package main

import (
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"sync"
	"time"
)

type sessionInfo struct {
	last time.Time
}

var (
	sessionMu sync.Mutex
	sessions  = make(map[string]*sessionInfo)
)

const (
	idleTimeout = 5 * time.Minute
	gcPeriod    = 1 * time.Hour
)

func WebCreateSession() string {
	buf := make([]byte, 32)
	rand.Read(buf)
	return hex.EncodeToString(buf)
}

func WebAddSession(id string) {
	sessionMu.Lock()
	sessions[id] = &sessionInfo{last: time.Now()}
	sessionMu.Unlock()
}

func WebHasSession(id string) bool {
	now := time.Now()

	sessionMu.Lock()
	defer sessionMu.Unlock()

	s, ok := sessions[id]
	if !ok {
		return false
	}

	if now.Sub(s.last) > idleTimeout {
		delete(sessions, id)
		return false
	}

	s.last = now
	return true
}

func WebCheckSession(r *http.Request) bool {
	c, err := r.Cookie("session_id")
	if err != nil {
		return false
	}
	return WebHasSession(c.Value)
}

func StartSessionCleaner() {
	go func() {
		ticker := time.NewTicker(gcPeriod)
		defer ticker.Stop()

		for range ticker.C {
			now := time.Now()

			sessionMu.Lock()
			for k, s := range sessions {
				if now.Sub(s.last) > idleTimeout {
					delete(sessions, k)
				}
			}
			sessionMu.Unlock()
		}
	}()
}