package services

import (
	"crypto/rand"
	"encoding/hex"
	"io"
	"time"
)

type SessionsService struct {
	ctx *Context
}

type SessionItem struct {
	Id        string `json:"id"`
	ExpiresAt int64  `json:"expiresAt"`
}

func (s *SessionsService) GetById(id string) (*SessionItem, error) {
	item := SessionItem{}

	row := s.ctx.DB.QueryRow("SELECT id, expires_at FROM sessions WHERE id = ? AND expires_at > ?", id, time.Now().Unix())

	err := row.Scan(&item.Id, &item.ExpiresAt)
	if err != nil {
		return nil, err
	}

	return &item, nil
}

func (s *SessionsService) Create() (*SessionItem, error) {
	item := SessionItem{
		// TODO: The key is not guaranteed to be unique, how do we guarantee that?
		Id:        hex.EncodeToString(generateRandomKey(128)),
		ExpiresAt: generateExpiryDate().Unix(),
	}

	_, err := s.ctx.DB.Exec("INSERT INTO sessions (id, expires_at) VALUES (?, ?)", item.Id, item.ExpiresAt)

	if err != nil {
		return nil, err
	}

	return &item, nil
}

func (s *SessionsService) Destroy(sessionId string) error {
	_, err := s.ctx.DB.Exec("DELETE FROM sessions WHERE id = ?", sessionId)

	return err
}

func (s *SessionsService) Extend(session *SessionItem) error {
	session.ExpiresAt = generateExpiryDate().Unix()

	_, err := s.ctx.DB.Exec("UPDATE sessions SET expires_at = ? WHERE id = ?", session.ExpiresAt, session.Id)

	return err
}

func (s *SessionsService) Cleanup() error {
	_, err := s.ctx.DB.Exec("DELETE FROM sessions WHERE expires_at < ?", time.Now().Unix())

	return err
}

func generateExpiryDate() time.Time {
	return time.Now().Add(time.Hour * 24)
}

func generateRandomKey(length int) []byte {
	k := make([]byte, length)
	if _, err := io.ReadFull(rand.Reader, k); err != nil {
		return nil
	}
	return k
}