/*
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 (
	"bufio"
	"fmt"
	"os"

	"github.com/spf13/cobra"
	"scm.dairydemon.net/filifa/mathtools/internal/lib/sieve"
)

var mobiusN uint

func mobius(cmd *cobra.Command, args []string) {
	bufStdout := bufio.NewWriter(os.Stdout)
	defer bufStdout.Flush()

	ch := sieve.MobiusSieve(mobiusN, 1000)
	for i := 0; ; i++ {
		v, ok := <-ch
		if !ok {
			break
		}

		if i == 0 {
			continue
		}

		fmt.Fprintln(bufStdout, v)
	}
}

// mobiusCmd represents the mobius command
var mobiusCmd = &cobra.Command{
	Use:   "mobius -n N",
	Short: "Compute the Möbius function for all numbers less than n",
	Long: `Compute the Möbius function for all numbers less than n.

The Möbius function mu(n) is a multiplicative function defined as follows for prime p:
mu(p) = -1
mu(p^k) = 0 for k > 1

This means for squarefree n, mu(n) = -1 if n has an odd number of prime factors and mu(n) = 1 if n has an even number of prime factors. mu(n) = 0 if n is not squarefree.`,
	Run: mobius,
}

func init() {
	sieveCmd.AddCommand(mobiusCmd)

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

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

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

	mobiusCmd.Flags().UintVarP(&mobiusN, "limit", "n", 0, "upper limit")
	mobiusCmd.MarkFlagRequired("limit")
}