feat: add admin-configurable transaction fees per accepted token

contracts/shade/src/components/admin.rs

@@ -1,7 +1,8 @@
 use crate::components::{core, reentrancy};
+use crate::errors::ContractError;
 use crate::events;
 use crate::types::DataKey;
-use soroban_sdk::{token, Address, Env, Vec};
+use soroban_sdk::{panic_with_error, token, Address, Env, Vec};
 
 pub fn add_accepted_token(env: &Env, admin: &Address, token: &Address) {
     reentrancy::enter(env);
@@ -49,6 +50,29 @@ pub fn is_accepted_token(env: &Env, token: &Address) -> bool {
     contains_token(&get_accepted_tokens(env), token)
 }
 
+pub fn set_fee(env: &Env, admin: &Address, token: &Address, fee: i128) {
+    reentrancy::enter(env);
+    core::assert_admin(env, admin);
+
+    if !is_accepted_token(env, token) {
+        panic_with_error!(env, ContractError::TokenNotAccepted);
+    }
+
+    env.storage()
+        .persistent()
+        .set(&DataKey::TokenFee(token.clone()), &fee);
+
+    events::publish_fee_set_event(env, token.clone(), fee, env.ledger().timestamp());
+    reentrancy::exit(env);
+}
+
+pub fn get_fee(env: &Env, token: &Address) -> i128 {
+    env.storage()
+        .persistent()
+        .get(&DataKey::TokenFee(token.clone()))
+        .unwrap_or(0)
+}
+
 fn get_accepted_tokens(env: &Env) -> Vec<Address> {
     env.storage()
         .persistent()

contracts/shade/src/errors.rs

@@ -15,4 +15,5 @@ pub enum ContractError {
     ContractPaused = 9,
     ContractNotPaused = 10,
     MerchantKeyNotFound = 11,
+    TokenNotAccepted = 12,
 }

contracts/shade/src/events.rs

@@ -174,6 +174,22 @@ pub fn publish_contract_unpaused_event(env: &Env, admin: Address, timestamp: u64
     ContractUnpausedEvent { admin, timestamp }.publish(env);
 }
 
+#[contractevent]
+pub struct FeeSetEvent {
+    pub token: Address,
+    pub fee: i128,
+    pub timestamp: u64,
+}
+
+pub fn publish_fee_set_event(env: &Env, token: Address, fee: i128, timestamp: u64) {
+    FeeSetEvent {
+        token,
+        fee,
+        timestamp,
+    }
+    .publish(env);
+}
+
 #[contractevent]
 pub struct ContractUpgradedEvent {
     pub new_wasm_hash: BytesN<32>,

contracts/shade/src/interface.rs

@@ -8,6 +8,8 @@ pub trait ShadeTrait {
     fn add_accepted_token(env: Env, admin: Address, token: Address);
     fn remove_accepted_token(env: Env, admin: Address, token: Address);
     fn is_accepted_token(env: Env, token: Address) -> bool;
+    fn set_fee(env: Env, admin: Address, token: Address, fee: i128);
+    fn get_fee(env: Env, token: Address) -> i128;
     fn register_merchant(env: Env, merchant: Address);
     fn get_merchant(env: Env, merchant_id: u64) -> Merchant;
     fn get_merchants(env: Env, filter: MerchantFilter) -> Vec<Merchant>;

contracts/shade/src/shade.rs

@@ -46,6 +46,15 @@ impl ShadeTrait for Shade {
         admin_component::is_accepted_token(&env, &token)
     }
 
+    fn set_fee(env: Env, admin: Address, token: Address, fee: i128) {
+        pausable_component::assert_not_paused(&env);
+        admin_component::set_fee(&env, &admin, &token, fee);
+    }
+
+    fn get_fee(env: Env, token: Address) -> i128 {
+        admin_component::get_fee(&env, &token)
+    }
+
     fn register_merchant(env: Env, merchant: Address) {
         pausable_component::assert_not_paused(&env);
         merchant_component::register_merchant(&env, &merchant);

contracts/shade/src/types.rs

@@ -12,6 +12,7 @@ pub enum DataKey {
     MerchantKey(Address),
     MerchantCount,
     MerchantId(Address),
+    TokenFee(Address),
     MerchantTokens,
     MerchantBalance(Address),
     Invoice(u64),