95 lines
2.5 KiB
TypeScript
95 lines
2.5 KiB
TypeScript
// TODO support events, constructors, fallbacks, array slots, types
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import abi from 'ethereumjs-abi';
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import BN from 'bn.js';
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// There are too many to enumerate since they're somewhat dynamic, list here
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// https://github.com/ethereum/wiki/wiki/Ethereum-Contract-ABI#types
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type ABIType = string;
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interface ABITypedSlot {
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name: string;
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type: ABIType;
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}
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interface ABIMethod {
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name: string;
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type: string;
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constant?: boolean;
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inputs: ABITypedSlot[];
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outputs?: ABITypedSlot[];
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// default - false
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payable?: boolean;
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}
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export type ABI = ABIMethod[];
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export interface DecodedCall {
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method: ABIMethod;
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args: BN[];
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}
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// Contract helper, returns data for given call
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export default class Contract {
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public abi: ABI;
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constructor(ethJsAbi: ABI) {
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// TODO: Check ABI, throw if it's malformed
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this.abi = ethJsAbi;
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}
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public getMethodAbi(name: string): ABIMethod {
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const method = this.abi.find(x => x.name === name);
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if (!method) {
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throw new Error('Unknown method');
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}
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if (method.type !== 'function') {
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throw new Error('Not a function');
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}
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return method;
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}
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public getMethodTypes(method: ABIMethod): string[] {
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return method.inputs.map(i => i.type);
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}
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public getMethodSelector(method: ABIMethod): string {
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return abi.methodID(method.name, this.getMethodTypes(method)).toString('hex');
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}
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public call(name: string, args: any[]): string {
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const method = this.getMethodAbi(name);
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return '0x' + this.getMethodSelector(method) + this.encodeArgs(method, args);
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}
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public $call(data: string): DecodedCall {
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const method = this.abi.find(mth => data.indexOf(this.getMethodSelector(mth)) !== -1);
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if (!method) {
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throw new Error('Unknown method');
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}
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return {
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method,
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args: this.decodeArgs(method, data)
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};
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}
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public encodeArgs(method: ABIMethod, args: any[]): string {
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if (method.inputs.length !== args.length) {
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throw new Error('Invalid number of arguments');
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}
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const inputTypes = method.inputs.map(input => input.type);
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return abi.rawEncode(inputTypes, args).toString('hex');
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}
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public decodeArgs(method: ABIMethod, argData: string): BN[] {
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// Remove method selector from data, if present
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argData = argData.replace(`0x${this.getMethodSelector(method)}`, '');
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// Convert argdata to a hex buffer for ethereumjs-abi
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const argBuffer = new Buffer(argData, 'hex');
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// Decode!
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return abi.rawDecode(this.getMethodTypes(method), argBuffer);
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}
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}
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