feat: add mempool support

See the changes in `ARCHITECTURE.md` for a detailed description.

- Add `MempoolManager` that activates after initial sync to monitor unconfirmed transactions via BIP37 bloom filters or local address matching. Includes peer relay management, dedup tracking, IS lock handling, and auto-rebuilding filters on address pool changes.
- Extend `WalletInterface` with `MempoolTransactionResult` return type and `watched_outpoints()` for bloom filter construction. Wire mempool manager into `SyncCoordinator` and propagate `confirmed_txids` through `BlockProcessed` events for mempool eviction.
- Add FFI bindings, dashd integration tests, and wallet unit tests.

Author: xdustinface

dash-spv-ffi/FFI_API.md

@@ -4,7 +4,7 @@ This document provides a comprehensive reference for all FFI (Foreign Function I
 
 **Auto-generated**: This documentation is automatically generated from the source code. Do not edit manually.
 
-**Total Functions**: 49
+**Total Functions**: 50
 
 ## Table of Contents
 
@@ -13,6 +13,7 @@ This document provides a comprehensive reference for all FFI (Foreign Function I
 - [Synchronization](#synchronization)
 - [Wallet Operations](#wallet-operations)
 - [Transaction Management](#transaction-management)
+- [Mempool Operations](#mempool-operations)
 - [Platform Integration](#platform-integration)
 - [Event Callbacks](#event-callbacks)
 - [Error Handling](#error-handling)
@@ -82,6 +83,14 @@ Functions: 1
 |----------|-------------|--------|
 | `dash_spv_ffi_client_broadcast_transaction` | Broadcasts a transaction to the Dash network via connected peers | client |
 
+### Mempool Operations
+
+Functions: 1
+
+| Function | Description | Module |
+|----------|-------------|--------|
+| `dash_spv_ffi_mempool_progress_destroy` | Destroy an `FFIMempoolProgress` object | types |
+
 ### Platform Integration
 
 Functions: 2
@@ -558,6 +567,24 @@ Broadcasts a transaction to the Dash network via connected peers.  # Safety  - `
 
 ---
 
+### Mempool Operations - Detailed
+
+#### `dash_spv_ffi_mempool_progress_destroy`
+
+```c
+dash_spv_ffi_mempool_progress_destroy(progress: *mut FFIMempoolProgress) -> ()
+```
+
+**Description:**
+Destroy an `FFIMempoolProgress` object.  # Safety - `progress` must be a pointer returned from this crate, or null.
+
+**Safety:**
+- `progress` must be a pointer returned from this crate, or null.
+
+**Module:** `types`
+
+---
+
 ### Platform Integration - Detailed
 
 #### `ffi_dash_spv_get_platform_activation_height`

dash-spv-ffi/include/dash_spv_ffi.h

@@ -38,6 +38,7 @@ typedef enum FFIManagerId {
   Masternodes = 4,
   ChainLocks = 5,
   InstantSend = 6,
+  Mempool = 7,
 } FFIManagerId;
 
 typedef enum FFIMempoolStrategy {
@@ -144,6 +145,18 @@ typedef struct FFIInstantSendProgress {
   uint64_t last_activity;
 } FFIInstantSendProgress;
 
+/**
+ * Progress for mempool transaction monitoring.
+ */
+typedef struct FFIMempoolProgress {
+  enum FFISyncState state;
+  uint32_t received;
+  uint32_t relevant;
+  uint32_t tracked;
+  uint32_t removed;
+  uint64_t last_activity;
+} FFIMempoolProgress;
+
 /**
  * Aggregate progress for all sync managers.
  * Provides a complete view of the parallel sync system's state.
@@ -162,6 +175,7 @@ typedef struct FFISyncProgress {
   struct FFIMasternodesProgress *masternodes;
   struct FFIChainLockProgress *chainlocks;
   struct FFIInstantSendProgress *instantsend;
+  struct FFIMempoolProgress *mempool;
 } FFISyncProgress;
 
 /**
@@ -249,6 +263,8 @@ typedef void (*OnBlocksNeededCallback)(const struct FFIBlockNeeded *blocks,
 typedef void (*OnBlockProcessedCallback)(uint32_t height,
                                          const uint8_t (*hash)[32],
                                          uint32_t new_address_count,
+                                         const uint8_t (*confirmed_txids)[32],
+                                         uint32_t confirmed_txid_count,
                                          void *user_data);
 
 /**
@@ -976,6 +992,14 @@ struct FFIResult ffi_dash_spv_get_platform_activation_height(struct FFIDashSpvCl
  */
  void dash_spv_ffi_instantsend_progress_destroy(struct FFIInstantSendProgress *progress) ;
 
+/**
+ * Destroy an `FFIMempoolProgress` object.
+ *
+ * # Safety
+ * - `progress` must be a pointer returned from this crate, or null.
+ */
+ void dash_spv_ffi_mempool_progress_destroy(struct FFIMempoolProgress *progress) ;
+
 /**
  * Destroy an `FFISyncProgress` object and all its nested pointers.
  *

dash-spv-ffi/src/bin/ffi_cli.rs

@@ -29,6 +29,7 @@ extern "C" fn on_sync_start(manager_id: FFIManagerId, _user_data: *mut c_void) {
         FFIManagerId::Masternodes => "Masternodes",
         FFIManagerId::ChainLocks => "ChainLocks",
         FFIManagerId::InstantSend => "InstantSend",
+        FFIManagerId::Mempool => "Mempool",
     };
     println!("[Sync] Manager started: {}", manager_name);
 }
@@ -76,9 +77,14 @@ extern "C" fn on_block_processed(
     height: u32,
     _hash: *const [u8; 32],
     new_address_count: u32,
+    _confirmed_txids: *const [u8; 32],
+    confirmed_txid_count: u32,
     _user_data: *mut c_void,
 ) {
-    println!("[Sync] Block processed: height={}, new_addresses={}", height, new_address_count);
+    println!(
+        "[Sync] Block processed: height={}, new_addresses={}, confirmed_txs={}",
+        height, new_address_count, confirmed_txid_count
+    );
 }
 
 extern "C" fn on_masternode_state_updated(height: u32, _user_data: *mut c_void) {

dash-spv-ffi/src/callbacks.rs

@@ -27,6 +27,7 @@ pub enum FFIManagerId {
     Masternodes = 4,
     ChainLocks = 5,
     InstantSend = 6,
+    Mempool = 7,
 }
 
 impl From<dash_spv::sync::ManagerIdentifier> for FFIManagerId {
@@ -39,6 +40,7 @@ impl From<dash_spv::sync::ManagerIdentifier> for FFIManagerId {
             dash_spv::sync::ManagerIdentifier::Masternode => FFIManagerId::Masternodes,
             dash_spv::sync::ManagerIdentifier::ChainLock => FFIManagerId::ChainLocks,
             dash_spv::sync::ManagerIdentifier::InstantSend => FFIManagerId::InstantSend,
+            dash_spv::sync::ManagerIdentifier::Mempool => FFIManagerId::Mempool,
         }
     }
 }
@@ -162,6 +164,8 @@ pub type OnBlockProcessedCallback = Option<
         height: u32,
         hash: *const [u8; 32],
         new_address_count: u32,
+        confirmed_txids: *const [u8; 32],
+        confirmed_txid_count: u32,
         user_data: *mut c_void,
     ),
 >;
@@ -350,13 +354,18 @@ impl FFISyncEventCallbacks {
                 block_hash,
                 height,
                 new_addresses,
+                confirmed_txids,
             } => {
                 if let Some(cb) = self.on_block_processed {
                     let hash_bytes = block_hash.as_byte_array();
+                    let txid_bytes: Vec<[u8; 32]> =
+                        confirmed_txids.iter().map(|txid| *txid.as_byte_array()).collect();
                     cb(
                         *height,
                         hash_bytes as *const [u8; 32],
                         new_addresses.len() as u32,
+                        txid_bytes.as_ptr(),
+                        txid_bytes.len() as u32,
                         self.user_data,
                     );
                 }

dash-spv-ffi/src/types.rs

@@ -1,8 +1,8 @@
 use dash_spv::client::config::MempoolStrategy;
 use dash_spv::sync::{
     BlockHeadersProgress, BlocksProgress, ChainLockProgress, FilterHeadersProgress,
-    FiltersProgress, InstantSendProgress, MasternodesProgress, ProgressPercentage, SyncProgress,
-    SyncState,
+    FiltersProgress, InstantSendProgress, MasternodesProgress, MempoolProgress, ProgressPercentage,
+    SyncProgress, SyncState,
 };
 use dash_spv::types::MempoolRemovalReason;
 use std::ffi::{CStr, CString};
@@ -259,6 +259,31 @@ impl From<&InstantSendProgress> for FFIInstantSendProgress {
     }
 }
 
+/// Progress for mempool transaction monitoring.
+#[repr(C)]
+#[derive(Debug, Clone, Default)]
+pub struct FFIMempoolProgress {
+    pub state: FFISyncState,
+    pub received: u32,
+    pub relevant: u32,
+    pub tracked: u32,
+    pub removed: u32,
+    pub last_activity: u64,
+}
+
+impl From<&MempoolProgress> for FFIMempoolProgress {
+    fn from(progress: &MempoolProgress) -> Self {
+        FFIMempoolProgress {
+            state: progress.state().into(),
+            received: progress.received(),
+            relevant: progress.relevant(),
+            tracked: progress.tracked(),
+            removed: progress.removed(),
+            last_activity: progress.last_activity().elapsed().as_secs(),
+        }
+    }
+}
+
 /// Aggregate progress for all sync managers.
 /// Provides a complete view of the parallel sync system's state.
 #[repr(C)]
@@ -274,6 +299,7 @@ pub struct FFISyncProgress {
     pub masternodes: *mut FFIMasternodesProgress,
     pub chainlocks: *mut FFIChainLockProgress,
     pub instantsend: *mut FFIInstantSendProgress,
+    pub mempool: *mut FFIMempoolProgress,
 }
 
 impl From<SyncProgress> for FFISyncProgress {
@@ -320,6 +346,12 @@ impl From<SyncProgress> for FFISyncProgress {
             .map(|p| Box::into_raw(Box::new(FFIInstantSendProgress::from(p))))
             .unwrap_or(std::ptr::null_mut());
 
+        let mempool = progress
+            .mempool()
+            .ok()
+            .map(|p| Box::into_raw(Box::new(FFIMempoolProgress::from(p))))
+            .unwrap_or(std::ptr::null_mut());
+
         Self {
             state: progress.state().into(),
             percentage: progress.percentage(),
@@ -331,6 +363,7 @@ impl From<SyncProgress> for FFISyncProgress {
             masternodes,
             chainlocks,
             instantsend,
+            mempool,
         }
     }
 }
@@ -486,6 +519,17 @@ pub unsafe extern "C" fn dash_spv_ffi_instantsend_progress_destroy(
     }
 }
 
+/// Destroy an `FFIMempoolProgress` object.
+///
+/// # Safety
+/// - `progress` must be a pointer returned from this crate, or null.
+#[no_mangle]
+pub unsafe extern "C" fn dash_spv_ffi_mempool_progress_destroy(progress: *mut FFIMempoolProgress) {
+    if !progress.is_null() {
+        let _ = Box::from_raw(progress);
+    }
+}
+
 /// Destroy an `FFISyncProgress` object and all its nested pointers.
 ///
 /// # Safety
@@ -517,5 +561,8 @@ pub unsafe extern "C" fn dash_spv_ffi_sync_progress_destroy(progress: *mut FFISy
         if !p.instantsend.is_null() {
             dash_spv_ffi_instantsend_progress_destroy(p.instantsend);
         }
+        if !p.mempool.is_null() {
+            dash_spv_ffi_mempool_progress_destroy(p.mempool);
+        }
     }
 }

dash-spv-ffi/tests/dashd_sync/callbacks.rs

@@ -233,14 +233,21 @@ extern "C" fn on_block_processed(
     height: u32,
     _hash: *const [u8; 32],
     new_address_count: u32,
+    _confirmed_txids: *const [u8; 32],
+    confirmed_txid_count: u32,
     user_data: *mut c_void,
 ) {
     let Some(tracker) = (unsafe { tracker_from(user_data) }) else {
         return;
     };
     tracker.processed_block_heights.lock().unwrap_or_else(|e| e.into_inner()).push(height);
     tracker.block_processed_count.fetch_add(1, Ordering::SeqCst);
-    tracing::debug!("on_block_processed: height={}, new_addresses={}", height, new_address_count);
+    tracing::debug!(
+        "on_block_processed: height={}, new_addresses={}, confirmed_txs={}",
+        height,
+        new_address_count,
+        confirmed_txid_count
+    );
 }
 
 extern "C" fn on_masternode_state_updated(height: u32, user_data: *mut c_void) {