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// 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 (

        "bufio"

        "bytes"

        "fmt"

        "io"

        "io/ioutil"

        "net"

        "net/http"

        "strings"

        "time"

)

// 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) SetDeadline(t time.Time) error      { return nil }

func (c *dumpConn) SetReadDeadline(t time.Time) error  { return nil }

func (c *dumpConn) SetWriteDeadline(t time.Time) 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) ([]byte, error) {

        save := req.Body

        if !body || req.Body == nil {

                req.Body = nil

        } else {

                var err error

                save, req.Body, err = drainBody(req.Body)

                if err != nil {

                        return nil, err

                }

        }

        // Use the actual Transport code to record what we would send

        // on the wire, but not using TCP.  Use a Transport with a

        // customer dialer that returns a fake net.Conn that waits

        // for the full input (and recording it), and then responds

        // with a dummy response.

        var buf bytes.Buffer // records the output

        pr, pw := io.Pipe()

        dr := &delegateReader{c: make(chan io.Reader)}

        // Wait for the request before replying with a dummy response:

        go func() {

                http.ReadRequest(bufio.NewReader(pr))

                dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\n\r\n")

        }()

        t := &http.Transport{

                Dial: func(net, addr string) (net.Conn, error) {

                        return &dumpConn{io.MultiWriter(pw, &buf), dr}, nil

                },

        }

        _, err := t.RoundTrip(req)

        req.Body = save

        if err != nil {

                return nil, err

        }

        return buf.Bytes(), nil

}

// delegateReader is a reader that delegates to another reader,

// once it arrives on a channel.

type delegateReader struct {

        c chan io.Reader

        r io.Reader // nil until received from c

}

func (r *delegateReader) Read(p []byte) (int, error) {

        if r.r == nil {

                r.r = <-r.c

        }

        return r.r.Read(p)

}

// 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

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

                req.URL.RequestURI(), 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

}