# src/connection.js

    // @flow

    import assert from 'assert';
    import {parse as urlParse, format as urlFormat} from 'url';
    import fetch from 'node-fetch';
    import jayson from 'jayson/lib/client/browser';
    import {struct} from 'superstruct';
    import {Client as RpcWebSocketClient} from 'rpc-websockets';

    import {DEFAULT_TICKS_PER_SLOT, NUM_TICKS_PER_SECOND} from './timing';
    import {PublicKey} from './publickey';
    import {Transaction} from './transaction';
    import {sleep} from './util/sleep';
    import type {Blockhash} from './blockhash';
    import type {FeeCalculator} from './fee-calculator';
    import type {Account} from './account';
    import type {TransactionSignature} from './transaction';

    type RpcRequest = (methodName: string, args: Array<any>) => any;

    /**
     * Information describing a cluster node
     *
     * @typedef {Object} ContactInfo
     * @property {string} pubkey Identity public key of the node
     * @property {string} gossip Gossip network address for the node
     * @property {string} tpu TPU network address for the node (null if not available)
     * @property {string|null} rpc JSON RPC network address for the node (null if not available)
     */
    type ContactInfo = {
      pubkey: string,
      gossip: string,
      tpu: string | null,
      rpc: string | null,
    };

    /**
     * Information describing a vote account
     *
     * @typedef {Object} VoteAccountInfo
     * @property {string} votePubkey Public key of the vote account
     * @property {string} nodePubkey Identity public key of the node voting with this account
     * @property {number} activatedStake The stake, in lamports, delegated to this vote account and activated
     * @property {boolean} epochVoteAccount Whether the vote account is staked for this epoch
     * @property {number} commission A 8-bit unsigned integer used as a fraction (commission/0xFF) for rewards payout
     * @property {number} lastVote Most recent slot voted on by this vote account
     */
    type VoteAccountInfo = {
      votePubkey: string,
      nodePubkey: string,
      activatedStake: number,
      epochVoteAccount: boolean,
      commission: number,
      lastVote: number,
    };

    /**
     * A collection of cluster vote accounts
     *
     * @typedef {Object} VoteAccountStatus
     * @property {Array<VoteAccountInfo>} current Active vote accounts
     * @property {Array<VoteAccountInfo>} delinquent Inactive vote accounts
     */
    type VoteAccountStatus = {
      current: Array<VoteAccountInfo>,
      delinquent: Array<VoteAccountInfo>,
    };

    /**
     * Network Inflation parameters
     *
     * @typedef {Object} Inflation TODO - link to book terminology?
     * @property {number} foundation TODO - link to book terminology?
     * @property {number} foundation_term TODO - link to book terminology?
     * @property {number} grant TODO - link to book terminology?
     * @property {number} grant_term TODO - link to book terminology?
     * @property {number} initial TODO - link to book terminology?
     * @property {number} storage TODO - link to book terminology?
     * @property {number} taper TODO - link to book terminology?
     * @property {number} terminal TODO - link to book terminology?
     */
    const GetInflationResult = struct({
      foundation: 'number',
      foundation_term: 'number',
      initial: 'number',
      storage: 'number',
      taper: 'number',
      terminal: 'number',
    });

    function createRpcRequest(url): RpcRequest {
      const server = jayson(async (request, callback) => {
        const options = {
          method: 'POST',
          body: request,
          headers: {
            'Content-Type': 'application/json',
          },
        };

        try {
          const res = await fetch(url, options);
          const text = await res.text();
          callback(null, text);
        } catch (err) {
          callback(err);
        }
      });

      return (method, args) => {
        return new Promise((resolve, reject) => {
          server.request(method, args, (err, response) => {
            if (err) {
              reject(err);
              return;
            }
            resolve(response);
          });
        });
      };
    }

    /**
     * Expected JSON RPC response for the "getInflation" message
     */
    const GetInflationRpcResult = struct({
      jsonrpc: struct.literal('2.0'),
      id: 'string',
      error: 'any?',
      result: GetInflationResult,
    });

    /**
     * Expected JSON RPC response for the "getBalance" message
     */
    const GetBalanceRpcResult = struct({
      jsonrpc: struct.literal('2.0'),
      id: 'string',
      error: 'any?',
      result: 'number?',
    });

    /**
     * @private
     */
    function jsonRpcResult(resultDescription: any) {
      const jsonRpcVersion = struct.literal('2.0');
      return struct.union([
        struct({
          jsonrpc: jsonRpcVersion,
          id: 'string',
          error: 'any',
        }),
        struct({
          jsonrpc: jsonRpcVersion,
          id: 'string',
          error: 'null?',
          result: resultDescription,
        }),
      ]);
    }

    /**
     * @private
     */
    const AccountInfoResult = struct({
      executable: 'boolean',
      owner: 'array',
      lamports: 'number',
      data: 'array',
      rent_epoch: 'number?',
    });

    /**
     * Expected JSON RPC response for the "getAccountInfo" message
     */
    const GetAccountInfoRpcResult = jsonRpcResult(AccountInfoResult);

    /***
     * Expected JSON RPC response for the "accountNotification" message
     */
    const AccountNotificationResult = struct({
      subscription: 'number',
      result: AccountInfoResult,
    });

    /**
     * @private
     */
    const ProgramAccountInfoResult = struct(['string', AccountInfoResult]);

    /***
     * Expected JSON RPC response for the "programNotification" message
     */
    const ProgramAccountNotificationResult = struct({
      subscription: 'number',
      result: ProgramAccountInfoResult,
    });

    /**
     * Expected JSON RPC response for the "getProgramAccounts" message
     */
    const GetProgramAccountsRpcResult = jsonRpcResult(
      struct.list([ProgramAccountInfoResult]),
    );

    /**
     * Expected JSON RPC response for the "confirmTransaction" message
     */
    const ConfirmTransactionRpcResult = jsonRpcResult('boolean');

    /**
     * Expected JSON RPC response for the "getSlot" message
     */
    const GetSlot = jsonRpcResult('number');

    /**
     * Expected JSON RPC response for the "getSlotLeader" message
     */
    const GetSlotLeader = jsonRpcResult('string');

    /**
     * Expected JSON RPC response for the "getClusterNodes" message
     */
    const GetClusterNodes = jsonRpcResult(
      struct.list([
        struct({
          pubkey: 'string',
          gossip: 'string',
          tpu: struct.union(['null', 'string']),
          rpc: struct.union(['null', 'string']),
        }),
      ]),
    );
    /**
     * @ignore
     */
    const GetClusterNodes_015 = jsonRpcResult(
      struct.list([
        struct({
          id: 'string',
          gossip: 'string',
          tpu: struct.union(['null', 'string']),
          rpc: struct.union(['null', 'string']),
        }),
      ]),
    );

    /**
     * Expected JSON RPC response for the "getVoteAccounts" message
     */
    const GetVoteAccounts = jsonRpcResult(
      struct({
        current: struct.list([
          struct({
            votePubkey: 'string',
            nodePubkey: 'string',
            activatedStake: 'number',
            epochVoteAccount: 'boolean',
            commission: 'number',
            lastVote: 'number',
            rootSlot: 'number?',
          }),
        ]),
        delinquent: struct.list([
          struct({
            votePubkey: 'string',
            nodePubkey: 'string',
            activatedStake: 'number',
            epochVoteAccount: 'boolean',
            commission: 'number',
            lastVote: 'number',
            rootSlot: 'number?',
          }),
        ]),
      }),
    );

    /**
     * Expected JSON RPC response for the "getSignatureStatus" message
     */
    const GetSignatureStatusRpcResult = jsonRpcResult(
      struct.union([
        'null',
        struct.union([struct({Ok: 'null'}), struct({Err: 'object'})]),
      ]),
    );

    /**
     * Expected JSON RPC response for the "getTransactionCount" message
     */
    const GetTransactionCountRpcResult = jsonRpcResult('number');

    /**
     * Expected JSON RPC response for the "getTotalSupply" message
     */
    const GetTotalSupplyRpcResult = jsonRpcResult('number');

    /**
     * Expected JSON RPC response for the "getMinimumBalanceForRentExemption" message
     */
    const GetMinimumBalanceForRentExemptionRpcResult = jsonRpcResult('number');

    /**
     * Expected JSON RPC response for the "getRecentBlockhash" message
     */
    const GetRecentBlockhash = jsonRpcResult([
      'string',
      struct({
        burnPercent: 'number',
        lamportsPerSignature: 'number',
        maxLamportsPerSignature: 'number',
        minLamportsPerSignature: 'number',
        targetLamportsPerSignature: 'number',
        targetSignaturesPerSlot: 'number',
      }),
    ]);
    /**
     * @ignore
     */
    const GetRecentBlockhash_016 = jsonRpcResult([
      'string',
      struct({
        lamportsPerSignature: 'number',
        maxLamportsPerSignature: 'number',
        minLamportsPerSignature: 'number',
        targetLamportsPerSignature: 'number',
        targetSignaturesPerSlot: 'number',
      }),
    ]);

    /**
     * Expected JSON RPC response for the "requestAirdrop" message
     */
    const RequestAirdropRpcResult = jsonRpcResult('string');

    /**
     * Expected JSON RPC response for the "sendTransaction" message
     */
    const SendTransactionRpcResult = jsonRpcResult('string');

    /**
     * Information describing an account
     *
     * @typedef {Object} AccountInfo
     * @property {number} lamports Number of lamports assigned to the account
     * @property {PublicKey} owner Identifier of the program that owns the account
     * @property {?Buffer} data Optional data assigned to the account
     * @property {boolean} executable `true` if this account's data contains a loaded program
     */
    type AccountInfo = {
      executable: boolean,
      owner: PublicKey,
      lamports: number,
      data: Buffer,
    };

    /**
     * Account information identified by pubkey
     *
     * @typedef {Object} KeyedAccountInfo
     * @property {PublicKey} accountId
     * @property {AccountInfo} accountInfo
     */
    type KeyedAccountInfo = {
      accountId: PublicKey,
      accountInfo: AccountInfo,
    };

    /**
     * Callback function for account change notifications
     */
    export type AccountChangeCallback = (accountInfo: AccountInfo) => void;

    /**
     * @private
     */
    type AccountSubscriptionInfo = {
      publicKey: string, // PublicKey of the account as a base 58 string
      callback: AccountChangeCallback,
      subscriptionId: null | number, // null when there's no current server subscription id
    };

    /**
     * Callback function for program account change notifications
     */
    export type ProgramAccountChangeCallback = (
      keyedAccountInfo: KeyedAccountInfo,
    ) => void;

    /**
     * @private
     */
    type ProgramAccountSubscriptionInfo = {
      programId: string, // PublicKey of the program as a base 58 string
      callback: ProgramAccountChangeCallback,
      subscriptionId: null | number, // null when there's no current server subscription id
    };

    /**
     * Signature status: Success
     *
     * @typedef {Object} SignatureSuccess
     */
    export type SignatureSuccess = {|
      Ok: null,
    |};

    /**
     * Signature status: TransactionError
     *
     * @typedef {Object} TransactionError
     */
    export type TransactionError = {|
      Err: Object,
    |};

    /**
     * @ignore
     */
    type BlockhashAndFeeCalculator = [Blockhash, FeeCalculator]; // This type exists to workaround an esdoc parse error

    /**
     * @ignore
     */
    type PublicKeyAndAccount = [PublicKey, AccountInfo]; // This type exists to workaround an esdoc parse error

    /**
     * A connection to a fullnode JSON RPC endpoint
     */
    export class Connection {
      _rpcRequest: RpcRequest;
      _rpcWebSocket: RpcWebSocketClient;
      _rpcWebSocketConnected: boolean = false;

      _blockhashInfo: {
        recentBlockhash: Blockhash | null,
        seconds: number,
        transactionSignatures: Array<string>,
      };
      _disableBlockhashCaching: boolean = false;
      _accountChangeSubscriptions: {[number]: AccountSubscriptionInfo} = {};
      _accountChangeSubscriptionCounter: number = 0;
      _programAccountChangeSubscriptions: {
        [number]: ProgramAccountSubscriptionInfo,
      } = {};
      _programAccountChangeSubscriptionCounter: number = 0;

      /**
       * Establish a JSON RPC connection
       *
       * @param endpoint URL to the fullnode JSON RPC endpoint
       */
      constructor(endpoint: string) {
        let url = urlParse(endpoint);

        this._rpcRequest = createRpcRequest(url.href);
        this._blockhashInfo = {
          recentBlockhash: null,
          seconds: -1,
          transactionSignatures: [],
        };

        url.protocol = url.protocol === 'https:' ? 'wss:' : 'ws:';
        url.host = '';
        url.port = String(Number(url.port) + 1);
        if (url.port === '1') {
          url.port = url.protocol === 'wss:' ? '8901' : '8900';
        }
        this._rpcWebSocket = new RpcWebSocketClient(urlFormat(url), {
          autoconnect: false,
          max_reconnects: Infinity,
        });
        this._rpcWebSocket.on('open', this._wsOnOpen.bind(this));
        this._rpcWebSocket.on('error', this._wsOnError.bind(this));
        this._rpcWebSocket.on('close', this._wsOnClose.bind(this));
        this._rpcWebSocket.on(
          'accountNotification',
          this._wsOnAccountNotification.bind(this),
        );
        this._rpcWebSocket.on(
          'programNotification',
          this._wsOnProgramAccountNotification.bind(this),
        );
      }

      /**
       * Fetch the balance for the specified public key
       */
      async getBalance(publicKey: PublicKey): Promise<number> {
        const unsafeRes = await this._rpcRequest('getBalance', [
          publicKey.toBase58(),
        ]);
        const res = GetBalanceRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Fetch all the account info for the specified public key
       */
      async getAccountInfo(publicKey: PublicKey): Promise<AccountInfo> {
        const unsafeRes = await this._rpcRequest('getAccountInfo', [
          publicKey.toBase58(),
        ]);
        const res = GetAccountInfoRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }

        const {result} = res;
        assert(typeof result !== 'undefined');

        return {
          executable: result.executable,
          owner: new PublicKey(result.owner),
          lamports: result.lamports,
          data: Buffer.from(result.data),
        };
      }

      /**
       * Fetch all the accounts owned by the specified program id
       */
      async getProgramAccounts(
        programId: PublicKey,
      ): Promise<Array<PublicKeyAndAccount>> {
        const unsafeRes = await this._rpcRequest('getProgramAccounts', [
          programId.toBase58(),
        ]);
        const res = GetProgramAccountsRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }

        const {result} = res;
        assert(typeof result !== 'undefined');

        return result.map(result => {
          return [
            result[0],
            {
              executable: result[1].executable,
              owner: new PublicKey(result[1].owner),
              lamports: result[1].lamports,
              data: Buffer.from(result[1].data),
            },
          ];
        });
      }

      /**
       * Confirm the transaction identified by the specified signature
       */
      async confirmTransaction(signature: TransactionSignature): Promise<boolean> {
        const unsafeRes = await this._rpcRequest('confirmTransaction', [signature]);
        const res = ConfirmTransactionRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Return the list of nodes that are currently participating in the cluster
       */
      async getClusterNodes(): Promise<Array<ContactInfo>> {
        const unsafeRes = await this._rpcRequest('getClusterNodes', []);

        // Legacy v0.15 response.  TODO: Remove in August 2019
        try {
          const res_015 = GetClusterNodes_015(unsafeRes);
          if (res_015.error) {
            console.log('no', res_015.error);
            throw new Error(res_015.error.message);
          }
          return res_015.result.map(node => {
            node.pubkey = node.id;
            node.id = undefined;
            return node;
          });
        } catch (e) {
          // Not legacy format
        }
        // End Legacy v0.15 response

        const res = GetClusterNodes(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Return the list of nodes that are currently participating in the cluster
       */
      async getVoteAccounts(): Promise<VoteAccountStatus> {
        const unsafeRes = await this._rpcRequest('getVoteAccounts', []);
        const res = GetVoteAccounts(unsafeRes);
        //const res = unsafeRes;
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Fetch the current slot that the node is processing
       */
      async getSlot(): Promise<number> {
        const unsafeRes = await this._rpcRequest('getSlot', []);
        const res = GetSlot(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Fetch the current slot leader of the cluster
       */
      async getSlotLeader(): Promise<string> {
        const unsafeRes = await this._rpcRequest('getSlotLeader', []);
        const res = GetSlotLeader(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Fetch the current transaction count of the cluster
       */
      async getSignatureStatus(
        signature: TransactionSignature,
      ): Promise<SignatureSuccess | TransactionError | null> {
        const unsafeRes = await this._rpcRequest('getSignatureStatus', [signature]);
        const res = GetSignatureStatusRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Fetch the current transaction count of the cluster
       */
      async getTransactionCount(): Promise<number> {
        const unsafeRes = await this._rpcRequest('getTransactionCount', []);
        const res = GetTransactionCountRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return Number(res.result);
      }

      /**
       * Fetch the current total currency supply of the cluster in lamports
       */
      async getTotalSupply(): Promise<number> {
        const unsafeRes = await this._rpcRequest('getTotalSupply', []);
        const res = GetTotalSupplyRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return Number(res.result);
      }

      /**
       * Fetch the cluster Inflation parameters (TODO - book link/terminology?)
       */
      async getInflation(): Promise<GetInflationRpcResult> {
        const unsafeRes = await this._rpcRequest('getInflation', []);
        const res = GetInflationRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return GetInflationResult(res.result);
      }

      /**
       * Fetch the minimum balance needed to exempt an account of `dataLength`
       * size from rent
       */
      async getMinimumBalanceForRentExemption(dataLength: number): Promise<number> {
        const unsafeRes = await this._rpcRequest(
          'getMinimumBalanceForRentExemption',
          [dataLength],
        );
        const res = GetMinimumBalanceForRentExemptionRpcResult(unsafeRes);
        if (res.error) {
          console.warn("Unable to fetch minimum balance for rent exemption");
          return 0;
        }
        assert(typeof res.result !== 'undefined');
        return Number(res.result);
      }

      /**
       * Fetch a recent blockhash from the cluster
       */
      async getRecentBlockhash(): Promise<BlockhashAndFeeCalculator> {
        const unsafeRes = await this._rpcRequest('getRecentBlockhash', []);

        // Legacy v0.16 response.  TODO: Remove in September 2019
        try {
          const res_016 = GetRecentBlockhash_016(unsafeRes);
          if (res_016.error) {
            throw new Error(res_016.error.message);
          }
          const [blockhash, feeCalculator] = res_016.result;
          feeCalculator.burnPercent = 0;
          return [blockhash, feeCalculator];
        } catch (e) {
          // Not legacy format
        }
        // End Legacy v0.16 response

        const res = GetRecentBlockhash(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Request an allocation of lamports to the specified account
       */
      async requestAirdrop(
        to: PublicKey,
        amount: number,
      ): Promise<TransactionSignature> {
        const unsafeRes = await this._rpcRequest('requestAirdrop', [
          to.toBase58(),
          amount,
        ]);
        const res = RequestAirdropRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Sign and send a transaction
       */
      async sendTransaction(
        transaction: Transaction,
        ...signers: Array<Account>
      ): Promise<TransactionSignature> {
        for (;;) {
          // Attempt to use a recent blockhash for up to 30 seconds
          const seconds = new Date().getSeconds();
          if (
            this._blockhashInfo.recentBlockhash != null &&
            this._blockhashInfo.seconds < seconds + 30
          ) {
            transaction.recentBlockhash = this._blockhashInfo.recentBlockhash;
            transaction.sign(...signers);
            if (!transaction.signature) {
              throw new Error('!signature'); // should never happen
            }

            // If the signature of this transaction has not been seen before with the
            // current recentBlockhash, all done.
            const signature = transaction.signature.toString();
            if (!this._blockhashInfo.transactionSignatures.includes(signature)) {
              this._blockhashInfo.transactionSignatures.push(signature);
              if (this._disableBlockhashCaching) {
                this._blockhashInfo.seconds = -1;
              }
              break;
            }
          }

          // Fetch a new blockhash
          let attempts = 0;
          const startTime = Date.now();
          for (;;) {
            const [
              recentBlockhash,
              //feeCalculator,
            ] = await this.getRecentBlockhash();

            if (this._blockhashInfo.recentBlockhash != recentBlockhash) {
              this._blockhashInfo = {
                recentBlockhash,
                seconds: new Date().getSeconds(),
                transactionSignatures: [],
              };
              break;
            }
            if (attempts === 50) {
              throw new Error(
                `Unable to obtain a new blockhash after ${Date.now() -
                  startTime}ms`,
              );
            }

            // Sleep for approximately half a slot
            await sleep((500 * DEFAULT_TICKS_PER_SLOT) / NUM_TICKS_PER_SECOND);

            ++attempts;
          }
        }

        const wireTransaction = transaction.serialize();
        return await this.sendRawTransaction(wireTransaction);
      }

      /**
       * @private
       */
      async validatorExit(): Promise<boolean> {
        const unsafeRes = await this._rpcRequest('validatorExit', []);
        const res = jsonRpcResult('boolean')(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        return res.result;
      }

      /**
       * Send a transaction that has already been signed and serialized into the
       * wire format
       */
      async sendRawTransaction(
        rawTransaction: Buffer,
      ): Promise<TransactionSignature> {
        const unsafeRes = await this._rpcRequest('sendTransaction', [
          [...rawTransaction],
        ]);
        const res = SendTransactionRpcResult(unsafeRes);
        if (res.error) {
          throw new Error(res.error.message);
        }
        assert(typeof res.result !== 'undefined');
        assert(res.result);
        return res.result;
      }

      /**
       * @private
       */
      _wsOnOpen() {
        this._rpcWebSocketConnected = true;
        this._updateSubscriptions();
      }

      /**
       * @private
       */
      _wsOnError(err: Error) {
        console.log('ws error:', err.message);
      }

      /**
       * @private
       */
      _wsOnClose(code: number, message: string) {
        // 1000 means _rpcWebSocket.close() was called explicitly
        if (code !== 1000) {
          console.log('ws close:', code, message);
        }
        this._rpcWebSocketConnected = false;
      }

      /**
       * @private
       */
      async _updateSubscriptions() {
        const accountKeys = Object.keys(this._accountChangeSubscriptions).map(
          Number,
        );
        const programKeys = Object.keys(
          this._programAccountChangeSubscriptions,
        ).map(Number);
        if (accountKeys.length === 0 && programKeys.length === 0) {
          this._rpcWebSocket.close();
          return;
        }

        if (!this._rpcWebSocketConnected) {
          for (let id of accountKeys) {
            this._accountChangeSubscriptions[id].subscriptionId = null;
          }
          for (let id of programKeys) {
            this._programAccountChangeSubscriptions[id].subscriptionId = null;
          }
          this._rpcWebSocket.connect();
          return;
        }

        for (let id of accountKeys) {
          const {subscriptionId, publicKey} = this._accountChangeSubscriptions[id];
          if (subscriptionId === null) {
            try {
              this._accountChangeSubscriptions[
                id
              ].subscriptionId = await this._rpcWebSocket.call('accountSubscribe', [
                publicKey,
              ]);
            } catch (err) {
              console.log(
                `accountSubscribe error for ${publicKey}: ${err.message}`,
              );
            }
          }
        }
        for (let id of programKeys) {
          const {
            subscriptionId,
            programId,
          } = this._programAccountChangeSubscriptions[id];
          if (subscriptionId === null) {
            try {
              this._programAccountChangeSubscriptions[
                id
              ].subscriptionId = await this._rpcWebSocket.call('programSubscribe', [
                programId,
              ]);
            } catch (err) {
              console.log(
                `programSubscribe error for ${programId}: ${err.message}`,
              );
            }
          }
        }
      }

      /**
       * @private
       */
      _wsOnAccountNotification(notification: Object) {
        const res = AccountNotificationResult(notification);
        if (res.error) {
          throw new Error(res.error.message);
        }

        const keys = Object.keys(this._accountChangeSubscriptions).map(Number);
        for (let id of keys) {
          const sub = this._accountChangeSubscriptions[id];
          if (sub.subscriptionId === res.subscription) {
            const {result} = res;
            assert(typeof result !== 'undefined');

            sub.callback({
              executable: result.executable,
              owner: new PublicKey(result.owner),
              lamports: result.lamports,
              data: Buffer.from(result.data),
            });
            return true;
          }
        }
      }

      /**
       * Register a callback to be invoked whenever the specified account changes
       *
       * @param publickey Public key of the account to monitor
       * @param callback Function to invoke whenever the account is changed
       * @return subscription id
       */
      onAccountChange(
        publicKey: PublicKey,
        callback: AccountChangeCallback,
      ): number {
        const id = ++this._accountChangeSubscriptionCounter;
        this._accountChangeSubscriptions[id] = {
          publicKey: publicKey.toBase58(),
          callback,
          subscriptionId: null,
        };
        this._updateSubscriptions();
        return id;
      }

      /**
       * Deregister an account notification callback
       *
       * @param id subscription id to deregister
       */
      async removeAccountChangeListener(id: number): Promise<void> {
        if (this._accountChangeSubscriptions[id]) {
          const {subscriptionId} = this._accountChangeSubscriptions[id];
          delete this._accountChangeSubscriptions[id];
          if (subscriptionId !== null) {
            try {
              await this._rpcWebSocket.call('accountUnsubscribe', [subscriptionId]);
            } catch (err) {
              console.log('accountUnsubscribe error:', err.message);
            }
          }
          this._updateSubscriptions();
        } else {
          throw new Error(`Unknown account change id: ${id}`);
        }
      }

      /**
       * @private
       */
      _wsOnProgramAccountNotification(notification: Object) {
        const res = ProgramAccountNotificationResult(notification);
        if (res.error) {
          throw new Error(res.error.message);
        }

        const keys = Object.keys(this._programAccountChangeSubscriptions).map(
          Number,
        );
        for (let id of keys) {
          const sub = this._programAccountChangeSubscriptions[id];
          if (sub.subscriptionId === res.subscription) {
            const {result} = res;
            assert(typeof result !== 'undefined');

            sub.callback({
              accountId: result[0],
              accountInfo: {
                executable: result[1].executable,
                owner: new PublicKey(result[1].owner),
                lamports: result[1].lamports,
                data: Buffer.from(result[1].data),
              },
            });
            return true;
          }
        }
      }

      /**
       * Register a callback to be invoked whenever accounts owned by the
       * specified program change
       *
       * @param programId Public key of the program to monitor
       * @param callback Function to invoke whenever the account is changed
       * @return subscription id
       */
      onProgramAccountChange(
        programId: PublicKey,
        callback: ProgramAccountChangeCallback,
      ): number {
        const id = ++this._programAccountChangeSubscriptionCounter;
        this._programAccountChangeSubscriptions[id] = {
          programId: programId.toBase58(),
          callback,
          subscriptionId: null,
        };
        this._updateSubscriptions();
        return id;
      }

      /**
       * Deregister an account notification callback
       *
       * @param id subscription id to deregister
       */
      async removeProgramAccountChangeListener(id: number): Promise<void> {
        if (this._programAccountChangeSubscriptions[id]) {
          const {subscriptionId} = this._programAccountChangeSubscriptions[id];
          delete this._programAccountChangeSubscriptions[id];
          if (subscriptionId !== null) {
            try {
              await this._rpcWebSocket.call('programUnsubscribe', [subscriptionId]);
            } catch (err) {
              console.log('programUnsubscribe error:', err.message);
            }
          }
          this._updateSubscriptions();
        } else {
          throw new Error(`Unknown account change id: ${id}`);
        }
      }
    }