Implement multi-asset milestone release

campaign/src/multi_asset_release.rs

@@ -0,0 +1,54 @@
+use soroban_sdk::{Address, Env, Vec, token};
+use crate::types::{Error, MilestoneStatus, StellarAsset};
+use crate::storage::{get_campaign, get_milestone, set_milestone, storage_get_total_raised};
+
+/// Issue #208 – Multi-asset milestone release
+///
+/// Releases milestone funds proportionally across all accepted assets.
+/// Each asset transferred separately; all succeed or all revert (atomic via Soroban).
+/// Release amount per asset = (asset_raised / total_raised) * milestone_release_amount
+pub fn release_milestone_multi_asset(env: &Env, milestone_index: u32, recipient: Address) {
+    let campaign = get_campaign(env).unwrap_or_else(|| {
+        soroban_sdk::panic_with_error!(env, Error::NotInitialized)
+    });
+
+    campaign.creator.require_auth();
+
+    let mut milestone = get_milestone(env, milestone_index).unwrap_or_else(|| {
+        soroban_sdk::panic_with_error!(env, Error::MilestoneNotFound)
+    });
+
+    if milestone.status != MilestoneStatus::Unlocked {
+        soroban_sdk::panic_with_error!(env, Error::InvalidMilestoneTransition);
+    }
+
+    let total_raised = storage_get_total_raised(env);
+    let milestone_release_amount = milestone.target_amount - milestone.released_amount;
+
+    if total_raised > 0 {
+        for asset in campaign.accepted_assets.iter() {
+            if let Some(issuer) = asset.issuer.clone() {
+                let token_client = token::Client::new(env, &issuer);
+                let asset_raised = token_client.balance(&env.current_contract_address());
+                // Proportional: (asset_raised / total_raised) * milestone_release_amount
+                let asset_release = (asset_raised * milestone_release_amount) / total_raised;
+                if asset_release > 0 {
+                    token_client.transfer(
+                        &env.current_contract_address(),
+                        &recipient,
+                        &asset_release,
+                    );
+                }
+            }
+        }
+    }
+
+    milestone.released_amount = milestone.target_amount;
+    milestone.status = MilestoneStatus::Released;
+    set_milestone(env, milestone_index, &milestone);
+
+    env.events().publish(
+        ("milestone", "multi_asset_released"),
+        (milestone_index, milestone_release_amount, recipient),
+    );
+}