chore: move token example to nep5 as package name (CityOfZion/neo-storm#19)

* feat: add token example

* feat: code splitted package

* feat: use updated apis

* chore: change token namespace to nep5

* chore: add transfer event and readme updates

Imported from CityOfZion/neo-storm (63ec2d7dc23a60f128a8b383ceda1eaa15d919c1).

examples/token/token.go

@@ -1,7 +1,7 @@
 package token_contract
 
 import (
-	"token"
+	"nep5"
 
 	"github.com/CityOfZion/neo-storm/interop/storage"
 	"github.com/CityOfZion/neo-storm/interop/util"
@@ -15,8 +15,8 @@ const (
 var owner = util.FromAddress("AK2nJJpJr6o664CWJKi1QRXjqeic2zRp8y")
 
 // CreateToken initializes the Token Interface for the Smart Contract to operate with
-func CreateToken() token.Token {
-	return token.Token{
+func CreateToken() nep5.Token {
+	return nep5.Token{
 		Name:           "Awesome NEO Token",
 		Symbol:         "ANT",
 		Decimals:       decimals,

examples/token/vendor/nep5/nep5.go

@@ -0,0 +1,112 @@
+package nep5
+
+import (
+	"github.com/CityOfZion/neo-storm/interop/engine"
+	"github.com/CityOfZion/neo-storm/interop/runtime"
+	"github.com/CityOfZion/neo-storm/interop/storage"
+)
+
+// Token holds all token info
+type Token struct {
+	// Token name
+	Name string
+	// Ticker symbol
+	Symbol string
+	// Amount of decimals
+	Decimals int
+	// Token owner address
+	Owner []byte
+	// Total tokens * multiplier
+	TotalSupply int
+	// Storage key for circulation value
+	CirculationKey string
+}
+
+// GetSupply gets the token totalSupply value from VM storage
+func (t Token) GetSupply(ctx storage.Context) interface{} {
+	return storage.Get(ctx, t.CirculationKey)
+}
+
+// BalanceOf gets the token balance of a specific address
+func (t Token) BalanceOf(ctx storage.Context, hodler []byte) interface{} {
+	return storage.Get(ctx, hodler)
+}
+
+// Transfer token from one user to another
+func (t Token) Transfer(ctx storage.Context, from []byte, to []byte, amount int) bool {
+	amountFrom := t.CanTransfer(ctx, from, to, amount)
+	if amountFrom == -1 {
+		return false
+	}
+
+	if amountFrom == 0 {
+		storage.Delete(ctx, from)
+	}
+
+	if amountFrom > 0 {
+		diff := amountFrom - amount
+		storage.Put(ctx, from, diff)
+	}
+
+	amountTo := storage.Get(ctx, to).(int)
+	totalAmountTo := amountTo + amount
+	storage.Put(ctx, to, totalAmountTo)
+	runtime.Notify("transfer", from, to, amount)
+	return true
+}
+
+// CanTransfer returns the amount it can transfer
+func (t Token) CanTransfer(ctx storage.Context, from []byte, to []byte, amount int) int {
+	if len(to) != 20 && !IsUsableAddress(from) {
+		return -1
+	}
+
+	amountFrom := storage.Get(ctx, from).(int)
+	if amountFrom < amount {
+		return -1
+	}
+
+	// Tell Transfer the result is equal - special case since it uses Delete
+	if amountFrom == amount {
+		return 0
+	}
+
+	// return amountFrom value back to Transfer, reduces extra Get
+	return amountFrom
+}
+
+// IsUsableAddress checks if the sender is either the correct NEO address or SC address
+func IsUsableAddress(addr []byte) bool {
+	if len(addr) == 20 {
+
+		if runtime.CheckWitness(addr) {
+			return true
+		}
+
+		// Check if a smart contract is calling scripthash
+		callingScriptHash := engine.GetCallingScriptHash()
+		if EqualAddresses(callingScriptHash, addr) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// EqualAddresses compares two addresses if they're equal
+// also returns false if one of the two - or both - aren't actual addresses
+func EqualAddresses(a []byte, b []byte) bool {
+	aLen := len(a)
+	bLen := len(b)
+	if aLen != bLen || aLen != 20 || bLen != 20 {
+		return false
+	}
+
+	for i := 0; i < aLen; i++ {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+
+	return true
+}

interop/runtime/runtime.go

@@ -12,7 +12,7 @@ func CheckWitness(hash []byte) bool {
 func Log(message string) {}
 
 // Notify an event to the VM.
-func Notify(arg interface{}) int {
+func Notify(arg ...interface{}) int {
 	return 0
 }
 
@@ -42,7 +42,7 @@ func Serialize(item interface{}) []byte {
 	return nil
 }
 
-// Deserializes an item from a bytearray.
+// Deserialize an item from a bytearray.
 func Deserialize(b []byte) interface{} {
 	return nil
 }

pkg/vm/compiler/compiler_test.go

@@ -23,7 +23,7 @@ func TestExamplesFolder(t *testing.T) {
 			t.Fatal(err)
 		}
 		if len(infos) > 1 {
-			t.Fatal("detected smart contract folder with more then 1 contract file")
+			t.Fatal("detected smart contract folder with more than 1 contract file")
 		}
 		if len(infos) == 0 {
 			t.Fatal("detected smart contract folder with no contract in it")