Add bsv-20 loan contract.

src/contracts/bsv20Loan.ts

@@ -0,0 +1,123 @@
+import { BSV20V2 } from 'scrypt-ord'
+import {
+    assert,
+    ByteString,
+    hash256,
+    method,
+    prop,
+    PubKey,
+    pubKey2Addr,
+    sha256,
+    Sha256,
+    Sig,
+    SmartContract,
+    toByteString,
+    Utils,
+} from 'scrypt-ts'
+
+export class Bsv20Loan extends BSV20V2 {
+    @prop()
+    lender: PubKey
+
+    @prop()
+    borrower: PubKey
+
+    // Lent BSV-20 token amount.
+    @prop()
+    tokenAmt: bigint
+
+    // Fixed interest rate of the load.
+    // 1 = 1%
+    @prop()
+    interestRate: bigint
+
+    // Collateral satoshis.
+    @prop()
+    collateral: bigint
+
+    // Deadline of the loan.
+    @prop()
+    deadline: bigint
+
+    // Flag that indicates wether the
+    // loan was already taken.
+    @prop(true)
+    taken: boolean
+
+    constructor(
+        id: ByteString,
+        sym: ByteString,
+        max: bigint,
+        dec: bigint,
+        lender: PubKey,
+        borrower: PubKey,
+        tokenAmt: bigint,
+        interestRate: bigint,
+        collateral: bigint,
+        deadline: bigint
+    ) {
+        super(id, sym, max, dec)
+        this.init(...arguments)
+
+        this.lender = lender
+        this.borrower = borrower
+        this.tokenAmt = tokenAmt
+        this.interestRate = interestRate
+        this.collateral = collateral
+        this.deadline = deadline
+        this.taken = false
+    }
+
+    @method()
+    public takeLoan() {
+        // Check loan isn't taken yet.
+        assert(this.taken == false, 'loan already taken')
+        this.taken = true
+
+        // Pay borrower the principal, i.e. token amount locked in the contract.
+        let outputs = BSV20V2.buildTransferOutput(
+            pubKey2Addr(this.borrower),
+            this.id,
+            this.tokenAmt
+        )
+
+        // Make sure borrower deposited collateral and propagate contract.
+        outputs += this.buildStateOutput(this.collateral)
+        outputs += this.buildChangeOutput()
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
+    }
+
+    @method()
+    public repay() {
+        // Check loan is already taken.
+        assert(this.taken == true, 'loan not taken yet')
+
+        // Pay lender back the principal token amount plus interest.
+        const interest = (this.tokenAmt * this.interestRate) / 100n
+        let outputs = BSV20V2.buildTransferOutput(
+            pubKey2Addr(this.lender),
+            this.id,
+            this.tokenAmt + interest
+        )
+
+        // Pay back borrowers collateral.
+        outputs += Utils.buildAddressOutput(
+            pubKey2Addr(this.borrower),
+            this.collateral
+        )
+
+        outputs += this.buildChangeOutput()
+
+        // Enforce outputs.
+        assert(hash256(outputs) == this.ctx.hashOutputs, 'hashOutputs mismatch')
+    }
+
+    @method()
+    public foreclose(sigLender: Sig) {
+        // Check lender sig.
+        assert(this.checkSig(sigLender, this.lender), 'invalid sig lender')
+
+        // Check if deadline reached.
+        assert(this.timeLock(this.deadline), 'deadline not yet reached')
+    }
+}