feat: get_change_output_and_fees match collateral value

dlc-manager/src/utils.rs

@@ -2,7 +2,7 @@
 use std::ops::Deref;
 
 use bitcoin::{consensus::Encodable, Txid};
-use dlc::{PartyParams, TxInputInfo};
+use dlc::{util::get_common_fee, PartyParams, TxInputInfo};
 use dlc_messages::{
     oracle_msgs::{OracleAnnouncement, OracleAttestation},
     FundingInput,
@@ -81,9 +81,18 @@ where
     let change_serial_id = get_new_serial_id();
 
     // Add base cost of fund tx + CET / 2 and a CET output to the collateral.
-    let appr_required_amount =
-        own_collateral + get_half_common_fee(fee_rate)? + dlc::util::weight_to_fee(124, fee_rate)?;
-    let utxos = wallet.get_utxos_for_amount(appr_required_amount, Some(fee_rate), true)?;
+
+    let utxos = match own_collateral {
+        0 => Vec::new(),
+        _ => {
+            let common_fee = get_common_fee(fee_rate)?;
+            let total_fee = common_fee + own_collateral;
+            let appr_required_amount =
+                own_collateral + total_fee + dlc::util::weight_to_fee(124, fee_rate)?;
+            let utxos = wallet.get_utxos_for_amount(appr_required_amount, Some(fee_rate), true)?;
+            utxos
+        }
+    };
 
     let mut funding_inputs_info: Vec<FundingInputInfo> = Vec::new();
     let mut funding_tx_info: Vec<TxInputInfo> = Vec::new();
@@ -141,11 +150,6 @@ where
     })
 }
 
-pub(crate) fn get_half_common_fee(fee_rate: u64) -> Result<u64, Error> {
-    let common_fee = dlc::util::get_common_fee(fee_rate)?;
-    Ok((common_fee as f64 / 2_f64).ceil() as u64)
-}
-
 pub(crate) fn get_range_info_and_oracle_sigs(
     contract_info: &ContractInfo,
     adaptor_info: &AdaptorInfo,

dlc/src/lib.rs

@@ -301,7 +301,7 @@ impl PartyParams {
 
         // Base weight (nLocktime, nVersion, ...) is distributed among parties
         // independently of inputs contributed
-        let this_party_fund_base_weight = FUND_TX_BASE_WEIGHT / 2;
+        let this_party_fund_base_weight = FUND_TX_BASE_WEIGHT;
 
         let total_fund_weight = checked_add!(
             this_party_fund_base_weight,
@@ -313,7 +313,7 @@ impl PartyParams {
 
         // Base weight (nLocktime, nVersion, funding input ...) is distributed
         // among parties independently of output types
-        let this_party_cet_base_weight = CET_BASE_WEIGHT / 2;
+        let this_party_cet_base_weight = CET_BASE_WEIGHT;
 
         // size of the payout script pubkey scaled by 4 from vBytes to weight units
         let output_spk_weight =
@@ -325,8 +325,12 @@ impl PartyParams {
         )))?;
         let total_cet_weight = checked_add!(this_party_cet_base_weight, output_spk_weight)?;
         let cet_or_refund_fee = util::weight_to_fee(total_cet_weight, fee_rate_per_vb)?;
-        let required_input_funds =
-            checked_add!(self.collateral, fund_fee, cet_or_refund_fee, extra_fee)?;
+        let required_input_funds: u64 = if self.collateral == 0 {
+            0
+        } else {
+            checked_add!(self.collateral, fund_fee, cet_or_refund_fee, extra_fee)?
+        };
+
         if self.input_amount < required_input_funds {
             return Err(Error::InvalidArgument(format!("[get_change_output_and_fees] error: input amount is lower than the sum of the collateral plus the required fees => input_amount: {}, collateral: {}, fund fee: {}, cet_or_refund_fee: {}, extra_fee: {}", self.input_amount, self.collateral, fund_fee, cet_or_refund_fee, extra_fee)));
         }
@@ -336,7 +340,11 @@ impl PartyParams {
             script_pubkey: self.change_script_pubkey.clone(),
         };
 
-        Ok((change_output, fund_fee, cet_or_refund_fee))
+        if fee_rate_per_vb == 0 {
+            Ok((change_output, 0, 0))
+        } else {
+            Ok((change_output, fund_fee, cet_or_refund_fee))
+        }
     }
 
     fn get_unsigned_tx_inputs_and_serial_ids(&self, sequence: Sequence) -> (Vec<TxIn>, Vec<u64>) {
@@ -411,8 +419,13 @@ pub(crate) fn create_fund_transaction_with_fees(
 ) -> Result<(Transaction, Script), Error> {
     let total_collateral = checked_add!(offer_params.collateral, accept_params.collateral)?;
 
-    let (offer_change_output, offer_fund_fee, offer_cet_fee) =
-        offer_params.get_change_output_and_fees(fee_rate_per_vb, extra_fee)?;
+    let offer_change_output = TxOut {
+        value: 0,
+        script_pubkey: offer_params.change_script_pubkey.clone(),
+    };
+    let offer_fund_fee = 0;
+    let offer_cet_fee = 0;
+
     let (accept_change_output, accept_fund_fee, accept_cet_fee) =
         accept_params.get_change_output_and_fees(fee_rate_per_vb, extra_fee)?;