// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package httputil

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"strings"
)

// One of the copies, say from b to r2, could be avoided by using a more
// elaborate trick where the other copy is made during Request/Response.Write.
// This would complicate things too much, given that these functions are for
// debugging only.
func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
	var buf bytes.Buffer
	if _, err = buf.ReadFrom(b); err != nil {
		return nil, nil, err
	}
	if err = b.Close(); err != nil {
		return nil, nil, err
	}
	return ioutil.NopCloser(&buf), ioutil.NopCloser(bytes.NewBuffer(buf.Bytes())), nil
}

// dumpConn is a net.Conn which writes to Writer and reads from Reader
type dumpConn struct {
	io.Writer
	io.Reader
}

func (c *dumpConn) Close() error                     { return nil }
func (c *dumpConn) LocalAddr() net.Addr              { return nil }
func (c *dumpConn) RemoteAddr() net.Addr             { return nil }
func (c *dumpConn) SetTimeout(nsec int64) error      { return nil }
func (c *dumpConn) SetReadTimeout(nsec int64) error  { return nil }
func (c *dumpConn) SetWriteTimeout(nsec int64) error { return nil }

// DumpRequestOut is like DumpRequest but includes
// headers that the standard http.Transport adds,
// such as User-Agent.
func DumpRequestOut(req *http.Request, body bool) (dump []byte, err error) {
	save := req.Body
	if !body || req.Body == nil {
		req.Body = nil
	} else {
		save, req.Body, err = drainBody(req.Body)
		if err != nil {
			return
		}
	}

	var b bytes.Buffer
	dialed := false
	t := &http.Transport{
		Dial: func(net, addr string) (c net.Conn, err error) {
			if dialed {
				return nil, errors.New("unexpected second dial")
			}
			c = &dumpConn{
				Writer: &b,
				Reader: strings.NewReader("HTTP/1.1 500 Fake Error\r\n\r\n"),
			}
			return
		},
	}

	_, err = t.RoundTrip(req)

	req.Body = save
	if err != nil {
		return
	}
	dump = b.Bytes()
	return
}

// Return value if nonempty, def otherwise.
func valueOrDefault(value, def string) string {
	if value != "" {
		return value
	}
	return def
}

var reqWriteExcludeHeaderDump = map[string]bool{
	"Host":              true, // not in Header map anyway
	"Content-Length":    true,
	"Transfer-Encoding": true,
	"Trailer":           true,
}

// dumpAsReceived writes req to w in the form as it was received, or
// at least as accurately as possible from the information retained in
// the request.
func dumpAsReceived(req *http.Request, w io.Writer) error {
	return nil
}

// DumpRequest returns the as-received wire representation of req,
// optionally including the request body, for debugging.
// DumpRequest is semantically a no-op, but in order to
// dump the body, it reads the body data into memory and
// changes req.Body to refer to the in-memory copy.
// The documentation for http.Request.Write details which fields
// of req are used.
func DumpRequest(req *http.Request, body bool) (dump []byte, err error) {
	save := req.Body
	if !body || req.Body == nil {
		req.Body = nil
	} else {
		save, req.Body, err = drainBody(req.Body)
		if err != nil {
			return
		}
	}

	var b bytes.Buffer

	urlStr := req.URL.Raw
	if urlStr == "" {
		urlStr = valueOrDefault(req.URL.EncodedPath(), "/")
		if req.URL.RawQuery != "" {
			urlStr += "?" + req.URL.RawQuery
		}
	}

	fmt.Fprintf(&b, "%s %s HTTP/%d.%d\r\n", valueOrDefault(req.Method, "GET"), urlStr,
		req.ProtoMajor, req.ProtoMinor)

	host := req.Host
	if host == "" && req.URL != nil {
		host = req.URL.Host
	}
	if host != "" {
		fmt.Fprintf(&b, "Host: %s\r\n", host)
	}

	chunked := len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked"
	if len(req.TransferEncoding) > 0 {
		fmt.Fprintf(&b, "Transfer-Encoding: %s\r\n", strings.Join(req.TransferEncoding, ","))
	}
	if req.Close {
		fmt.Fprintf(&b, "Connection: close\r\n")
	}

	err = req.Header.WriteSubset(&b, reqWriteExcludeHeaderDump)
	if err != nil {
		return
	}

	io.WriteString(&b, "\r\n")

	if req.Body != nil {
		var dest io.Writer = &b
		if chunked {
			dest = NewChunkedWriter(dest)
		}
		_, err = io.Copy(dest, req.Body)
		if chunked {
			dest.(io.Closer).Close()
			io.WriteString(&b, "\r\n")
		}
	}

	req.Body = save
	if err != nil {
		return
	}
	dump = b.Bytes()
	return
}

// DumpResponse is like DumpRequest but dumps a response.
func DumpResponse(resp *http.Response, body bool) (dump []byte, err error) {
	var b bytes.Buffer
	save := resp.Body
	savecl := resp.ContentLength
	if !body || resp.Body == nil {
		resp.Body = nil
		resp.ContentLength = 0
	} else {
		save, resp.Body, err = drainBody(resp.Body)
		if err != nil {
			return
		}
	}
	err = resp.Write(&b)
	resp.Body = save
	resp.ContentLength = savecl
	if err != nil {
		return
	}
	dump = b.Bytes()
	return
}