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tpl.go
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tpl.go
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package main
import (
"bytes"
"encoding/json"
"flag"
"fmt"
"os"
"path"
"reflect"
"regexp"
"strings"
"text/template"
"github.com/Masterminds/sprig/v3"
)
var environment = make(map[string]interface{})
var templateFile *string
// add custom functions
var customFuctions = template.FuncMap{
"include": include,
"mustInclude": mustInclude,
}
func inputToObject(inputStr string, debug *bool) (result interface{}, err error) {
if *debug {
fmt.Fprintf(os.Stderr, "----\ninput is: %v\n", inputStr)
}
// try to parse a plain json first
jsonStr := inputStr
err = json.Unmarshal([]byte(jsonStr), &result)
// now try to enrich unquoted json
if err != nil {
// insert " after , if next is none of [ { "
jsonStr = regexp.MustCompile(`,([^[{"])`).ReplaceAllString(jsonStr, ",\"$1")
// insert " before , if previous is none of ] } "
jsonStr = regexp.MustCompile(`([^]}"]),`).ReplaceAllString(jsonStr, "$1\",")
// insert " after [ { if next is none of ] [ } { , "
jsonStr = regexp.MustCompile(`([\[{])([^][}{,"])`).ReplaceAllString(jsonStr, "$1\"$2")
// insert " before ] } if previous is none of ] [ } { , "
jsonStr = regexp.MustCompile(`([^][}{,"])([\]}])`).ReplaceAllString(jsonStr, "$1\"$2")
// insert " after : if next is none of : [ { "
jsonStr = regexp.MustCompile(`([^:]):([^:[{"])`).ReplaceAllString(jsonStr, "$1:\"$2")
// insert " before : if previous is not :
jsonStr = regexp.MustCompile(`([^:"]):([^:])`).ReplaceAllString(jsonStr, "$1\":$2")
// replace :: with : (double colons can be used to escape a colon)
jsonStr = regexp.MustCompile(`::`).ReplaceAllString(jsonStr, ":")
}
if *debug {
fmt.Fprintf(os.Stderr, "json is: %v\n", jsonStr)
}
// try parsing json again, if it fails fall back to the plain input value
err = json.Unmarshal([]byte(jsonStr), &result)
if err != nil || result == nil || reflect.TypeOf(result).Kind() == reflect.Float64 {
result = inputStr
}
if *debug {
if err != nil {
fmt.Fprintf(os.Stderr, "result is: %v, error: %v\n----\n", result, err)
} else {
fmt.Fprintf(os.Stderr, "result is: %v\n----\n", result)
}
}
return result, err
}
func renderInclude(fileName string, safeMode bool) string {
// lookup relative file names in same directory like main template
lookupDir := ""
if !strings.HasPrefix(fileName, "/") && !strings.HasPrefix(fileName, "/") {
lookupDir = path.Dir(*templateFile)
}
// ignore non-existing files
if safeMode {
if _, err := os.Stat(path.Join(lookupDir, fileName)); os.IsNotExist(err) {
return ""
}
}
tpl := template.Must(template.New(path.Base(fileName)).Funcs(sprig.TxtFuncMap()).ParseFiles(path.Join(lookupDir, fileName)))
var result bytes.Buffer
tpl.Execute(&result, environment)
return result.String()
}
func include(fileName string) string {
return renderInclude(fileName, true)
}
func mustInclude(fileName string) string {
return renderInclude(fileName, false)
}
func main() {
// set and parse cmd line flags
debug := flag.Bool("d", false, "enable debug mode")
prefix := flag.String("p", "", "only consider variables starting with prefix")
templateFile = flag.String("t", "", "template file")
version := flag.Bool("v", false, "show version")
outputFile := flag.String("o", "", "output file")
flag.Parse()
if *version {
fmt.Fprintf(os.Stdout, "version %s\n", "0.7.1")
os.Exit(0)
}
if len(*templateFile) == 0 {
flag.Usage()
os.Exit(1)
}
if _, err := os.Stat(*templateFile); os.IsNotExist(err) {
fmt.Fprintf(os.Stderr, "%s not found\n", *templateFile)
os.Exit(2)
}
// generate environment map
for _, envVar := range os.Environ() {
envKeyValuePair := strings.SplitN(envVar, "=", 2)
envKey, envValue := envKeyValuePair[0], envKeyValuePair[1]
if !strings.HasPrefix(envKey, *prefix) {
continue
}
data, err := inputToObject(envValue, debug)
if err != nil {
environment[envKey] = envValue
} else {
environment[envKey] = data
}
}
if *debug {
fmt.Fprintf(os.Stderr, "environment map is: %v\n", environment)
}
outputWriter := os.Stdout
if len(*outputFile) > 0 {
// Create file and truncate it if it already exists
out, err := os.OpenFile(*outputFile, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
if err != nil {
fmt.Fprintf(os.Stderr, "Error opening output file: %s", err)
return
}
outputWriter = out
}
// render template
tpl := template.Must(template.New(path.Base(*templateFile)).Funcs(sprig.TxtFuncMap()).Funcs(customFuctions).ParseFiles(*templateFile))
err := tpl.Execute(outputWriter, environment)
if err != nil {
fmt.Fprintf(os.Stderr, "error rendering template %v: %v\n", *templateFile, err)
os.Exit(2)
}
}