From 99e5198b00d2e422e6a9183c490d665555e9a6e7 Mon Sep 17 00:00:00 2001
From: Marc O'Morain <marc@circleci.com>
Date: Wed, 18 Jul 2018 11:50:18 +0100
Subject: [PATCH] Add an `update check` command to check for updates.

---
 client/client.go   |  2 +-
 cmd/root.go        |  1 +
 cmd/root_test.go   |  2 +-
 cmd/update.go      | 81 ++++++++++++++++++++++++++++++++++++++++++++++
 cmd/version.go     |  1 -
 version/version.go |  9 ++++++
 6 files changed, 93 insertions(+), 3 deletions(-)
 create mode 100644 cmd/update.go

diff --git a/client/client.go b/client/client.go
index 7b29bc224..51fa866e6 100644
--- a/client/client.go
+++ b/client/client.go
@@ -28,7 +28,7 @@ func NewClient(endpoint string, logger *logger.Logger) *graphql.Client {
 func NewAuthorizedRequest(token, query string) *graphql.Request {
 	req := graphql.NewRequest(query)
 	req.Header.Set("Authorization", token)
-	req.Header.Set("User-Agent", fmt.Sprintf("circleci-cli/%s-%s", version.Version, version.Commit))
+	req.Header.Set("User-Agent", version.UserAgent())
 	return req
 }
 
diff --git a/cmd/root.go b/cmd/root.go
index 4d1ba8372..77e40192c 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -48,6 +48,7 @@ func MakeCommands() *cobra.Command {
 	rootCmd.AddCommand(newOrbCommand())
 	rootCmd.AddCommand(newBuildCommand())
 	rootCmd.AddCommand(newVersionCommand())
+	rootCmd.AddCommand(newUpdateCommand())
 	rootCmd.PersistentFlags().BoolP("verbose", "v", false, "Enable verbose logging.")
 	rootCmd.PersistentFlags().StringP("endpoint", "e", defaultEndpoint, "the endpoint of your CircleCI GraphQL API")
 	rootCmd.PersistentFlags().StringP("token", "t", "", "your token for using CircleCI")
diff --git a/cmd/root_test.go b/cmd/root_test.go
index 27d3bf0e3..52af4e799 100644
--- a/cmd/root_test.go
+++ b/cmd/root_test.go
@@ -16,7 +16,7 @@ var _ = Describe("Root", func() {
 
 		It("can create commands", func() {
 			commands := cmd.MakeCommands()
-			Expect(len(commands.Commands())).To(Equal(8))
+			Expect(len(commands.Commands())).To(Equal(9))
 		})
 
 	})
diff --git a/cmd/update.go b/cmd/update.go
new file mode 100644
index 000000000..78b1d20c4
--- /dev/null
+++ b/cmd/update.go
@@ -0,0 +1,81 @@
+package cmd
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"unicode/utf8"
+
+	"github.com/CircleCI-Public/circleci-cli/version"
+	"github.com/spf13/cobra"
+)
+
+func newUpdateCommand() *cobra.Command {
+	update := &cobra.Command{
+		Use:   "update",
+		Short: "Update the tool",
+	}
+
+	update.AddCommand(&cobra.Command{
+		Use:   "check",
+		Short: "Check if there are any updates available",
+		RunE:  checkForUpdates,
+	})
+
+	return update
+}
+
+func trimFirstRune(s string) string {
+	_, i := utf8.DecodeRuneInString(s)
+	return s[i:]
+}
+
+func checkForUpdates(cmd *cobra.Command, args []string) error {
+
+	url := "https://api.github.com/repos/CircleCI-Public/circleci-cli/releases/latest"
+
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("User-Agent", version.UserAgent())
+
+	client := http.Client{}
+	res, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return err
+	}
+
+	var release struct {
+		// There are other fields in this response that we could use to download the
+		// binaries on behalf of the user.
+		// https://developer.github.com/v3/repos/releases/#get-the-latest-release
+		HTML string `json:"html_url"`
+		Tag  string `json:"tag_name"`
+	}
+
+	if err := json.Unmarshal(body, &release); err != nil {
+		return err
+	}
+
+	latest := trimFirstRune(release.Tag)
+
+	Logger.Debug("Latest version: %s", latest)
+	Logger.Debug("Current Version: %s", version.Version)
+
+	if latest == version.Version {
+		Logger.Info("Already up-to-date.")
+	} else {
+		Logger.Infof("A new release is available (%s)", release.Tag)
+		Logger.Infof("You are running %s", version.Version)
+		Logger.Infof("You can download it from %s", release.HTML)
+	}
+
+	return nil
+}
diff --git a/cmd/version.go b/cmd/version.go
index 544372372..1dc62bbc7 100644
--- a/cmd/version.go
+++ b/cmd/version.go
@@ -13,5 +13,4 @@ func newVersionCommand() *cobra.Command {
 			Logger.Infof("%s (%s)", version.Version, version.Commit)
 		},
 	}
-
 }
diff --git a/version/version.go b/version/version.go
index ba3bfd01e..a77b2c193 100644
--- a/version/version.go
+++ b/version/version.go
@@ -1,5 +1,9 @@
 package version
 
+import (
+	"fmt"
+)
+
 // These vars set by `goreleaser`:
 var (
 	// Version is the current Git tag (the v prefix is stripped) or the name of the snapshot, if you’re using the --snapshot flag
@@ -7,3 +11,8 @@ var (
 	// Commit is the current git commit SHA
 	Commit = "dirty-local-tree"
 )
+
+// UserAgent returns the user agent that should be user for external requests
+func UserAgent() string {
+	return fmt.Sprintf("circleci-cli/%s-%s", Version, Commit)
+}