package internal

import "reflect"

func ToLower(s string) string {
	if isLower(s) {
		return s
	}

	b := make([]byte, len(s))
	for i := range b {
		c := s[i]
		if c >= 'A' && c <= 'Z' {
			c += 'a' - 'A'
		}
		b[i] = c
	}
	return BytesToString(b)
}

func isLower(s string) bool {
	for i := 0; i < len(s); i++ {
		c := s[i]
		if c >= 'A' && c <= 'Z' {
			return false
		}
	}
	return true
}

func MakeSliceNextElemFunc(v reflect.Value) func() reflect.Value {
	elemType := v.Type().Elem()

	if elemType.Kind() == reflect.Ptr {
		elemType = elemType.Elem()
		return func() reflect.Value {
			if v.Len() < v.Cap() {
				v.Set(v.Slice(0, v.Len()+1))
				elem := v.Index(v.Len() - 1)
				if elem.IsNil() {
					elem.Set(reflect.New(elemType))
				}
				return elem.Elem()
			}

			elem := reflect.New(elemType)
			v.Set(reflect.Append(v, elem))
			return elem.Elem()
		}
	}

	zero := reflect.Zero(elemType)
	return func() reflect.Value {
		if v.Len() < v.Cap() {
			v.Set(v.Slice(0, v.Len()+1))
			return v.Index(v.Len() - 1)
		}

		v.Set(reflect.Append(v, zero))
		return v.Index(v.Len() - 1)
	}
}