Implement custom ABI decoder

1 files changed, 66 insertions, 0 deletions

diff --git a/src/utils/abi_decoder.ts b/src/utils/abi_decoder.ts
new file mode 100644
index 000000000..0600f86f2
--- /dev/null
+++ b/src/utils/abi_decoder.ts
@@ -0,0 +1,66 @@
+import * as Web3 from 'web3';
+import * as _ from 'lodash';
+import {AbiType, DecodedLogArgs, DecodedArgs} from '../types';
+import * as SolidityCoder from 'web3/lib/solidity/coder.js';
+
+export class AbiDecoder {
+    private savedABIs: Web3.AbiDefinition[] = [];
+    private methodIDs: {[signatureHash: string]: Web3.EventAbi} = {};
+    constructor(abiArrays: Web3.AbiDefinition[][]) {
+        _.map(abiArrays, this.addABI.bind(this));
+    }
+    public decodeLog(logItem: Web3.LogEntry): DecodedArgs|undefined {
+        const methodID = logItem.topics[0];
+        const event = this.methodIDs[methodID];
+        if (!_.isUndefined(event)) {
+            const logData = logItem.data;
+            const decodedParams: DecodedLogArgs = {};
+            let dataIndex = 0;
+            let topicsIndex = 1;
+
+            const nonIndexedInputs = _.filter(event.inputs, input => !input.indexed);
+            const dataTypes = _.map(nonIndexedInputs, input => input.type);
+            const decodedData = SolidityCoder.decodeParams(dataTypes, logData.slice(2));
+            _.map(event.inputs, (param: Web3.EventParameter) => {
+                let value;
+                if (param.indexed) {
+                    value = logItem.topics[topicsIndex];
+                    topicsIndex++;
+                } else {
+                    value = decodedData[dataIndex];
+                    dataIndex++;
+                }
+                if (param.type === 'address') {
+                    value = this.padZeros(new Web3().toBigNumber(value).toString(16));
+                } else if (param.type === 'uint256' || param.type === 'uint8' || param.type === 'int' ) {
+                    value = new Web3().toBigNumber(value).toString(10);
+                }
+                decodedParams[param.name] = value;
+            });
+
+            return {
+                event: event.name,
+                args: decodedParams,
+            };
+        }
+    }
+    private addABI(abiArray: Web3.AbiDefinition[]): void {
+        _.map(abiArray, (abi: Web3.AbiDefinition) => {
+            if (abi.type === AbiType.Event) {
+                const signature = `${abi.name}(${_.map(abi.inputs, input => input.type).join(',')})`;
+                const signatureHash = new Web3().sha3(signature);
+                this.methodIDs[signatureHash] = abi;
+            }
+        });
+        this.savedABIs = this.savedABIs.concat(abiArray);
+    }
+    private padZeros(address: string) {
+      let formatted = address;
+      if (formatted.indexOf('0x') !== -1) {
+        formatted = formatted.slice(2);
+      }
+
+      formatted = _.padStart(formatted, 40, '0');
+      return '0x' + formatted;
+    }
+}