Remove melt_request (#819)

* Fix SQLite race condition

Bug: https://github.com/crodas/cdk/actions/runs/15732950296/job/44339804072#step:5:1853

Reason: When melting in parallel, many update the melt status and attempt to
add proofs and they fail when adding the proof and the rollback code kicks in.
The loser process removes all the proofs, and the winner process has no proof
later on.

Fix: Modify `update_melt_quote_state` requirements and implementation to allow
only one winner.

This will be solved by design with a transaction writer trait

* Remove `melt_request`

Fixes #809

* Remove `get_melt_request` from db trait

crates/cdk-sqlite/src/mint/mod.rs

@@ -8,7 +8,7 @@ use std::str::FromStr;
 use async_rusqlite::{query, DatabaseExecutor};
 use async_trait::async_trait;
 use bitcoin::bip32::DerivationPath;
-use cdk_common::common::{PaymentProcessorKey, QuoteTTL};
+use cdk_common::common::QuoteTTL;
 use cdk_common::database::{
     self, MintDatabase, MintKeysDatabase, MintProofsDatabase, MintQuotesDatabase,
     MintSignaturesDatabase,
@@ -20,8 +20,8 @@ use cdk_common::secret::Secret;
 use cdk_common::state::check_state_transition;
 use cdk_common::util::unix_time;
 use cdk_common::{
-    Amount, BlindSignature, BlindSignatureDleq, CurrencyUnit, Id, MeltQuoteState, MeltRequest,
-    MintInfo, MintQuoteState, PaymentMethod, Proof, Proofs, PublicKey, SecretKey, State,
+    Amount, BlindSignature, BlindSignatureDleq, CurrencyUnit, Id, MeltQuoteState, MintInfo,
+    MintQuoteState, Proof, Proofs, PublicKey, SecretKey, State,
 };
 use error::Error;
 use lightning_invoice::Bolt11Invoice;
@@ -733,60 +733,6 @@ impl MintQuotesDatabase for MintSqliteDatabase {
 
         Ok(())
     }
-
-    async fn add_melt_request(
-        &self,
-        melt_request: MeltRequest<Uuid>,
-        ln_key: PaymentProcessorKey,
-    ) -> Result<(), Self::Err> {
-        query(
-            r#"
-                INSERT INTO melt_request
-                (id, inputs, outputs, method, unit)
-                VALUES
-                (:id, :inputs, :outputs, :method, :unit)
-                ON CONFLICT(id) DO UPDATE SET
-                    inputs = excluded.inputs,
-                    outputs = excluded.outputs,
-                    method = excluded.method,
-                    unit = excluded.unit
-        "#,
-        )
-        .bind(":id", melt_request.quote().to_string())
-        .bind(":inputs", serde_json::to_string(&melt_request.inputs())?)
-        .bind(":outputs", serde_json::to_string(&melt_request.outputs())?)
-        .bind(":method", ln_key.method.to_string())
-        .bind(":unit", ln_key.unit.to_string())
-        .execute(&self.pool)
-        .await?;
-
-        Ok(())
-    }
-
-    async fn get_melt_request(
-        &self,
-        quote_id: &Uuid,
-    ) -> Result<Option<(MeltRequest<Uuid>, PaymentProcessorKey)>, Self::Err> {
-        Ok(query(
-            r#"
-            SELECT
-                id,
-                inputs,
-                outputs,
-                method,
-                unit
-            FROM
-                melt_request
-            WHERE
-                id=?;
-            "#,
-        )
-        .bind(":id", quote_id.hyphenated().to_string())
-        .fetch_one(&self.pool)
-        .await?
-        .map(sqlite_row_to_melt_request)
-        .transpose()?)
-    }
 }
 
 #[async_trait]
@@ -1353,35 +1299,6 @@ fn sqlite_row_to_blind_signature(row: Vec<Column>) -> Result<BlindSignature, Err
     })
 }
 
-fn sqlite_row_to_melt_request(
-    row: Vec<Column>,
-) -> Result<(MeltRequest<Uuid>, PaymentProcessorKey), Error> {
-    unpack_into!(
-        let (
-            id,
-            inputs,
-            outputs,
-            method,
-            unit
-        ) = row
-    );
-
-    let id = column_as_string!(id);
-
-    let melt_request = MeltRequest::new(
-        Uuid::parse_str(&id).map_err(|_| Error::InvalidUuid(id))?,
-        column_as_string!(&inputs, serde_json::from_str),
-        column_as_nullable_string!(&outputs).and_then(|w| serde_json::from_str(&w).ok()),
-    );
-
-    let ln_key = PaymentProcessorKey {
-        unit: column_as_string!(&unit, CurrencyUnit::from_str),
-        method: column_as_string!(&method, PaymentMethod::from_str),
-    };
-
-    Ok((melt_request, ln_key))
-}
-
 #[cfg(test)]
 mod tests {
     use std::fs::remove_file;