// Copyright (c) 2023 IBM Corp.
// All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package generic

import (
	F "github.com/IBM/fp-go/function"
	O "github.com/IBM/fp-go/option"
	P "github.com/IBM/fp-go/pair"
)

// First returns the first item in an iterator if such an item exists
func First[GU ~func() O.Option[P.Pair[GU, U]], U any](mu GU) O.Option[U] {
	return F.Pipe1(
		mu(),
		O.Map(P.Tail[GU, U]),
	)
}