refactor: remove dead storage helpers and unify interest-rate calculation (Closes #331)

project_registry/src/lib.rs

@@ -1223,9 +1223,9 @@ fn require_multisig_disabled(env: &Env) {
 }
 
 fn compute_rate(credit_quality: u32, green_impact: u32) -> u32 {
-    let avg = (credit_quality + green_impact) / 2;
-    let discount = avg * MAX_DISCOUNT_BPS / 100;
-    BASE_RATE_BPS - discount
+    // Single source of truth: logic::calculate_interest_rate already applies
+    // the underflow guard this local copy lacked.
+    logic::calculate_interest_rate(BASE_RATE_BPS, MAX_DISCOUNT_BPS, credit_quality, green_impact)
 }
 
 fn read_state_version(env: &Env) -> u32 {

project_registry/src/logic.rs

@@ -1,6 +1,3 @@
-use crate::types::{CertificationStatus, ProjectData};
-use soroban_sdk::{Address, Env, String};
-
 /// Interest-rate calculation for green-bond projects.
 ///
 /// Heliobond uses a two-dimensional scoring model to determine each project's

project_registry/src/storage.rs

@@ -1,35 +1,7 @@
-use crate::types::{DataKey, ProjectData, Proposal};
-use soroban_sdk::{Address, Env};
-
-pub fn read_project(env: &Env, id: u32) -> Option<ProjectData> {
-    env.storage().persistent().get(&DataKey::Project(id))
-}
-
-pub fn write_project(env: &Env, id: u32, project: &ProjectData) {
-    env.storage()
-        .persistent()
-        .set(&DataKey::Project(id), project);
-}
-
-pub fn read_proposal(env: &Env, id: u32) -> Option<Proposal> {
-    env.storage().persistent().get(&DataKey::Proposal(id))
-}
-
-pub fn write_proposal(env: &Env, id: u32, proposal: &Proposal) {
-    env.storage()
-        .persistent()
-        .set(&DataKey::Proposal(id), proposal);
-}
-
-pub fn read_whitelist(env: &Env, account: Address) -> bool {
-    env.storage()
-        .persistent()
-        .get(&DataKey::Whitelist(account))
-        .unwrap_or(false)
-}
-
-pub fn write_whitelist(env: &Env, account: Address, status: bool) {
-    env.storage()
-        .persistent()
-        .set(&DataKey::Whitelist(account), &status);
-}
+//! Storage-accessor helpers.
+//!
+//! Historically this module exposed read_project / write_project /
+//! read_proposal / write_proposal / read_whitelist / write_whitelist wrappers
+//! around env.storage(), but lib.rs inlines env.storage() calls directly and
+//! never referenced them. They were removed to eliminate dead, drift-prone
+//! abstractions (#331).