Allow to decode contract call without function name (#297)

* Improve `AciContractCallEncoder:decodeCall` return type

* Decode function details by contract calldata

Author: davidyuk

src/AciContractCallEncoder.js

@@ -72,20 +72,43 @@ class AciContractCallEncoder {
      * const data = encoder.decodeCall('Test', 'test_string', 'cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==')
      * console.log(`Decoded data: ${data}`)
      * // Outputs:
-     * // Decoded data: ["whoolymoly"]
+     * // Decoded data: { functionId: "f0cc2b95", args: ["whoolymoly"] }
      *
      * @param {string} contract - The contract name as defined in the ACI.
      * @param {string} funName - The function name as defined in the ACI.
      * @param {string} data - Encoded calldata in canonical format.
      * @returns {string} Decoded data
     */
     decodeCall(contract, funName, data) {
-        const {types, _required} = this._typeResolver.getCallTypes(contract, funName)
+        const {types} = this._typeResolver.getCallTypes(contract, funName)
         const calldataType = FateTypeCalldata(funName, types)
 
         return this._byteArrayEncoder.decodeWithType(data, calldataType)
     }
 
+    /**
+     * Decodes function details by contract calldata
+     *
+     * @example
+     * const data = encoder.decodeFunction('cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==')
+     * console.log(`Decoded data: ${data}`)
+     * // Outputs:
+     * // Decoded data: {
+     * //   contractName: "Test",
+     * //   functionName: "test_string",
+     * //   functionId: "f0cc2b95",
+     * // }
+     *
+     * @param {string} data - Encoded calldata in canonical format.
+     * @returns {object} Decoded function details
+    */
+    decodeFunction(data) {
+        const {functionId} = this._byteArrayEncoder.decodeWithType(data, FateTypeCalldata())
+        const {contractName, functionName} = this._typeResolver.getFunction(functionId)
+
+        return {contractName, functionName, functionId}
+    }
+
     /**
      * Decodes successful (resultType = ok) contract call return data
      *

src/AciTypeResolver.js

@@ -1,6 +1,8 @@
 import TypeResolver from './TypeResolver.js'
 import TypeResolveError from './Errors/TypeResolveError.js'
 import {FateTypeEvent} from './FateTypes.js'
+import {symbolIdentifier} from './utils/hash.js'
+import {byteArray2Hex} from './utils/int2ByteArray.js'
 
 const isObject = (value) => {
     return value && typeof value === 'object' && value.constructor === Object
@@ -140,6 +142,18 @@ class AciTypeResolver extends TypeResolver {
 
         return [typeDef, vars]
     }
+
+    getFunction(functionId) {
+        const { contract } = this.aci.at(-1)
+        const functionName = contract.functions
+            .map(e => e.name)
+            .find((name) => byteArray2Hex(symbolIdentifier(name)) === functionId)
+        if (functionName == null) {
+            throw new TypeResolveError(`Unknown function id ${functionId}`)
+        }
+
+        return { contractName: contract.name, functionName }
+    }
 }
 
 export default AciTypeResolver

src/api/AciContractCallEncoder.js

@@ -39,7 +39,7 @@ class AciContractCallEncoder {
      * const data = encoder.decodeCall('Test', 'test_string', 'cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==')
      * console.log(`Decoded data: ${data}`)
      * // Outputs:
-     * // Decoded data: ["whoolymoly"]
+     * // Decoded data: { functionId: "f0cc2b95", args: ["whoolymoly"] }
      *
      * @param {string} contract - The contract name as defined in the ACI.
      * @param {string} funName - The function name as defined in the ACI.
@@ -50,6 +50,26 @@ class AciContractCallEncoder {
         return this._internalEncoder.decodeCall(contract, funName, data)
     }
 
+    /**
+     * * Decodes function details by contract calldata
+     *
+     * @example
+     * const data = encoder.decodeFunction('cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==')
+     * console.log(`Decoded data: ${data}`)
+     * // Outputs:
+     * // Decoded data: {
+     * //   contractName: "Test",
+     * //   functionName: "test_string",
+     * //   functionId: "f0cc2b95",
+     * // }
+     *
+     * @param {string} data - Encoded calldata in canonical format.
+     * @returns {object} Decoded function details
+    */
+    decodeFunction(data) {
+        return this._internalEncoder.decodeFunction(data)
+    }
+
     /**
      * Decodes successful (resultType = ok) contract call return data
      *

src/main.d.ts

@@ -26,7 +26,16 @@ export class AciContractCallEncoder {
 
   encodeCall(contract: string, funName: string, args: any[]): `cb_${string}`;
 
-  decodeCall(contract: string, funName: string, data: `cb_${string}`): any;
+  decodeCall(contract: string, funName: string, data: `cb_${string}`): {
+    functionId: string;
+    args: any[];
+  };
+
+  decodeFunction(data: `cb_${string}`): {
+    contractName: string;
+    functionName: string;
+    functionId: string;
+  };
 
   decodeResult(
     contract: string,

tests/AciContractCallEncoder.js

@@ -82,6 +82,22 @@ test('Decode calldata', t => {
     )
 })
 
+test('Decode calldata without function name', t => {
+    t.plan(1)
+    const decoded = encoder.decodeFunction(
+        'cb_KxGu5Sw8G6+CAAQBSzsrAgQGCK+EAAABAAIbFCg7KwIEBgj8xaf6',
+    )
+
+    t.deepEqual(
+        decoded,
+        {
+            contractName: CONTRACT,
+            functionName: 'test_template_maze',
+            functionId: 'aee52c3c',
+        }
+    )
+})
+
 test('Decode implicit init (void) result', t => {
     t.plan(1)
     t.is(