/*
 * Wiki - A wiki with editor
 * Copyright (c) 2021 Peter Stuifzand
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"os"
	"sync"
	"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, fmt.Errorf("getSessionCookie failed: %w", err)
	}
	session := &Session{ID: sessionID}
	err = loadSession(session)
	if err != nil {
		return nil, fmt.Errorf("loadSession failed: %w" , err)
	}
	return session, nil
}

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

var fileMutex sync.RWMutex

func saveSession(sess *Session) error {
	filename := generateFilename(sess.ID)
	err := os.Mkdir("session", 0755)
	fileMutex.Lock()
	defer fileMutex.Unlock()
	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)
	fileMutex.RLock()
	defer fileMutex.RUnlock()
	f, err := os.Open(filename)
	if err != nil {
		if os.IsNotExist(err) {
			// add defaults to session?
			return nil
		}
		return fmt.Errorf("while opening file %s: %w", filename, err)
	}
	defer f.Close()
	err = json.NewDecoder(f).Decode(sess)
	if err != nil {
		return fmt.Errorf("while decoding json from file %s: %w", filename, err)
	}
	return nil
}

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 && errors.Is(err, http.ErrNoCookie) {
		sessionVar = RandStringBytes(16)
		c = &http.Cookie{
			Name:    "session",
			Value:   sessionVar,
			Expires: time.Now().Add(24 * time.Hour),
			Path:    "/",
		}
	} else {
		sessionVar = c.Value
		c.Expires = time.Now().Add(24 * time.Hour)
	}

	http.SetCookie(w, c)

	return sessionVar, nil
}