From 5b8abe929df38ffd42e4b3cc71df132f1aa1a67a Mon Sep 17 00:00:00 2001
From: Yura Lazaryev <Yuriy.Lazaryev@iohk.io>
Date: Wed, 6 Nov 2024 11:35:12 +0100
Subject: [PATCH] withCurrencySymbol

---
 .../src/PlutusLedgerApi/V1/Data/Value.hs      | 37 ++++++++++----
 .../src/PlutusLedgerApi/V1/Value.hs           | 50 ++++++++++++-------
 .../9.6/currencySymbolValueOf.pir.golden      |  4 +-
 .../9.6/currencySymbolValueOf.pir.golden      |  4 +-
 4 files changed, 61 insertions(+), 34 deletions(-)

diff --git a/plutus-ledger-api/src/PlutusLedgerApi/V1/Data/Value.hs b/plutus-ledger-api/src/PlutusLedgerApi/V1/Data/Value.hs
index caff2a24787..254d5d876a7 100644
--- a/plutus-ledger-api/src/PlutusLedgerApi/V1/Data/Value.hs
+++ b/plutus-ledger-api/src/PlutusLedgerApi/V1/Data/Value.hs
@@ -50,6 +50,7 @@ module PlutusLedgerApi.V1.Data.Value (
     , Value(..)
     , singleton
     , valueOf
+    , withCurrencySymbol
     , currencySymbolValueOf
     , lovelaceValue
     , lovelaceValueOf
@@ -361,20 +362,34 @@ instance MeetSemiLattice Value where
 -- | Get the quantity of the given currency in the 'Value'.
 -- Assumes that the underlying map doesn't contain duplicate keys.
 valueOf :: Value -> CurrencySymbol -> TokenName -> Integer
-valueOf (Value mp) cur tn =
-    case Map.lookup cur mp of
-        Nothing -> 0
-        Just i  -> case Map.lookup tn i of
+valueOf value cur tn =
+  withCurrencySymbol cur value 0 \tokens ->
+    case Map.lookup tn tokens of
             Nothing -> 0
             Just v  -> v
 
-{-# INLINABLE currencySymbolValueOf #-}
--- | Get the total value of the currency symbol in the 'Value' map.
--- Assumes that the underlying map doesn't contain duplicate keys.
+{-# INLINEABLE withCurrencySymbol #-}
+
+{- | Apply a continuation function to the token quantities of the given currency
+symbol in the value or return a default value if the currency symbol is not present
+in the value.
+-}
+withCurrencySymbol :: CurrencySymbol -> Value -> a -> (Map TokenName Integer -> a) -> a
+withCurrencySymbol currency value def k =
+  case Map.lookup currency (getValue value) of
+    Nothing              -> def
+    Just tokenQuantities -> k tokenQuantities
+
+{-# INLINEABLE currencySymbolValueOf #-}
+
+{- | Get the total value of the currency symbol in the 'Value' map.
+Assumes that the underlying map doesn't contain duplicate keys.
+
+Note that each token of the currency symbol may have a value that is positive,
+zero or negative.
+-}
 currencySymbolValueOf :: Value -> CurrencySymbol -> Integer
-currencySymbolValueOf (Value mp) cur = case Map.lookup cur mp of
-    Nothing     -> 0
-    Just tokens ->
+currencySymbolValueOf value cur = withCurrencySymbol cur value 0 \tokens ->
         -- This is more efficient than `PlutusTx.sum (Map.elems tokens)`, because
         -- the latter materializes the intermediate result of `Map.elems tokens`.
         Map.foldr (\amt acc -> amt + acc) 0 tokens
@@ -402,7 +417,7 @@ lovelaceValueOf v = Lovelace (valueOf v adaSymbol adaToken)
 {-# INLINABLE assetClassValue #-}
 -- | A 'Value' containing the given amount of the asset class.
 assetClassValue :: AssetClass -> Integer -> Value
-assetClassValue (AssetClass (c, t)) i = singleton c t i
+assetClassValue (AssetClass (c, t)) = singleton c t
 
 {-# INLINABLE assetClassValueOf #-}
 -- | Get the quantity of the given 'AssetClass' class in the 'Value'.
diff --git a/plutus-ledger-api/src/PlutusLedgerApi/V1/Value.hs b/plutus-ledger-api/src/PlutusLedgerApi/V1/Value.hs
index 2ce3301245a..2cd03a54f1a 100644
--- a/plutus-ledger-api/src/PlutusLedgerApi/V1/Value.hs
+++ b/plutus-ledger-api/src/PlutusLedgerApi/V1/Value.hs
@@ -46,6 +46,7 @@ module PlutusLedgerApi.V1.Value (
     , Value(..)
     , singleton
     , valueOf
+    , withCurrencySymbol
     , currencySymbolValueOf
     , lovelaceValue
     , lovelaceValueOf
@@ -353,26 +354,37 @@ instance MeetSemiLattice Value where
 -- | Get the quantity of the given currency in the 'Value'.
 -- Assumes that the underlying map doesn't contain duplicate keys.
 valueOf :: Value -> CurrencySymbol -> TokenName -> Integer
-valueOf (Value mp) cur tn =
-    case Map.lookup cur mp of
-        Nothing -> 0
-        Just i  -> case Map.lookup tn i of
-            Nothing -> 0
-            Just v  -> v
-
-{-# INLINABLE currencySymbolValueOf #-}
--- | Get the total value of the currency symbol in the 'Value' map.
--- Assumes that the underlying map doesn't contain duplicate keys.
---
--- Note that each token of the currency symbol may have a value that is positive,
--- zero or negative.
+valueOf value cur tn =
+  withCurrencySymbol cur value 0 \tokens ->
+    case Map.lookup tn tokens of
+      Nothing -> 0
+      Just v  -> v
+
+{-# INLINEABLE withCurrencySymbol #-}
+
+{- | Apply a continuation function to the token quantities of the given currency
+symbol in the value or return a default value if the currency symbol is not present
+in the value.
+-}
+withCurrencySymbol :: CurrencySymbol -> Value -> a -> (Map TokenName Integer -> a) -> a
+withCurrencySymbol currency value def k =
+  case Map.lookup currency (getValue value) of
+    Nothing              -> def
+    Just tokenQuantities -> k tokenQuantities
+
+{-# INLINEABLE currencySymbolValueOf #-}
+
+{- | Get the total value of the currency symbol in the 'Value' map.
+Assumes that the underlying map doesn't contain duplicate keys.
+
+Note that each token of the currency symbol may have a value that is positive,
+zero or negative.
+-}
 currencySymbolValueOf :: Value -> CurrencySymbol -> Integer
-currencySymbolValueOf (Value mp) cur = case Map.lookup cur mp of
-    Nothing     -> 0
-    Just tokens ->
-        -- This is more efficient than `PlutusTx.sum (Map.elems tokens)`, because
-        -- the latter materializes the intermediate result of `Map.elems tokens`.
-        PlutusTx.List.foldr (\(_, amt) acc -> amt + acc) 0 (Map.toList tokens)
+currencySymbolValueOf value cur = withCurrencySymbol cur value 0 \tokens ->
+  -- This is more efficient than `PlutusTx.sum (Map.elems tokens)`, because
+  -- the latter materializes the intermediate result of `Map.elems tokens`.
+  PlutusTx.List.foldr (\(_, amt) acc -> amt + acc) 0 (Map.toList tokens)
 
 {-# INLINABLE symbols #-}
 -- | The list of 'CurrencySymbol's of a 'Value'.
diff --git a/plutus-ledger-api/test-plugin/Spec/Budget/9.6/currencySymbolValueOf.pir.golden b/plutus-ledger-api/test-plugin/Spec/Budget/9.6/currencySymbolValueOf.pir.golden
index b850a7c45a0..8da8925e8d2 100644
--- a/plutus-ledger-api/test-plugin/Spec/Budget/9.6/currencySymbolValueOf.pir.golden
+++ b/plutus-ledger-api/test-plugin/Spec/Budget/9.6/currencySymbolValueOf.pir.golden
@@ -31,7 +31,7 @@ let
     True : Bool
     False : Bool
 in
-\(ds :
+\(value :
     (\k v -> List (Tuple2 k v))
       bytestring
       ((\k v -> List (Tuple2 k v)) bytestring integer))
@@ -76,4 +76,4 @@ in
                         {all dead. dead}))
             {all dead. dead}
   in
-  go ds
\ No newline at end of file
+  go value
\ No newline at end of file
diff --git a/plutus-ledger-api/test-plugin/Spec/Data/Budget/9.6/currencySymbolValueOf.pir.golden b/plutus-ledger-api/test-plugin/Spec/Data/Budget/9.6/currencySymbolValueOf.pir.golden
index b63efc48ea5..9a00939539f 100644
--- a/plutus-ledger-api/test-plugin/Spec/Data/Budget/9.6/currencySymbolValueOf.pir.golden
+++ b/plutus-ledger-api/test-plugin/Spec/Data/Budget/9.6/currencySymbolValueOf.pir.golden
@@ -15,7 +15,7 @@ let
     Just : a -> Maybe a
     Nothing : Maybe a
 in
-\(ds :
+\(value :
     (\k a -> list (pair data data))
       bytestring
       ((\k a -> list (pair data data)) bytestring integer))
@@ -45,7 +45,7 @@ in
                  (/\dead -> go)
                  {all dead. dead})
     in
-    go ds)
+    go value)
     {integer}
     (\(a : data) ->
        let