add initial version

.gitignore

@@ -0,0 +1 @@
+korvike

app.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"sync"
+	"text/template"
+
+	"github.com/Luzifer/go_helpers/env"
+	"github.com/Luzifer/rconfig"
+)
+
+var (
+	cfg = struct {
+		Input          string   `flag:"in,i" default:"-" description:"Source to read the template from ('-' = stdin)"`
+		KeyPairs       []string `flag:"key-value,v" default:"" description:"Key-value pairs to use in templating (-v key=value)"`
+		Output         string   `flag:"out,o" default:"-" description:"Destination to write the output to ('-' = stdout)"`
+		VersionAndExit bool     `flag:"version" default:"false" description:"Prints current version and exits"`
+	}{}
+
+	templateFunctions     = template.FuncMap{}
+	templateFunctionsLock sync.Mutex
+
+	version = "dev"
+)
+
+func registerFunction(name string, f interface{}) error {
+	templateFunctionsLock.Lock()
+	defer templateFunctionsLock.Unlock()
+	if _, ok := templateFunctions[name]; ok {
+		return errors.New("Duplicate function for name " + name)
+	}
+	templateFunctions[name] = f
+	return nil
+}
+
+func init() {
+	if err := rconfig.Parse(&cfg); err != nil {
+		log.Fatalf("Unable to parse commandline options: %s", err)
+	}
+
+	if cfg.VersionAndExit {
+		fmt.Printf("korvike %s\n", version)
+		os.Exit(0)
+	}
+}
+
+func openInput(f string) (io.Reader, error) {
+	if f == "-" {
+		return os.Stdin, nil
+	}
+
+	if _, err := os.Stat(f); err != nil {
+		return nil, errors.New("Could not find file " + f)
+	}
+
+	return os.Open(f)
+}
+
+func openOutput(f string) (io.Writer, error) {
+	if f == "-" {
+		return os.Stdout, nil
+	}
+
+	return os.Create(f)
+}
+
+func main() {
+	in, err := openInput(cfg.Input)
+	if err != nil {
+		log.Fatalf("Unable to open input: %s", err)
+	}
+
+	out, err := openOutput(cfg.Output)
+	if err != nil {
+		log.Fatalf("Unable to open output: %s", err)
+	}
+
+	rawTpl, err := ioutil.ReadAll(in)
+	if err != nil {
+		log.Fatalf("Unable to read from input: %s", err)
+	}
+
+	tpl, err := template.New("in").Funcs(templateFunctions).Parse(string(rawTpl))
+	if err != nil {
+		log.Fatalf("Unable to parse template: %s", err)
+	}
+
+	if err := tpl.Execute(out, env.ListToMap(cfg.KeyPairs)); err != nil {
+		log.Fatalf("Unable to execute template: %s", err)
+	}
+}

func_env.go

@@ -0,0 +1,16 @@
+package main
+
+import "os"
+
+func init() {
+	registerFunction("env", func(name string, v ...string) string {
+		defaultValue := ""
+		if len(v) > 0 {
+			defaultValue = v[0]
+		}
+		if value, ok := os.LookupEnv(name); ok {
+			return value
+		}
+		return defaultValue
+	})
+}