compiler: implement engine.AppCall interop

pkg/compiler/analysis.go

@@ -14,7 +14,7 @@ var (
 	builtinFuncs = []string{
 		"len", "append", "SHA256",
 		"SHA1", "Hash256", "Hash160",
-		"VerifySignature",
+		"VerifySignature", "AppCall",
 		"FromAddress", "Equals",
 	}
 )
@@ -180,6 +180,11 @@ func isBuiltin(expr ast.Expr) bool {
 	return false
 }
 
+func isAppCall(expr ast.Expr) bool {
+	t, ok := expr.(*ast.SelectorExpr)
+	return ok && t.Sel.Name == "AppCall"
+}
+
 func isByteArray(lit *ast.CompositeLit, tInfo *types.Info) bool {
 	if len(lit.Elts) == 0 {
 		return false

pkg/compiler/codegen.go

@@ -2,6 +2,7 @@ package compiler
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/constant"
@@ -488,8 +489,16 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			return nil
 		}
 
+		args := n.Args
+		isAppCall := isAppCall(n.Fun)
+		// When using APPCALL, script hash is a part of the instruction so
+		// script hash should be emitted after APPCALL.
+		if isAppCall {
+			args = n.Args[1:]
+		}
+
 		// Handle the arguments
-		for _, arg := range n.Args {
+		for _, arg := range args {
 			ast.Walk(c, arg)
 		}
 		// Do not swap for builtin functions.
@@ -513,6 +522,16 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			// Use the ident to check, builtins are not in func scopes.
 			// We can be sure builtins are of type *ast.Ident.
 			c.convertBuiltin(n)
+
+			if isAppCall {
+				buf := c.getByteArray(n.Args[0])
+				if len(buf) != 20 {
+					c.prog.Err = errors.New("invalid script hash")
+					return nil
+				}
+
+				c.prog.WriteBytes(buf)
+			}
 		case isSyscall(f):
 			c.convertSyscall(f.selector.Name, f.name)
 		default:
@@ -634,6 +653,26 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 	return c
 }
 
+// getByteArray returns byte array value from constant expr.
+// Only literals are supported.
+func (c *codegen) getByteArray(expr ast.Expr) []byte {
+	switch t := expr.(type) {
+	case *ast.CompositeLit:
+		if !isByteArray(t, c.typeInfo) {
+			return nil
+		}
+		buf := make([]byte, len(t.Elts))
+		for i := 0; i < len(t.Elts); i++ {
+			t := c.typeInfo.Types[t.Elts[i]]
+			val, _ := constant.Int64Val(t.Value)
+			buf[i] = byte(val)
+		}
+		return buf
+	default:
+		return nil
+	}
+}
+
 func (c *codegen) convertSyscall(api, name string) {
 	api, ok := syscalls[api][name]
 	if !ok {
@@ -687,6 +726,8 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		emitOpcode(c.prog.BinWriter, opcode.HASH160)
 	case "VerifySignature":
 		emitOpcode(c.prog.BinWriter, opcode.VERIFY)
+	case "AppCall":
+		emitOpcode(c.prog.BinWriter, opcode.APPCALL)
 	case "Equals":
 		emitOpcode(c.prog.BinWriter, opcode.EQUAL)
 	case "FromAddress":

pkg/compiler/interop_test.go

@@ -0,0 +1,76 @@
+package compiler_test
+
+import (
+	"fmt"
+	"math/big"
+	"strings"
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/compiler"
+	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
+	"github.com/CityOfZion/neo-go/pkg/util"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAppCall(t *testing.T) {
+	srcInner := `
+	package foo
+	func Main(args []interface{}) int {
+		a := args[0].(int)
+		b := args[1].(int)
+		return a + b
+	}
+	`
+
+	inner, err := compiler.Compile(strings.NewReader(srcInner))
+	require.NoError(t, err)
+
+	ih := hash.Hash160(inner)
+	getScript := func(u util.Uint160) []byte {
+		if u.Equals(ih) {
+			return inner
+		}
+		return nil
+	}
+
+	t.Run("valid script", func(t *testing.T) {
+		src := getAppCallScript(fmt.Sprintf("%#v", ih.BytesBE()))
+		v := vmAndCompile(t, src)
+		v.SetScriptGetter(getScript)
+
+		require.NoError(t, v.Run())
+
+		assertResult(t, v, big.NewInt(42))
+	})
+
+	t.Run("missing script", func(t *testing.T) {
+		h := ih
+		h[0] = ^h[0]
+
+		src := getAppCallScript(fmt.Sprintf("%#v", h.BytesBE()))
+		v := vmAndCompile(t, src)
+		v.SetScriptGetter(getScript)
+
+		require.Error(t, v.Run())
+	})
+
+	t.Run("invalid script address", func(t *testing.T) {
+		src := getAppCallScript("[]byte{1, 2, 3}")
+
+		_, err := compiler.Compile(strings.NewReader(src))
+		require.Error(t, err)
+	})
+}
+
+func getAppCallScript(h string) string {
+	return `
+	package foo
+	import "github.com/CityOfZion/neo-go/pkg/interop/engine"
+	func Main() int {
+		x := 13
+		y := 29
+		result := engine.AppCall(` + h + `, []interface{}{x, y})
+		return result.(int)
+	}
+	`
+}

pkg/interop/engine/engine.go

@@ -27,3 +27,8 @@ func GetCallingScriptHash() []byte {
 func GetEntryScriptHash() []byte {
 	return nil
 }
+
+// AppCall executes script with specified hash using provided arguments.
+func AppCall(scriptHash []byte, args []interface{}) interface{} {
+	return nil
+}