Add anyprevout and anyprevoutscript flags to sighash type

coinlib/lib/src/tx/sighash/sighash_type.dart

@@ -2,24 +2,32 @@
 /// Signatures may sign different output and inputs to allow for transaction
 /// modifications. To sign an entire transaction the [all] constructor should be
 /// used.
+/// Supports SIGHASH_ANYPREVOUT and SIGHASH_ANYPREVOUTANYSCRIPT.
 class SigHashType {
-
   /// Special value representing the default Schnorr behaviour to sign
   /// everything. This is encoded as an absent byte.
   static const schnorrDefaultValue = 0;
 
   /// Value to sign all outputs
   static const allValue = 1;
+
   /// Value to sign no outputs
   static const noneValue = 2;
+
   /// Value to sign the output at the same index as the input
   static const singleValue = 3;
+
   /// Flag that can be combined with other hash type values to only sign the
   /// input containing the signature
   static const anyOneCanPayFlag = 0x80;
 
-  /// The single byte representation of the sighash type. Use [all], [none],
-  /// [single] and [anyOneCanPay] to extract details of the type.
+  /// Flag for SIGHASH_ANYPREVOUT (APO)
+  static const anyPrevOutFlag = 0x40;
+
+  /// Flag for SIGHASH_ANYPREVOUTANYSCRIPT (APOAS)
+  static const anyPrevOutAnyScriptFlag = 0xC0;
+
+  /// The single-byte representation of the sighash type.
   final int value;
 
   /// Returns true if the sighash type value is valid.
@@ -45,40 +53,65 @@ class SigHashType {
   /// only acceptable for Taproot Schnorr signatures.
   const SigHashType.schnorrDefault() : value = schnorrDefaultValue;
 
-  /// Sign all of the outputs. If [anyOneCanPay] is true, then only the input
-  /// containing the signature will be signed.
-  /// If [anyOneCanPay] is false and a Taproot input is being signed, this will
-  /// be treated as "SIGHASH_DEFAULT".
-  const SigHashType.all({ bool anyOneCanPay = false })
-    : value = allValue | (anyOneCanPay ? anyOneCanPayFlag : 0);
+  /// Sign all outputs. Optional flags can be set to modify the behavior.
+  const SigHashType.all({
+    bool anyOneCanPay = false,
+    bool anyPrevOut = false,
+    bool anyPrevOutAnyScript = false,
+  }) : value = allValue |
+            (anyOneCanPay ? anyOneCanPayFlag : 0) |
+            (anyPrevOutAnyScript
+                ? anyPrevOutAnyScriptFlag
+                : (anyPrevOut ? anyPrevOutFlag : 0));
 
-  /// Sign no outputs. If [anyOneCanPay] is true, then only the input containing
-  /// the signature will be signed.
-  const SigHashType.none({ bool anyOneCanPay = false })
-    : value = noneValue | (anyOneCanPay ? anyOneCanPayFlag : 0);
+  /// Sign no outputs. Optional flags can be set to modify the behavior.
+  const SigHashType.none({
+    bool anyOneCanPay = false,
+    bool anyPrevOut = false,
+    bool anyPrevOutAnyScript = false,
+  }) : value = noneValue |
+            (anyOneCanPay ? anyOneCanPayFlag : 0) |
+            (anyPrevOutAnyScript
+                ? anyPrevOutAnyScriptFlag
+                : (anyPrevOut ? anyPrevOutFlag : 0));
 
-  /// Sign the output at the same index as the input. If [anyOneCanPay] is true,
-  /// then only the input containing the signature will be signed.
-  const SigHashType.single({ bool anyOneCanPay = false })
-    : value = singleValue | (anyOneCanPay ? anyOneCanPayFlag : 0);
+  /// Sign the output at the same index as the input. Optional flags can be set.
+  const SigHashType.single({
+    bool anyOneCanPay = false,
+    bool anyPrevOut = false,
+    bool anyPrevOutAnyScript = false,
+  }) : value = singleValue |
+            (anyOneCanPay ? anyOneCanPayFlag : 0) |
+            (anyPrevOutAnyScript
+                ? anyPrevOutAnyScriptFlag
+                : (anyPrevOut ? anyPrevOutFlag : 0));
 
-  /// If this is the default hash type for a Schnorr signature.
+  /// Checks if this is the default hash type for a Schnorr signature.
   bool get schnorrDefault => value == schnorrDefaultValue;
 
-  /// All outputs shall be signed
-  bool get all => value == schnorrDefaultValue
-    || (value & ~anyOneCanPayFlag) == allValue;
-  /// No outputs shall be signed
-  bool get none => (value & ~anyOneCanPayFlag) == noneValue;
-  /// Only the output with the same index as the input shall be signed
-  bool get single => (value & ~anyOneCanPayFlag) == singleValue;
-  /// Only the input receiving the signature shall be signed
+  /// All outputs shall be signed.
+  bool get all => value == schnorrDefaultValue || (value & 0x03) == allValue;
+
+  /// No outputs shall be signed.
+  bool get none => (value & 0x03) == noneValue;
+
+  /// Only the output with the same index as the input shall be signed.
+  bool get single => (value & 0x03) == singleValue;
+
+  /// Only the input receiving the signature shall be signed.
   bool get anyOneCanPay => (value & anyOneCanPayFlag) != 0;
 
+  /// The signature can sign any previous output.
+  bool get anyPrevOut => (value & anyPrevOutFlag) != 0 || anyPrevOutAnyScript;
+
+  /// The signature can sign any previous output and any script.
+  bool get anyPrevOutAnyScript =>
+      (value & anyPrevOutAnyScriptFlag) == anyPrevOutAnyScriptFlag;
+
   @override
-  bool operator==(Object other) => other is SigHashType && value == other.value;
+  bool operator ==(Object other) =>
+      other is SigHashType && value == other.value;
 
   @override
   int get hashCode => value;
-
 }