feat: melt tokens

lnbits/extensions/cashu/crud.py

@@ -93,7 +93,9 @@ async def delete_cashu(cashu_id) -> None:
 ##########################################
 
 
-async def store_promises(amounts: List[int], B_s: List[str], C_s: List[str], cashu_id: str):
+async def store_promises(
+    amounts: List[int], B_s: List[str], C_s: List[str], cashu_id: str
+):
     for amount, B_, C_ in zip(amounts, B_s, C_s):
         await store_promise(amount, B_, C_, cashu_id)
 
@@ -113,21 +115,21 @@ async def store_promise(amount: int, B_: str, C_: str, cashu_id: str):
 
 async def get_promises(cashu_id) -> Optional[Cashu]:
     row = await db.fetchall(
-        "SELECT * FROM cashu.promises WHERE cashu_id = ?", (promises_id,)
+        "SELECT * FROM cashu.promises WHERE cashu_id = ?", (cashu_id,)
     )
     return Promises(**row) if row else None
 
 
 async def get_proofs_used(cashu_id):
     rows = await db.fetchall(
-        "SELECT secret from cashu.proofs_used WHERE id = ?", (cashu_id,)
+        "SELECT secret from cashu.proofs_used WHERE cashu_id = ?", (cashu_id,)
     )
     return [row[0] for row in rows]
 
 
-async def invalidate_proof(proof: Proof, cashu_id):
+async def invalidate_proof(cashu_id: str, proof: Proof):
     invalidate_proof_id = urlsafe_short_hash()
-    await (conn or db).execute(
+    await db.execute(
         """
         INSERT INTO cashu.proofs_used
           (id, amount, C, secret, cashu_id)

lnbits/extensions/cashu/mint.py

@@ -1,9 +1,16 @@
-from typing import List
+import math
+from typing import List, Set
+
+from lnbits import bolt11
+from lnbits.core.services import check_transaction_status, fee_reserve, pay_invoice
+from lnbits.extensions.cashu.models import Cashu
+from lnbits.wallets.base import PaymentStatus
 
 from .core.b_dhke import step2_bob
-from .core.base import BlindedSignature
+from .core.base import BlindedSignature, Proof
 from .core.secp import PublicKey
-from .mint_helper import derive_keys, derive_pubkeys
+from .crud import get_proofs_used, invalidate_proof
+from .mint_helper import derive_keys, derive_pubkeys, verify_proof
 
 # todo: extract const
 MAX_ORDER = 64
@@ -39,3 +46,52 @@ async def generate_promise(master_prvkey: str, amount: int, B_: PublicKey):
     secret_key = derive_keys(master_prvkey)[amount]  # Get the correct key
     C_ = step2_bob(B_, secret_key)
     return BlindedSignature(amount=amount, C_=C_.serialize().hex())
+
+
+async def melt(cashu: Cashu, proofs: List[Proof], invoice: str):
+    """Invalidates proofs and pays a Lightning invoice."""
+    # Verify proofs
+    proofs_used: Set[str] = set(await get_proofs_used(cashu.id))
+    # if not all([verify_proof(cashu.prvkey, proofs_used, p) for p in proofs]):
+    #     raise Exception("could not verify proofs.")
+    for p in proofs:
+        await verify_proof(cashu.prvkey, proofs_used, p)    
+
+    total_provided = sum([p["amount"] for p in proofs])
+    invoice_obj = bolt11.decode(invoice)
+    amount = math.ceil(invoice_obj.amount_msat / 1000)
+
+    fees_msat = await check_fees(cashu.wallet, invoice_obj)
+    assert total_provided >= amount + fees_msat / 1000, Exception(
+        "provided proofs not enough for Lightning payment."
+    )
+
+    await pay_invoice(
+        wallet_id=cashu.wallet,
+        payment_request=invoice,
+        description=f"pay cashu invoice",
+        extra={"tag": "cashu", "cahsu_name": cashu.name},
+    )
+
+    status: PaymentStatus = await check_transaction_status(
+        cashu.wallet, invoice_obj.payment_hash
+    )
+    if status.paid == True:
+        await invalidate_proofs(cashu.id, proofs)
+        return status.paid, status.preimage
+    return False, ""
+
+
+async def check_fees(wallet_id: str, decoded_invoice):
+    """Returns the fees (in msat) required to pay this pr."""
+    amount = math.ceil(decoded_invoice.amount_msat / 1000)
+    status: PaymentStatus = await check_transaction_status(
+        wallet_id, decoded_invoice.payment_hash
+    )
+    fees_msat = fee_reserve(amount * 1000) if status.paid != True else 0
+    return fees_msat
+
+async def invalidate_proofs(cashu_id: str, proofs: List[Proof]):
+    """Adds secrets of proofs to the list of knwon secrets and stores them in the db."""
+    for p in proofs:
+        await invalidate_proof(cashu_id, p)

lnbits/extensions/cashu/mint_helper.py

@@ -1,7 +1,9 @@
 import hashlib
-from typing import List
+from typing import List, Set
 
-from .core.secp import PrivateKey
+from .core.b_dhke import verify
+from .core.secp import PrivateKey, PublicKey
+from .models import Proof
 
 # todo: extract const
 MAX_ORDER = 64
@@ -21,6 +23,19 @@ def derive_keys(master_key: str):
     }
 
 
-
 def derive_pubkeys(keys: List[PrivateKey]):
     return {amt: keys[amt].pubkey for amt in [2**i for i in range(MAX_ORDER)]}
+
+
+async def verify_proof(master_prvkey: str, proofs_used: Set[str], proof: Proof):
+    """Verifies that the proof of promise was issued by this ledger."""
+    if proof.secret in proofs_used:
+        raise Exception(f"tokens already spent. Secret: {proof.secret}")
+
+    secret_key = derive_keys(master_prvkey)[
+        proof.amount
+    ]  # Get the correct key to check against
+    C = PublicKey(bytes.fromhex(proof.C), raw=True)
+    validMintSig = verify(secret_key, C, proof.secret)
+    if validMintSig != True:
+         raise Exception(f"tokens not valid. Secret: {proof.secret}")

lnbits/extensions/cashu/models.py

@@ -146,9 +146,3 @@ class MeltPayload(BaseModel):
     proofs: List[Proof]
     amount: int
     invoice: str
-
-
-class CreateTokens(BaseModel):
-    # cashu_id: str = Query(None)
-    payloads: MintPayloads
-    payment_hash: Union[str, None] = None

lnbits/extensions/cashu/views_api.py

@@ -28,11 +28,10 @@ from .crud import (
     update_lightning_invoice,
 )
 from .ledger import mint, request_mint
-from .mint import generate_promises, get_pubkeys
+from .mint import generate_promises, get_pubkeys, melt
 from .models import (
     Cashu,
     CheckPayload,
-    CreateTokens,
     Invoice,
     MeltPayload,
     MintPayloads,
@@ -248,7 +247,7 @@ async def mint_pay_request(
     except Exception as e:
         logger.error(e)
         raise HTTPException(
-            status_code=HTTPStatus.INTERNAL_SERVER_ERROR, detail=str(cashu_id)
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR, detail=str(e)
         )
 
     return {"pr": payment_request, "hash": payment_hash}
@@ -265,7 +264,6 @@ async def mint_coins(
     Requests the minting of tokens belonging to a paid payment request.
     Call this endpoint after `GET /mint`.
     """
-    print("############################ amount")
     cashu: Cashu = await get_cashu(cashu_id)
     if cashu is None:
         raise HTTPException(
@@ -282,12 +280,11 @@ async def mint_coins(
         )
     if invoice.issued == True:
         raise HTTPException(
-            status_code=HTTPStatus.PAYMENT_REQUIRED, detail="Tokens already issued for this invoice."
+            status_code=HTTPStatus.PAYMENT_REQUIRED,
+            detail="Tokens already issued for this invoice.",
         )
 
-    status: PaymentStatus = await check_transaction_status(
-        cashu.wallet, payment_hash
-    )
+    status: PaymentStatus = await check_transaction_status(cashu.wallet, payment_hash)
     # todo: revert to: status.paid != True:
     if status.paid == False:
         raise HTTPException(
@@ -302,21 +299,33 @@ async def mint_coins(
             amounts.append(payload.amount)
             B_s.append(PublicKey(bytes.fromhex(payload.B_), raw=True))
 
-        
             promises = await generate_promises(cashu.prvkey, amounts, B_s)
             for amount, B_, p in zip(amounts, B_s, promises):
                 await store_promise(amount, B_.serialize().hex(), p.C_, cashu_id)
-    
+
             return promises
-    except Exception as exc:
-        return CashuError(error=str(exc))
+    except Exception as e:
+        logger.error(e)
+        raise HTTPException(
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR, detail=str(e)
+        )
 
 
-@cashu_ext.post("/melt")
+@cashu_ext.post("/api/v1/melt/{cashu_id}")
 async def melt_coins(payload: MeltPayload, cashu_id: str = Query(None)):
-
-    ok, preimage = await melt(payload.proofs, payload.amount, payload.invoice, cashu_id)
-    return {"paid": ok, "preimage": preimage}
+    cashu: Cashu = await get_cashu(cashu_id)
+    if cashu is None:
+        raise HTTPException(
+            status_code=HTTPStatus.NOT_FOUND, detail="Mint does not exist."
+        )
+    try:
+        ok, preimage = await melt(cashu, payload.proofs, payload.invoice)
+        return {"paid": ok, "preimage": preimage}
+    except Exception as e:
+        logger.error(e)
+        raise HTTPException(
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR, detail=str(e)
+        )
 
 
 @cashu_ext.post("/check")