@indigo-labs/indigo-sdk/src/contracts/interest-oracle.ts

Indigo SDK for interacting with Indigo endpoints via lucid-evolution

import { Constr, Data } from "@lucid-evolution/lucid";
import { InterestOracleDatum } from "../types/indigo/interest-oracle";
import { oneYear } from "../helpers/time-helpers";

const unitaryInterestPrecision = 1_000_000_000_000_000_000n;
const decimalUnit = 1_000_000n;

export class InterestOracleContract {
    static decodeInterestOracleDatum(datum: string): InterestOracleDatum {
        const oracleDatum = Data.from(datum) as any;
        if (oracleDatum.index != 0 || oracleDatum.fields.length !== 3 || oracleDatum.fields[1].index !== 0)
            throw 'Invalid Interest Oracle Datum provided.'
        
        return {
            unitaryInterest: oracleDatum.fields[0],
            interestRate: oracleDatum.fields[1].fields[0],
            lastUpdated: oracleDatum.fields[2],
        }
    }
    
    static encodeInterestOracleDatum(datum: InterestOracleDatum): string {
        return Data.to(
            new Constr(0, [
                datum.unitaryInterest,
                new Constr(0, [datum.interestRate]),
                datum.lastUpdated,
            ])
        )
    }

    static calculateUnitaryInterestSinceOracleLastUpdated(now: bigint, oracleDatum: InterestOracleDatum): bigint {
        return InterestOracleContract.calculateUnitaryInterest(now - oracleDatum.lastUpdated, oracleDatum.interestRate);
    }

    static calculateUnitaryInterest(timePeriod: bigint, interestRate: bigint): bigint {
        return ((timePeriod * interestRate * unitaryInterestPrecision) / oneYear) / decimalUnit;
    }

    static calculateAccruedInterest(now: bigint, unitaryInterestSnapshot: bigint, mintedAmount: bigint, interestLastSettled: bigint, interestOracleDatum: InterestOracleDatum): bigint {
        if (interestOracleDatum.unitaryInterest >= unitaryInterestSnapshot) {
            const interestFromPreviousRates = ((interestOracleDatum.unitaryInterest - unitaryInterestSnapshot) * mintedAmount) / unitaryInterestPrecision;
            const lastRateInterest = (((now - interestOracleDatum.lastUpdated) * interestOracleDatum.interestRate * mintedAmount) / oneYear) / decimalUnit;

            return interestFromPreviousRates + lastRateInterest;
        } else {
            return (((now - interestLastSettled) * interestOracleDatum.interestRate * mintedAmount) / oneYear) / decimalUnit;
        }
    }
}