feat: initial implementation

main.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Config struct {
+	Suffix     string            `yaml:"suffix"`
+	Shortmarks map[string]string `yaml:"shortmarks"`
+}
+
+func main() {
+	err := mainE()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func mainE() error {
+	f := flag.NewFlagSet("shortmarks", flag.ExitOnError)
+	configFileFlag := f.String("c", "", "yaml config file")
+	portFlag := f.String("p", "", "listening port")
+	err := f.Parse(os.Args[1:])
+	if err != nil {
+		return err
+	}
+
+	configFile := os.Getenv("SHORTMARKS_CONFIG")
+	if configFileFlag != nil && *configFileFlag != "" {
+		configFile = *configFileFlag
+	}
+	if configFile == "" {
+		log.Fatal("config file is required")
+	}
+
+	config := &Config{}
+
+	content, err := os.ReadFile(configFile)
+	if err != nil {
+		return err
+	}
+	err = yaml.Unmarshal([]byte(content), config)
+	if err != nil {
+		return err
+	}
+
+	srv := &http.Server{
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 5 * time.Second,
+		IdleTimeout:  30 * time.Second,
+		Handler:      http.HandlerFunc(handler(config)),
+	}
+
+	port := "8080"
+	if v := os.Getenv("PORT"); v != "" {
+		port = v
+	}
+	if portFlag != nil && *portFlag != "" {
+		port = *portFlag
+	}
+
+	ln, err := net.Listen("tcp", ":"+port)
+	if err != nil {
+		return err
+	}
+
+	log.Fatal(srv.Serve(ln))
+
+	return nil
+}
+
+func handler(config *Config) http.HandlerFunc {
+	return func(w http.ResponseWriter, req *http.Request) {
+		if config.Suffix == "" || len(config.Shortmarks) == 0 {
+			http.Error(w, "not found", http.StatusNotFound)
+			return
+		}
+
+		var short string
+
+		hostname := strings.SplitN(req.Host, ":", 2)[0]
+		if strings.HasSuffix(hostname, config.Suffix) {
+			short = strings.TrimSuffix(hostname, config.Suffix)
+		}
+
+		target, ok := config.Shortmarks[short]
+		if !ok {
+			http.Error(w, "not found", http.StatusNotFound)
+			return
+		}
+
+		if req.URL.Path != "/" {
+			target += req.URL.Path
+		}
+		if req.URL.RawQuery != "" {
+			target += "?" + req.URL.RawQuery
+		}
+
+		w.Header().Set("Connection", "close")
+		http.Redirect(w, req, target, http.StatusTemporaryRedirect)
+	}
+}