package tools

import "strings"

// ApplySelection 按 +name / -name 调整默认工具集。
// 规格为空时返回 base 的副本。出现不带正负号的名字时，先用这些名字替换默认集，再应用增减。
// 分隔符为空格、逗号或换行。
func ApplySelection(base []string, spec string) []string {
	spec = strings.TrimSpace(spec)
	if spec == "" {
		return append([]string{}, base...)
	}
	fields := strings.FieldsFunc(spec, func(r rune) bool {
		return r == ',' || r == ' ' || r == '\n' || r == '\t'
	})
	hasBare := false
	for _, f := range fields {
		if f != "" && f[0] != '+' && f[0] != '-' {
			hasBare = true
			break
		}
	}
	var out []string
	if !hasBare {
		out = append(out, base...)
	}
	for _, f := range fields {
		if f == "" {
			continue
		}
		switch f[0] {
		case '+':
			out = addName(out, f[1:])
		case '-':
			out = dropName(out, f[1:])
		default:
			out = addName(out, f)
		}
	}
	return out
}

func addName(names []string, name string) []string {
	if name == "" {
		return names
	}
	for _, n := range names {
		if n == name {
			return names
		}
	}
	return append(names, name)
}

func dropName(names []string, name string) []string {
	if name == "" {
		return names
	}
	out := names[:0]
	for _, n := range names {
		if n != name {
			out = append(out, n)
		}
	}
	return out
}