feat(contracts): add optional approver field and approve_invoice to i…

contracts/split/src/lib.rs

@@ -311,6 +311,7 @@ impl SplitContract {
         )
     }
 
+    #[allow(clippy::too_many_arguments)]
     fn _create_invoice_inner(
         env: &Env,
         creator: Address,
@@ -645,6 +646,7 @@ impl SplitContract {
     ///
     /// For tranche invoices, only distributes tranches whose timestamp ≤ now.
     /// Blocks with "prerequisite not released" until the prerequisite invoice is Released.
+    /// If an approver is set, requires the invoice to be approved first (issue #25).
     pub fn release(env: Env, invoice_id: u64) {
         require_not_paused(&env);
         let caller = env.current_contract_address();
@@ -659,6 +661,11 @@ impl SplitContract {
         let total: i128 = invoice.amounts.iter().sum();
         assert!(invoice.funded >= total, "invoice not fully funded");
 
+        // Approval check (issue #25).
+        if invoice.approver.is_some() && !invoice.approved {
+            panic!("awaiting approval");
+        }
+
         // Prerequisite check (issue #22).
         if let Some(prereq_id) = invoice.prerequisite_id {
             let prereq = load_invoice(&env, prereq_id);
@@ -696,6 +703,21 @@ impl SplitContract {
         }
     }
 
+    /// Approve an invoice if it has an approver set (issue #25).
+    ///
+    /// Requires authentication from the approver address.
+    pub fn approve_invoice(env: Env, invoice_id: u64) {
+        require_not_paused(&env);
+        let mut invoice = load_invoice(&env, invoice_id);
+
+        let approver = invoice.approver.as_ref().expect("no approver set on this invoice");
+        approver.require_auth();
+
+        invoice.approved = true;
+        save_invoice(&env, invoice_id, &invoice);
+        append_audit_entry(&env, invoice_id, symbol_short!("aprv"), approver);
+    }
+
     /// Distribute tranches unlocked by the current ledger time (issue #23).
     fn _release_tranches(env: &Env, invoice_id: u64, invoice: &mut Invoice, actor: &Address) {
         let now = env.ledger().timestamp();