package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

type SessionProvider interface {
	Create(user User, expr time.Duration) (string, error)
	Get(key string) (User, error)
	Refresh(key string, user User, expr time.Duration) error
}

type PageProvider interface {
	Page(key string) (*Page, error)
	Save(key string, page *Page) error
}

type RootHandler struct {
	Sessions  SessionProvider
	Pages     PageProvider
	StaticDir string
}

type AdminHandler struct {
	Sessions SessionProvider
}

func (h *AdminHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("admin route"))
}

func (h *RootHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if strings.HasPrefix(r.URL.Path, "/admin") {
		(&AdminHandler{
			Sessions: h.Sessions,
		}).ServeHTTP(w, r)
		return
	}
	// attempt to serve from the managed pages
	page, err := h.Pages.Page(r.URL.Path)
	if err == nil {
		w.Write(page.Contents)
		return
	}
	// fall back to serving out of the static directory, but:
	// 1. prevent the generated indexes from rendering
	if strings.HasSuffix(r.URL.Path, "/") {
		h.ErrorHandle(404, w)
		return
	}
	// 2. prevent hidden paths from rendering
	for _, seg := range strings.Split(r.URL.Path, "/") {
		if strings.HasPrefix(seg, ".") {
			h.ErrorHandle(404, w)
			return
		}
	}
	// 3. catch files that would 404 and serve our own 404 page
	if !staticFileExists(filepath.Join(h.StaticDir, r.URL.Path)) {
		h.ErrorHandle(404, w)
		return
	}
	// finally, use the built-in fileserver to serve
	fs := http.FileServer(http.Dir(h.StaticDir))
	fs.ServeHTTP(w, r)
}

func (h *RootHandler) ErrorHandle(status int, w http.ResponseWriter) {
	f, err := os.Open(filepath.Join(h.StaticDir, strconv.Itoa(status)+".html"))
	if err == nil {
		w.WriteHeader(status)
		_, err = io.Copy(w, f)
		if err != nil {
			fmt.Fprintf(w, "Internal Server Error while loading %d page\n", status)
		}
		return
	}
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.WriteHeader(404)
	fmt.Fprintf(w, "%d\n", status)
}

func staticFileExists(name string) bool {
	f, err := os.Open(name)
	if err != nil {
		return false
	}
	defer f.Close()
	_, err = f.Stat()
	return err == nil
}

func main() {
	handler := &RootHandler{
		Sessions:  &Sessions{},
		Pages:     &Index{},
		StaticDir: "./static",
	}
	handler.Pages.Save("foo", &Page{
		Contents: []byte("foobar"),
	})
	handler.Pages.Save("index", &Page{
		Contents: []byte("root"),
	})

	err := http.ListenAndServe(":8080", handler)
	log.Fatalf("server error: %v", err)
}