toolbox: add template command

cmd/toolbox/cmd/template.go

@@ -0,0 +1,128 @@
+// Copyright 2019 Sorint.lab
+//
+// 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 cmd
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"runtime"
+	"strconv"
+	"text/template"
+	"time"
+
+	"github.com/spf13/cobra"
+)
+
+var cmdTemplate = &cobra.Command{
+	Use:   "template",
+	Run:   templateRun,
+	Short: "executes the provided template from stdin and returns the output in stdout",
+}
+
+func init() {
+	CmdToolbox.AddCommand(cmdTemplate)
+}
+
+func md5sum(filename string) (string, error) {
+	if filename == "" {
+		return "", errors.New("empty filename")
+	}
+
+	if info, err := os.Stat(filename); err == nil {
+		if info.Size() > 1024*1024 {
+			return "", fmt.Errorf("file %q is too big", filename)
+		}
+	} else {
+		return "", err
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return "", err
+	}
+
+	h := md5.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
+}
+
+func sha256sum(filename string) (string, error) {
+	if filename == "" {
+		return "", errors.New("empty filename")
+	}
+
+	if info, err := os.Stat(filename); err == nil {
+		if info.Size() > 1024*1024 {
+			return "", fmt.Errorf("file %q is too big", filename)
+		}
+	} else {
+		return "", err
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return "", err
+	}
+
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
+}
+
+type tmplData struct {
+	Environment map[string]string
+}
+
+func templateRun(cmd *cobra.Command, args []string) {
+
+	funcMap := map[string]interface{}{
+		"md5sum":    md5sum,
+		"sha256sum": sha256sum,
+		"env":       func(s string) string { return os.Getenv(s) },
+		"os":        func() string { return runtime.GOOS },
+		"arch":      func() string { return runtime.GOARCH },
+		"unixtime":  func() string { return strconv.FormatInt(time.Now().UnixNano(), 10) },
+		"year":      func() string { return time.Now().Format("2006") },
+		"month":     func() string { return time.Now().Format("01") },
+		"day":       func() string { return time.Now().Format("02") },
+	}
+
+	tmplStr, err := ioutil.ReadAll(os.Stdin)
+	if err != nil {
+		log.Fatalf("failed to read template: %v", err)
+	}
+
+	tmpl, err := template.New("base").Funcs(funcMap).Parse(string(tmplStr))
+	if err != nil {
+		log.Fatalf("failed to parse template: %v", err)
+	}
+
+	data := &tmplData{}
+	if err := tmpl.Execute(os.Stdout, data); err != nil {
+		log.Fatalf("failed to execute template: %v", err)
+	}
+}