all tests pass

types/valuerenderer/valuerenderer.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"unicode"
 
+
 	"github.com/cosmos/cosmos-sdk/types"
 	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
 
@@ -124,22 +125,35 @@ func (dvr DefaultValueRenderer) Format(x interface{}) (string, error) {
 		}
 
 		metadata := dvr.denomQuerier(coin.Denom)
-		var srcExp, dstExp int64
+		var coinExp, displayExp int64
 		for _, denomUnit := range metadata.DenomUnits {
 			// TODO  test  23000000 mregen 3  =>  "regen" exp 0
 			if denomUnit.Denom == coin.Denom {
-				srcExp = int64(denomUnit.Exponent)
+				coinExp = int64(denomUnit.Exponent)
 			}
 
 			if denomUnit.Denom == metadata.Display {
-				dstExp = int64(denomUnit.Exponent)
+				displayExp = int64(denomUnit.Exponent)
 			}
 		}
 
-		exp := int64(math.Abs(float64(dstExp - srcExp)))
-
-		amount := types.NewDecFromIntWithPrec(coin.Amount, exp).TruncateInt64()
-
+		expSub := float64(displayExp - coinExp)
+		var amount int64
+
+		switch  {
+		// negative , convert mregen to regen less zeroes
+		case math.Signbit(expSub):
+			// TODO or should i use math package?
+			amount = types.NewDecFromIntWithPrec(coin.Amount, int64(math.Abs(expSub))).TruncateInt64() // use Dec or just golang built in methods
+		// positive, convert mregen to uregen
+		case !math.Signbit(expSub):  
+			amount = coin.Amount.Mul(types.NewInt(int64(math.Pow(10, expSub)))).Int64()
+		// == 0, convert regen to regen, amount does not change
+		default:
+			amount = coin.Amount.Int64()
+		}
+
+
 		newAmount, newDenom := p.Sprintf("%d", amount), metadata.Display
 		sb.WriteString(newAmount)
 		sb.WriteString(newDenom)

types/valuerenderer/valuerenderer_test.go

@@ -37,7 +37,7 @@ func TestFormatCoin(t *testing.T) {
 			false,
 		},
 		{
-			"convert 23000000mregen to 1000regen",
+			"convert 23000000mregen to 23000regen",
 			valuerenderer.NewDefaultValueRendererWithDenom("regen"),
 			types.NewCoin("mregen", types.NewInt(int64(23000000))),
 			"23,000regen",
@@ -47,10 +47,23 @@ func TestFormatCoin(t *testing.T) {
 			"convert 23000000mregen to 23000000000uregen",
 			valuerenderer.NewDefaultValueRendererWithDenom("uregen"),
 			types.NewCoin("mregen", types.NewInt(int64(23000000))),
-			"23000000000uregen",
+			"23,000,000,000uregen",
+			false,
+		},
+		{
+			"convert 23000000regen to 23000000000mregen",
+			valuerenderer.NewDefaultValueRendererWithDenom("mregen"),
+			types.NewCoin("regen", types.NewInt(int64(23000000))),
+			"23,000,000,000mregen",
+			false,
+		},
+		{
+			"convert 23000regen to 23000regen",
+			valuerenderer.NewDefaultValueRendererWithDenom("regen"),
+			types.NewCoin("regen", types.NewInt(int64(23000))),
+			"23,000regen",
 			false,
 		},
-
 	}
 
 	for _, tc := range tt {
@@ -67,18 +80,25 @@ func TestFormatDec(t *testing.T) {
 		d valuerenderer.DefaultValueRenderer
 	)
 	// TODO add more cases and error cases
+
 	tt := []struct {
 		name   string
 		input  types.Dec
 		expRes string
 		expErr bool
 	}{
 		{
-			"Decimal, no error",
+			"10 thousands decimal",
 			types.NewDecFromIntWithPrec(types.NewInt(1000000), 2), // 10000.000000000000000000
 			"10,000.000000000000000000",
 			false,
 		},
+		{
+			"10 mil decimal",
+			types.NewInt(10000000).ToDec(),
+			"10,000,000.000000000000000000",
+			false,
+		},
 
 		//{"invalid string input panic", "qwerty", "", true, true},
 	}