feat: implement decode pay req endpoint

closes #16

app/models/lightning.py

@@ -48,25 +48,25 @@ class Feature(BaseModel):
     is_required: bool
     is_known: bool
 
-
-def feature_from_grpc(f):
-    return Feature(
-        name=f.name,
-        is_required=f.is_required,
-        is_known=f.is_known,
-    )
+    @classmethod
+    def from_grpc(cls, f):
+        return cls(
+            name=f.name,
+            is_required=f.is_required,
+            is_known=f.is_known,
+        )
 
 
 class FeaturesEntry(BaseModel):
     key: int
     value: Feature
 
-
-def features_entry_from_grpc(entry_key, feature):
-    return FeaturesEntry(
-        key=entry_key,
-        value=feature_from_grpc(feature),
-    )
+    @classmethod
+    def from_grpc(cls, entry_key, feature):
+        return cls(
+            key=entry_key,
+            value=Feature.from_grpc(feature),
+        )
 
 
 class AMP(BaseModel):
@@ -187,15 +187,15 @@ class RouteHint(BaseModel):
     # The time-lock delta of the channel.
     cltv_expiry_delta: int
 
-
-def route_hint_from_grpc(h) -> RouteHint:
-    return RouteHint(
-        node_id=h.node_id,
-        chan_id=h.chan_id,
-        fee_base_msat=h.fee_base_msat,
-        fee_proportional_millionths=h.fee_proportional_millionths,
-        cltv_expiry_delta=h.cltv_expiry_delta,
-    )
+    @classmethod
+    def from_grpc(cls, h) -> "RouteHint":
+        return cls(
+            node_id=h.node_id,
+            chan_id=h.chan_id,
+            fee_base_msat=h.fee_base_msat,
+            fee_proportional_millionths=h.fee_proportional_millionths,
+            cltv_expiry_delta=h.cltv_expiry_delta,
+        )
 
 
 class Invoice(BaseModel):
@@ -311,7 +311,7 @@ def invoice_from_grpc(i) -> Invoice:
     def _route_hints(hints):
         l = []
         for h in hints:
-            l.append(route_hint_from_grpc(h))
+            l.append(RouteHint.from_grpc((h)))
         return l
 
     def _htlcs(htlcs):
@@ -323,7 +323,7 @@ def invoice_from_grpc(i) -> Invoice:
     def _features(features):
         l = []
         for k in features:
-            l.append(features_entry_from_grpc(k, features[k]))
+            l.append(FeaturesEntry.from_grpc(k, features[k]))
         return l
 
     return Invoice(
@@ -833,7 +833,7 @@ def ln_info_from_grpc(i) -> LnInfo:
 
     _features = []
     for f in i.features:
-        _features.append(features_entry_from_grpc(f, i.features[f]))
+        _features.append(FeaturesEntry.from_grpc(f, i.features[f]))
 
     _uris = [u for u in i.uris]
 
@@ -935,3 +935,37 @@ class WalletBalance(BaseModel):
             channel_pending_open_local_balance=channel.pending_open_local_balance.msat,
             channel_pending_open_remote_balance=channel.pending_open_remote_balance.msat,
         )
+
+
+class PaymentRequest(BaseModel):
+    destination: str
+    payment_hash: str
+    num_satoshis: int
+    timestamp: int
+    expiry: int
+    description: str
+    description_hash: str
+    fallback_addr: Optional[str]
+    cltv_expiry: int
+    route_hints: List[RouteHint] = Query([])
+    payment_addr: str = Query(..., description="The payment address in hex format")
+    num_msat: int
+    features: List[FeaturesEntry] = Query([])
+
+    @classmethod
+    def from_grpc(cls, r):
+        return cls(
+            destination=r.destination,
+            payment_hash=r.payment_hash,
+            num_satoshis=r.num_satoshis,
+            timestamp=r.timestamp,
+            expiry=r.expiry,
+            description=r.description,
+            description_hash=r.description_hash,
+            fallback_addr=r.fallback_addr,
+            cltv_expiry=r.cltv_expiry,
+            route_hints=[RouteHint.from_grpc(rh) for rh in r.route_hints],
+            payment_addr=r.payment_addr.hex(),
+            num_msat=r.num_msat,
+            features=[FeaturesEntry.from_grpc(k, r.features[k]) for k in r.features],
+        )

app/repositories/lightning.py

@@ -1,12 +1,19 @@
 import asyncio
 
-from app.models.lightning import Invoice, LightningStatus, LnInfo, Payment
+from app.models.lightning import (
+    Invoice,
+    LightningStatus,
+    LnInfo,
+    Payment,
+    PaymentRequest,
+)
 from app.utils import SSE, lightning_config, send_sse_message
 from decouple import config
 
 if lightning_config.ln_node == "lnd":
     from app.repositories.ln_impl.lnd import (
         add_invoice_impl,
+        decode_pay_request_impl,
         get_implementation_name,
         get_ln_info_impl,
         get_wallet_balance_impl,
@@ -16,6 +23,7 @@ if lightning_config.ln_node == "lnd":
 else:
     from app.repositories.ln_impl.clightning import (
         add_invoice_impl,
+        decode_pay_request_impl,
         get_implementation_name,
         get_ln_info_impl,
         get_wallet_balance_impl,
@@ -44,6 +52,10 @@ async def add_invoice(
     return await add_invoice_impl(memo, value_msat, expiry, is_keysend)
 
 
+async def decode_pay_request(pay_req: str) -> PaymentRequest:
+    return await decode_pay_request_impl(pay_req)
+
+
 async def send_payment(
     pay_req: str, timeout_seconds: int, fee_limit_msat: int
 ) -> Payment:

app/repositories/ln_impl/clightning.py

@@ -1,4 +1,4 @@
-from app.models.lightning import Invoice, LnInfo, Payment
+from app.models.lightning import Invoice, LnInfo, Payment, PaymentRequest
 
 
 def get_implementation_name() -> str:
@@ -15,6 +15,10 @@ async def add_invoice_impl(
     raise NotImplementedError("c-lightning not yet implemented")
 
 
+async def decode_pay_request_impl(pay_req: str) -> PaymentRequest:
+    raise NotImplementedError("c-lightning not yet implemented")
+
+
 async def send_payment_impl(
     pay_req: str, timeout_seconds: int, fee_limit_msat: int
 ) -> Payment:

app/repositories/ln_impl/lnd.py

@@ -9,6 +9,7 @@ from app.models.lightning import (
     InvoiceState,
     LnInfo,
     Payment,
+    PaymentRequest,
     WalletBalance,
     invoice_from_grpc,
     ln_info_from_grpc,
@@ -62,6 +63,25 @@ async def add_invoice_impl(
     return invoice
 
 
+async def decode_pay_request_impl(pay_req: str) -> PaymentRequest:
+    try:
+        req = ln.PayReqString(pay_req=pay_req)
+        res = await lncfg.lnd_stub.DecodePayReq(req)
+        return PaymentRequest.from_grpc(res)
+    except grpc.aio._call.AioRpcError as error:
+        if (
+            error.details() != None
+            and error.details().find("checksum failed.") > -1
+        ):
+            raise HTTPException(
+                status.HTTP_400_BAD_REQUEST, detail="Invalid payment request string"
+            )
+        else:
+            raise HTTPException(
+                status.HTTP_500_INTERNAL_SERVER_ERROR, detail=error.details()
+            )
+
+
 async def send_payment_impl(
     pay_req: str, timeout_seconds: int, fee_limit_msat: int
 ) -> Payment:

app/routers/lightning.py

@@ -4,17 +4,19 @@ from app.models.lightning import (
     LightningStatus,
     LnInfo,
     Payment,
+    PaymentRequest,
     WalletBalance,
 )
 from app.repositories.lightning import (
     add_invoice,
+    decode_pay_request,
     get_ln_info,
     get_ln_status,
     get_wallet_balance,
     send_payment,
 )
 from app.routers.lightning_docs import send_payment_desc
-from fastapi import APIRouter, HTTPException, status
+from fastapi import APIRouter, HTTPException, Query, status
 from fastapi.params import Depends
 
 router = APIRouter(prefix="/lightning", tags=["Lightning"])
@@ -107,3 +109,17 @@ async def get_info():
         raise HTTPException(r.status_code, detail=r.detail)
     except NotImplementedError as r:
         raise HTTPException(status.HTTP_501_NOT_IMPLEMENTED, detail=r.args[0])
+
+
+@router.get(
+    "/decode-pay-req",
+    name="lightning.decode-pay-req",
+    summary="DecodePayReq takes an encoded payment request string and attempts to decode it, returning a full description of the conditions encoded within the payment request.",
+    response_model=PaymentRequest,
+    response_description="A fully decoded payment request or a HTTP status 400 if the payment request cannot be decoded.",
+    dependencies=[Depends(JWTBearer())],
+)
+async def get_decode_pay_request(
+    pay_req: str = Query(..., description="The payment request string to be decoded")
+):
+    return await decode_pay_request(pay_req)