Add convenience methods on WitnessTemplate

src/miniscript/satisfy.rs

@@ -28,7 +28,7 @@ use sync::Arc;
 
 use super::context::SigType;
 use crate::descriptor::DescriptorType;
-use crate::plan::{AssetProvider, Plan};
+use crate::plan::{AssetProvider, Plan, RequiredPreimage, RequiredSig};
 use crate::prelude::*;
 use crate::util::witness_size;
 use crate::{
@@ -721,6 +721,35 @@ impl<Pk: MiniscriptKey + ToPublicKey> WitnessTemplate<Placeholder<Pk>> {
                 .collect(),
         }
     }
+
+    /// Returns the list of required signatures
+    pub fn required_signatures(&self) -> Vec<RequiredSig<'_, Pk>> {
+        self.stack
+            .iter()
+            .filter_map(|item| match item {
+                Placeholder::EcdsaSigPk(pk) => Some(RequiredSig::Ecdsa(pk)),
+                Placeholder::SchnorrSig(pk, None) => Some(RequiredSig::SchnorrTapKey(pk)),
+                Placeholder::SchnorrSig(pk, Some(lh)) => {
+                    Some(RequiredSig::SchnorrTapScript(pk, lh))
+                }
+                _ => None,
+            })
+            .collect()
+    }
+
+    /// Returns the list of required preimages
+    pub fn required_preimages(&self) -> Vec<RequiredPreimage<'_, Pk>> {
+        self.stack
+            .iter()
+            .filter_map(|item| match item {
+                Placeholder::Sha256Preimage(h) => Some(RequiredPreimage::Sha256(h)),
+                Placeholder::Hash256Preimage(h) => Some(RequiredPreimage::Hash256(h)),
+                Placeholder::Ripemd160Preimage(h) => Some(RequiredPreimage::Ripemd160(h)),
+                Placeholder::Hash160Preimage(h) => Some(RequiredPreimage::Hash160(h)),
+                _ => None,
+            })
+            .collect()
+    }
 }
 
 impl<Pk: MiniscriptKey + ToPublicKey> WitnessTemplate<PartialSatisfaction<Pk>> {

src/plan.rs

@@ -215,6 +215,30 @@ where
     }
 }
 
+/// Enum defining the type of signature required
+#[derive(Debug, Clone)]
+pub enum RequiredSig<'pk, Pk: MiniscriptKey> {
+    /// ECDSA (legacy or Segwit-v0) signature
+    Ecdsa(&'pk Pk),
+    /// Schnorr key-spend signature (BIP-341)
+    SchnorrTapKey(&'pk Pk),
+    /// Schnorr script-spend signature (BIP-341)
+    SchnorrTapScript(&'pk Pk, &'pk TapLeafHash),
+}
+
+/// Enum defining the type of preimage required
+#[derive(Debug, Clone)]
+pub enum RequiredPreimage<'h, Pk: MiniscriptKey> {
+    /// HASH160 preimage
+    Hash160(&'h <Pk as MiniscriptKey>::Hash160),
+    /// RIPEMD160 preimage
+    Ripemd160(&'h <Pk as MiniscriptKey>::Ripemd160),
+    /// HASH256 preimage
+    Hash256(&'h <Pk as MiniscriptKey>::Hash256),
+    /// SHA256 preimage
+    Sha256(&'h <Pk as MiniscriptKey>::Sha256),
+}
+
 /// Representation of a particular spending path on a descriptor. Contains the witness template
 /// and the timelocks needed for satisfying the plan.
 /// Calling `get_plan` on a Descriptor will return this structure,