/*
Copyright © 2025 filifa

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 cmd

import (
	"fmt"
	"strconv"

	"github.com/spf13/cobra"
)

func totientSieve(n int) chan int {
	totients := make([]int, n)
	totients[0] = 0
	totients[1] = 1
	for i := 2; i < n; i++ {
		totients[i] = i - 1
	}

	ch := make(chan int)
	go func() {
		for i := 0; i < n; i++ {
			ch <- totients[i]
			if i == 0 || i == 1 || totients[i] != i-1 {
				continue
			}

			for j := 2 * i; j < n; j += i {
				totients[j] -= totients[j] / i
			}
		}

		close(ch)
	}()

	return ch
}

func totient(cmd *cobra.Command, args []string) {
	n, err := strconv.Atoi(args[0])
	if err != nil {
		cobra.CheckErr(err)
	}

	for v := range totientSieve(n) {
		fmt.Println(v)
	}
}

// totientCmd represents the totient command
var totientCmd = &cobra.Command{
	Use:   "totient",
	Short: "Compute the totient function for all numbers less than n",
	Long:  `Compute the totient function for all numbers less than n.`,
	Run:   totient,
}

func init() {
	sieveCmd.AddCommand(totientCmd)

	// Here you will define your flags and configuration settings.

	// Cobra supports Persistent Flags which will work for this command
	// and all subcommands, e.g.:
	// totientCmd.PersistentFlags().String("foo", "", "A help for foo")

	// Cobra supports local flags which will only run when this command
	// is called directly, e.g.:
	// totientCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
}