fix(markets): add min_bet field to enforce minimum bet threshold

contracts/markets/benches/main.rs

@@ -1,4 +1,4 @@
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use markets::{MarketsContract, MarketsContractClient};
 use soroban_sdk::{testutils::Address as _, Address, Env, String, Vec};
 
@@ -88,6 +88,7 @@
                 &end_time,
                 &resolution_source,
                 &outcome_tags,
+                &black_box(1i128),
             ))
         })
     });
@@ -120,6 +121,7 @@
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     );
 
     c.bench_function("contract_place_bet", |b| {
@@ -158,6 +160,7 @@
                 &end_time,
                 &resolution_source,
                 &outcome_tags,
+                &1i128,
             );
             black_box(client.resolve_market(&creator, &market_id, &0u32))
         })

contracts/markets/src/lib.rs

@@ -153,6 +153,9 @@ pub struct MarketData {
     pub winning_outcome: u32,
     /// Whether the market has been cancelled.
     pub cancelled: bool,
+    /// Minimum bet amount in stroops. Any `place_bet` call with `amount < min_bet`
+    /// is rejected with `StakeTooSmall`. Must be >= 1.
+    pub min_bet: i128,
 }
 
 /// On-chain record of a user's bet on a market.
@@ -845,6 +848,7 @@ impl MarketsContract {
         end_time: u64,
         resolution_source: String,
         outcome_tags: Vec<String>,
+        min_bet: i128,
     ) -> u32 {
         Self::create_market_with_curve(
             env.clone(),
@@ -855,6 +859,7 @@ impl MarketsContract {
             resolution_source,
             outcome_tags,
             PayoutCurveConfig::winner_takes_all(&env),
+            min_bet,
         )
     }
 
@@ -868,13 +873,18 @@ impl MarketsContract {
         resolution_source: String,
         outcome_tags: Vec<String>,
         curve: PayoutCurveConfig,
+        min_bet: i128,
     ) -> u32 {
         creator.require_auth();
 
         if outcome_tags.len() < 2 {
             panic_with_error!(env, ContractError::InvalidConfig);
         }
 
+        if min_bet < 1 {
+            panic_with_error!(env, ContractError::InvalidConfig);
+        }
+
         Self::validate_payout_curve(&env, &curve, outcome_tags.len());
 
         let counter: u32 = env
@@ -905,6 +915,7 @@ impl MarketsContract {
             resolved: false,
             winning_outcome: 0,
             cancelled: false,
+            min_bet,
         };
         env.storage()
             .persistent()
@@ -1001,7 +1012,7 @@ impl MarketsContract {
             panic_with_error!(env, ContractError::InvalidOutcome);
         }
 
-        if amount <= 0 {
+        if amount <= 0 || amount < market.min_bet {
             panic_with_error!(env, ContractError::StakeTooSmall);
         }
 

contracts/markets/tests/auth_boundary.rs

@@ -91,6 +91,7 @@ fn create_market_with_mock_auth(setup: &TestSetup<'_>) -> u32 {
                 end_time,
                 resolution_source.clone(),
                 outcome_tags.clone(),
+                1i128,
             )
                 .into_val(env),
             sub_invokes: &[],
@@ -104,6 +105,7 @@ fn create_market_with_mock_auth(setup: &TestSetup<'_>) -> u32 {
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     )
 }
 
@@ -126,6 +128,7 @@ fn create_market_with_auth_check(setup: &TestSetup<'_>) -> u32 {
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     )
 }
 
@@ -159,6 +162,7 @@ fn test_create_market_requires_auth() {
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     );
     assert!(
         result.is_err(),
@@ -213,6 +217,7 @@ fn test_market_limit_blocks_both_creation_entrypoints() {
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     );
     assert_eq!(
         regular_result.unwrap_err().unwrap(),
@@ -228,6 +233,7 @@ fn test_market_limit_blocks_both_creation_entrypoints() {
         &resolution_source,
         &outcome_tags,
         &curve,
+        &1i128,
     );
     assert_eq!(
         curve_result.unwrap_err().unwrap(),
@@ -280,6 +286,7 @@ fn test_create_market_requires_auth_market_creator() {
         &end_time,
         &resolution_source,
         &outcome_tags,
+        &1i128,
     );
     assert!(result.is_ok(), "Authorized market creator should succeed");
 }