// Package mnemonic is the command that prints a child mnemonic.
package mnemonic

import (
	"fmt"

	"git.eeqj.de/sneak/keyfunc/internal/childmnemonic"
	"git.eeqj.de/sneak/keyfunc/internal/cli/options"
	"git.eeqj.de/sneak/keyfunc/internal/derive"
	"github.com/spf13/cobra"
)

// Command returns the mnemonic command.
func Command() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "mnemonic",
		Short: "print a child mnemonic derived from the main one",
		Args:  cobra.NoArgs,
		RunE: func(cmd *cobra.Command, _ []string) error {
			child, err := derived(cmd)
			if err != nil {
				return err
			}

			_, err = fmt.Fprintln(cmd.OutOrStdout(), child)
			if err != nil {
				return fmt.Errorf("writing the mnemonic: %w", err)
			}

			return nil
		},
	}

	cmd.Flags().Uint32(
		"words", childmnemonic.DefaultWords,
		"how long the child mnemonic is: 12, 18 or 24 words",
	)

	return cmd
}

// derived returns the child mnemonic this run asks for.
func derived(cmd *cobra.Command) (string, error) {
	index, err := options.Index(cmd)
	if err != nil {
		return "", err
	}

	words, err := cmd.Flags().GetUint32("words")
	if err != nil {
		return "", fmt.Errorf("reading the word count: %w", err)
	}

	parent, err := options.Mnemonic(cmd)
	if err != nil {
		return "", err
	}

	master, err := derive.Master(parent)
	if err != nil {
		return "", err
	}

	return childmnemonic.Derive(master, words, index)
}