@gear-js/api

---

Description

The Gear-JS API provides a set of utilities, libraries and tools that enable JavaScript applications to interact with smart contracts running in the Gear-based networks via queries to a Gear node.

Installation

npm install @gear-js/api

or

yarn add @gear-js/api

---

Getting started

Start an API connection to a running node on localhost:

import { GearApi } from '@gear-js/api';

const gearApi = await GearApi.create();

You can also connect to a different node:

const gearApi = await GearApi.create({ providerAddress: 'wss://someIP:somePort' });

Getting node info:

const chain = await gearApi.chain();
const nodeName = await gearApi.nodeName();
const nodeVersion = await gearApi.nodeVersion();
const genesis = gearApi.genesisHash.toHex();

Since different networks can have different runtime versions, they can have different extrinsics / rpc calls signatures. In general you may use GearApi class to interact with the node, but it can be more convivnient to use classes based on a specific runtime version. For example for interacting with the network that has runtime version more than 1010 you can use the VaraApiV1010 class.

Payloads and metadata

Encode / decode payloads

It's necessary to send only bytes to interact with programs on blockchain. For that purpose we use the scale-codec implementation from @polkadot-js

You can use static CreateType.create method to encode and decode data with standart types

import { CreateType } from '@gear-js/api';

const result = CreateType.create('TypeName', somePayload);

The result of these functions is the data of type Codec and it has the following methods:

result.toHex(); // - returns a hex represetation of the value
result.toHuman(); // - returns human friendly object representation of the value
result.toString(); //  - returns a string represetation of the value
result.toU8a(); // - encodes the value as a Unit8Array
result.toJSON(); // - converts the value to JSON

Getting metadata

There're 2 types of metadata.

1. ProgramMetadata is used to encode/decode messages to/from a program as well as to read the whole state of the program

You can use ProgramMetadata.from method to create the program metadata. The method takes metadata of the program in format of hex string. It will return object of ProgramMetadata class that has property types that contains all types of the program.

You should pass an object of this class to function arguments when you want to send some extrinsics that require encoding payloads

import { ProgramMetadata } from '@gear-js/api';

const meta = ProgramMetadata.from(`0x...`);
meta.types.init.input; // can be used to encode input message for init entrypoint of the program
meta.types.init.output; // can be used to decode output message for init entrypoint of the program
// the same thing available for all entrypoints of the program

meta.types.state; // contains type for decoding state output

2. StateMetadata is used to encode input/decode output payloads that is needed to read state using a specific wasm.

You can use getStateMetadata function to create program metadata. The function takes wasm as Buffer to read state. It will return object of StateMetadata class that has property functions that contains available function of wasm and input/output types

import { getStateMetadata } from '@gear-js/api';

const fileBuffer = fs.readFileSync('path/to/state.meta.wasm');
const meta = await getStateMetadata(fileBuffer);
meta.functions; // is an object whose keys are names of funtions and values are objects of input/output types

Both ProgramMetadata and StateMetadata classes have a few methods that can help to understand what some type is or get the name of some type (because types are represented as number in regestry) as well as encode and decode data.

import { ProgramMetadata } from '@gear-js/api';

const meta = ProgramMetadata.from(`0x...`);

meta.getTypeName(4); // will return name of type with this index
// or
meta.getTypeName(meta.types.handle.input);

meta.getTypeDef(4); // will return structure of this type
meta.getTypeDef(4, true); // if you need to get type structre with additional field (name, type, kind, len) you have to pass the second argument

meta.getAllTypes(); // will return all custom types existed in the registry of the program

meta.createType(4, { value: 'value' }); // to encode or decode data

---

Gear extrinsics

Extrinsics are used to interact with programs running on blockchain networks powered by Gear Protocol

In all cases of sending extrinsics, there is no need to encode the payloads by yourself. It's sufficient to pass the program metadata obtained from the ProgramMetadata.from method to the methods that creates extrinsics.

Upload program

Use api.program.upload method to create upload_program extrinsic

const code = fs.readFileSync('path/to/program.wasm');

const program = {
  code,
  gasLimit: 1000000,
  value: 1000,
  initPayload: somePayload,
};

const { programId, codeId, salt, extrinsic } = gearApi.program.upload(program, meta);

await extrinsic.signAndSend(keyring, (event) => {
  console.log(event.toHuman());
});

Upload code

Use api.code.upload method to create upload_code extrinsic

const code = fs.readFileSync('path/to/program.opt.wasm');

const { codeHash } = await gearApi.code.upload(code);

gearApi.code.signAndSend(alice, () => {
  events.forEach(({ event: { method, data } }) => {
    if (method === 'ExtrinsicFailed') {
      throw new Error(data.toString());
    } else if (method === 'CodeChanged') {
      console.log(data.toHuman());
    }
  });
});

Create program from the code uploaded on chain

Use api.program.create method to create create_program extrinsic

const codeId = '0x...';

const program = {
  codeId,
  gasLimit: 1000000,
  value: 1000,
  initPayload: somePayload,
};

const { programId, salt, extrinsic } = gearApi.program.create(program, meta);

await extrinsic.signAndSend(keyring, (event) => {
  console.log(event.toHuman());
});

Send a message

Use api.message.send method to create send_message extrinsic

try {
  const message = {
    destination: destination, // programId
    payload: somePayload,
    gasLimit: 10000000,
    value: 1000,
    keepAlive: true, // if set to true the account is protected against removal due to low balances.
  };
  // In that case payload will be encoded using meta.handle_input type
  let extrinsic = await gearApi.message.send(message, meta);
  // So if you want to use another type you can specify it
  extrinsic = await gearApi.message.send(message, meta, meta.async_handle_input);
} catch (error) {
  console.error(`${error.name}: ${error.message}`);
}
try {
  await extrinsic.signAndSend(keyring, (event) => {
    console.log(events.toHuman());
  });
} catch (error) {
  console.error(`${error.name}: ${error.message}`);
}

Send a reply message

Use api.message.reply method to create send_reply extrinsic

const reply = {
  replyToId: messageId,
  payload: somePayload,
  gasLimit: 10000000,
  value: 1000,
  keepAlive: true,
};
const extrinsic = await gearApi.message.sendReply(reply, meta);
await extrinsic(keyring, (events) => {
  console.log(events.toHuman());
});

Get a transaction fee

To get a transaction fee before sending a transaction you can use paymentInfo method.

const api = await GearApi.create();
api.program.upload({ code, gasLimit });
// same for api.message, api.reply and others
const paymentInfo = await api.program.paymentInfo(alice);
const transactionFee = paymentInfo.partialFee.toNumber();
consolg.log(transactionFee);

Calculate gas for messages

To find out the minimum gas amount to send extrinsic, use gearApi.program.calculateGas.[method]. There are 4 methods to use:

• init - to calculate the gas of init message that will be applied to upload_program extrinsic
• initCreate - to calculate the gas of init message that will be applied to create_program extrinsic
• handle - to calculate the gas of handle message that will be applied to send_message extrinsic
• reply - to calculate the gas of reply message that will be applied to send_reply extrinsic

Gas calculation returns GasInfo object contains 5 parameters:

• min_limit - Minimum gas limit required for execution
• reserved - Gas amount that will be reserved for some other on-chain interactions
• burned - Number of gas burned during message processing
• may_be_returned - value that can be returned in some cases
• waited - notifies that the message will be added to waitlist

Example of using calculateGas.handle method

const code = fs.readFileSync('demo_meta.opt.wasm');
const meta = ProgramMetadata.from('0x...');
const gas = await gearApi.program.calculateGas.handle(
  '0x...', // source id
  '0x...', //program id
  {
    id: {
      decimal: 64,
      hex: '0x...',
    },
  }, // payload
  0, // value
  false, // allow other panics
  meta, // the metadata of the program
);
console.log(gas.toHuman());

---

Resume paused program

To resume paused program use api.program.resumeSession methods. init - To start new session to resume program push - To push a bunch of the program pages commit - To finish resume session

const program = await api.programStorage.getProgram(programId, oneBlockBeforePauseHash);
const initTx = api.program.resumeSession.init({
  programId,
  allocations: program.allocations,
  codeHash: program.codeHash.toHex(),
});

let sessionId: HexString;
initTx.signAndSend(account, ({ events }) => {
  events.forEach(({ event: { method, data }}) => {
    if (method === 'ProgramResumeSessionStarted') {
      sessionId = data.sessionId.toNumber();
    }
  })
})

const pages = await api.programStorage.getProgramPages(programId, program, oneBlockBeforePauseHash);
for (const memPage of Object.entries(page)) {
  const tx = api.program.resumeSession.push({ sessionId, memoryPages: [memPage] });
  tx.signAndSend(account);
}

const tx = api.program.resumeSession.commit({ sessionId, blockCount: 20_000 });
tx.signAndSend(account);

Issue a voucher

Use api.voucher.issue method to issue a new voucher for a user to be used to pay for sending messages to programs.

import { VoucherIssued } from '@gear-js/api';

const programs = ['0x1234...', '0x5678...'];
const spenderAddress = '0x...';
const validForOneHour = (60 * 60) / 3; // number of blocks in one hour

const { extrinsic } = await api.voucher.issue(spenderAddress, 100 * 10 ** 12, validForOneHour, programs, true);

// To allow the voucher to be used for code uploading, set the last argument of the `.issue` method to true

extrinsic.signAndSend(account, ({ events }) => {
  const voucherIssuedEvent = events.find(({event: { method }}) => method === 'VoucherIssued')?.event as VoucherIssued;

  if (voucherIssuedEvent) {
    console.log(voucherIssuedEvent.toJSON());
  }
})

Check that the voucher exists for a particular user and program

The api.voucher.exists method returns a boolean value indicates whether the voucher exists or not.

const voucherExists = await api.voucher.exists(accountId, programId)

Get all voucher for an account

The api.voucher.getAllForAccount method returns an object whose key is the voucher id and value is an array of programs for which the voucher can be used.

const allVouchers = await api.voucher.getAllForAccount(accountId);

Get voucher details

const details = api.voucher.details(spenderAddress, voucherId);
console.log(`Voucher details:
  owner: ${details.owner}
  programs: ${details.programs}
  expiry: ${details.expiry}`);

Send a message with the issued voucher

To send message with voucher you can use api.voucher.call method.

const messageTx = api.message.send({
  destination: destination,
  payload: somePayload,
  gasLimit: 10000000,
  value: 1000
}, meta);

const voucherTx = api.voucher.call(voucherId, { SendMessage: messageTx });
await voucherTx.signAndSend(account, (events) => {
  console.log(events.toHuman());
});

Send a reply with issued voucher

It works in the same way as sending message with voucher

const messageTx = api.message.sendReply(...);

const voucherTx = api.voucher.call(voucherId, { SendReply: messageTx });
await voucherTx.signAndSend(account, (events) => {
  console.log(events.toHuman());
});

Upload code with issued voucher

const { extrinsic } = await api.code.upload(code);

const tx = api.voucher.call(voucherId, { UploadCode: extrinsic })
await tx.signAndSend(account, (events) => {
  console.log(events.toHuman());
});

Update voucher

The api.voucher.update can be used to update the voucher. All parameters in the 3rd argument are optional, but at least one parameter must be specified.

const tx = await api.voucher.update(
  spenderAddress, 
  voucherId,
  {
    moveOwnership: newOwnerAddress, // The new voucher owner
    balanceTopUp: 1_000 * 10 ** 12, // Top up voucher balance
    appendPrograms: ['0x9123...', '0x4567...'], // Append programs for which the voucher can be used
    prolongValidity: 1_000_000 // Prolong the voucher validity for 1_000_000 blocks
  }
)

Revoke voucher

The api.voucher.revoke is used to revoke an issued voucher. It's possible to revoke a voucher only after the validity period has expired.

const tx = api.voucher.revoke(spenderAddress, voucherId);
tx.signAndSend(...);

Decline voucher

The api.voucher.decline can be used to decline existing and not expired voucher. It will make the voucher expired

const tx = api.voucher.decline(voucherId);
tx.signAndSend(...);

Work with programs and blockchain state

Check that the address belongs to some program

To find out if an address belongs to a program use the api.program.exists method.

const programId = '0x...';
const programExists = await api.program.exists(programId);

console.log(`Program with address ${programId} ${programExists ? 'exists' : "doesn't exist"}`);

Send message to the program and get the reply

Since v1.2.0 release of the gear pallet, it's possible to send a message to the program and get the reply without transaction. The api.message.calculateReply method can be used for that purpose.

const programId = '0x..';
const origin = '0x...'; // the address of the sender
const meta = ProgramMetadata.from('0x...');
const result = await api.message.calculateReply({
  origin,
  destination: programId,
  payload: { myPayload: [] },
  value: 0
}, meta);

console.log(result.toJSON());
console.log('reply payload:', meta.createType(meta.types.handle.output, result.payload).toJSON());

Read state of a program

There are 2 ways to read state of a program.

1. Read full state of a program. To read full state of the program you need to provide metadata of this program and input payload expected by the program. You can call api.programState.read method to get the state.

   await api.programState.read({ programId: `0x...`, payload: [1, 2, 3] }, programMetadata);
   
   // Also you can read the state of the program at some specific block.
   await api.programState.read({ programId: `0x...`, payload: [1, 2, 3], at: `0x...` }, programMetadata);

2. Read state using wasm. If you have some program that is able to read state and return you only necessary data you need to use api.programState.readUsingWasm method. Note that since state function of gear programs expects input payload you need to provide it in the parameters of readUsingWasm method

   const wasm = readFileSync('path/to/state.meta.wasm');
   const stateMetadata = await getStateMetadata(wasm);
   const programMetadata = ProgramMetadata.from('0x...');
   const state = await api.programState.readUsingWasm(
     { programId, fn_name: 'name_of_function_to_execute', wasm, payload: [1, 2, 3], argument: { input: 'payload' } },
     stateMetadata,
     programMetadata
   );

Get ids of all uploaded codes

To get all ids of uploaded codes use api.code.all method. It returns array of code ids

const codeIds = await gearApi.code.all();
console.log(codeIds);

Mailbox

The mailbox contains messages that are waiting for user action.

Read

To read the mailbox use api.mailbox.read method.

const api = await GearApi.create();
const mailbox = await api.mailbox.read('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY');
console.log(mailbox);

Claim value

To claim value from a message in the mailbox use api.mailbox.claimValue.submit method.

const api = await GearApi.create();
const submitted = await api.mailbox.claimValue.submit(messageId);
await api.mailbox.claimValue.signAndSend(...);

Waitlist

To read the program's waitlist use api.waitlist.read method.

const gearApi = await GearApi.create();
const programId = '0x1234...';
const waitlist = await api.waitlist.read(programId);
console.log(waitlist);

---

Events

Subscribe to all events

const unsub = await gearApi.query.system.events((events) => {
  console.log(events.toHuman());
});
// Unsubscribe
unsub();

Check what the event is

gearApi.query.system.events((events) => {
  events
    .filter(({ event }) => gearApi.events.gear.MessageEnqueued.is(event))
    .forEach(({ event: { data } }) => {
      console.log(data.toHuman());
    });

  events
    .filter(({ event }) => gearApi.events.balances.Transfer.is(event))
    .forEach(({ event: { data } }) => {
      console.log(data.toHuman());
    });
});

Subscribe to specific gear events

There is an oportunity to subscribe to a specific event of the Gear pallet without filtering events manually.

const unsub = api.gearEvents.subscribeToGearEvent(
  'UserMessageSent', // pass here name of event you're interested in
  ({
    data: {
      message: { id, source, destination, payload, value, reply },
    },
  }) => {
    console.log(`
  messageId: ${id.toHex()}
  source: ${source.toHex()}
  payload: ${payload.toHuman()}
  `);
  },
);
// Unsubscribe
unsub();

---

Blocks

Get block data

const data = await gearApi.blocks.get(blockNumberOrBlockHash);
console.log(data.toHuman());

Get block timestamp

const ts = await gearApi.blocks.getBlockTimestamp(blockNumberOrBlockHash);
console.log(ts.toNumber());

Get blockHash by block number

const hash = await gearApi.blocks.getBlockHash(blockNumber);
console.log(hash.toHex());

Get block number by blockhash

const hash = await gearApi.blocks.getBlockNumber(blockHash);
console.log(hash.toNumber());

Get all block's events

const events = await gearApi.blocks.getEvents(blockHash);
events.forEach((event) => {
  console.log(event.toHuman());
});

Get all block's extrinsics

const extrinsics = await gearApi.blocks.getExtrinsics(blockHash);
extrinsics.forEach((extrinsic) => {
  console.log(extrinsic.toHuman());
});

---

Keyring

Create keyring

To create keyring you can use static methods of GearKeyring class.

Example

• Creating a new keyring

import { GearKeyring } from '@gear-js/api';
const { keyring, json } = await GearKeyring.create('keyringName', 'passphrase');

• Getting a keyring from JSON

const jsonKeyring = fs.readFileSync('path/to/keyring.json').toString();
const keyring = GearKeyring.fromJson(jsonKeyring, 'passphrase');

• Getting JSON for keyring

const json = GearKeyring.toJson(keyring, 'passphrase');

• Getting a keyring from seed

const seed = '0x496f9222372eca011351630ad276c7d44768a593cecea73685299e06acef8c0a';
const keyring = await GearKeyring.fromSeed(seed, 'name');

• Getting a keyring from mnemonic

const mnemonic = 'slim potato consider exchange shiver bitter drop carpet helmet unfair cotton eagle';
const keyring = GearKeyring.fromMnemonic(mnemonic, 'name');

• Generate mnemonic and seed

const { mnemonic, seed } = GearKeyring.generateMnemonic();

// Getting a seed from mnemonic
const { seed } = GearKeyring.generateSeed(mnemonic);

Sign data

Example

1. Create signature

import { GearKeyring } from '@gear-js/api';
const message = 'your message';
const signature = GearKeyring.sign(keyring, message);

2. Validate signature

import { signatureIsValid } from '@gear-js/api';
const publicKey = keyring.address;
const verified = signatureIsValid(publicKey, signature, message);

Convert public keys into ss58 format and back

Use encodeAddress and decodeAddress functions to convert the public key into ss58 format and back.

Example

1. Convert to raw format

import { decodeAddress } from '@gear-js/api';
console.log(decodeAddress('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY'));

2. Convert to ss58 format

import { encodeAddress } from '@gear-js/api';
console.log(encodeAddress('0xd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d'));