Use builder terminology instead of factory

This is not really a factory as a factory design pattern is about
producing several instances.

In the current usage, we are only interested in one swap instance. Once
the swap instance is created, the factory becomes useless. Hence, it is
more of a builder pattern.

swap/src/main.rs

@@ -23,7 +23,7 @@ use swap::{
     config::Config,
     database::Database,
     monero,
-    protocol::{alice, bob, bob::SwapFactory, StartingBalances},
+    protocol::{alice, bob, bob::Builder},
     trace::init_tracing,
     SwapAmounts,
 };
@@ -82,7 +82,7 @@ async fn main() -> Result<()> {
                 send_monero, receive_bitcoin, swap_id
             );
 
-            let alice_factory = alice::SwapFactory::new(
+            let alice_factory = alice::Builder::new(
                 seed,
                 config,
                 swap_id,
@@ -92,7 +92,8 @@ async fn main() -> Result<()> {
                 listen_addr,
             )
             .await;
-            let (swap, mut event_loop) = alice_factory.new_swap(swap_amounts).await?;
+            let (swap, mut event_loop) =
+                alice_factory.with_init_params(swap_amounts).build().await?;
 
             tokio::spawn(async move { event_loop.run().await });
             alice::run(swap).await?;
@@ -126,7 +127,7 @@ async fn main() -> Result<()> {
                 send_bitcoin, receive_monero, swap_id
             );
 
-            let bob_factory = SwapFactory::new(
+            let bob_factory = Builder::new(
                 seed,
                 db_path,
                 swap_id,
@@ -135,7 +136,10 @@ async fn main() -> Result<()> {
                 alice_addr,
                 alice_peer_id,
             );
-            let (swap, event_loop) = bob_factory.new_swap(swap_amounts, config).await?;
+            let (swap, event_loop) = bob_factory
+                .with_init_params(swap_amounts, config)
+                .build()
+                .await?;
 
             tokio::spawn(async move { event_loop.run().await });
             bob::run(swap).await?;
@@ -169,7 +173,7 @@ async fn main() -> Result<()> {
             )
             .await?;
 
-            let alice_factory = alice::SwapFactory::new(
+            let alice_factory = alice::Builder::new(
                 seed,
                 config,
                 swap_id,
@@ -179,7 +183,7 @@ async fn main() -> Result<()> {
                 listen_addr,
             )
             .await;
-            let (swap, mut event_loop) = alice_factory.resume().await?;
+            let (swap, mut event_loop) = alice_factory.build().await?;
 
             tokio::spawn(async move { event_loop.run().await });
             alice::run(swap).await?;
@@ -200,7 +204,7 @@ async fn main() -> Result<()> {
             )
             .await?;
 
-            let bob_factory = SwapFactory::new(
+            let bob_factory = Builder::new(
                 seed,
                 db_path,
                 swap_id,
@@ -209,7 +213,7 @@ async fn main() -> Result<()> {
                 alice_addr,
                 alice_peer_id,
             );
-            let (swap, event_loop) = bob_factory.resume().await?;
+            let (swap, event_loop) = bob_factory.build().await?;
 
             tokio::spawn(async move { event_loop.run().await });
             bob::run(swap).await?;

swap/src/protocol/alice.rs

@@ -24,10 +24,7 @@ pub use self::{
     state::*,
     swap::{run, run_until},
 };
-use crate::{
-    config::Config, database::Database, network::transport::build, protocol::StartingBalances,
-    seed::Seed,
-};
+use crate::{config::Config, database::Database, network::transport::build, seed::Seed};
 use libp2p::{core::Multiaddr, identity::Keypair};
 use rand::rngs::OsRng;
 use std::{path::PathBuf, sync::Arc};
@@ -53,7 +50,7 @@ pub struct Swap {
     pub db: Database,
 }
 
-pub struct SwapFactory {
+pub struct Builder {
     swap_id: Uuid,
     identity: Keypair,
     peer_id: PeerId,
@@ -64,9 +61,16 @@ pub struct SwapFactory {
 
     bitcoin_wallet: Arc<bitcoin::Wallet>,
     monero_wallet: Arc<monero::Wallet>,
+
+    init_params: InitParams,
 }
 
-impl SwapFactory {
+enum InitParams {
+    None,
+    New { swap_amounts: SwapAmounts },
+}
+
+impl Builder {
     pub async fn new(
         seed: Seed,
         config: Config,
@@ -89,10 +93,20 @@ impl SwapFactory {
             listen_address,
             bitcoin_wallet,
             monero_wallet,
+            init_params: InitParams::None,
         }
     }
 
-    pub async fn new_swap(self, swap_amounts: SwapAmounts) -> Result<(Swap, EventLoop)> {
+    pub fn with_init_params(self, swap_amounts: SwapAmounts) -> Self {
+        Self {
+            init_params: InitParams::New { swap_amounts },
+            ..self
+        }
+    }
+
+    pub async fn build(self) -> Result<(Swap, EventLoop)> {
+        match self.init_params {
+            InitParams::New { swap_amounts } => {
                 let initial_state = init_alice_state(
                     swap_amounts.btc,
                     swap_amounts.xmr,
@@ -122,12 +136,12 @@ impl SwapFactory {
                     event_loop,
                 ))
             }
-
-    pub async fn resume(self) -> Result<(Swap, EventLoop)> {
+            InitParams::None => {
                 // reopen the existing database
                 let db = Database::open(self.db_path.as_path())?;
 
-        let resume_state = if let database::Swap::Alice(state) = db.get_state(self.swap_id)? {
+                let resume_state =
+                    if let database::Swap::Alice(state) = db.get_state(self.swap_id)? {
                         state.into()
                     } else {
                         bail!(
@@ -155,6 +169,8 @@ impl SwapFactory {
                     event_loop,
                 ))
             }
+        }
+    }
 
     pub fn peer_id(&self) -> PeerId {
         self.peer_id.clone()

swap/src/protocol/bob.rs

@@ -23,10 +23,7 @@ pub use self::{
     state::*,
     swap::{run, run_until},
 };
-use crate::{
-    config::Config, database::Database, network::transport::build, protocol::StartingBalances,
-    seed::Seed,
-};
+use crate::{config::Config, database::Database, network::transport::build, seed::Seed};
 use libp2p::identity::Keypair;
 use rand::rngs::OsRng;
 use std::{path::PathBuf, sync::Arc};
@@ -50,7 +47,7 @@ pub struct Swap {
     pub swap_id: Uuid,
 }
 
-pub struct SwapFactory {
+pub struct Builder {
     swap_id: Uuid,
     identity: Keypair,
     peer_id: PeerId,
@@ -61,9 +58,19 @@ pub struct SwapFactory {
 
     bitcoin_wallet: Arc<bitcoin::Wallet>,
     monero_wallet: Arc<monero::Wallet>,
+
+    init_params: InitParams,
 }
 
-impl SwapFactory {
+enum InitParams {
+    None,
+    New {
+        swap_amounts: SwapAmounts,
+        config: Config,
+    },
+}
+
+impl Builder {
     pub fn new(
         seed: Seed,
         db_path: PathBuf,
@@ -85,14 +92,26 @@ impl SwapFactory {
             alice_peer_id,
             bitcoin_wallet,
             monero_wallet,
+            init_params: InitParams::None,
         }
     }
 
-    pub async fn new_swap(
-        self,
-        swap_amounts: SwapAmounts,
-        config: Config,
-    ) -> Result<(bob::Swap, bob::EventLoop)> {
+    pub fn with_init_params(self, swap_amounts: SwapAmounts, config: Config) -> Self {
+        Self {
+            init_params: InitParams::New {
+                swap_amounts,
+                config,
+            },
+            ..self
+        }
+    }
+
+    pub async fn build(self) -> Result<(bob::Swap, bob::EventLoop)> {
+        match self.init_params {
+            InitParams::New {
+                swap_amounts,
+                config,
+            } => {
                 let initial_state = self
                     .make_initial_state(swap_amounts.btc, swap_amounts.xmr, config)
                     .await?;
@@ -113,8 +132,7 @@ impl SwapFactory {
                     event_loop,
                 ))
             }
-
-    pub async fn resume(self) -> Result<(bob::Swap, bob::EventLoop)> {
+            InitParams::None => {
                 // reopen the existing database
                 let db = Database::open(self.db_path.as_path())?;
 
@@ -141,7 +159,8 @@ impl SwapFactory {
                     event_loop,
                 ))
             }
-
+        }
+    }
     fn init_event_loop(
         &self,
     ) -> Result<(bob::event_loop::EventLoop, bob::event_loop::EventLoopHandle)> {

swap/tests/testutils/mod.rs

@@ -9,7 +9,7 @@ use swap::{
     bitcoin,
     config::Config,
     monero,
-    protocol::{alice, alice::AliceState, bob, bob::BobState, StartingBalances},
+    protocol::{alice, alice::AliceState, bob, bob::BobState},
     seed::Seed,
     SwapAmounts,
 };
@@ -28,12 +28,12 @@ pub struct StartingBalances {
 pub struct TestContext {
     swap_amounts: SwapAmounts,
 
-    alice_swap_factory: Option<alice::SwapFactory>,
+    alice_swap_factory: Option<alice::Builder>,
     alice_starting_balances: StartingBalances,
     alice_bitcoin_wallet: Arc<bitcoin::Wallet>,
     alice_monero_wallet: Arc<monero::Wallet>,
 
-    bob_swap_factory: Option<bob::SwapFactory>,
+    bob_swap_factory: Option<bob::Builder>,
     bob_starting_balances: StartingBalances,
     bob_bitcoin_wallet: Arc<bitcoin::Wallet>,
     bob_monero_wallet: Arc<monero::Wallet>,
@@ -45,7 +45,8 @@ impl TestContext {
             .alice_swap_factory
             .take()
             .unwrap()
-            .new_swap(self.swap_amounts)
+            .with_init_params(self.swap_amounts)
+            .build()
             .await
             .unwrap();
 
@@ -59,7 +60,8 @@ impl TestContext {
             .bob_swap_factory
             .take()
             .unwrap()
-            .new_swap(self.swap_amounts, Config::regtest())
+            .with_init_params(self.swap_amounts, Config::regtest())
+            .build()
             .await
             .unwrap();
 
@@ -73,7 +75,7 @@ impl TestContext {
             .alice_swap_factory
             .take()
             .unwrap()
-            .resume()
+            .build()
             .await
             .unwrap();
 
@@ -83,13 +85,7 @@ impl TestContext {
     }
 
     pub async fn recover_bob_from_db(&mut self) -> bob::Swap {
-        let (swap, event_loop) = self
-            .bob_swap_factory
-            .take()
-            .unwrap()
-            .resume()
-            .await
-            .unwrap();
+        let (swap, event_loop) = self.bob_swap_factory.take().unwrap().build().await.unwrap();
 
         tokio::spawn(async move { event_loop.run().await });
 
@@ -283,7 +279,7 @@ where
     )
     .await;
 
-    let alice_swap_factory = alice::SwapFactory::new(
+    let alice_swap_factory = alice::Builder::new(
         Seed::random().unwrap(),
         config,
         Uuid::new_v4(),
@@ -308,7 +304,7 @@ where
     )
     .await;
 
-    let bob_swap_factory = bob::SwapFactory::new(
+    let bob_swap_factory = bob::Builder::new(
         Seed::random().unwrap(),
         tempdir().unwrap().path().to_path_buf(),
         Uuid::new_v4(),