From 4b7382c06da2610f28fef8427908c0a406c7c85e Mon Sep 17 00:00:00 2001
From: KtorZ <matthias.benkort@gmail.com>
Date: Wed, 15 Dec 2021 18:41:50 +0100
Subject: [PATCH] Add 'IsScriptWitnessInCtx'

  Makes it easier to write functions that are polymorphic in the witness context.
---
 cardano-api/src/Cardano/Api.hs        |  1 +
 cardano-api/src/Cardano/Api/Script.hs | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/cardano-api/src/Cardano/Api.hs b/cardano-api/src/Cardano/Api.hs
index 7e5178c3354..3cde898d1e7 100644
--- a/cardano-api/src/Cardano/Api.hs
+++ b/cardano-api/src/Cardano/Api.hs
@@ -369,6 +369,7 @@ module Cardano.Api (
     Witness(..),
     KeyWitnessInCtx(..),
     ScriptWitnessInCtx(..),
+    IsScriptWitnessInCtx(..),
     ScriptDatum(..),
     ScriptRedeemer,
     scriptWitnessScript,
diff --git a/cardano-api/src/Cardano/Api/Script.hs b/cardano-api/src/Cardano/Api/Script.hs
index 995d1c68471..84bb19ee123 100644
--- a/cardano-api/src/Cardano/Api/Script.hs
+++ b/cardano-api/src/Cardano/Api/Script.hs
@@ -53,6 +53,7 @@ module Cardano.Api.Script (
     Witness(..),
     KeyWitnessInCtx(..),
     ScriptWitnessInCtx(..),
+    IsScriptWitnessInCtx(..),
     ScriptDatum(..),
     ScriptRedeemer,
     scriptWitnessScript,
@@ -851,6 +852,17 @@ deriving instance Show (KeyWitnessInCtx witctx)
 deriving instance Eq   (ScriptWitnessInCtx witctx)
 deriving instance Show (ScriptWitnessInCtx witctx)
 
+class IsScriptWitnessInCtx ctx where
+  scriptWitnessInCtx :: ScriptWitnessInCtx ctx
+
+instance IsScriptWitnessInCtx WitCtxTxIn where
+  scriptWitnessInCtx = ScriptWitnessForSpending
+
+instance IsScriptWitnessInCtx WitCtxMint where
+  scriptWitnessInCtx = ScriptWitnessForMinting
+
+instance IsScriptWitnessInCtx WitCtxStake where
+  scriptWitnessInCtx = ScriptWitnessForStakeAddr
 
 -- ----------------------------------------------------------------------------
 -- Script execution units