From cdeba6d4173660c8d814aa27c0efcc1c91bfdaed Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Fri, 6 Mar 2020 14:56:55 +0300
Subject: [PATCH] rpc: implement (*Client).NEP5* methods

---
 pkg/rpc/client/nep5.go | 114 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 pkg/rpc/client/nep5.go

diff --git a/pkg/rpc/client/nep5.go b/pkg/rpc/client/nep5.go
new file mode 100644
index 000000000..7970f03ce
--- /dev/null
+++ b/pkg/rpc/client/nep5.go
@@ -0,0 +1,114 @@
+package client
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
+)
+
+// NEP5Decimals invokes `decimals` NEP5 method on a specified contract.
+func (c *Client) NEP5Decimals(tokenHash util.Uint160) (int64, error) {
+	result, err := c.InvokeFunction(tokenHash.StringLE(), "decimals", []smartcontract.Parameter{})
+	if err != nil {
+		return 0, err
+	} else if result.State != "HALT" || len(result.Stack) == 0 {
+		return 0, errors.New("invalid VM state")
+	}
+
+	return topIntFromStack(result.Stack)
+}
+
+// NEP5Name invokes `name` NEP5 method on a specified contract.
+func (c *Client) NEP5Name(tokenHash util.Uint160) (string, error) {
+	result, err := c.InvokeFunction(tokenHash.StringLE(), "name", []smartcontract.Parameter{})
+	if err != nil {
+		return "", err
+	} else if result.State != "HALT" || len(result.Stack) == 0 {
+		return "", errors.New("invalid VM state")
+	}
+
+	return topStringFromStack(result.Stack)
+}
+
+// NEP5Symbol invokes `symbol` NEP5 method on a specified contract.
+func (c *Client) NEP5Symbol(tokenHash util.Uint160) (string, error) {
+	result, err := c.InvokeFunction(tokenHash.StringLE(), "symbol", []smartcontract.Parameter{})
+	if err != nil {
+		return "", err
+	} else if result.State != "HALT" || len(result.Stack) == 0 {
+		return "", errors.New("invalid VM state")
+	}
+
+	return topStringFromStack(result.Stack)
+}
+
+// NEP5TotalSupply invokes `totalSupply` NEP5 method on a specified contract.
+func (c *Client) NEP5TotalSupply(tokenHash util.Uint160) (int64, error) {
+	result, err := c.InvokeFunction(tokenHash.StringLE(), "totalSupply", []smartcontract.Parameter{})
+	if err != nil {
+		return 0, err
+	} else if result.State != "HALT" || len(result.Stack) == 0 {
+		return 0, errors.New("invalid VM state")
+	}
+
+	return topIntFromStack(result.Stack)
+}
+
+// NEP5BalanceOf invokes `balanceOf` NEP5 method on a specified contract.
+func (c *Client) NEP5BalanceOf(tokenHash util.Uint160) (int64, error) {
+	result, err := c.InvokeFunction(tokenHash.StringLE(), "balanceOf", []smartcontract.Parameter{})
+	if err != nil {
+		return 0, err
+	} else if result.State != "HALT" || len(result.Stack) == 0 {
+		return 0, errors.New("invalid VM state")
+	}
+
+	return topIntFromStack(result.Stack)
+}
+
+func topIntFromStack(st []smartcontract.Parameter) (int64, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	var decimals int64
+	switch typ := st[index].Type; typ {
+	case smartcontract.IntegerType:
+		var ok bool
+		decimals, ok = st[index].Value.(int64)
+		if !ok {
+			return 0, errors.New("invalid Integer item")
+		}
+	case smartcontract.ByteArrayType:
+		data, ok := st[index].Value.([]byte)
+		if !ok {
+			return 0, errors.New("invalid ByteArray item")
+		}
+		decimals = emit.BytesToInt(data).Int64()
+	default:
+		return 0, fmt.Errorf("invalid stack item type: %s", typ)
+	}
+	return decimals, nil
+}
+
+func topStringFromStack(st []smartcontract.Parameter) (string, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	var s string
+	switch typ := st[index].Type; typ {
+	case smartcontract.StringType:
+		var ok bool
+		s, ok = st[index].Value.(string)
+		if !ok {
+			return "", errors.New("invalid String item")
+		}
+	case smartcontract.ByteArrayType:
+		data, ok := st[index].Value.([]byte)
+		if !ok {
+			return "", errors.New("invalid ByteArray item")
+		}
+		s = string(data)
+	default:
+		return "", fmt.Errorf("invalid stack item type: %s", typ)
+	}
+	return s, nil
+}