From d4c9c15c1d47c58e6b98898e9c3ac1371e2b7842 Mon Sep 17 00:00:00 2001
From: Pol Espinasa <pol.espinasa@uab.cat>
Date: Fri, 17 May 2024 10:19:28 +0200
Subject: [PATCH] Implement group close by prio fee rate

It makes no sense to maintain groups that pay higher commissions than those required to enter the next block. With this commit every time a transaction is added, it is checked if any of the existing groups can be closed following that condition, if it can, the group is closed.
---
 server/grouphug-server/src/main.rs         | 87 ++++++++++++++++------
 server/grouphug-server/src/server/group.rs |  2 +-
 2 files changed, 66 insertions(+), 23 deletions(-)

diff --git a/server/grouphug-server/src/main.rs b/server/grouphug-server/src/main.rs
index b188da3..a810c5b 100644
--- a/server/grouphug-server/src/main.rs
+++ b/server/grouphug-server/src/main.rs
@@ -19,6 +19,9 @@ use std::{
 use once_cell::sync::Lazy;
 use hex::decode as hex_decode;
 use bdk::bitcoin::{Transaction,consensus::encode::deserialize};
+use bdk::electrum_client::{Client, ConfigBuilder, ElectrumApi};
+use bdk::blockchain::{ElectrumBlockchain};
+use bdk::{FeeRate};
 
 pub static CONFIG: Lazy<Config> = Lazy::new(|| {
     
@@ -106,6 +109,44 @@ fn handle_get_groups_info(mut stream: TcpStream) {
     stream.write(end_line.as_bytes()).unwrap();
     return
 }
+
+fn close_group_by_fee() {
+    // Check the actual feerate for the network and close all groups that have a fee rate bigger than the actual fee rate by 2 sat/vb.
+    
+    let config = ConfigBuilder::new().validate_domain(crate::CONFIG.electrum.certificate_validation).build();
+    let client = Client::from_config(&crate::CONFIG.electrum.endpoint, config.clone()).unwrap();
+    let blockchain = ElectrumBlockchain::from(client);
+
+    let target: usize = 1;
+    let mut matching_fee_rates: Vec<f32> = Vec::new();
+
+    let mut groups = GLOBAL_GROUPS.lock().unwrap();
+    match blockchain.estimate_fee(target) {
+        Ok(rate) => {
+            let fee_rate = FeeRate::from_btc_per_kvb(rate as f32);
+            // compare needed fee rate for the target confirmation with the group fee rate
+            // close the ones that pay more than what is needed
+            for group in groups.iter_mut() {
+                if (fee_rate.as_sat_per_vb() as f32) < ((group.fee_rate - 2.0) as f32) {
+                    if group.close_group() {
+                        matching_fee_rates.push(group.fee_rate);
+                    }  
+                }
+            }
+        },
+        Err(e) => {
+            eprintln!("There was an error estimating fees for the next {:?} blocks: {:?}", target, e);
+        }
+    }
+
+    for rate in matching_fee_rates {
+        // delete the closed groups from the group list 
+        groups.retain(|g| g.fee_rate != rate);
+    }
+    return;    
+    
+}
+
 fn handle_addtx(transaction: &str, mut stream: TcpStream) {
 
     // Validate that the tx has the correct format and satisfies all the rules
@@ -134,33 +175,35 @@ fn handle_addtx(transaction: &str, mut stream: TcpStream) {
     // Calculate the group fee rate.
     let expected_group_fee = ((fee_rate / &crate::CONFIG.fee.range).floor() * &crate::CONFIG.fee.range) as f32;
 
-    // Unlock the GLOBAL_GROUPS variable
-    let mut groups = GLOBAL_GROUPS.lock().unwrap();
+    { // Use this so we unlock the GLOBAL_GROUPS variable after using it
 
-    // Search for the group corresponing to the transaction fee rate
-    let group = groups.iter_mut().find(|g| g.fee_rate == expected_group_fee);
+        // Unlock the GLOBAL_GROUPS variable
+        let mut groups = GLOBAL_GROUPS.lock().unwrap();
 
-    let close_group;
-    match group {
-        Some(group) => {
-            // If some then the group already exist so we add the tx to that group
-            close_group = group.add_tx(transaction);
-        },
-        None => {
-            // If none then there is no group for this fee rate so we create one
-            let mut new_group = Group::new(expected_group_fee);
-            println!("New group created with fee_rate {}sat/vB", new_group.fee_rate);
-            close_group = new_group.add_tx(transaction);
-            groups.push(new_group);
+        // Search for the group corresponing to the transaction fee rate
+        let group = groups.iter_mut().find(|g| g.fee_rate == expected_group_fee);
+
+        let close_group;
+        match group {
+            Some(group) => {
+                // If some then the group already exist so we add the tx to that group
+                close_group = group.add_tx(transaction);
+            },
+            None => {
+                // If none then there is no group for this fee rate so we create one
+                let mut new_group = Group::new(expected_group_fee);
+                println!("New group created with fee_rate {}sat/vB", new_group.fee_rate);
+                close_group = new_group.add_tx(transaction);
+                groups.push(new_group);
+            }
         }
-    }
 
-    if close_group {
-        // If the group has been closed during the add_tx function we delete it from the groups vector
-        groups.retain(|g| g.fee_rate != expected_group_fee);
+        if close_group {
+            // If the group has been closed during the add_tx function we delete it from the groups vector
+            groups.retain(|g| g.fee_rate != expected_group_fee);
+        }
     }
-    
-
+    close_group_by_fee();
     // Send an OK message if the tx was added successfuly
     stream.write(msg.as_bytes()).unwrap();
 
diff --git a/server/grouphug-server/src/server/group.rs b/server/grouphug-server/src/server/group.rs
index 43f8ebb..ca388fa 100644
--- a/server/grouphug-server/src/server/group.rs
+++ b/server/grouphug-server/src/server/group.rs
@@ -84,7 +84,7 @@ impl Group {
     }
     
 
-    fn close_group(&mut self) -> bool {
+    pub fn close_group(&mut self) -> bool {
         // Finalize the transaction and send it to the network
     
         // Connect to Electrum node