Add multi-mint swap to CLI and API (#212)

* Add multi-mint swap to CLI and API

* Add confirmation prompt to CLI

* Replace several assert statements

* Define response for API endpoint swap

* Adapt to latest changes on main

* Fix: missing argument after latest changes on main

* API: use local wallet for swap

* Improve swap command

* clean up cli swap

* fix comment

* clean up router

* fix up

* remove outgoing

---------

Co-authored-by: callebtc <93376500+callebtc@users.noreply.github.com>

cashu/wallet/api/responses.py

@@ -17,6 +17,13 @@ class InvoiceResponse(BaseModel):
     hash: Optional[str] = None
 
 
+class SwapResponse(BaseModel):
+    outgoing_mint: str
+    incoming_mint: str
+    invoice: Invoice
+    balances: Dict
+
+
 class BalanceResponse(BaseModel):
     balance: int
     keysets: Optional[Dict] = None

cashu/wallet/api/router.py

@@ -30,6 +30,7 @@ from .responses import (
     PendingResponse,
     ReceiveResponse,
     SendResponse,
+    SwapResponse,
     WalletsResponse,
 )
 
@@ -130,6 +131,53 @@ async def invoice(
     return
 
 
+@router.post(
+    "/swap",
+    name="Multi-mint swaps",
+    summary="Swap funds between mints",
+    response_model=SwapResponse,
+)
+async def swap(
+    amount: int = Query(default=..., description="Amount to swap between mints"),
+    outgoing_mint: str = Query(default=..., description="URL of outgoing mint"),
+    incoming_mint: str = Query(default=..., description="URL of incoming mint"),
+):
+    if not settings.lightning:
+        raise Exception("lightning not supported")
+    incoming_wallet = await load_mint(wallet, mint=incoming_mint)
+    outgoing_wallet = await load_mint(wallet, mint=outgoing_mint)
+    if incoming_wallet.url == outgoing_wallet.url:
+        raise Exception("mints for swap have to be different")
+
+    # request invoice from incoming mint
+    invoice = await incoming_wallet.request_mint(amount)
+
+    # pay invoice from outgoing mint
+    await outgoing_wallet.load_proofs()
+    total_amount, fee_reserve_sat = await outgoing_wallet.get_pay_amount_with_fees(
+        invoice.pr
+    )
+    assert total_amount > 0, "amount must be positive"
+    if outgoing_wallet.available_balance < total_amount:
+        raise Exception("balance too low")
+
+    _, send_proofs = await outgoing_wallet.split_to_send(
+        outgoing_wallet.proofs, total_amount, set_reserved=True
+    )
+    await outgoing_wallet.pay_lightning(send_proofs, invoice.pr, fee_reserve_sat)
+
+    # mint token in incoming mint
+    await incoming_wallet.mint(amount, hash=invoice.hash)
+    await incoming_wallet.load_proofs()
+    mint_balances = await incoming_wallet.balance_per_minturl()
+    return SwapResponse(
+        outgoing_mint=outgoing_mint,
+        incoming_mint=incoming_mint,
+        invoice=invoice,
+        balances=mint_balances,
+    )
+
+
 @router.get(
     "/balance",
     name="Balance",

cashu/wallet/cli/cli.py

@@ -209,6 +209,48 @@ async def invoice(ctx: Context, amount: int, hash: str, split: int):
     return
 
 
+@cli.command("swap", help="Swap funds between mints.")
+@click.pass_context
+@coro
+async def swap(ctx: Context):
+    if not settings.lightning:
+        raise Exception("lightning not supported.")
+    print("Select the mint to swap from:")
+    outgoing_wallet = await get_mint_wallet(ctx, force_select=True)
+
+    print("Select the mint to swap to:")
+    incoming_wallet = await get_mint_wallet(ctx, force_select=True)
+
+    await incoming_wallet.load_mint()
+    await outgoing_wallet.load_mint()
+
+    if incoming_wallet.url == outgoing_wallet.url:
+        raise Exception("mints for swap have to be different")
+
+    amount = int(input("Enter amount to swap in sats: "))
+    assert amount > 0, "amount is not positive"
+
+    # request invoice from incoming mint
+    invoice = await incoming_wallet.request_mint(amount)
+
+    # pay invoice from outgoing mint
+    total_amount, fee_reserve_sat = await outgoing_wallet.get_pay_amount_with_fees(
+        invoice.pr
+    )
+    if outgoing_wallet.available_balance < total_amount:
+        raise Exception("balance too low")
+    _, send_proofs = await outgoing_wallet.split_to_send(
+        outgoing_wallet.proofs, total_amount, set_reserved=True
+    )
+    await outgoing_wallet.pay_lightning(send_proofs, invoice.pr, fee_reserve_sat)
+
+    # mint token in incoming mint
+    await incoming_wallet.mint(amount, hash=invoice.hash)
+
+    await incoming_wallet.load_proofs(reload=True)
+    await print_mint_balances(incoming_wallet, show_mints=True)
+
+
 @cli.command("balance", help="Balance.")
 @click.option(
     "--verbose",

cashu/wallet/cli/cli_helpers.py

@@ -21,16 +21,17 @@ from ...wallet.crud import get_keyset
 from ...wallet.wallet import Wallet as Wallet
 
 
-async def get_mint_wallet(ctx: Context):
+async def get_mint_wallet(ctx: Context, force_select: bool = False):
     """
     Helper function that asks the user for an input to select which mint they want to load.
     Useful for selecting the mint that the user wants to send tokens from.
     """
     # we load a dummy wallet so we can check the balance per mint
     wallet: Wallet = ctx.obj["WALLET"]
+    await wallet.load_proofs(reload=True)
     mint_balances = await wallet.balance_per_minturl()
 
-    if ctx.obj["HOST"] not in mint_balances:
+    if ctx.obj["HOST"] not in mint_balances and not force_select:
         mint_url = wallet.url
     elif len(mint_balances) > 1:
         # if we have balances on more than one mint, we ask the user to select one

cashu/wallet/wallet.py

@@ -614,6 +614,8 @@ class Wallet(LedgerAPI):
                 time_paid=time.time(),
                 hash="",
             )
+            # we have a unique constraint on the hash, so we generate a random one if it doesn't exist
+            invoice_obj.hash = invoice_obj.hash or self._generate_secret()
             await store_lightning_invoice(db=self.db, invoice=invoice_obj)
 
             # handle change and produce proofs
@@ -824,7 +826,7 @@ class Wallet(LedgerAPI):
             )
 
     async def invalidate(self, proofs: List[Proof], check_spendable=True):
-        """Invalidates all spendable tokens supplied in proofs.
+        """Invalidates all unspendable tokens supplied in proofs.
 
         Args:
             proofs (List[Proof]): Which proofs to delete