        const decoded = bs58.decode(value);
        if (decoded.length != PUBLIC_KEY_LENGTH) {
          throw new Error(`Invalid public key input`);
        }
        this._bn = new BN(decoded);
      } else {
        this._bn = new BN(value);
      }

      if (this._bn.byteLength() > PUBLIC_KEY_LENGTH) {
        throw new Error(`Invalid public key input`);
      }
    }
  }

  /**
   * Returns a unique PublicKey for tests and benchmarks using a counter
   */
  static unique(): PublicKey {
    const key = new PublicKey(uniquePublicKeyCounter);
    uniquePublicKeyCounter += 1;
    return new PublicKey(key.toBuffer());
  }

  /**
   * Default public key value. The base58-encoded string representation is all ones (as seen below)
   * The underlying BN number is 32 bytes that are all zeros
   */
  static default: PublicKey = new PublicKey('11111111111111111111111111111111');

  /**
   * Checks if two publicKeys are equal
   */
  equals(publicKey: PublicKey): boolean {
    return this._bn.eq(publicKey._bn);
  }

  /**
   * Return the base-58 representation of the public key
   */
  toBase58(): string {
    return bs58.encode(this.toBytes());
  }

  toJSON(): string {
    return this.toBase58();
  }

  /**
   * Return the byte array representation of the public key in big endian
   */
  toBytes(): Uint8Array {
    const buf = this.toBuffer();
    return new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength);
  }

  /**
   * Return the Buffer representation of the public key in big endian
   */
  toBuffer(): Buffer {
    const b = this._bn.toArrayLike(Buffer);
    if (b.length === PUBLIC_KEY_LENGTH) {
      return b;
    }

    const zeroPad = Buffer.alloc(32);
    b.copy(zeroPad, 32 - b.length);
    return zeroPad;
  }

  get [Symbol.toStringTag](): string {
    return `PublicKey(${this.toString()})`;
  }

  /**
   * Return the base-58 representation of the public key
   */
  toString(): string {
    return this.toBase58();
  }

  /**
   * Derive a public key from another key, a seed, and a program ID.
   * The program ID will also serve as the owner of the public key, giving
   * it permission to write data to the account.
   */
  /* eslint-disable require-await */
  static async createWithSeed(
    fromPublicKey: PublicKey,
    seed: string,
    programId: PublicKey,
  ): Promise<PublicKey> {
    const buffer = Buffer.concat([
      fromPublicKey.toBuffer(),
      Buffer.from(seed),
      programId.toBuffer(),
    ]);
    const publicKeyBytes = sha256(buffer);
    return new PublicKey(publicKeyBytes);
  }
}