// Copyright 2019 Unknwon

//

// 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 ini

import (

	"bytes"

	"fmt"

	"io"

	"io/ioutil"

	"os"

)

var (

	_ dataSource = (*sourceFile)(nil)

	_ dataSource = (*sourceData)(nil)

	_ dataSource = (*sourceReadCloser)(nil)

)

// dataSource is an interface that returns object which can be read and closed.

type dataSource interface {

	ReadCloser() (io.ReadCloser, error)

}

// sourceFile represents an object that contains content on the local file system.

type sourceFile struct {

	name string

}

func (s sourceFile) ReadCloser() (_ io.ReadCloser, err error) {

	return os.Open(s.name)

}

// sourceData represents an object that contains content in memory.

type sourceData struct {

	data []byte

}

func (s *sourceData) ReadCloser() (io.ReadCloser, error) {

	return ioutil.NopCloser(bytes.NewReader(s.data)), nil

}

// sourceReadCloser represents an input stream with Close method.

type sourceReadCloser struct {

	reader io.ReadCloser

}

func (s *sourceReadCloser) ReadCloser() (io.ReadCloser, error) {

	return s.reader, nil

}

func parseDataSource(source interface{}) (dataSource, error) {

	switch s := source.(type) {

	case string:

		return sourceFile{s}, nil

	case []byte:

		return &sourceData{s}, nil

	case io.ReadCloser:

		return &sourceReadCloser{s}, nil

	default:

		return nil, fmt.Errorf("error parsing data source: unknown type %q", s)

	}

}