feat: implement local execution of view methods (#1172)

.changeset/bright-nails-glow.md

@@ -0,0 +1,5 @@
+---
+"@near-js/accounts": patch
+---
+
+Implement local execution of contract view methods

packages/accounts/package.json

@@ -27,6 +27,7 @@
     "bn.js": "5.2.1",
     "borsh": "1.0.0",
     "depd": "^2.0.0",
+    "lru_map": "^0.4.1",
     "near-abi": "0.1.1"
   },
   "devDependencies": {

packages/accounts/src/contract.ts

@@ -1,5 +1,6 @@
 import { getTransactionLastResult } from '@near-js/utils';
 import { ArgumentTypeError, PositionalArgsError } from '@near-js/types';
+import { LocalViewExecution } from './local-view-execution';
 import Ajv from 'ajv';
 import addFormats from 'ajv-formats';
 import BN from 'bn.js';
@@ -99,6 +100,11 @@ export interface ContractMethods {
      * ABI defining this contract's interface.
      */
     abi?: AbiRoot;
+
+    /**
+     * Executes view methods locally. This flag is useful when multiple view calls will be made for the same blockId
+     */
+    useLocalViewExecution: boolean;
 }
 
 /**
@@ -138,6 +144,7 @@ export interface ContractMethods {
 export class Contract {
     readonly account: Account;
     readonly contractId: string;
+    readonly lve: LocalViewExecution;
 
     /**
      * @param account NEAR account to sign change method transactions
@@ -147,7 +154,8 @@ export class Contract {
     constructor(account: Account, contractId: string, options: ContractMethods) {
         this.account = account;
         this.contractId = contractId;
-        const { viewMethods = [], changeMethods = [], abi: abiRoot } = options;
+        this.lve = new LocalViewExecution(account);
+        const { viewMethods = [], changeMethods = [], abi: abiRoot, useLocalViewExecution } = options;
 
         let viewMethodsWithAbi = viewMethods.map((name) => ({ name, abi: null as AbiFunction }));
         let changeMethodsWithAbi = changeMethods.map((name) => ({ name, abi: null as AbiFunction }));
@@ -177,6 +185,20 @@ export class Contract {
                         validateArguments(args, abi, ajv, abiRoot);
                     }
 
+                    if (useLocalViewExecution) {
+                        try {
+                            return await this.lve.viewFunction({
+                                contractId: this.contractId,
+                                methodName: name,
+                                args,
+                                ...options,
+                            });
+                        } catch (error) {
+                            console.warn(`Local view execution failed with: "${error.message}"`);
+                            console.warn(`Fallback to normal RPC call`);
+                        }
+                    }
+
                     return this.account.viewFunction({
                         contractId: this.contractId,
                         methodName: name,

packages/accounts/src/local-view-execution/index.ts

@@ -0,0 +1,84 @@
+import { BlockReference, ContractCodeView } from '@near-js/types';
+import { printTxOutcomeLogs } from '@near-js/utils';
+import { Account, FunctionCallOptions } from '../account';
+import { Storage } from './storage';
+import { Runtime } from './runtime';
+import { ContractState } from './types';
+
+interface ViewFunctionCallOptions extends FunctionCallOptions {
+    blockQuery?: BlockReference
+}
+
+export class LocalViewExecution {
+    private readonly account: Account;
+    private readonly storage: Storage;
+
+    constructor(account: Account) {
+        this.account = account;
+        this.storage = new Storage();
+    }
+
+    private async fetchContractCode(contractId: string, blockQuery: BlockReference) {
+        const result = await this.account.connection.provider.query<ContractCodeView>({
+            request_type: 'view_code',
+            account_id: contractId,
+            ...blockQuery,
+        });
+
+        return result.code_base64;
+    }
+
+    private async fetchContractState(blockQuery: BlockReference): Promise<ContractState> {
+        return this.account.viewState('', blockQuery);
+    }
+
+    private async fetch(contractId: string, blockQuery: BlockReference) {
+        const block = await this.account.connection.provider.block(blockQuery);
+        const blockHash = block.header.hash;
+        const blockHeight = block.header.height;
+        const blockTimestamp = block.header.timestamp;
+
+        const contractCode = await this.fetchContractCode(contractId, blockQuery);
+        const contractState = await this.fetchContractState(blockQuery);
+
+        return {
+            blockHash,
+            blockHeight,
+            blockTimestamp,
+            contractCode,
+            contractState,
+        };
+    }
+
+    private async loadOrFetch(contractId: string, blockQuery: BlockReference) {
+        const stored = this.storage.load(blockQuery);
+
+        if (stored) {
+            return stored;
+        }
+
+        const { blockHash, ...fetched } = await this.fetch(contractId, blockQuery);
+
+        this.storage.save(blockHash, fetched);
+
+        return fetched;
+    }
+
+    public async viewFunction({ contractId, methodName, args = {}, blockQuery = { finality: 'optimistic' }, ...ignored }: ViewFunctionCallOptions) {
+        const methodArgs = JSON.stringify(args);
+
+        const { contractCode, contractState, blockHeight, blockTimestamp } = await this.loadOrFetch(
+            contractId,
+            blockQuery
+        );
+        const runtime = new Runtime({ contractId, contractCode, contractState, blockHeight, blockTimestamp, methodArgs });
+
+        const { result, logs } = await runtime.execute(methodName);
+
+        if (logs) {
+            printTxOutcomeLogs({ contractId, logs });
+        }
+
+        return JSON.parse(Buffer.from(result).toString());
+    }
+}