codegen/golang: Add new codegen options

- Generate main function
- Format code with gofmt or goimports style
- Debug mode

Author: nickng

codegen/golang/gen.go

@@ -24,7 +24,7 @@ import (
 	"go.nickng.io/asyncpi/types"
 )
 
-// Generate writes Go code of the Process to w.
+// Generate writes Go code of the Process p to w.
 func Generate(p asyncpi.Process, w io.Writer) error {
 	if err := asyncpi.Bind(&p); err != nil {
 		return err

codegen/golang/genopts.go

@@ -0,0 +1,103 @@
+// Copyright 2018 Nicholas Ng
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package golang
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+
+	"go.nickng.io/asyncpi"
+	"golang.org/x/tools/imports"
+)
+
+// FormatOptions defines options for changing
+// the format of generated code.
+type FormatOptions struct {
+	Main     bool
+	Debug    bool
+	Format   bool
+	FmtStyle FormatStyle
+}
+
+// FormatStyle defines the tools to use for formatting code
+type FormatStyle int
+
+const (
+	// Gofmt is the option to use go/format style
+	Gofmt FormatStyle = iota
+	// GoImports is the option to use goimports style
+	GoImports
+)
+
+// GenerateOpts writes Go code of the Process p to w using options opt.
+func GenerateOpts(p asyncpi.Process, opt FormatOptions, w io.Writer) error {
+	var program bytes.Buffer
+	const progHeader = `package main
+	func main() {
+`
+	const progFooter = `
+}`
+
+	if opt.Main {
+		fmt.Fprintf(&program, progHeader)
+	}
+	if opt.Debug {
+		fmt.Fprintf(&program, "// Process %s\n", p.Calculi())
+		fmt.Fprint(&program, `fmt.Fprintln(os.Stderr, "--- start ---");`)
+	}
+	if err := Generate(p, &program); err != nil {
+		return err
+	}
+	if opt.Debug {
+		fmt.Fprint(&program, `fmt.Fprintln(os.Stderr, "--- end ---");`)
+	}
+	if opt.Main {
+		fmt.Fprint(&program, progFooter)
+	}
+	if opt.Format {
+		switch opt.FmtStyle {
+		case Gofmt:
+			b, err := format.Source(program.Bytes())
+			if err != nil {
+				return err
+			}
+			_, err = w.Write(b)
+			if err != nil {
+				return err
+			}
+		case GoImports:
+			b, err := imports.Process("/tmp/tmp.go", program.Bytes(), &imports.Options{
+				Comments:  true,
+				Fragment:  !opt.Main,
+				TabIndent: true,
+			})
+			if err != nil {
+				return err
+			}
+			_, err = w.Write(b)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+	_, err := io.Copy(w, &program)
+	if err != nil {
+		return err
+	}
+	return nil
+}