// Copyright 2015 go-swagger maintainers
//
// 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 runtime

import (
	"bufio"
	"context"
	"errors"
	"io"
	"net/http"
	"strings"

	"github.com/go-openapi/swag"
)

// CanHaveBody returns true if this method can have a body
func CanHaveBody(method string) bool {
	mn := strings.ToUpper(method)
	return mn == "POST" || mn == "PUT" || mn == "PATCH" || mn == "DELETE"
}

// IsSafe returns true if this is a request with a safe method
func IsSafe(r *http.Request) bool {
	mn := strings.ToUpper(r.Method)
	return mn == "GET" || mn == "HEAD"
}

// AllowsBody returns true if the request allows for a body
func AllowsBody(r *http.Request) bool {
	mn := strings.ToUpper(r.Method)
	return mn != "HEAD"
}

// HasBody returns true if this method needs a content-type
func HasBody(r *http.Request) bool {
	// happy case: we have a content length set
	if r.ContentLength > 0 {
		return true
	}

	if r.Header.Get("content-length") != "" {
		// in this case, no Transfer-Encoding should be present
		// we have a header set but it was explicitly set to 0, so we assume no body
		return false
	}

	rdr := newPeekingReader(r.Body)
	r.Body = rdr
	return rdr.HasContent()
}

func newPeekingReader(r io.ReadCloser) *peekingReader {
	if r == nil {
		return nil
	}
	return &peekingReader{
		underlying: bufio.NewReader(r),
		orig:       r,
	}
}

type peekingReader struct {
	underlying interface {
		Buffered() int
		Peek(int) ([]byte, error)
		Read([]byte) (int, error)
	}
	orig io.ReadCloser
}

func (p *peekingReader) HasContent() bool {
	if p == nil {
		return false
	}
	if p.underlying.Buffered() > 0 {
		return true
	}
	b, err := p.underlying.Peek(1)
	if err != nil {
		return false
	}
	return len(b) > 0
}

func (p *peekingReader) Read(d []byte) (int, error) {
	if p == nil {
		return 0, io.EOF
	}
	if p.underlying == nil {
		return 0, io.ErrUnexpectedEOF
	}
	return p.underlying.Read(d)
}

func (p *peekingReader) Close() error {
	if p.underlying == nil {
		return errors.New("reader already closed")
	}
	p.underlying = nil
	if p.orig != nil {
		return p.orig.Close()
	}
	return nil
}

// JSONRequest creates a new http request with json headers set.
//
// It uses context.Background.
func JSONRequest(method, urlStr string, body io.Reader) (*http.Request, error) {
	req, err := http.NewRequestWithContext(context.Background(), method, urlStr, body)
	if err != nil {
		return nil, err
	}
	req.Header.Add(HeaderContentType, JSONMime)
	req.Header.Add(HeaderAccept, JSONMime)
	return req, nil
}

// Gettable for things with a method GetOK(string) (data string, hasKey bool, hasValue bool)
type Gettable interface {
	GetOK(string) ([]string, bool, bool)
}

// ReadSingleValue reads a single value from the source
func ReadSingleValue(values Gettable, name string) string {
	vv, _, hv := values.GetOK(name)
	if hv {
		return vv[len(vv)-1]
	}
	return ""
}

// ReadCollectionValue reads a collection value from a string data source
func ReadCollectionValue(values Gettable, name, collectionFormat string) []string {
	v := ReadSingleValue(values, name)
	return swag.SplitByFormat(v, collectionFormat)
}