90 lines
2.1 KiB
JavaScript
90 lines
2.1 KiB
JavaScript
|
// @flow
|
||
|
|
// TODO support events, constructors, fallbacks, array slots, types
|
||
|
|
import { sha3, setLengthLeft, toBuffer } from 'ethereumjs-util';
|
||
|
|
import Big from 'bignumber.js';
|
||
|
|
|
||
|
|
type ABIType = 'address' | 'uint256' | 'bool';
|
||
|
|
|
||
|
|
type ABITypedSlot = {
|
||
|
|
name: string,
|
||
|
|
type: ABIType
|
||
|
|
};
|
||
|
|
|
||
|
|
type ABIMethod = {
|
||
|
|
name: string,
|
||
|
|
type: 'function',
|
||
|
|
constant: boolean,
|
||
|
|
inputs: ABITypedSlot[],
|
||
|
|
outputs: ABITypedSlot[],
|
||
|
|
// default - false
|
||
|
|
payable?: boolean
|
||
|
|
};
|
||
|
|
|
||
|
|
export type ABI = ABIMethod[];
|
||
|
|
|
||
|
|
function assertString(arg: any) {
|
||
|
|
if (typeof arg !== 'string') {
|
||
|
|
throw new Error('Expected string');
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Contract helper, returns data for given call
|
||
|
|
export default class Contract {
|
||
|
|
abi: ABI;
|
||
|
|
constructor(abi: ABI) {
|
||
|
|
this.abi = abi;
|
||
|
|
}
|
||
|
|
|
||
|
|
getMethodAbi(name: string): ABIMethod {
|
||
|
|
const method = this.abi.find(x => x.name === name);
|
||
|
|
if (!method) {
|
||
|
|
throw new Error('Unknown method');
|
||
|
|
}
|
||
|
|
if (method.type !== 'function') {
|
||
|
|
throw new Error('Not a function');
|
||
|
|
}
|
||
|
|
return method;
|
||
|
|
}
|
||
|
|
|
||
|
|
call(name: string, args: any[]): string {
|
||
|
|
const method = this.getMethodAbi(name);
|
||
|
|
const selector = sha3(
|
||
|
|
`${name}(${method.inputs.map(i => i.type).join(',')})`
|
||
|
|
);
|
||
|
|
|
||
|
|
// TODO: Add explanation, why slice the first 8?
|
||
|
|
return (
|
||
|
|
'0x' +
|
||
|
|
selector.toString('hex').slice(0, 8) +
|
||
|
|
this.encodeArgs(method, args)
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
encodeArgs(method: ABIMethod, args: any[]): string {
|
||
|
|
if (method.inputs.length !== args.length) {
|
||
|
|
throw new Error('Invalid number of arguments');
|
||
|
|
}
|
||
|
|
|
||
|
|
return method.inputs
|
||
|
|
.map((input, idx) => this.encodeArg(input, args[idx]))
|
||
|
|
.join('');
|
||
|
|
}
|
||
|
|
|
||
|
|
encodeArg(input: ABITypedSlot, arg: any): string {
|
||
|
|
switch (input.type) {
|
||
|
|
case 'address':
|
||
|
|
case 'uint160':
|
||
|
|
assertString(arg);
|
||
|
|
return setLengthLeft(toBuffer(arg), 32).toString('hex');
|
||
|
|
case 'uint256':
|
||
|
|
if (arg instanceof Big) {
|
||
|
|
arg = '0x' + arg.toString(16);
|
||
|
|
}
|
||
|
|
assertString(arg);
|
||
|
|
return setLengthLeft(toBuffer(arg), 32).toString('hex');
|
||
|
|
default:
|
||
|
|
throw new Error(`Dont know how to handle abi type ${input.type}`);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|