package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"path"
	"strconv"
	"strings"
	"syscall"
)

var myLDAP = LDAP{
	Host:     "localhost",
	Port:     389,
	BaseDN:   "dc=example,dc=com",
	MailPort: 587,
}

type ResponseWriterPrefix struct {
	real   http.ResponseWriter
	prefix string
}

func (r ResponseWriterPrefix) Header() http.Header {
	return r.real.Header()
}

func (r ResponseWriterPrefix) WriteHeader(s int) {
	if v, exists := r.real.Header()["Location"]; exists {
		r.real.Header().Set("Location", r.prefix+v[0])
	}
	r.real.WriteHeader(s)
}

func (r ResponseWriterPrefix) Write(z []byte) (int, error) {
	return r.real.Write(z)
}

func StripPrefix(prefix string, h http.Handler) http.Handler {
	if prefix == "" {
		return h
	}
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if prefix != "/" && r.URL.Path == "/" {
			http.Redirect(w, r, prefix+"/", http.StatusFound)
		} else if p := strings.TrimPrefix(r.URL.Path, prefix); len(p) < len(r.URL.Path) {
			r2 := new(http.Request)
			*r2 = *r
			r2.URL = new(url.URL)
			*r2.URL = *r.URL
			r2.URL.Path = p
			h.ServeHTTP(ResponseWriterPrefix{w, prefix}, r2)
		} else {
			h.ServeHTTP(w, r)
		}
	})
}

func main() {
	var bind = flag.String("bind", "127.0.0.1:8080", "Bind port/socket")
	var baseURL = flag.String("baseurl", "/", "URL prepended to each URL")
	var configfile = flag.String("config", "", "path to the configuration file")
	flag.Parse()

	// Sanitize options
	log.Println("Checking paths...")
	if *baseURL != "/" {
		tmp := path.Clean(*baseURL)
		baseURL = &tmp
	} else {
		tmp := ""
		baseURL = &tmp
	}

	// Load config file
	if configfile != nil && *configfile != "" {
		if fd, err := os.Open(*configfile); err != nil {
			log.Fatal(err)
		} else if cnt, err := ioutil.ReadAll(fd); err != nil {
			log.Fatal(err)
		} else if err := json.Unmarshal(cnt, &myLDAP); err != nil {
			log.Fatal(err)
		}
	}

	// Read configuration from environment
	if val, ok := os.LookupEnv("LDAP_HOST"); ok {
		myLDAP.Host = val
	}
	if val, ok := os.LookupEnv("LDAP_PORT"); ok {
		if port, err := strconv.Atoi(val); err == nil {
			myLDAP.Port = port
		} else {
			log.Println("Invalid value for LDAP_PORT:", val)
		}
	}
	if val, ok := os.LookupEnv("LDAP_STARTTLS"); ok {
		myLDAP.Starttls = val == "1" || val == "on" || val == "true"
	}
	if val, ok := os.LookupEnv("LDAP_SSL"); ok {
		myLDAP.Ssl = val == "1" || val == "on" || val == "true"
	}
	if val, ok := os.LookupEnv("LDAP_BASEDN"); ok {
		myLDAP.BaseDN = val
	}
	if val, ok := os.LookupEnv("LDAP_SERVICEDN"); ok {
		myLDAP.ServiceDN = val
	}
	if val, ok := os.LookupEnv("LDAP_SERVICE_PASSWORD_FILE"); ok {
		if fd, err := os.Open(val); err != nil {
			log.Fatal(err)
		} else if cnt, err := ioutil.ReadAll(fd); err != nil {
			log.Fatal(err)
		} else {
			myLDAP.ServicePassword = string(cnt)
		}
	} else if val, ok := os.LookupEnv("LDAP_SERVICE_PASSWORD"); ok {
		myLDAP.ServicePassword = val
	}

	if val, ok := os.LookupEnv("SMTP_HOST"); ok {
		myLDAP.MailHost = val
	}
	if val, ok := os.LookupEnv("SMTP_PORT"); ok {
		if port, err := strconv.Atoi(val); err == nil {
			myLDAP.MailPort = port
		} else {
			log.Println("Invalid value for SMTP_PORT:", val)
		}
	}
	if val, ok := os.LookupEnv("SMTP_USER"); ok {
		myLDAP.MailUser = val
	}
	if val, ok := os.LookupEnv("SMTP_PASSWORD"); ok {
		myLDAP.MailPassword = val
	}

	// Prepare graceful shutdown
	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt, syscall.SIGTERM)

	// Register handlers
	http.HandleFunc(fmt.Sprintf("%s/", *baseURL), changePassword)
	http.HandleFunc(fmt.Sprintf("%s/auth", *baseURL), httpBasicAuth)
	http.HandleFunc(fmt.Sprintf("%s/login", *baseURL), tryLogin)
	http.HandleFunc(fmt.Sprintf("%s/change", *baseURL), changePassword)
	http.HandleFunc(fmt.Sprintf("%s/reset", *baseURL), resetPassword)
	http.HandleFunc(fmt.Sprintf("%s/lost", *baseURL), lostPassword)

	srv := &http.Server{
		Addr: *bind,
	}

	// Serve content
	go func() {
		log.Fatal(srv.ListenAndServe())
	}()
	log.Println(fmt.Sprintf("Ready, listening on %s", *bind))

	// Wait shutdown signal
	<-interrupt

	log.Print("The service is shutting down...")
	srv.Shutdown(context.Background())
	log.Println("done")
}