Move CurrencyToString to size

common/size.go

@@ -1,6 +1,9 @@
 package common
 
-import "fmt"
+import (
+	"fmt"
+	"math/big"
+)
 
 type StorageSize float64
 
@@ -13,3 +16,60 @@ func (self StorageSize) String() string {
 		return fmt.Sprintf("%.2f B", self)
 	}
 }
+
+// The different number of units
+var (
+	Douglas  = BigPow(10, 42)
+	Einstein = BigPow(10, 21)
+	Ether    = BigPow(10, 18)
+	Finney   = BigPow(10, 15)
+	Szabo    = BigPow(10, 12)
+	Shannon  = BigPow(10, 9)
+	Babbage  = BigPow(10, 6)
+	Ada      = BigPow(10, 3)
+	Wei      = big.NewInt(1)
+)
+
+//
+// Currency to string
+// Returns a string representing a human readable format
+func CurrencyToString(num *big.Int) string {
+	var (
+		fin   *big.Int = num
+		denom string   = "Wei"
+	)
+
+	switch {
+	case num.Cmp(Douglas) >= 0:
+		fin = new(big.Int).Div(num, Douglas)
+		denom = "Douglas"
+	case num.Cmp(Einstein) >= 0:
+		fin = new(big.Int).Div(num, Einstein)
+		denom = "Einstein"
+	case num.Cmp(Ether) >= 0:
+		fin = new(big.Int).Div(num, Ether)
+		denom = "Ether"
+	case num.Cmp(Finney) >= 0:
+		fin = new(big.Int).Div(num, Finney)
+		denom = "Finney"
+	case num.Cmp(Szabo) >= 0:
+		fin = new(big.Int).Div(num, Szabo)
+		denom = "Szabo"
+	case num.Cmp(Shannon) >= 0:
+		fin = new(big.Int).Div(num, Shannon)
+		denom = "Shannon"
+	case num.Cmp(Babbage) >= 0:
+		fin = new(big.Int).Div(num, Babbage)
+		denom = "Babbage"
+	case num.Cmp(Ada) >= 0:
+		fin = new(big.Int).Div(num, Ada)
+		denom = "Ada"
+	}
+
+	// TODO add comment clarifying expected behavior
+	if len(fin.String()) > 5 {
+		return fmt.Sprintf("%sE%d %s", fin.String()[0:5], len(fin.String())-5, denom)
+	}
+
+	return fmt.Sprintf("%v %s", fin, denom)
+}