package ffmd

import (
	"fmt"
	"sort"
	"strings"

	"github.com/peterbourgon/ff/v3/ffcli"
)

// Tree returns a tree-representation of a ffcli.Command
func Tree(cmd *ffcli.Command) string {
	t := tree{cmd.Name: commandTree(cmd)}
	s := t.String(true, "")
	return strings.TrimSpace(s)
}

type tree map[string]tree

func commandTree(cmd *ffcli.Command) tree {
	t := tree{}
	for _, sub := range cmd.Subcommands {
		t[sub.Name] = commandTree(sub)
	}
	return t
}

func (t tree) keys() []string {
	k := make([]string, 0, len(t))
	for key, _ := range t {
		k = append(k, key)
	}
	sort.Strings(k)
	return k
}

func (t tree) String(root bool, padding string) string {
	var s strings.Builder
	index := 0
	for _, k := range t.keys() {
		v := t[k]
		p := pipe(index, len(t))
		s.WriteString(fmt.Sprintf("%s%s\n", padding+pipePad(root, p), k))
		op := outerPipe(index, len(t))
		s.WriteString(v.String(false, padding+pipePad(root, op)))
		index++
	}
	return s.String()
}

func pipe(index int, len int) string {
	switch {
	case index+1 > len:
		return "  "
	case index+1 == len:
		return "└─"
	default:
		return "├─"
	}
}

func outerPipe(index int, len int) string {
	switch {
	case index+1 == len:
		return "  "
	default:
		return "│ "
	}
}

func pipePad(root bool, box string) string {
	if root {
		return ""
	}
	return box + " "
}