From c9fa861e055106e5b789a0b350a31df8343d38df Mon Sep 17 00:00:00 2001
From: xqcxx <praisechinonso21@gmail.com>
Date: Wed, 25 Mar 2026 20:04:50 +0100
Subject: [PATCH] Add maximum participant cap to campaign contract

- Add CapacityReached error variant (Error code 102)
- Add MAX_CAP and PARTICIPANT_COUNT storage keys
- Implement set_max_cap admin function to set capacity limit
- Update register function to check and enforce capacity
- Track participant count automatically on registration
- Add get_participant_count and get_max_cap query functions
- Cap value of 0 means unlimited participants (default behavior)

Closes #4
---
 contracts/campaign/src/lib.rs | 72 +++++++++++++++++++++++++++++++----
 1 file changed, 65 insertions(+), 7 deletions(-)

diff --git a/contracts/campaign/src/lib.rs b/contracts/campaign/src/lib.rs
index 88837f38..84594035 100644
--- a/contracts/campaign/src/lib.rs
+++ b/contracts/campaign/src/lib.rs
@@ -5,7 +5,7 @@
 
 #![no_std]
 
-use soroban_sdk::{contract, contractimpl, contractmeta, contracterror, symbol_short, Env, Symbol};
+use soroban_sdk::{contract, contracterror, contractimpl, contractmeta, symbol_short, Env, Symbol};
 
 #[contracterror]
 #[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord)]
@@ -13,18 +13,18 @@ use soroban_sdk::{contract, contractimpl, contractmeta, contracterror, symbol_sh
 pub enum Error {
     Unauthorized = 100,
     OutsideTimeWindow = 101,
+    CapacityReached = 102,
 }
 
-contractmeta!(
-    key = "Description",
-    val = "Trivela campaign configuration"
-);
+contractmeta!(key = "Description", val = "Trivela campaign configuration");
 
 const ADMIN: Symbol = symbol_short!("admin");
 const CAMPAIGN_ACTIVE: Symbol = symbol_short!("active");
 const PARTICIPANT: Symbol = symbol_short!("partic");
 const START_TIME: Symbol = symbol_short!("start");
 const END_TIME: Symbol = symbol_short!("end");
+const MAX_CAP: Symbol = symbol_short!("maxcap");
+const PARTICIPANT_COUNT: Symbol = symbol_short!("count");
 
 #[contract]
 pub struct CampaignContract;
@@ -37,6 +37,7 @@ impl CampaignContract {
         env.storage().instance().set(&CAMPAIGN_ACTIVE, &true);
         env.storage().instance().set(&START_TIME, &0u64);
         env.storage().instance().set(&END_TIME, &u64::MAX);
+        env.storage().instance().set(&PARTICIPANT_COUNT, &0u64);
         Ok(())
     }
 
@@ -68,6 +69,17 @@ impl CampaignContract {
         Ok(())
     }
 
+    /// Set maximum participant cap (admin only). Set to 0 for unlimited.
+    pub fn set_max_cap(env: Env, admin: soroban_sdk::Address, max_cap: u64) -> Result<(), Error> {
+        admin.require_auth();
+        let stored: soroban_sdk::Address = env.storage().instance().get(&ADMIN).unwrap();
+        if stored != admin {
+            return Err(Error::Unauthorized);
+        }
+        env.storage().instance().set(&MAX_CAP, &max_cap);
+        Ok(())
+    }
+
     /// Register a participant (authorized caller).
     pub fn register(env: Env, participant: soroban_sdk::Address) -> Result<bool, Error> {
         participant.require_auth();
@@ -81,10 +93,40 @@ impl CampaignContract {
         }
 
         let key = (PARTICIPANT, participant.clone());
-        if env.storage().instance().get::<_, bool>(&key).unwrap_or(false) {
+        if env
+            .storage()
+            .instance()
+            .get::<_, bool>(&key)
+            .unwrap_or(false)
+        {
             return Ok(false);
         }
+
+        // Check capacity if max_cap is set
+        let max_cap: u64 = env.storage().instance().get(&MAX_CAP).unwrap_or(0);
+        if max_cap > 0 {
+            let count: u64 = env
+                .storage()
+                .instance()
+                .get(&PARTICIPANT_COUNT)
+                .unwrap_or(0);
+            if count >= max_cap {
+                return Err(Error::CapacityReached);
+            }
+        }
+
         env.storage().instance().set(&key, &true);
+
+        // Increment participant count
+        let count: u64 = env
+            .storage()
+            .instance()
+            .get(&PARTICIPANT_COUNT)
+            .unwrap_or(0);
+        env.storage()
+            .instance()
+            .set(&PARTICIPANT_COUNT, &(count + 1));
+
         env.storage().instance().extend_ttl(50, 100);
         Ok(true)
     }
@@ -99,7 +141,23 @@ impl CampaignContract {
 
     /// Check if campaign is active.
     pub fn is_active(env: Env) -> bool {
-        env.storage().instance().get(&CAMPAIGN_ACTIVE).unwrap_or(false)
+        env.storage()
+            .instance()
+            .get(&CAMPAIGN_ACTIVE)
+            .unwrap_or(false)
+    }
+
+    /// Get current participant count.
+    pub fn get_participant_count(env: Env) -> u64 {
+        env.storage()
+            .instance()
+            .get(&PARTICIPANT_COUNT)
+            .unwrap_or(0)
+    }
+
+    /// Get maximum participant cap (0 means unlimited).
+    pub fn get_max_cap(env: Env) -> u64 {
+        env.storage().instance().get(&MAX_CAP).unwrap_or(0)
     }
 }