Check for updates when printing version info

Author: jotaen

src/app/cli/cmd_version.go

@@ -0,0 +1,58 @@
+package cli
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"klog/app"
+	"net/http"
+	"time"
+)
+
+type Version struct {
+}
+
+func (args *Version) Run(ctx *app.Context) error {
+	fmt.Printf("Version: %s\n(Build %s)\n\n", ctx.MetaInfo().Version, ctx.MetaInfo().BuildHash)
+
+	fmt.Printf("Checking for newer version...\n")
+	v := fetchVersionInfo("https://klog.jotaen.net/latest-stable-version.json")
+	if v == nil {
+		return errors.New("Failed to check for new version, please try again later")
+	}
+	if v.Latest.Version == ctx.MetaInfo().Version && v.Latest.BuildHash == ctx.MetaInfo().BuildHash {
+		fmt.Printf("You already have the latest version!\n")
+	} else {
+		fmt.Printf("New version available: %s (%s)\n", v.Latest.Version, v.Latest.BuildHash)
+		fmt.Printf("See: https://github.com/jotaen/klog\n")
+	}
+	return nil
+}
+
+func fetchVersionInfo(url string) *versionInfo {
+	req, _ := http.NewRequest(http.MethodGet, url, nil)
+	res, err := (&http.Client{
+		Timeout: time.Second * 5,
+	}).Do(req)
+	if err != nil {
+		return nil
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil
+	}
+	v := &versionInfo{}
+	err = json.Unmarshal(body, &v)
+	if err != nil {
+		return nil
+	}
+	return v
+}
+
+type versionInfo struct {
+	Latest struct {
+		Version   string `json:"version"`
+		BuildHash string `json:"buildHash"`
+	} `json:"latest"`
+}

src/app/cli/exec.go

@@ -10,10 +10,10 @@ import (
 )
 
 type cli struct {
-	Print   Print  `cmd help:"Pretty-print records"`
-	Eval    Eval   `cmd help:"Evaluate records"`
-	Widget  Widget `cmd help:"Start menu bar widget (MacOS only)"`
-	Version kong.VersionFlag
+	Print   Print   `cmd help:"Pretty-print records"`
+	Eval    Eval    `cmd help:"Evaluate records"`
+	Widget  Widget  `cmd help:"Start menu bar widget (MacOS only)"`
+	Version Version `cmd help:"Print version info and check for updates"`
 }
 
 func Execute() int {
@@ -32,9 +32,6 @@ func Execute() int {
 			datePrototype, _ := klog.NewDate(1, 1, 1)
 			return kong.TypeMapper(reflect.TypeOf(&datePrototype).Elem(), dateDecoder())
 		}(),
-		kong.Vars{
-			"version": ctx.MetaInfo().Version + "\n(" + ctx.MetaInfo().BuildHash + ")",
-		},
 	)
 	err = args.Run(ctx)
 	if err != nil {