package services

import (
	"basic-sensor-receiver/models"
	"crypto/rand"
	"math/big"
)

type SensorsService struct {
	ctx *Context
}

func (s *SensorsService) GetList() ([]models.SensorItem, error) {
	sensors := []models.SensorItem{}

	err := s.ctx.DB.Select(&sensors, "SELECT id, name, auth_key, last_contact_at FROM sensors")

	if err != nil {
		return nil, err
	}

	return sensors, nil
}

func (s *SensorsService) Create(name string) (*models.SensorItem, error) {
	authKey, err := generateRandomString(32)

	if err != nil {
		return nil, err
	}

	item := models.SensorItem{
		Name:    name,
		AuthKey: authKey,
	}

	res, err := s.ctx.DB.Exec("INSERT INTO sensors (name, auth_key) VALUES (?, ?)", item.Name, item.AuthKey)

	if err != nil {
		return nil, err
	}

	item.Id, err = res.LastInsertId()

	if err != nil {
		return nil, err
	}

	return &item, nil
}

func (s *SensorsService) GetById(id int64) (*models.SensorItem, error) {
	item := models.SensorItem{}

	err := s.ctx.DB.Get(&item, "SELECT id, name, auth_key, last_contact_at FROM sensors WHERE id = $1", id)

	if err != nil {
		return nil, err
	}

	return &item, nil
}

func (s *SensorsService) Update(id int64, name string) (*models.SensorItem, error) {
	item, err := s.GetById(id)

	if err != nil {
		return nil, err
	}

	item.Name = name

	_, err = s.ctx.DB.Exec("UPDATE sensors SET name = ? WHERE id = ?", item.Name, item.Id)

	if err != nil {
		return nil, err
	}

	return item, nil
}

func (s *SensorsService) DeleteById(id int64) error {
	item, err := s.GetById(id)

	if err != nil {
		return err
	}

	_, err = s.ctx.DB.Exec("DELETE FROM sensor_values WHERE sensor_id = ?", item.Id)

	if err != nil {
		return err
	}

	_, err = s.ctx.DB.Exec("DELETE FROM sensors WHERE id = ?", item.Id)

	return err
}

var randomKeySource = []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

func generateRandomString(length int) (string, error) {
	key := make([]byte, length)

	for i := range key {
		value, err := rand.Int(rand.Reader, big.NewInt(int64(len(randomKeySource))))

		if err != nil {
			return "", err
		}

		key[i] = randomKeySource[value.Int64()]
	}

	return string(key), nil
}