feat(looping): persist looping position state and close positions (#414)

quantara/soroban/contracts/looping/Cargo.toml

@@ -14,6 +14,7 @@ soroban-sdk = { version = "22.0.0" }
 common = { path = "../common", version = "0.1.0" }
 
 [dev-dependencies]
+proptest = "1.4.0"
 soroban-sdk = { version = "22.0.0", features = ["testutils"] }
 ed25519-dalek = "<3"
 rand_core = "<0.7"

quantara/soroban/contracts/looping/fuzz/fuzz_targets/fuzz_looping_open_position.rs

@@ -1,7 +1,8 @@
 //! cargo-fuzz harness for LoopingContract::open_position entry-point.
 //!
 //! Invariants checked:
-//! - Valid inputs (collateral > 0, leverage 100–500) must succeed.
+//! - Valid inputs (collateral_amount > 0, debt_amount >= 0, leverage 100–500)
+//!   must succeed.
 //! - Returned position IDs are >= 1.
 //!
 //! Run:
@@ -16,16 +17,19 @@ use soroban_sdk::{testutils::Address as _, Address, Env, IntoVal, Symbol};
 use looping::LoopingContract;
 
 fuzz_target!(|data: &[u8]| {
-    if data.len() < 12 {
+    if data.len() < 20 {
         return;
     }
-    let collateral = i64::from_le_bytes(data[..8].try_into().unwrap()) as i128;
-    let leverage = u32::from_le_bytes(data[8..12].try_into().unwrap());
+    let collateral_amount = i64::from_le_bytes(data[..8].try_into().unwrap()) as i128;
+    let debt_amount = i64::from_le_bytes(data[8..16].try_into().unwrap()) as i128;
+    let leverage = u32::from_le_bytes(data[16..20].try_into().unwrap());
 
     let env = Env::default();
     env.mock_all_auths();
     let contract_id = env.register(LoopingContract, ());
     let user = Address::generate(&env);
+    let collateral_asset = Address::generate(&env);
+    let debt_asset = Address::generate(&env);
 
     // try_invoke_contract returns `Result<Result<u64, ContractError>, HostError>`;
     // explicitly specify the host error type so type inference succeeds.
@@ -35,12 +39,15 @@ fuzz_target!(|data: &[u8]| {
         soroban_sdk::vec![
             &env,
             user.to_val(),
-            collateral.into_val(&env),
+            collateral_asset.to_val(),
+            collateral_amount.into_val(&env),
+            debt_asset.to_val(),
+            debt_amount.into_val(&env),
             leverage.into_val(&env),
         ],
     );
 
-    if collateral > 0 && (100..=500).contains(&leverage) {
+    if collateral_amount > 0 && debt_amount >= 0 && (100..=500).contains(&leverage) {
         // Unwrap the outer (host) Err first, then the inner (contract) Err.
         let position_id = result
             .expect("open_position returned a host error")