From 710329c4e0022b45603c4de1a1067fa069aef6a5 Mon Sep 17 00:00:00 2001
From: Santiago Carmuega <santiago@carmuega.me>
Date: Wed, 20 Nov 2024 13:31:18 -0300
Subject: [PATCH 1/2] feat: implement read-params interface

---
 balius-runtime/src/ledgers/mock.rs |  8 ++++++++
 balius-runtime/src/ledgers/mod.rs  |  7 +++++++
 balius-runtime/src/ledgers/u5c.rs  | 26 ++++++++++++++++++++++++++
 wit/balius.wit                     |  2 ++
 4 files changed, 43 insertions(+)

diff --git a/balius-runtime/src/ledgers/mock.rs b/balius-runtime/src/ledgers/mock.rs
index b537a3c..67cf44f 100644
--- a/balius-runtime/src/ledgers/mock.rs
+++ b/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())
+    }
 }
diff --git a/balius-runtime/src/ledgers/mod.rs b/balius-runtime/src/ledgers/mod.rs
index 5eb3855..07fcc3b 100644
--- a/balius-runtime/src/ledgers/mod.rs
+++ b/balius-runtime/src/ledgers/mod.rs
@@ -44,4 +44,11 @@ impl wit::Host for Ledger {
             Ledger::U5C(ledger) => ledger.search_utxos(pattern, start, max_items).await,
         }
     }
+
+    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,
+        }
+    }
 }
diff --git a/balius-runtime/src/ledgers/u5c.rs b/balius-runtime/src/ledgers/u5c.rs
index 4b094fb..da9a22b 100644
--- a/balius-runtime/src/ledgers/u5c.rs
+++ b/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(),
+            )),
+        }
+    }
 }
diff --git a/wit/balius.wit b/wit/balius.wit
index 54a44d3..b10e611 100644
--- a/wit/balius.wit
+++ b/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 {

From c064f6c535973fb22636bca8605c8f5901d128d4 Mon Sep 17 00:00:00 2001
From: Santiago Carmuega <santiago@carmuega.me>
Date: Wed, 20 Nov 2024 13:33:49 -0300
Subject: [PATCH 2/2] add to builder

---
 balius-sdk/src/txbuilder/build.rs | 13 ++++++++-----
 balius-sdk/src/txbuilder/mod.rs   |  8 ++------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/balius-sdk/src/txbuilder/build.rs b/balius-sdk/src/txbuilder/build.rs
index 6582560..ab12481 100644
--- a/balius-sdk/src/txbuilder/build.rs
+++ b/balius-sdk/src/txbuilder/build.rs
@@ -51,6 +51,13 @@ impl crate::txbuilder::Ledger for ExtLedgerFacade {
     fn search_utxos(&self, pattern: &UtxoPattern) -> Result<UtxoSet, BuildError> {
         todo!()
     }
+
+    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>
@@ -60,11 +67,7 @@ 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()?,
         estimated_fee: 1,
         ledger: Box::new(ledger),
         tx_body: None,
diff --git a/balius-sdk/src/txbuilder/mod.rs b/balius-sdk/src/txbuilder/mod.rs
index 93a8a3f..e7adf82 100644
--- a/balius-sdk/src/txbuilder/mod.rs
+++ b/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 {