server.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

/*
A simple http server interface to Swarm
*/
package http

import (
	"archive/tar"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"mime"
	"mime/multipart"
	"net/http"
	"os"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/XinFinOrg/XDPoSChain/common"
	"github.com/XinFinOrg/XDPoSChain/log"
	"github.com/XinFinOrg/XDPoSChain/metrics"
	"github.com/XinFinOrg/XDPoSChain/swarm/api"
	"github.com/XinFinOrg/XDPoSChain/swarm/storage"
	"github.com/rs/cors"
)

// setup metrics
var (
	postRawCount     = metrics.NewRegisteredCounter("api.http.post.raw.count", nil)
	postRawFail      = metrics.NewRegisteredCounter("api.http.post.raw.fail", nil)
	postFilesCount   = metrics.NewRegisteredCounter("api.http.post.files.count", nil)
	postFilesFail    = metrics.NewRegisteredCounter("api.http.post.files.fail", nil)
	deleteCount      = metrics.NewRegisteredCounter("api.http.delete.count", nil)
	deleteFail       = metrics.NewRegisteredCounter("api.http.delete.fail", nil)
	getCount         = metrics.NewRegisteredCounter("api.http.get.count", nil)
	getFail          = metrics.NewRegisteredCounter("api.http.get.fail", nil)
	getFileCount     = metrics.NewRegisteredCounter("api.http.get.file.count", nil)
	getFileNotFound  = metrics.NewRegisteredCounter("api.http.get.file.notfound", nil)
	getFileFail      = metrics.NewRegisteredCounter("api.http.get.file.fail", nil)
	getFilesCount    = metrics.NewRegisteredCounter("api.http.get.files.count", nil)
	getFilesFail     = metrics.NewRegisteredCounter("api.http.get.files.fail", nil)
	getListCount     = metrics.NewRegisteredCounter("api.http.get.list.count", nil)
	getListFail      = metrics.NewRegisteredCounter("api.http.get.list.fail", nil)
	requestCount     = metrics.NewRegisteredCounter("http.request.count", nil)
	htmlRequestCount = metrics.NewRegisteredCounter("http.request.html.count", nil)
	jsonRequestCount = metrics.NewRegisteredCounter("http.request.json.count", nil)
	requestTimer     = metrics.NewRegisteredResettingTimer("http.request.time", nil)
)

// ServerConfig is the basic configuration needed for the HTTP server and also
// includes CORS settings.
type ServerConfig struct {
	Addr       string
	CorsString string
}

// browser API for registering bzz url scheme handlers:
// https://developer.mozilla.org/en/docs/Web-based_protocol_handlers
// electron (chromium) api for registering bzz url scheme handlers:
// https://github.com/atom/electron/blob/master/docs/api/protocol.md

// starts up http server
func StartHttpServer(api *api.Api, config *ServerConfig) {
	var allowedOrigins []string
	for _, domain := range strings.Split(config.CorsString, ",") {
		allowedOrigins = append(allowedOrigins, strings.TrimSpace(domain))
	}
	c := cors.New(cors.Options{
		AllowedOrigins: allowedOrigins,
		AllowedMethods: []string{"POST", "GET", "DELETE", "PATCH", "PUT"},
		MaxAge:         600,
		AllowedHeaders: []string{"*"},
	})
	hdlr := c.Handler(NewServer(api))

	go http.ListenAndServe(config.Addr, hdlr)
}

func NewServer(api *api.Api) *Server {
	return &Server{api}
}

type Server struct {
	api *api.Api
}

// Request wraps http.Request and also includes the parsed bzz URI
type Request struct {
	http.Request

	uri *api.URI
}

// HandlePostRaw handles a POST request to a raw bzz-raw:/ URI, stores the request
// body in swarm and returns the resulting storage key as a text/plain response
func (s *Server) HandlePostRaw(w http.ResponseWriter, r *Request) {
	postRawCount.Inc(1)
	if r.uri.Path != "" {
		postRawFail.Inc(1)
		s.BadRequest(w, r, "raw POST request cannot contain a path")
		return
	}

	if r.Header.Get("Content-Length") == "" {
		postRawFail.Inc(1)
		s.BadRequest(w, r, "missing Content-Length header in request")
		return
	}

	key, err := s.api.Store(r.Body, r.ContentLength, nil)
	if err != nil {
		postRawFail.Inc(1)
		s.Error(w, r, err)
		return
	}
	s.logDebug("content for %s stored", key.Log())

	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, key)
}

// HandlePostFiles handles a POST request (or deprecated PUT request) to
// bzz:/<hash>/<path> which contains either a single file or multiple files
// (either a tar archive or multipart form), adds those files either to an
// existing manifest or to a new manifest under <path> and returns the
// resulting manifest hash as a text/plain response
func (s *Server) HandlePostFiles(w http.ResponseWriter, r *Request) {
	postFilesCount.Inc(1)
	contentType, params, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if err != nil {
		postFilesFail.Inc(1)
		s.BadRequest(w, r, err.Error())
		return
	}

	var key storage.Key
	if r.uri.Addr != "" {
		key, err = s.api.Resolve(r.uri)
		if err != nil {
			postFilesFail.Inc(1)
			s.Error(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
			return
		}
	} else {
		key, err = s.api.NewManifest()
		if err != nil {
			postFilesFail.Inc(1)
			s.Error(w, r, err)
			return
		}
	}

	newKey, err := s.updateManifest(key, func(mw *api.ManifestWriter) error {
		switch contentType {

		case "application/x-tar":
			return s.handleTarUpload(r, mw)

		case "multipart/form-data":
			return s.handleMultipartUpload(r, params["boundary"], mw)

		default:
			return s.handleDirectUpload(r, mw)
		}
	})
	if err != nil {
		postFilesFail.Inc(1)
		s.Error(w, r, fmt.Errorf("error creating manifest: %s", err))
		return
	}

	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, newKey)
}

func (s *Server) handleTarUpload(req *Request, mw *api.ManifestWriter) error {
	tr := tar.NewReader(req.Body)
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			return nil
		} else if err != nil {
			return fmt.Errorf("error reading tar stream: %s", err)
		}

		// only store regular files
		if !hdr.FileInfo().Mode().IsRegular() {
			continue
		}

		// add the entry under the path from the request
		path := path.Join(req.uri.Path, hdr.Name)
		entry := &api.ManifestEntry{
			Path:        path,
			ContentType: hdr.Xattrs["user.swarm.content-type"],
			Mode:        hdr.Mode,
			Size:        hdr.Size,
			ModTime:     hdr.ModTime,
		}
		s.logDebug("adding %s (%d bytes) to new manifest", entry.Path, entry.Size)
		contentKey, err := mw.AddEntry(tr, entry)
		if err != nil {
			return fmt.Errorf("error adding manifest entry from tar stream: %s", err)
		}
		s.logDebug("content for %s stored", contentKey.Log())
	}
}

func (s *Server) handleMultipartUpload(req *Request, boundary string, mw *api.ManifestWriter) error {
	mr := multipart.NewReader(req.Body, boundary)
	for {
		part, err := mr.NextPart()
		if err == io.EOF {
			return nil
		} else if err != nil {
			return fmt.Errorf("error reading multipart form: %s", err)
		}

		var size int64
		var reader io.Reader = part
		if contentLength := part.Header.Get("Content-Length"); contentLength != "" {
			size, err = strconv.ParseInt(contentLength, 10, 64)
			if err != nil {
				return fmt.Errorf("error parsing multipart content length: %s", err)
			}
			reader = part
		} else {
			// copy the part to a tmp file to get its size
			tmp, err := os.CreateTemp("", "swarm-multipart")
			if err != nil {
				return err
			}
			defer os.Remove(tmp.Name())
			defer tmp.Close()
			size, err = io.Copy(tmp, part)
			if err != nil {
				return fmt.Errorf("error copying multipart content: %s", err)
			}
			if _, err := tmp.Seek(0, io.SeekStart); err != nil {
				return fmt.Errorf("error copying multipart content: %s", err)
			}
			reader = tmp
		}

		// add the entry under the path from the request
		name := part.FileName()
		if name == "" {
			name = part.FormName()
		}
		path := path.Join(req.uri.Path, name)
		entry := &api.ManifestEntry{
			Path:        path,
			ContentType: part.Header.Get("Content-Type"),
			Size:        size,
			ModTime:     time.Now(),
		}
		s.logDebug("adding %s (%d bytes) to new manifest", entry.Path, entry.Size)
		contentKey, err := mw.AddEntry(reader, entry)
		if err != nil {
			return fmt.Errorf("error adding manifest entry from multipart form: %s", err)
		}
		s.logDebug("content for %s stored", contentKey.Log())
	}
}

func (s *Server) handleDirectUpload(req *Request, mw *api.ManifestWriter) error {
	key, err := mw.AddEntry(req.Body, &api.ManifestEntry{
		Path:        req.uri.Path,
		ContentType: req.Header.Get("Content-Type"),
		Mode:        0644,
		Size:        req.ContentLength,
		ModTime:     time.Now(),
	})
	if err != nil {
		return err
	}
	s.logDebug("content for %s stored", key.Log())
	return nil
}

// HandleDelete handles a DELETE request to bzz:/<manifest>/<path>, removes
// <path> from <manifest> and returns the resulting manifest hash as a
// text/plain response
func (s *Server) HandleDelete(w http.ResponseWriter, r *Request) {
	deleteCount.Inc(1)
	key, err := s.api.Resolve(r.uri)
	if err != nil {
		deleteFail.Inc(1)
		s.Error(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
		return
	}

	newKey, err := s.updateManifest(key, func(mw *api.ManifestWriter) error {
		s.logDebug("removing %s from manifest %s", r.uri.Path, key.Log())
		return mw.RemoveEntry(r.uri.Path)
	})
	if err != nil {
		deleteFail.Inc(1)
		s.Error(w, r, fmt.Errorf("error updating manifest: %s", err))
		return
	}

	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, newKey)
}

// HandleGet handles a GET request to
//   - bzz-raw://<key> and responds with the raw content stored at the
//     given storage key
//   - bzz-hash://<key> and responds with the hash of the content stored
//     at the given storage key as a text/plain response
func (s *Server) HandleGet(w http.ResponseWriter, r *Request) {
	getCount.Inc(1)
	key, err := s.api.Resolve(r.uri)
	if err != nil {
		getFail.Inc(1)
		s.NotFound(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
		return
	}

	// if path is set, interpret <key> as a manifest and return the
	// raw entry at the given path
	if r.uri.Path != "" {
		walker, err := s.api.NewManifestWalker(key, nil)
		if err != nil {
			getFail.Inc(1)
			s.BadRequest(w, r, fmt.Sprintf("%s is not a manifest", key))
			return
		}
		var entry *api.ManifestEntry
		walker.Walk(func(e *api.ManifestEntry) error {
			// if the entry matches the path, set entry and stop
			// the walk
			if e.Path == r.uri.Path {
				entry = e
				// return an error to cancel the walk
				return errors.New("found")
			}

			// ignore non-manifest files
			if e.ContentType != api.ManifestType {
				return nil
			}

			// if the manifest's path is a prefix of the
			// requested path, recurse into it by returning
			// nil and continuing the walk
			if strings.HasPrefix(r.uri.Path, e.Path) {
				return nil
			}

			return api.SkipManifest
		})
		if entry == nil {
			getFail.Inc(1)
			s.NotFound(w, r, fmt.Errorf("Manifest entry could not be loaded"))
			return
		}
		key = storage.Key(common.Hex2Bytes(entry.Hash))
	}

	// check the root chunk exists by retrieving the file's size
	reader := s.api.Retrieve(key)
	if _, err := reader.Size(nil); err != nil {
		getFail.Inc(1)
		s.NotFound(w, r, fmt.Errorf("Root chunk not found %s: %s", key, err))
		return
	}

	switch {
	case r.uri.Raw() || r.uri.DeprecatedRaw():
		// allow the request to overwrite the content type using a query
		// parameter
		contentType := "application/octet-stream"
		if typ := r.URL.Query().Get("content_type"); typ != "" {
			contentType = typ
		}
		w.Header().Set("Content-Type", contentType)

		http.ServeContent(w, &r.Request, "", time.Now(), reader)
	case r.uri.Hash():
		w.Header().Set("Content-Type", "text/plain")
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, key)
	}
}

// HandleGetFiles handles a GET request to bzz:/<manifest> with an Accept
// header of "application/x-tar" and returns a tar stream of all files
// contained in the manifest
func (s *Server) HandleGetFiles(w http.ResponseWriter, r *Request) {
	getFilesCount.Inc(1)
	if r.uri.Path != "" {
		getFilesFail.Inc(1)
		s.BadRequest(w, r, "files request cannot contain a path")
		return
	}

	key, err := s.api.Resolve(r.uri)
	if err != nil {
		getFilesFail.Inc(1)
		s.NotFound(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
		return
	}

	walker, err := s.api.NewManifestWalker(key, nil)
	if err != nil {
		getFilesFail.Inc(1)
		s.Error(w, r, err)
		return
	}

	tw := tar.NewWriter(w)
	defer tw.Close()
	w.Header().Set("Content-Type", "application/x-tar")
	w.WriteHeader(http.StatusOK)

	err = walker.Walk(func(entry *api.ManifestEntry) error {
		// ignore manifests (walk will recurse into them)
		if entry.ContentType == api.ManifestType {
			return nil
		}

		// retrieve the entry's key and size
		reader := s.api.Retrieve(storage.Key(common.Hex2Bytes(entry.Hash)))
		size, err := reader.Size(nil)
		if err != nil {
			return err
		}

		// write a tar header for the entry
		hdr := &tar.Header{
			Name:    entry.Path,
			Mode:    entry.Mode,
			Size:    size,
			ModTime: entry.ModTime,
			Xattrs: map[string]string{
				"user.swarm.content-type": entry.ContentType,
			},
		}
		if err := tw.WriteHeader(hdr); err != nil {
			return err
		}

		// copy the file into the tar stream
		n, err := io.Copy(tw, io.LimitReader(reader, hdr.Size))
		if err != nil {
			return err
		} else if n != size {
			return fmt.Errorf("error writing %s: expected %d bytes but sent %d", entry.Path, size, n)
		}

		return nil
	})
	if err != nil {
		getFilesFail.Inc(1)
		s.logError("error generating tar stream: %s", err)
	}
}

// HandleGetList handles a GET request to bzz-list:/<manifest>/<path> and returns
// a list of all files contained in <manifest> under <path> grouped into
// common prefixes using "/" as a delimiter
func (s *Server) HandleGetList(w http.ResponseWriter, r *Request) {
	getListCount.Inc(1)
	// ensure the root path has a trailing slash so that relative URLs work
	if r.uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
		http.Redirect(w, &r.Request, r.URL.Path+"/", http.StatusMovedPermanently)
		return
	}

	key, err := s.api.Resolve(r.uri)
	if err != nil {
		getListFail.Inc(1)
		s.NotFound(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
		return
	}

	list, err := s.getManifestList(key, r.uri.Path)

	if err != nil {
		getListFail.Inc(1)
		s.Error(w, r, err)
		return
	}

	// if the client wants HTML (e.g. a browser) then render the list as a
	// HTML index with relative URLs
	if strings.Contains(r.Header.Get("Accept"), "text/html") {
		w.Header().Set("Content-Type", "text/html")
		err := htmlListTemplate.Execute(w, &htmlListData{
			URI: &api.URI{
				Scheme: "bzz",
				Addr:   r.uri.Addr,
				Path:   r.uri.Path,
			},
			List: &list,
		})
		if err != nil {
			getListFail.Inc(1)
			s.logError("error rendering list HTML: %s", err)
		}
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(&list)
}

func (s *Server) getManifestList(key storage.Key, prefix string) (list api.ManifestList, err error) {
	walker, err := s.api.NewManifestWalker(key, nil)
	if err != nil {
		return
	}

	err = walker.Walk(func(entry *api.ManifestEntry) error {
		// handle non-manifest files
		if entry.ContentType != api.ManifestType {
			// ignore the file if it doesn't have the specified prefix
			if !strings.HasPrefix(entry.Path, prefix) {
				return nil
			}

			// if the path after the prefix contains a slash, add a
			// common prefix to the list, otherwise add the entry
			suffix := strings.TrimPrefix(entry.Path, prefix)
			if index := strings.Index(suffix, "/"); index > -1 {
				list.CommonPrefixes = append(list.CommonPrefixes, prefix+suffix[:index+1])
				return nil
			}
			if entry.Path == "" {
				entry.Path = "/"
			}
			list.Entries = append(list.Entries, entry)
			return nil
		}

		// if the manifest's path is a prefix of the specified prefix
		// then just recurse into the manifest by returning nil and
		// continuing the walk
		if strings.HasPrefix(prefix, entry.Path) {
			return nil
		}

		// if the manifest's path has the specified prefix, then if the
		// path after the prefix contains a slash, add a common prefix
		// to the list and skip the manifest, otherwise recurse into
		// the manifest by returning nil and continuing the walk
		if strings.HasPrefix(entry.Path, prefix) {
			suffix := strings.TrimPrefix(entry.Path, prefix)
			if index := strings.Index(suffix, "/"); index > -1 {
				list.CommonPrefixes = append(list.CommonPrefixes, prefix+suffix[:index+1])
				return api.SkipManifest
			}
			return nil
		}

		// the manifest neither has the prefix or needs recursing in to
		// so just skip it
		return api.SkipManifest
	})

	return list, nil
}

// HandleGetFile handles a GET request to bzz://<manifest>/<path> and responds
// with the content of the file at <path> from the given <manifest>
func (s *Server) HandleGetFile(w http.ResponseWriter, r *Request) {
	getFileCount.Inc(1)
	// ensure the root path has a trailing slash so that relative URLs work
	if r.uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
		http.Redirect(w, &r.Request, r.URL.Path+"/", http.StatusMovedPermanently)
		return
	}

	key, err := s.api.Resolve(r.uri)
	if err != nil {
		getFileFail.Inc(1)
		s.NotFound(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
		return
	}

	reader, contentType, status, err := s.api.Get(key, r.uri.Path)
	if err != nil {
		switch status {
		case http.StatusNotFound:
			getFileNotFound.Inc(1)
			s.NotFound(w, r, err)
		default:
			getFileFail.Inc(1)
			s.Error(w, r, err)
		}
		return
	}

	//the request results in ambiguous files
	//e.g. /read with readme.md and readinglist.txt available in manifest
	if status == http.StatusMultipleChoices {
		list, err := s.getManifestList(key, r.uri.Path)

		if err != nil {
			getFileFail.Inc(1)
			s.Error(w, r, err)
			return
		}

		s.logDebug(fmt.Sprintf("Multiple choices! -->  %v", list))
		//show a nice page links to available entries
		ShowMultipleChoices(w, r, list)
		return
	}

	// check the root chunk exists by retrieving the file's size
	if _, err := reader.Size(nil); err != nil {
		getFileNotFound.Inc(1)
		s.NotFound(w, r, fmt.Errorf("File not found %s: %s", r.uri, err))
		return
	}

	w.Header().Set("Content-Type", contentType)

	http.ServeContent(w, &r.Request, "", time.Now(), reader)
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if metrics.Enabled {
		//The increment for request count and request timer themselves have a flag check
		//for metrics.Enabled. Nevertheless, we introduce the if here because we
		//are looking into the header just to see what request type it is (json/html).
		//So let's take advantage and add all metrics related stuff here
		requestCount.Inc(1)
		defer requestTimer.UpdateSince(time.Now())
		if r.Header.Get("Accept") == "application/json" {
			jsonRequestCount.Inc(1)
		} else {
			htmlRequestCount.Inc(1)
		}
	}
	s.logDebug("HTTP %s request URL: '%s', Host: '%s', Path: '%s', Referer: '%s', Accept: '%s'", r.Method, r.RequestURI, r.URL.Host, r.URL.Path, r.Referer(), r.Header.Get("Accept"))

	if r.RequestURI == "/" && strings.Contains(r.Header.Get("Accept"), "text/html") {

		err := landingPageTemplate.Execute(w, nil)
		if err != nil {
			s.logError("error rendering landing page: %s", err)
		}
		return
	}

	uri, err := api.Parse(strings.TrimLeft(r.URL.Path, "/"))
	req := &Request{Request: *r, uri: uri}
	if err != nil {
		s.logError("Invalid URI %q: %s", r.URL.Path, err)
		s.BadRequest(w, req, fmt.Sprintf("Invalid URI %q: %s", r.URL.Path, err))
		return
	}
	s.logDebug("%s request received for %s", r.Method, uri)

	switch r.Method {
	case "POST":
		if uri.Raw() || uri.DeprecatedRaw() {
			s.HandlePostRaw(w, req)
		} else {
			s.HandlePostFiles(w, req)
		}

	case "PUT":
		// DEPRECATED:
		//   clients should send a POST request (the request creates a
		//   new manifest leaving the existing one intact, so it isn't
		//   strictly a traditional PUT request which replaces content
		//   at a URI, and POST is more ubiquitous)
		if uri.Raw() || uri.DeprecatedRaw() {
			ShowError(w, req, fmt.Sprintf("No PUT to %s allowed.", uri), http.StatusBadRequest)
			return
		} else {
			s.HandlePostFiles(w, req)
		}

	case "DELETE":
		if uri.Raw() || uri.DeprecatedRaw() {
			ShowError(w, req, fmt.Sprintf("No DELETE to %s allowed.", uri), http.StatusBadRequest)
			return
		}
		s.HandleDelete(w, req)

	case "GET":
		if uri.Raw() || uri.Hash() || uri.DeprecatedRaw() {
			s.HandleGet(w, req)
			return
		}

		if uri.List() {
			s.HandleGetList(w, req)
			return
		}

		if r.Header.Get("Accept") == "application/x-tar" {
			s.HandleGetFiles(w, req)
			return
		}

		s.HandleGetFile(w, req)

	default:
		ShowError(w, req, fmt.Sprintf("Method "+r.Method+" is not supported.", uri), http.StatusMethodNotAllowed)

	}
}

func (s *Server) updateManifest(key storage.Key, update func(mw *api.ManifestWriter) error) (storage.Key, error) {
	mw, err := s.api.NewManifestWriter(key, nil)
	if err != nil {
		return nil, err
	}

	if err := update(mw); err != nil {
		return nil, err
	}

	key, err = mw.Store()
	if err != nil {
		return nil, err
	}
	s.logDebug("generated manifest %s", key)
	return key, nil
}

func (s *Server) logDebug(format string, v ...interface{}) {
	log.Debug(fmt.Sprintf("[BZZ] HTTP: "+format, v...))
}

func (s *Server) logError(format string, v ...interface{}) {
	log.Error(fmt.Sprintf("[BZZ] HTTP: "+format, v...))
}

func (s *Server) BadRequest(w http.ResponseWriter, r *Request, reason string) {
	ShowError(w, r, fmt.Sprintf("Bad request %s %s: %s", r.Request.Method, r.uri, reason), http.StatusBadRequest)
}

func (s *Server) Error(w http.ResponseWriter, r *Request, err error) {
	ShowError(w, r, fmt.Sprintf("Error serving %s %s: %s", r.Request.Method, r.uri, err), http.StatusInternalServerError)
}

func (s *Server) NotFound(w http.ResponseWriter, r *Request, err error) {
	ShowError(w, r, fmt.Sprintf("NOT FOUND error serving %s %s: %s", r.Request.Method, r.uri, err), http.StatusNotFound)
}