Remove input_type and sequence from Context

Input type and sequence can be computed at little cost from the original
PSBT, which is already included in RequestContext/ContextV1. Remove
those fields from those structs and compute them when needed.

payjoin/src/send/mod.rs

@@ -31,7 +31,7 @@ use bitcoin::psbt::Psbt;
 use bitcoin::secp256k1::rand;
 #[cfg(feature = "v2")]
 use bitcoin::secp256k1::PublicKey;
-use bitcoin::{AddressType, Amount, FeeRate, Script, ScriptBuf, Sequence, TxOut, Weight};
+use bitcoin::{Amount, FeeRate, Script, ScriptBuf, TxOut, Weight};
 pub use error::{CreateRequestError, ResponseError, ValidationError};
 pub(crate) use error::{InternalCreateRequestError, InternalValidationError};
 #[cfg(feature = "v2")]
@@ -225,22 +225,12 @@ impl<'a> RequestBuilder<'a> {
  )?;
  clear_unneeded_fields(&mut psbt);
 
- let zeroth_input = psbt.input_pairs().next().ok_or(InternalCreateRequestError::NoInputs)?;
-
- let sequence = zeroth_input.txin.sequence;
- let input_type = zeroth_input
- .address_type()
- .map_err(InternalCreateRequestError::AddressType)?
- .to_string();
-
  Ok(RequestContext {
  psbt,
  endpoint,
  disable_output_substitution,
  fee_contribution,
  payee,
- input_type,
- sequence,
  min_fee_rate: self.min_fee_rate,
  #[cfg(feature = "v2")]
  e: crate::v2::HpkeKeyPair::gen_keypair().secret_key().clone(),
@@ -256,8 +246,6 @@ pub struct RequestContext {
  disable_output_substitution: bool,
  fee_contribution: Option<(bitcoin::Amount, usize)>,
  min_fee_rate: FeeRate,
- input_type: String,
- sequence: Sequence,
  payee: ScriptBuf,
  #[cfg(feature = "v2")]
  e: crate::v2::HpkeSecretKey,
@@ -282,8 +270,6 @@ impl RequestContext {
  disable_output_substitution: self.disable_output_substitution,
  fee_contribution: self.fee_contribution,
  payee: self.payee.clone(),
- input_type: AddressType::from_str(&self.input_type).expect("Unknown address type"),
- sequence: self.sequence,
  min_fee_rate: self.min_fee_rate,
  },
  ))
@@ -352,9 +338,6 @@ impl RequestContext {
  disable_output_substitution: self.disable_output_substitution,
  fee_contribution: self.fee_contribution,
  payee: self.payee.clone(),
- input_type: AddressType::from_str(&self.input_type)
- .expect("Unknown address type"),
- sequence: self.sequence,
  min_fee_rate: self.min_fee_rate,
  },
  rs: Some(self.extract_rs_pubkey()?),
@@ -397,8 +380,6 @@ pub struct ContextV1 {
  disable_output_substitution: bool,
  fee_contribution: Option<(bitcoin::Amount, usize)>,
  min_fee_rate: FeeRate,
- input_type: AddressType,
- sequence: Sequence,
  payee: ScriptBuf,
 }
 
@@ -565,6 +546,11 @@ impl ContextV1 {
  }
  // theirs (receiver)
  None | Some(_) => {
+ let original = self
+ .original_psbt
+ .input_pairs()
+ .next()
+ .expect("original PSBT should have an input");
  // Verify the PSBT input is finalized
  ensure!(
  proposed.psbtin.final_script_sig.is_some()
@@ -577,8 +563,8 @@ impl ContextV1 {
  || proposed.psbtin.non_witness_utxo.is_some(),
  ReceiverTxinMissingUtxoInfo
  );
- ensure!(proposed.txin.sequence == self.sequence, MixedSequence);
- check_eq!(proposed.address_type()?, self.input_type, MixedInputTypes);
+ ensure!(proposed.txin.sequence == original.txin.sequence, MixedSequence);
+ check_eq!(proposed.address_type()?, original.address_type()?, MixedInputTypes);
  }
  }
  }
@@ -855,8 +841,6 @@ mod test {
  fee_contribution: Some((bitcoin::Amount::from_sat(182), 0)),
  min_fee_rate: FeeRate::ZERO,
  payee,
- input_type: bitcoin::AddressType::P2sh,
- sequence,
  };
  ctx
  }
@@ -911,8 +895,6 @@ mod test {
  disable_output_substitution: false,
  fee_contribution: None,
  min_fee_rate: FeeRate::ZERO,
- input_type: bitcoin::AddressType::P2sh.to_string(),
- sequence: Sequence::MAX,
  payee: ScriptBuf::from(vec![0x00]),
  e: HpkeSecretKey(
  <hpke::kem::SecpK256HkdfSha256 as hpke::Kem>::PrivateKey::from_bytes(&[0x01; 32])