2 files changed, 67 insertions, 0 deletions
diff --git a/packages/utils/src/calldata_decoder.ts b/packages/utils/src/calldata_decoder.ts
new file mode 100644
index 000000000..780332514
--- /dev/null
+++ b/packages/utils/src/calldata_decoder.ts
@@ -0,0 +1,66 @@
+// Decodes any 0x transaction
+
+import * as ContractArtifacts from '@0x/contract-artifacts';
+import { SimpleContractArtifact } from '@0x/types';
+import { ContractAbi, MethodAbi } from 'ethereum-types';
+import * as _ from 'lodash';
+import { AbiEncoder } from '.';
+
+export interface DecodedCalldata {
+    functionName: string;
+    functionSignature: string;
+    functionArguments: any;
+}
+
+interface AbiEncoderBySelector {
+    [index: string]: AbiEncoder.Method;
+}
+
+export class CalldataDecoder {
+    private readonly _abiEncoderBySelector: AbiEncoderBySelector = {};
+    private static _instance: CalldataDecoder;
+
+    public static getInstance(): CalldataDecoder {
+        if (!CalldataDecoder._instance) {
+            CalldataDecoder._instance = new CalldataDecoder();
+        }
+        return CalldataDecoder._instance;
+    }
+
+    public constructor() {
+        _.each(ContractArtifacts, (contractArtifactAsJson: any) => {
+            const conractArtifact = contractArtifactAsJson as SimpleContractArtifact;
+            const contractAbi: ContractAbi = conractArtifact.compilerOutput.abi;
+            const functionAbis = _.filter(contractAbi, (abiEntry) => {return abiEntry.type === 'function'}) as MethodAbi[];
+            _.each(functionAbis, (functionAbi) => {
+                const abiEncoder = new AbiEncoder.Method(functionAbi);
+                const functionSelector = abiEncoder.getSelector();
+                if (_.has(this._abiEncoderBySelector, functionSelector)) {
+                    return;
+                }
+                this._abiEncoderBySelector[functionSelector] = abiEncoder;
+            });
+        });
+    }
+
+    public static decode(calldata: string, rules?: AbiEncoder.DecodingRules): DecodedCalldata {
+        if (!calldata.startsWith('0x') || calldata.length < 10) {
+            throw new Error(`Malformed calldata. Must include hex prefix '0x' and 4-byte function selector. Got '${calldata}'`);
+        }
+        const functionSelector = calldata.substr(0, 10);
+        const instance = CalldataDecoder.getInstance();
+        const abiEncoder = instance._abiEncoderBySelector[functionSelector];
+        if (_.isUndefined(abiEncoder)) {
+            throw new Error(`Could not find matching abi encoder for selector '${functionSelector}'`);
+        }
+        const functionName = abiEncoder.getDataItem().name;
+        const functionSignature = abiEncoder.getSignatureType();
+        const functionArguments = abiEncoder.decode(calldata, rules);
+        const decodedCalldata = {
+            functionName,
+            functionSignature,
+            functionArguments
+        }
+        return decodedCalldata;
+    }
+}
+\ No newline at end of file
diff --git a/packages/utils/src/index.ts b/packages/utils/src/index.ts
index 082aff6bb..3e5058edc 100644
--- a/packages/utils/src/index.ts
+++ b/packages/utils/src/index.ts
@@ -11,3 +11,4 @@ export { errorUtils } from './error_utils';
 export { fetchAsync } from './fetch_async';
 export { signTypedDataUtils } from './sign_typed_data_utils';
 export import AbiEncoder = require('./abi_encoder');
+export { CalldataDecoder } from './calldata_decoder';