Remove contract_type() from SwapCoin trait

I think this style is too OOP and not enough rustic. Now that
we have separate structs Incoming/OutgoingSwapCoin we can more
simply say that Outgoing = timelock and Incoming = hashlock

src/contracts.rs

@@ -51,7 +51,6 @@ pub trait SwapCoin {
     fn verify_contract_tx_receiver_sig(&self, sig: &Signature) -> bool;
     fn verify_contract_tx_sender_sig(&self, sig: &Signature) -> bool;
     fn apply_privkey(&mut self, privkey: SecretKey) -> Result<(), Error>;
-    fn contract_type(&self) -> &str;
     fn is_known(&self) -> bool;
 }
 
@@ -506,10 +505,6 @@ impl SwapCoin for IncomingSwapCoin {
         Ok(())
     }
 
-    fn contract_type(&self) -> &str {
-        self.type_string()
-    }
-
     fn is_known(&self) -> bool {
         self.contract_privkey_is_known()
     }
@@ -560,10 +555,6 @@ impl SwapCoin for OutgoingSwapCoin {
         }
     }
 
-    fn contract_type(&self) -> &str {
-        self.type_string()
-    }
-
     fn is_known(&self) -> bool {
         self.contract_privkey_is_known()
     }
@@ -656,10 +647,6 @@ impl SwapCoin for WatchOnlySwapCoin {
         }
     }
 
-    fn contract_type(&self) -> &str {
-        "watchonly"
-    }
-
     fn is_known(&self) -> bool {
         false
     }

src/main.rs

@@ -4,6 +4,7 @@ extern crate bitcoincore_rpc;
 
 use dirs::home_dir;
 use std::io;
+use std::iter::repeat;
 use std::path::PathBuf;
 use std::sync::{Arc, RwLock};
 
@@ -186,13 +187,16 @@ fn display_wallet_balance(wallet_file_name: &PathBuf, long_form: Option<bool>) {
                 "{:16} {:8} {:8} {:<15} {:<7} value",
                 "outpoint", "type", "preimage", "locktime/blocks", "conf",
             );
-            for (utxo, swapcoin) in utxo_incoming_swapcoins
+
+            for ((utxo, swapcoin), contract_type) in utxo_incoming_swapcoins
                 .iter()
                 .map(|(l, i)| (l, (*i as &dyn SwapCoin)))
+                .zip(repeat("hashlock"))
                 .chain(
                     utxo_outgoing_swapcoins
                         .iter()
-                        .map(|(l, o)| (l, (*o as &dyn SwapCoin))),
+                        .map(|(l, o)| (l, (*o as &dyn SwapCoin)))
+                        .zip(repeat("timelock")),
                 )
             {
                 let txid = utxo.txid.to_hex();
@@ -203,7 +207,7 @@ fn display_wallet_balance(wallet_file_name: &PathBuf, long_form: Option<bool>) {
                     if long_form { "" } else { ".." },
                     if long_form { &"" } else { &txid[58..64] },
                     utxo.vout,
-                    swapcoin.contract_type(),
+                    contract_type,
                     if swapcoin.is_known() { "known" } else { "unknown" },
                     read_locktime_from_contract(&swapcoin.get_contract_redeemscript())
                         .expect("unable to read locktime from contract"),

src/wallet_sync.rs

@@ -154,10 +154,6 @@ impl IncomingSwapCoin {
         }
     }
 
-    pub fn type_string(&self) -> &str {
-        "hashlock"
-    }
-
     pub fn contract_privkey_is_known(&self) -> bool {
         self.other_privkey.is_some() || self.hash_preimage.is_some()
     }
@@ -193,10 +189,6 @@ impl OutgoingSwapCoin {
         }
     }
 
-    pub fn type_string(&self) -> &str {
-        "timelock"
-    }
-
     pub fn contract_privkey_is_known(&self) -> bool {
         self.hash_preimage.is_some()
     }