licensing: introduce spdxconv tool

Signed-off-by: Louis DeLosSantos <louis.delos@isovalent.com>

tools/spdxconv/main.go

@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2019 Authors of Cilium
+
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"log"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+const (
+	usage = `spdxconv is a tool for converting Cilium's copyright and license header
+to a SPDX compliant one
+
+Usage:
+    spdxconv [package_dir] - provide spdxconv with a absolute path to the go package you'd like to convert.
+
+`
+)
+
+var (
+	// RegexMap maps an identifying regexp expression
+	// with the SPDX string that replaces it.
+	RegexpMap = map[*regexp.Regexp]string{
+		regexp.MustCompile(`(?m)Apache License, Version 2.0`): "// SPDX-License-Identifier: Apache-2.0",
+	}
+)
+
+type SPDXConverter struct {
+	// the root directory to begin replacing
+	// license clauses to spdx clauses
+	rootDir string
+}
+
+// Walk will begin walking the tree rooted at
+// rootDir.
+//
+// For each .go file it encounters it will parse
+// that file's AST and discover the comments.
+//
+// If the comments indicate a non spdx license
+// it will convert it to one and write the file back
+// to disk.
+func (s *SPDXConverter) Walk() error {
+	err := filepath.WalkDir(s.rootDir, func(path string, d os.DirEntry, e error) error {
+		if e != nil {
+			return e
+		}
+		if filepath.Ext(path) != ".go" {
+			return nil
+		}
+		fs := token.NewFileSet()
+		astFd, err := parser.ParseFile(fs, path, nil, parser.ParseComments)
+		if err != nil {
+			return fmt.Errorf("error while parsing %v: %w", path, err)
+		}
+
+		err = s.conv(path, fs, astFd)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	})
+	return err
+}
+
+func (s *SPDXConverter) conv(path string, fset *token.FileSet, f *ast.File) error {
+	if len(f.Comments) == 0 {
+		return nil
+	}
+	cg := f.Comments[0]
+	if !strings.HasPrefix(cg.List[0].Text, "// Copyright") {
+		log.Printf("file %v did not start with a Copyright string. skipping...", path)
+		return nil
+	}
+	var spdx string
+	for exp, tmp := range RegexpMap {
+		if exp.MatchString(cg.Text()) {
+			spdx = tmp
+		}
+	}
+	if spdx == "" {
+		log.Printf("could not determine license for %v", path)
+		return nil
+	}
+
+	copyRight := cg.List[0].Text
+	cg.List[0].Text, cg.List[1].Text = spdx, copyRight
+	cg.List = cg.List[:2]
+
+	fd, err := os.OpenFile(path, os.O_TRUNC|os.O_RDWR, 0660)
+	if err != nil {
+		return fmt.Errorf("failed to open original source file for conversion: %w", err)
+	}
+	defer fd.Close()
+
+	err = format.Node(fd, fset, f)
+	if err != nil {
+		return fmt.Errorf("failed to write converted file %v: %w", path, err)
+	}
+
+	return nil
+}
+
+func main() {
+	switch {
+	case len(os.Args) != 2:
+		fmt.Print(usage)
+		os.Exit(1)
+	case os.Args[1] == "help":
+		fmt.Print(usage)
+		os.Exit(0)
+	}
+
+	path := os.Args[1]
+	dir, err := os.Stat(path)
+	if err != nil {
+		fmt.Printf("provided path %v could not be opened: %v", path, err)
+		os.Exit(1)
+	}
+	if !dir.IsDir() {
+		fmt.Println("provided path is not a directory")
+		os.Exit(1)
+	}
+
+	conv := &SPDXConverter{
+		rootDir: path,
+	}
+	if err := conv.Walk(); err != nil {
+		log.Fatal(err.Error())
+	}
+}