/*
Copyright © 2026 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"
	"strconv"

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

var convolveA string
var convolveB string

func readSequenceFromFile(filepath string) ([]complex128, error) {
	// initial length 1 so index math works
	seq := make([]complex128, 1)
	file, err := os.Open(filepath)
	if err != nil {
		return seq, err
	}
	defer file.Close()

	lines := splitLines(file)
	for _, line := range lines {
		x, err := strconv.ParseComplex(line, 128)
		if err != nil {
			return seq, err
		}

		seq = append(seq, x)
	}

	return seq, nil
}

func convolve(cmd *cobra.Command, args []string) {
	a, err := readSequenceFromFile(convolveA)
	if err != nil {
		cobra.CheckErr(err)
	}

	b, err := readSequenceFromFile(convolveB)
	if err != nil {
		cobra.CheckErr(err)
	}

	bufStdout := bufio.NewWriter(os.Stdout)
	defer bufStdout.Flush()

	for i, n := range lib.DirichletConvolve(a, b) {
		if i == 0 {
			continue
		}

		if imag(n) == 0 {
			fmt.Fprintln(bufStdout, real(n))
		} else {
			fmt.Fprintln(bufStdout, n)
		}
	}
}

// convolveCmd represents the convolve command
var convolveCmd = &cobra.Command{
	Use:   "convolve",
	Short: "Compute the Dirichlet convolution of two sequences",
	Long: `Compute the Dirichlet convolution of two sequences.

Each sequence is provided as a file, where line k of the file gives the kth term of the sequence.
`,
	Run: convolve,
}

func init() {
	rootCmd.AddCommand(convolveCmd)

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

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

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

	convolveCmd.Flags().StringVarP(&convolveA, "first", "a", "", "first sequence")
	convolveCmd.MarkFlagRequired("first")

	convolveCmd.Flags().StringVarP(&convolveB, "second", "b", "", "second sequence")
	convolveCmd.MarkFlagRequired("second")
}