import { Signer, providers, utils, Wallet } from 'ethers';
import { ProviderSettings } from '@ew-did-registry/did-resolver-interface';
import { Keys } from '@ew-did-registry/keys';
import { getProvider } from '../utils';

type EIP1193ProviderType =
  | providers.ExternalProvider
  | providers.JsonRpcFetchFunc;

/**
 * A signer class that encapsulates the ethers Signer and ensures that publicKey is available.
 * The public is necessary for verification of signatures made by the signer.
 * The purpose of the ethers encapsulation is to allow consumers more flexiblity in ethers version.
 */
export class EwSigner extends Signer {
  public readonly provider: providers.Provider;

  public readonly publicKey: string;

  /**
   * A private constructor as this class uses factory method for instantiation API.
   */
  private constructor(
    public readonly signer: Signer,
    publicKey: string,
    public readonly privateKey?: string
  ) {
    super();
    if (!signer.provider) {
      throw new Error(
        'Signer is not connected to chain. Provider must be defined'
      );
    }
    if (!publicKey) {
      throw new Error('Public key should be a non-empty string');
    }
    const publicKeyWithoutHexPrefix =
      publicKey.slice(0, 2) === '0x' ? publicKey.slice(2) : publicKey;
    this.publicKey = new Keys({
      publicKey: publicKeyWithoutHexPrefix,
    }).publicKey;
    this.provider = signer.provider;
  }

  getAddress(): Promise<string> {
    return this.signer.getAddress();
  }

  sendTransaction(
    transaction: providers.TransactionRequest
  ): Promise<providers.TransactionResponse> {
    return this.signer.sendTransaction(transaction);
  }

  signMessage(message: string | utils.Bytes): Promise<string> {
    return this.signer.signMessage(message);
  }

  signTransaction(transaction: providers.TransactionRequest): Promise<string> {
    return this.signer.signTransaction(transaction);
  }

  connect(provider: providers.Provider): Signer {
    return this.signer.connect(provider);
  }

  /**
   * A factory method to create an EwSigner from a private key.
   * ```typescript
   * import {
   *   Operator,
   *   EwSigner
   * } from '@ew-did-registry/did-ethr-resolver';
   * import { Keys } from '@ew-did-registry/keys';
   *
   * const keys = new Keys();
   * const providerSettings = { type: ProviderTypes.HTTP, };
   * const signer = EwSigner.fromPrivateKey(keys.privateKey, providerSettings);
   * const operator = new Operator(signer, registrySettings);
   * ```
   * @param privateKey a secp256k1 private key.
   * @param providerSettings settings from which a web3 provider can be obtained
   */
  public static fromPrivateKey(
    privateKey: string,
    providerSettings: ProviderSettings
  ): EwSigner {
    const provider = getProvider(providerSettings);
    const wallet = new Wallet(privateKey, provider);
    const compressedPubKey = utils.computePublicKey(wallet.publicKey, true);
    return new EwSigner(wallet, compressedPubKey, privateKey);
  }

  /**
   * A factory method to create an EwSigner using an ethers library Signer.
   * This is convenient if a suitable ethers signer is available.
   * If instead an EIP1993 provider is available, see {@linkcode fromEIP1193}
   * @param signer an ethers Signer connected to chain
   * @param publicKey the publicKey of the signer associated with the provider
   */
  public static fromEthersSigner(signer: Signer, publicKey: string): EwSigner {
    return new EwSigner(signer, publicKey);
  }

  /**
   * A factory method to create an EwSigner without needing a specific ethers object.
   * Instead, any object which conforms to the necessary interface can be used.
   * See https://docs.ethers.io/v5/api/providers/other/#Web3Provider for interface description.
   *
   * @example
   * ```typescript
   * import { Operator, EwSigner } from '@ew-did-registry/did-ethr-resolver';
   * import detectMetamask from "@metamask/detect-provider";
   *
   * const web3Provider = await detectMetamask();
   * const web3Signer = EwSigner.fromEIP1193(web3Provider, publicKey);
   * const operator = new Operator(web3Signer, registrySettings);
   * ```
   * @param eip1993Provider an EIP1193 provider (https://docs.ethers.io/v5/api/providers/other/#Web3Provider)
   * @param publicKey the publicKey of the signer associated with the provider
   */
  // eslint-disable-next-line max-len
  public static async fromEIP1193(
    eip1993Provider: EIP1193ProviderType,
    publicKey: string
  ): Promise<EwSigner> {
    const provider = new providers.Web3Provider(eip1993Provider);
    const signer = provider.getSigner();
    try {
      // Call getAddress() to check that signer has address
      // Signer could be returned by not actually have an address
      // Best to check now and "fail fast"
      await signer.getAddress();
    } catch (error) {
      if (error instanceof Error) {
        error.message = `Error instantiating EwSigner from ethers Provider. Provider must have signer with address. ${error.message}`;
        throw new Error(error.message);
      }
    }
    return new EwSigner(signer, publicKey);
  }
}