From cf7b03efcdbe041d1bd37dbbf4a643ff94da6634 Mon Sep 17 00:00:00 2001
From: Hanjun Kim <hallazzang@gmail.com>
Date: Wed, 14 Apr 2021 00:01:21 +0900
Subject: [PATCH] add AddAmount/SubAmount methods to sdk.Coin (#9091)

Co-authored-by: Marko <marbar3778@yahoo.com>
Co-authored-by: Amaury <1293565+amaurym@users.noreply.github.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
---
 CHANGELOG.md       |  1 +
 types/coin.go      | 15 +++++++++++++++
 types/coin_test.go | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63275b512..6a96d38f4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -53,6 +53,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
   * updated the keyring display structure (it uses protobuf JSON serialization) - the output is more verbose.
   * Renamed `MarshalAny` and `UnmarshalAny` to `MarshalInterface` and `UnmarshalInterface` respectively. These functions must take an interface as parameter (not a concrete type nor `Any` object). Underneath they use `Any` wrapping for correct protobuf serialization.
   * CLI: removed `--text` flag from `show-node-id` command; the text format for public keys is not used any more - instead we use ProtoJSON.
+* (types) [\#9079](https://github.com/cosmos/cosmos-sdk/issues/9079) Add `AddAmount`/`SubAmount` methods to `sdk.Coin`.
 
 ### API Breaking Changes
 
diff --git a/types/coin.go b/types/coin.go
index b86cff518..352dcf6ac 100644
--- a/types/coin.go
+++ b/types/coin.go
@@ -100,6 +100,11 @@ func (coin Coin) Add(coinB Coin) Coin {
 	return Coin{coin.Denom, coin.Amount.Add(coinB.Amount)}
 }
 
+// AddAmount adds an amount to the Coin.
+func (coin Coin) AddAmount(amount Int) Coin {
+	return Coin{coin.Denom, coin.Amount.Add(amount)}
+}
+
 // Sub subtracts amounts of two coins with same denom. If the coins differ in denom
 // then it panics.
 func (coin Coin) Sub(coinB Coin) Coin {
@@ -115,6 +120,16 @@ func (coin Coin) Sub(coinB Coin) Coin {
 	return res
 }
 
+// SubAmount subtracts an amount from the Coin.
+func (coin Coin) SubAmount(amount Int) Coin {
+	res := Coin{coin.Denom, coin.Amount.Sub(amount)}
+	if res.IsNegative() {
+		panic("negative coin amount")
+	}
+
+	return res
+}
+
 // IsPositive returns true if coin amount is positive.
 //
 // TODO: Remove once unsigned integers are used.
diff --git a/types/coin_test.go b/types/coin_test.go
index ab69f16a1..fad7f2f52 100644
--- a/types/coin_test.go
+++ b/types/coin_test.go
@@ -145,6 +145,21 @@ func (s *coinTestSuite) TestAddCoin() {
 	}
 }
 
+func (s *coinTestSuite) TestAddCoinAmount() {
+	cases := []struct {
+		coin     sdk.Coin
+		amount   sdk.Int
+		expected sdk.Coin
+	}{
+		{sdk.NewInt64Coin(testDenom1, 1), sdk.NewInt(1), sdk.NewInt64Coin(testDenom1, 2)},
+		{sdk.NewInt64Coin(testDenom1, 1), sdk.NewInt(0), sdk.NewInt64Coin(testDenom1, 1)},
+	}
+	for i, tc := range cases {
+		res := tc.coin.AddAmount(tc.amount)
+		s.Require().Equal(tc.expected, res, "result of addition is incorrect, tc #%d", i)
+	}
+}
+
 func (s *coinTestSuite) TestSubCoin() {
 	cases := []struct {
 		inputOne    sdk.Coin
@@ -178,6 +193,30 @@ func (s *coinTestSuite) TestSubCoin() {
 	s.Require().Equal(tc.expected, res.Amount.Int64())
 }
 
+func (s *coinTestSuite) TestSubCoinAmount() {
+	cases := []struct {
+		coin        sdk.Coin
+		amount      sdk.Int
+		expected    sdk.Coin
+		shouldPanic bool
+	}{
+		{sdk.NewInt64Coin(testDenom1, 2), sdk.NewInt(1), sdk.NewInt64Coin(testDenom1, 1), false},
+		{sdk.NewInt64Coin(testDenom1, 10), sdk.NewInt(1), sdk.NewInt64Coin(testDenom1, 9), false},
+		{sdk.NewInt64Coin(testDenom1, 5), sdk.NewInt(3), sdk.NewInt64Coin(testDenom1, 2), false},
+		{sdk.NewInt64Coin(testDenom1, 5), sdk.NewInt(0), sdk.NewInt64Coin(testDenom1, 5), false},
+		{sdk.NewInt64Coin(testDenom1, 1), sdk.NewInt(5), sdk.Coin{}, true},
+	}
+
+	for i, tc := range cases {
+		if tc.shouldPanic {
+			s.Require().Panics(func() { tc.coin.SubAmount(tc.amount) })
+		} else {
+			res := tc.coin.SubAmount(tc.amount)
+			s.Require().Equal(tc.expected, res, "result of subtraction is incorrect, tc #%d", i)
+		}
+	}
+}
+
 func (s *coinTestSuite) TestIsGTECoin() {
 	cases := []struct {
 		inputOne sdk.Coin