feat: add strict get_invoice view function (closes #1)

contracts/invoice_nft/src/lib.rs

@@ -14,8 +14,8 @@ pub struct Invoice {
 
 #[contracttype]
 pub enum DataKey {
-    Invoice(u64), // Maps ID -> Invoice
-    TokenId,      // Tracks the next available ID
+    Invoice(u64),  // Maps ID -> Invoice
+    TokenId,       // Tracks the next available ID
     BackendPubkey, // Backend public key for signature verification
 }
 
@@ -32,7 +32,10 @@ impl InvoiceContract {
 
     // Helper function to check admin authorization
     fn require_admin(env: &Env) {
-        let admin: Address = env.storage().instance().get(&DataKey::BackendPubkey)
+        let admin: Address = env
+            .storage()
+            .instance()
+            .get(&DataKey::BackendPubkey)
             .expect("Backend pubkey not set");
         admin.require_auth();
     }
@@ -41,13 +44,24 @@ impl InvoiceContract {
     pub fn set_backend_pubkey(env: Env, pubkey: BytesN<32>) {
         // For simplicity, we'll allow anyone to set this initially
         // In production, this should be admin-only
-        env.storage().instance().set(&DataKey::BackendPubkey, &pubkey);
+        env.storage()
+            .instance()
+            .set(&DataKey::BackendPubkey, &pubkey);
         Self::extend_storage_ttl(&env);
     }
 
     // Helper function to verify backend signature
-    fn verify_signature(env: &Env, user: &Address, amount: i128, risk_score: u32, signature: &BytesN<64>) -> bool {
-        let backend_pubkey: BytesN<32> = env.storage().instance().get(&DataKey::BackendPubkey)
+    fn verify_signature(
+        env: &Env,
+        _user: &Address,
+        amount: i128,
+        risk_score: u32,
+        signature: &BytesN<64>,
+    ) -> bool {
+        let backend_pubkey: BytesN<32> = env
+            .storage()
+            .instance()
+            .get(&DataKey::BackendPubkey)
             .expect("Backend pubkey not set");
 
         // Create message payload: (user_address, invoice_amount, risk_score)
@@ -60,7 +74,14 @@ impl InvoiceContract {
     }
 
     // 1. MINT: Create a new Invoice NFT with signature verification
-    pub fn mint(env: Env, owner: Address, amount: i128, due_date: u64, risk_score: u32, signature: BytesN<64>) -> u64 {
+    pub fn mint(
+        env: Env,
+        owner: Address,
+        amount: i128,
+        due_date: u64,
+        risk_score: u32,
+        signature: BytesN<64>,
+    ) -> u64 {
         owner.require_auth(); // Ensure the caller is who they say they are
 
         // Check if invoice is expired
@@ -75,7 +96,11 @@ impl InvoiceContract {
         }
 
         // Get the current ID count
-        let mut current_id = env.storage().instance().get(&DataKey::TokenId).unwrap_or(0u64);
+        let mut current_id = env
+            .storage()
+            .instance()
+            .get(&DataKey::TokenId)
+            .unwrap_or(0u64);
         current_id += 1;
 
         // Create the invoice object
@@ -88,7 +113,9 @@ impl InvoiceContract {
         };
 
         // Save to storage
-        env.storage().instance().set(&DataKey::Invoice(current_id), &invoice);
+        env.storage()
+            .instance()
+            .set(&DataKey::Invoice(current_id), &invoice);
         env.storage().instance().set(&DataKey::TokenId, &current_id);
         Self::extend_storage_ttl(&env);
 
@@ -99,22 +126,34 @@ impl InvoiceContract {
     }
 
     // 2. GET: Read invoice details
-    pub fn get_invoice(env: Env, id: u64) -> Option<Invoice> {
-        env.storage().instance().get(&DataKey::Invoice(id))
+    /// Get invoice details by ID (read-only view function)
+    ///
+    /// Panics with "InvoiceNotFound" if the ID does not exist
+    pub fn get_invoice(env: Env, id: u64) -> Invoice {
+        env.storage()
+            .instance()
+            .get(&DataKey::Invoice(id))
+            .unwrap_or_else(|| panic!("InvoiceNotFound"))
     }
 
     // 3. REPAY: Mark the invoice as paid
     pub fn repay(env: Env, id: u64) {
-        let mut invoice: Invoice = env.storage().instance().get(&DataKey::Invoice(id)).expect("Invoice not found");
-
+        let mut invoice: Invoice = env
+            .storage()
+            .instance()
+            .get(&DataKey::Invoice(id))
+            .expect("Invoice not found");
+
         invoice.owner.require_auth(); // Only the owner can repay
 
         // (In a real app, we would transfer USDC here. For MVP, we just flip the switch.)
         invoice.is_repaid = true;
 
-        env.storage().instance().set(&DataKey::Invoice(id), &invoice);
+        env.storage()
+            .instance()
+            .set(&DataKey::Invoice(id), &invoice);
         Self::extend_storage_ttl(&env);
 
         env.events().publish((symbol_short!("repay"), invoice.owner), id);
     }
-}
+}

contracts/invoice_nft/src/tests.rs

@@ -1,5 +1,5 @@
-use soroban_sdk::contracterror;
 use crate::InvoiceContract;
+use soroban_sdk::contracterror;
 
 #[contracterror]
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
@@ -15,8 +15,8 @@ pub enum Error {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use soroban_sdk::{testutils::Address as TestAddress, testutils::Bytes as TestBytes, Bytes};
     use soroban_sdk::contractclient::InvoiceContractClient;
+    use soroban_sdk::{testutils::Address as TestAddress, testutils::Bytes as TestBytes, Bytes};
 
     #[test]
     fn test_mint_invoice_success() {
@@ -30,7 +30,7 @@ mod tests {
 
         // Create a valid signature (mock)
         let signature = [2u8; 64];
-        
+
         let due_date = env.ledger().timestamp() + 86400; // Tomorrow
         let invoice_id = client.mint(&owner, &1000, &due_date, &750, &signature);