package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"time"
)

type Session struct {
	ID                    string
	LoggedIn              bool
	Me                    string
	AuthorizationEndpoint string
	RedirectURI           string
	State                 string
	NextURI               string
}

func NewSession(w http.ResponseWriter, r *http.Request) (*Session, error) {
	sessionID, err := getSessionCookie(w, r)
	if err != nil {
		return nil, err
	}
	session := &Session{ID: sessionID}
	err = loadSession(session)
	if err != nil {
		return nil, err
	}
	return session, nil
}

func (sess *Session) Flush() error {
	return saveSession(sess)
}

func saveSession(sess *Session) error {
	filename := generateFilename(sess.ID)
	err := os.Mkdir("session", 0755)
	f, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer f.Close()
	err = json.NewEncoder(f).Encode(sess)
	return err
}

func loadSession(sess *Session) error {
	filename := generateFilename(sess.ID)
	err := os.Mkdir("session", 0755)
	f, err := os.Open(filename)
	if err != nil {
		if os.IsNotExist(err) {
			// add defaults to session?
			return nil
		}
		return err
	}
	defer f.Close()
	err = json.NewDecoder(f).Decode(sess)
	return err
}

func generateFilename(id string) string {
	return fmt.Sprintf("session/%s.json", id)
}

func getSessionCookie(w http.ResponseWriter, r *http.Request) (string, error) {
	c, err := r.Cookie("session")
	var sessionVar string

	if err != nil {
		if err == http.ErrNoCookie {
			sessionVar = RandStringBytes(16)
			newCookie := &http.Cookie{
				Name:    "session",
				Value:   sessionVar,
				Expires: time.Now().Add(24 * time.Hour),
				Path:    "/",
			}

			http.SetCookie(w, newCookie)
			return sessionVar, nil
		}

		return "", err
	} else {
		sessionVar = c.Value
	}

	return sessionVar, nil
}