Add the /v1/about API endpoint

README.md

@@ -255,6 +255,7 @@ Authentication tokens can be acquired using the `/v1/login/token/` endpoint desc
 
 ### Endpoints
 
+* [About](#about)
 * [Search](#search)
 * [Browse](#browse)
 * [Play a Song](#play-a-song)
@@ -270,6 +271,25 @@ Authentication tokens can be acquired using the `/v1/login/token/` endpoint desc
 * [Token Request](#token-request)
 * [Register Token](#register-token)
 
+### About
+
+Query information about the server.
+
+```sh
+GET /v1/about
+```
+
+The returned response includes the server version. Example response:
+
+```js
+{
+    "server_version":"v1.5.4"
+}
+```
+
+This information could be used by clients to know what APIs are supported by the
+server.
+
 ### Search
 
 One can do a search query at the following endpoint

src/webserver/apiv1_endpoints.go

@@ -4,6 +4,7 @@ import "net/http"
 
 // The following are URL Path endpoints for certain API calls.
 const (
+	APIv1EndpointAbout          = "/v1/about"
 	APIv1EndpointFile           = "/v1/file/{fileID}"
 	APIv1EndpointAlbumArtwork   = "/v1/album/{albumID}/artwork"
 	APIv1EndpointDownloadAlbum  = "/v1/album/{albumID}"
@@ -18,6 +19,7 @@ const (
 // APIv1Methods defines on which HTTP methods APIv1 endpoints will respond to.
 // It is an uri_path => list of HTTP methods map.
 var APIv1Methods map[string][]string = map[string][]string{
+	APIv1EndpointAbout:          {http.MethodGet},
 	APIv1EndpointFile:           {http.MethodGet},
 	APIv1EndpointDownloadAlbum:  {http.MethodGet},
 	APIv1EndpointBrowse:         {http.MethodGet},

src/webserver/handler_about.go

@@ -0,0 +1,38 @@
+package webserver
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/ironsmile/euterpe/src/version"
+)
+
+type aboutHandler struct {
+	resp aboutResponse
+}
+
+// NewAboutHandler returns the HTTP handler which shows a JSON with information
+// about the server.
+func NewAboutHandler() http.Handler {
+	return &aboutHandler{
+		resp: aboutResponse{
+			ServerVersion: version.Version,
+		},
+	}
+}
+
+func (h *aboutHandler) ServeHTTP(writer http.ResponseWriter, req *http.Request) {
+	writer.Header().Add("Content-Type", "application/json; charset=utf-8")
+	enc := json.NewEncoder(writer)
+	if err := enc.Encode(h.resp); err != nil {
+		writer.Header().Set("Content-Type", "plain/text; charset=utf-8")
+		msg := fmt.Sprintf("Failed to encode JSON response: %s", err)
+		http.Error(writer, msg, http.StatusInternalServerError)
+		return
+	}
+}
+
+type aboutResponse struct {
+	ServerVersion string `json:"server_version"`
+}

src/webserver/webserver.go

@@ -101,6 +101,7 @@ func (srv *Server) serveGoroutine() {
 	artistImageHandler := NewArtistImagesHandler(srv.library)
 	browseHandler := NewBrowseHandler(srv.library)
 	mediaFileHandler := NewFileHandler(srv.library)
+	aboutHandler := NewAboutHandler()
 	loginHandler := NewLoginHandler(srv.cfg.Authenticate)
 	loginTokenHandler := NewLoginTokenHandler(srv.cfg.Authenticate)
 	logoutHandler := NewLogoutHandler()
@@ -125,6 +126,9 @@ func (srv *Server) serveGoroutine() {
 	router.UseEncodedPath()
 
 	// API v1 methods.
+	router.Handle(APIv1EndpointAbout, aboutHandler).Methods(
+		APIv1Methods[APIv1EndpointAbout]...,
+	)
 	router.Handle(APIv1EndpointFile, mediaFileHandler).Methods(
 		APIv1Methods[APIv1EndpointFile]...,
 	)