Allow multiple formats for response, add html and json response

• If a request comes in to the root path, look at accept header and
   parse it. Check for hmtl, json, and text. If no known accept header
   comes in, return text/plain
 • Add route for /json that always returns json response
 • Add route for /text that always returns text response
 • Add route for /html that always returns html response

ip.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"errors"
 	"net"
 )
@@ -11,10 +12,6 @@ type IP struct {
 	version string
 }
 
-func (ip *IP) isV6() bool {
-	return ip.To4() == nil
-}
-
 // NewIP returns a new instance of an IP address
 func NewIP(addr string) (*IP, error) {
 	parsedIP := net.ParseIP(addr)
@@ -31,3 +28,18 @@ func NewIP(addr string) (*IP, error) {
 
 	return result, nil
 }
+
+// MarshalJSON for marshalling ip to json for response
+func (ip *IP) MarshalJSON() ([]byte, error) {
+	return json.Marshal(&struct {
+		IP      string `json:"ip"`
+		Version string `json:"version"`
+	}{
+		IP:      ip.String(),
+		Version: ip.version,
+	})
+}
+
+func (ip *IP) isV6() bool {
+	return ip.To4() == nil
+}

server.go

@@ -1,18 +1,37 @@
 package main
 
 import (
+	"bytes"
+	"html/template"
 	"io"
 	"net"
 	"net/http"
+	"strings"
+
+	"github.com/pkg/errors"
 )
 
 // Server that handles http responses
 type Server struct {
 	headerNames []string
 	logger      LoggerHandler
+	tmpl        *template.Template
+}
+
+type responseFormat int
+
+const (
+	unknownResponse responseFormat = iota
+	jsonResponse
+	textResponse
+	htmlResponse
+)
+
+func (s *Server) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
+	s.handleHTTP(resp, req, s.getResponseType(req))
 }
 
-func (s *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+func (s *Server) handleHTTP(resp http.ResponseWriter, req *http.Request, responseType responseFormat) {
 	for _, headerName := range s.headerNames {
 		possibleIP := req.Header.Get(headerName)
 		if possibleIP == "" {
@@ -24,28 +43,89 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			continue
 		}
 
-		s.sendResponse(w, ip)
+		s.sendResponse(resp, ip, responseType)
 		return
 	}
 
 	addr, _, err := net.SplitHostPort(req.RemoteAddr)
 	if err != nil {
-		s.handleError(w, http.StatusBadRequest, err, "Could not get IP address from request")
+		s.handleError(resp, http.StatusBadRequest, err, "Could not get IP address from request")
 		return
 	}
 
 	ip, err := NewIP(addr)
 	if err != nil {
-		s.handleError(w, http.StatusBadRequest, err, "Could not parse IP address"+addr)
+		s.handleError(resp, http.StatusBadRequest, err, "Could not parse IP address"+addr)
 		return
 	}
 
-	s.sendResponse(w, ip)
+	s.sendResponse(resp, ip, responseType)
 }
 
-func (s *Server) sendResponse(resp http.ResponseWriter, ip *IP) {
+func hasType(accepts, valid []string) bool {
-	io.WriteString(resp, ip.String()+"\n")
+	for _, accept := range accepts {
+		value := strings.Trim(strings.Split(accept, ";")[0], " ")
+		for _, check := range valid {
+			if check == value {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func (s *Server) getResponseType(req *http.Request) responseFormat {
+	accepts := strings.Split(req.Header.Get("Accept"), ",")
+	if hasType(accepts, []string{"text/html", "application/xhtml+xml"}) {
+		return htmlResponse
+	}
+	if hasType(accepts, []string{"application/json", "text/json", "text/javascript"}) {
+		return jsonResponse
+	}
+	if hasType(accepts, []string{"text/plain"}) {
+		return textResponse
+	}
+	return unknownResponse
+}
+
+func (s *Server) sendResponse(resp http.ResponseWriter, ip *IP, responseType responseFormat) {
 	s.logger.Printf("Request from %s %s\n", ip.version, ip)
+
+	var body []byte
+	var contentType = "text/plain"
+	var err error
+
+	switch responseType {
+
+	case jsonResponse:
+		jsonBody, marshalErr := ip.MarshalJSON()
+		if marshalErr != nil {
+			err = errors.Wrap(marshalErr, "could not marshal json")
+		}
+		contentType = "application/json"
+		body = jsonBody
+
+	case htmlResponse:
+		buffer := bytes.NewBuffer([]byte{})
+		exeErr := s.tmpl.Execute(buffer, map[string]string{"IP": ip.String()})
+		if exeErr != nil {
+			err = errors.Wrap(exeErr, "could not get html")
+		}
+		contentType = "text/html"
+		body = buffer.Bytes()
+
+	default:
+		body = []byte(ip.String())
+	}
+
+	if err != nil {
+		const errorMessage = "could not send response"
+		s.handleError(resp, http.StatusInternalServerError, errors.Wrap(err, errorMessage), errorMessage)
+		return
+	}
+
+	resp.Header().Set("Content-Type", contentType)
+	resp.Write(body)
 }
 
 func (s *Server) handleError(resp http.ResponseWriter, status int, err error, message string) {

what-is-my-ip.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"errors"
+	"html/template"
 	"net/http"
 	"os"
 
@@ -18,7 +19,7 @@ const (
 func main() {
 	app := cli.NewApp()
 	app.Name = appName
-	app.Version = "0.3.0"
+	app.Version = "0.4.0"
 	app.Usage = "Webapp that gives the IP address for incoming requests"
 	app.Action = action
 
@@ -67,6 +68,7 @@ func getHandler(headers []string) (http.Handler, *Server) {
 	service := &Server{
 		headerNames: headers,
 		logger:      NewLogger(),
+		tmpl:        template.Must(template.New("html").Parse(htmlTemplate)),
 	}
 
 	recover := negroni.NewRecovery()
@@ -74,6 +76,18 @@ func getHandler(headers []string) (http.Handler, *Server) {
 
 	router := pat.New()
 
+	router.Get("/json", func(resp http.ResponseWriter, req *http.Request) {
+		service.handleHTTP(resp, req, jsonResponse)
+	})
+
+	router.Get("/text", func(resp http.ResponseWriter, req *http.Request) {
+		service.handleHTTP(resp, req, textResponse)
+	})
+
+	router.Get("/html", func(resp http.ResponseWriter, req *http.Request) {
+		service.handleHTTP(resp, req, htmlResponse)
+	})
+
 	router.Get("/", func(resp http.ResponseWriter, req *http.Request) {
 		if req.URL.Path == "/" {
 			service.ServeHTTP(resp, req)
@@ -90,3 +104,15 @@ func getHandler(headers []string) (http.Handler, *Server) {
 
 	return n, service
 }
+
+const htmlTemplate = `<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="UTF-8" />
+    <title>What is My IP?</title>
+    <style> .ip { text-align: center; } </style>
+  </head>
+  <body>
+    <div class="ip">{{.IP}}</div>
+  </body>
+</html>`