feat: Add token locking mechanism and SDK retry logic (#191, #170)

contracts/property-token/src/events.rs

@@ -172,14 +172,7 @@ pub struct DividendsWithdrawn {
     pub amount: u128,
 }
 
-#[ink(event)]
-pub struct VestedTokensClaimed {
-    #[ink(topic)]
-    pub token_id: TokenId,
-    #[ink(topic)]
-    pub account: AccountId,
-    pub amount: u128,
-}
+
 
 // =========================================================================
 // Metadata Events
@@ -206,6 +199,8 @@ pub struct TokenURIUpdated {
 // Governance Events
 // =========================================================================
 
+
+
 #[ink(event)]
 pub struct ProposalCreated {
     #[ink(topic)]

contracts/property-token/src/lib.rs

@@ -588,6 +588,8 @@ pub mod property_token {
             }
         }
 
+
+
         /// ERC-721: Returns the balance of tokens owned by an account
         #[ink(message)]
         pub fn balance_of(&self, owner: AccountId) -> u32 {
@@ -646,6 +648,8 @@ pub mod property_token {
                 return Err(Error::Unauthorized);
             }
 
+
+
             // Perform the transfer
             self.remove_token_from_owner(from, token_id)?;
             self.add_token_to_owner(to, token_id)?;
@@ -803,6 +807,7 @@ pub mod property_token {
                 let token_id = ids[i];
                 let amount = amounts[i];
                 let from_balance = self.balances.get((&from, &token_id)).unwrap_or(0);
+
                 self.balances
                     .insert((&from, &token_id), &(from_balance - amount));
                 let to_balance = self.balances.get((&to, &token_id)).unwrap_or(0);

sdk/frontend/src/client/PropertyTokenClient.ts

@@ -35,6 +35,7 @@ import type {
 import { TxProgressStatus } from '../types';
 import { decodeContractError, TransactionError, GasEstimationError } from '../utils/errors';
 import { decodeTransactionEvents, subscribeToNamedEvent } from '../utils/events';
+import { withExponentialBackoff } from '../utils/connection';
 import type { PropChainEventName, PropChainEventMap } from '../types/events';
 
 export type Signer = KeyringPair | string;
@@ -610,7 +611,8 @@ export class PropertyTokenClient {
   // ==========================================================================
 
   private async query(method: string, args: unknown[]): Promise<unknown> {
-    const queryFn = this.contract.query[method];
+    return withExponentialBackoff(async () => {
+      const queryFn = this.contract.query[method];
     if (!queryFn) {
       throw new Error(`Unknown query method: ${method}`);
     }
@@ -623,7 +625,8 @@ export class PropertyTokenClient {
       throw decodeContractError(errorVariant);
     }
 
-    return output ? output.toJSON() : null;
+      return output ? output.toJSON() : null;
+    });
   }
 
   private async submitTx(

sdk/frontend/src/utils/connection.ts

@@ -142,6 +142,43 @@ export async function connectToNetwork(networkName: string): Promise<ApiPromise>
   return createApi(config.wsEndpoint);
 }
 
+/**
+ * Executes a Promise-returning operation with exponential backoff retry logic.
+ *
+ * @param operation - The function to execute
+ * @param maxRetries - Maximum number of retries (default: 3)
+ * @param baseDelayMs - Base delay between retries in ms (default: 1000)
+ * @returns The result of the operation
+ * @throws The last error encountered after exhausting all retries
+ */
+export async function withExponentialBackoff<T>(
+  operation: () => Promise<T>,
+  maxRetries: number = 3,
+  baseDelayMs: number = 1000,
+): Promise<T> {
+  let attempt = 0;
+  let lastError: Error | undefined;
+
+  while (attempt <= maxRetries) {
+    try {
+      return await operation();
+    } catch (error) {
+      lastError = error instanceof Error ? error : new Error(String(error));
+
+      // Do not retry if we've reached maxRetries
+      if (attempt === maxRetries) {
+        break;
+      }
+
+      const delay = baseDelayMs * Math.pow(2, attempt);
+      await sleep(delay);
+      attempt++;
+    }
+  }
+
+  throw lastError;
+}
+
 /**
  * Gets the network configuration for a preset name.
  *