feat: implement read-params interface

balius-runtime/src/ledgers/mock.rs

@@ -1,3 +1,5 @@
+use serde_json::json;
+
 use crate::wit::balius::app::ledger as wit;
 
 #[derive(Clone)]
@@ -37,4 +39,10 @@ impl Ledger {
     ) -> Result<wit::UtxoPage, wit::LedgerError> {
         todo!()
     }
+
+    pub async fn read_params(&mut self) -> Result<wit::Json, wit::LedgerError> {
+        let json = json!({ "param1": 4 });
+        let bytes = serde_json::to_vec(&json).unwrap();
+        Ok(bytes.into())
+    }
 }

balius-runtime/src/ledgers/mod.rs

@@ -59,4 +59,11 @@ impl wit::Host for Ledger {
             }
         }
     }
+
+    async fn read_params(&mut self) -> Result<wit::Json, wit::LedgerError> {
+        match self {
+            Ledger::Mock(ledger) => ledger.read_params().await,
+            Ledger::U5C(ledger) => ledger.read_params().await,
+        }
+    }
 }

balius-runtime/src/ledgers/u5c.rs

@@ -119,4 +119,30 @@ impl Ledger {
         let utxos = self.queries.match_utxos(pattern, start, max_items).await?;
         Ok(utxos.into())
     }
+
+    pub async fn read_params(&mut self) -> Result<wit::Json, wit::LedgerError> {
+        let req = utxorpc::spec::query::ReadParamsRequest::default();
+        let res = self
+            .queries
+            .read_params(req)
+            .await
+            .map_err(|err| wit::LedgerError::Upstream(format!("{:?}", err)))?
+            .into_inner();
+
+        let params = res
+            .values
+            .and_then(|v| v.params)
+            .ok_or(wit::LedgerError::Upstream(
+                "unexpected response from read_params".to_string(),
+            ))?;
+
+        match params {
+            utxorpc::spec::query::any_chain_params::Params::Cardano(params) => {
+                Ok(serde_json::to_vec(&params).unwrap())
+            }
+            _ => Err(wit::LedgerError::Upstream(
+                "unexpected response from read_params".to_string(),
+            )),
+        }
+    }
 }

balius-sdk/src/txbuilder/build.rs

@@ -74,6 +74,13 @@ impl crate::txbuilder::Ledger for ExtLedgerFacade {
         }
         Ok(utxos.into())
     }
+
+    fn read_params(&self) -> Result<PParams, BuildError> {
+        let bytes = crate::wit::balius::app::ledger::read_params()?;
+
+        serde_json::from_slice(&bytes)
+            .map_err(|_| BuildError::LedgerError("failed to parse params json".to_string()))
+    }
 }
 
 pub fn build<T, L>(tx: T, ledger: L) -> Result<primitives::Tx, BuildError>
@@ -83,11 +90,7 @@ where
 {
     let mut ctx = BuildContext {
         network: primitives::NetworkId::Testnet,
-        pparams: PParams {
-            min_fee_a: 4,
-            min_fee_b: 3,
-            min_utxo_value: 2,
-        },
+        pparams: ledger.read_params()?,
         total_input: primitives::Value::Coin(0),
         spent_output: primitives::Value::Coin(0),
         estimated_fee: 0,

balius-sdk/src/txbuilder/mod.rs

@@ -46,16 +46,12 @@ impl From<crate::wit::balius::app::ledger::LedgerError> for BuildError {
 
 pub use pallas_codec as codec;
 pub use pallas_primitives::conway as primitives;
-
-pub struct PParams {
-    pub min_fee_a: u64,
-    pub min_fee_b: u64,
-    pub min_utxo_value: u64,
-}
+pub use utxorpc_spec::utxorpc::v1alpha::cardano::PParams;
 
 pub trait Ledger {
     fn read_utxos(&self, refs: &[dsl::TxoRef]) -> Result<dsl::UtxoSet, BuildError>;
     fn search_utxos(&self, pattern: &dsl::UtxoPattern) -> Result<dsl::UtxoSet, BuildError>;
+    fn read_params(&self) -> Result<PParams, BuildError>;
 }
 
 pub struct BuildContext {

wit/balius.wit

@@ -11,6 +11,7 @@ interface kv {
 
 interface ledger {
     type cbor = list<u8>;
+    type json = list<u8>;
 
     variant ledger-error {
         upstream(string),
@@ -49,6 +50,7 @@ interface ledger {
 
     read-utxos: func(refs: list<txo-ref>) -> result<list<utxo>, ledger-error>;
     search-utxos: func(pattern: utxo-pattern, start: option<string>, max-items: u32) -> result<utxo-page, ledger-error>;
+    read-params: func() -> result<json, ledger-error>;
 }
 
 interface submit {