// Copyright (C) 2022 Marius Schellenberger

package srv

import (
	"errors"
	"io"
	stdfs "io/fs"
	"net/http"
	"os"
	"path"
	"runtime"
	"strings"

	"cachefs/pkg/fs"

	"github.com/go-logr/logr"
)

func PrintStack() {
	os.Stderr.Write(Stack())
}

func Stack() []byte {
	buf := make([]byte, 1024)
	for {
		n := runtime.Stack(buf, true)
		if n < len(buf) {
			return buf[:n]
		}
		buf = make([]byte, 2*len(buf))
	}
}

type FileServer struct {
	log logr.Logger
	fs  *fs.FS
	h   http.Handler
}

func NewFileServer(fs *fs.FS, log logr.Logger) http.Handler {
	return &FileServer{log, fs, http.FileServer(fs)}
}

func skipLog(path string) bool {
	return strings.HasSuffix(path, "favicon.ico")
}

func (fs *FileServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	s := &statusInterceptor{w: w}
	w = s
	if !skipLog(r.RequestURI) {
		defer func() {
			if s.Status() == http.StatusPartialContent {
				return
			}
			fs.log.Info("access",
				"client", r.RemoteAddr,
				"method", r.Method,
				"status", s.Status(),
				"uri", r.RequestURI,
			)
		}()
	}
	upath := r.URL.Path
	if !strings.HasPrefix(upath, "/") {
		upath = "/" + upath
		r.URL.Path = upath
	}
	p := path.Clean(upath)
	option := r.FormValue("o")
	if option == "debug" {
		PrintStack()
	}
	d, _, err := fs.fs.StatWithOffline(p)
	if err != nil {
		msg, code := toHTTPError(err)
		http.Error(w, msg, code)
		return
	}
	//option := r.FormValue("o")
	if option == "v" {
		err = video.Execute(w, r.URL.Path)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
		return
	}

	if !d.IsDir() {
		if option == "p" || option == "s" {
			if option == "p" {
				fs.fs.Preload(p)
			} else if option == "s" {
				fs.fs.CancelPreload(p)
			}
			rdir := "/"
			if i := strings.LastIndex(p, "/"); i > 0 {
				rdir = p[:i]
			}
			http.Redirect(w, r, rdir+"#"+anchor(p), http.StatusFound)
			return
		}
		if option == "n" {
			fs.fs.NoCache.ServeHTTP(w, r)
			return
		}
		fs.h.ServeHTTP(w, r)
		return
	}

	i := &responseInterceptor{w: w}
	// TODO implement directory listing cache
	offline := true
	if offline {
		r.Header.Del("If-Modified-Since")
		r.Header.Del("Cache-Control")
	}
	fs.h.ServeHTTP(i, r)
	if offline {
		w.Header().Del("Last-Modified")
	}
	paths, err := i.GetPaths(p, fs.fs)
	if err == io.EOF {
		w.WriteHeader(i.Status())
		return
	}
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(i.Status())
	err = index.Execute(w, paths)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func toHTTPError(err error) (string, int) {
	if errors.Is(err, stdfs.ErrNotExist) {
		return "404 page not found", http.StatusNotFound
	}
	if errors.Is(err, stdfs.ErrPermission) {
		return "403 Forbidden", http.StatusForbidden
	}
	return "500 Internal Server Error", http.StatusInternalServerError
}