package main

import (
	"crypto/sha512"
	"math/rand"
	"encoding/base64"
	"flag"
)

var (
	tokenSalt *string
	sessions = []string{}
)

func registerSessionFlags() {
	tokenSalt = flag.String("sessionSalt", "", "Salt for the session token")
}

// Generates a random token
func randToken() string {
	// Generating the random part
	randBuff := make([]byte, 128)
	rand.Read(randBuff)

	// Hashing the random part
	hasher := sha512.New()
	hasher.Write(randBuff)
	hasher.Write([]byte(*tokenSalt))
	hashBuff := hasher.Sum(nil)

	// Returning that
	return base64.URLEncoding.EncodeToString(hashBuff)
}

// Verifies a given session token against the internal session array
func isValidSession(sessionToken string) (bool){
	for _, token := range sessions {
		if token == sessionToken {
			return true
		}
	}
	return false
}

// Generates a new session token and adds it to the internal session array
func createSession() (string) {
	newToken := randToken()
	sessions = append(sessions, newToken)
	return newToken
}

// Removes a session from the internal session array
func destroySession(sessionToken string) {
	for index, token := range sessions {
		if token == sessionToken {
			// delete session from slice
			sessions = append(sessions[:index], sessions[:index + 1] ...)
		}
	}
}