Feat [Golang] [Package] Updater (#38)

* Feat [Golang] [Package] Updater

- [+] feat(updater): add updater package for automatically updating Go applications

* [Golang] [Package] [Updater] Reduce gocyclo

- [+] feat(updater): add functionality to download and update the application
- [+] fix(updater): change temporary file name for downloaded asset
- [+] feat(updater): add functionality to find matching asset for current platform
- [+] feat(updater): add functionality to download asset from URL and write it to temporary file
- [+] feat(updater): add functionality to apply update by replacing current binary with new one
- [+] feat(updater): add functionality to restart the application after update is applied

* [Golang] [Package] [Updater] Fix Assets Name

- [+] fix(app.go): update asset name format to match the current project name
- [+] fix(app.go): update command to restart the application with the correct executable name

* Feat [Golang] [Package] Updater

- [+] feat(updater): add updater package for automatically updating Go applications

* [Golang] [Package] [Updater] Reduce gocyclo

- [+] feat(updater): add functionality to download and update the application
- [+] fix(updater): change temporary file name for downloaded asset
- [+] feat(updater): add functionality to find matching asset for current platform
- [+] feat(updater): add functionality to download asset from URL and write it to temporary file
- [+] feat(updater): add functionality to apply update by replacing current binary with new one
- [+] feat(updater): add functionality to restart the application after update is applied

* [Golang] [Package] [Updater] Fix Assets Name

- [+] fix(app.go): update asset name format to match the current project name
- [+] fix(app.go): update command to restart the application with the correct executable name

updater/app.go

@@ -0,0 +1,209 @@
+// Copyright (c) 2023 H0llyW00dzZ
+//
+// Package updater provides functionality to automatically update a Go application
+// by checking for the latest release on GitHub and, if available, downloading and
+// applying the update. It is designed to work with applications that are distributed
+// with GitHub releases.
+//
+// The updater checks the latest release by calling the GitHub Releases API and
+// compares the tag name of the latest release with the current version of the
+// application. If the tag name indicates a newer version, the updater downloads
+// the release asset that matches the running application's operating system and
+// architecture, replaces the current executable, and restarts the application.
+//
+// Usage:
+//
+// To use the updater, you should include it in your application's main package:
+//
+//	import "github.com/H0llyW00dzZ/ChatGPT-Next-Web-Session-Exporter/updater"
+//
+//	func main() {
+//	    if err := updater.UpdateApplication(); err != nil {
+//	        // Handle error
+//	    }
+//	    // Continue with application logic
+//	}
+//
+// The updater assumes that the GitHub repository's release assets follow a
+// naming convention that includes the OS and architecture. It also assumes that
+// the binary to be updated is named "myapp" and is located in the current working
+// directory of the running application.
+//
+// Note that the updater package defines a constant `currentVersion` that must
+// be updated to match the application's current version string before building
+// a new release. This version string is used to compare against the tag name of
+// the latest release on GitHub.
+//
+// The updater package is designed with simplicity in mind and does not handle
+// complex update scenarios such as database migrations, configuration changes,
+// or rollback of failed updates. It is recommended to test the update process
+// thoroughly in a controlled environment before deploying it in a production setting.
+//
+// Security Considerations:
+//
+// The updater performs a direct binary replacement and restarts the application.
+// Users should ensure that the GitHub repository and release assets are secure
+// and that the release process includes steps to verify the integrity and
+// authenticity of the binaries, such as signing the releases.
+//
+// # Additional Note: This Package Currently under development.
+package updater
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"runtime"
+)
+
+const (
+	currentVersion = "1.3.3.7"
+	githubRepo     = "H0llyW00dzZ/ChatGPT-Next-Web-Session-Exporter"
+)
+
+// releaseInfo defines the structure for storing information about a GitHub release.
+// It captures the tag name of the release and a slice of assets that are part of the release.
+type releaseInfo struct {
+	TagName string `json:"tag_name"` // The name of the tag for the release.
+	Assets  []struct {
+		Name               string `json:"name"`                 // The name of the asset.
+		BrowserDownloadURL string `json:"browser_download_url"` // The URL for downloading the asset.
+	} `json:"assets"` // A list of assets available for the release.
+}
+
+// getLatestRelease fetches the latest release information from the GitHub repository.
+// It constructs a request to the GitHub API to retrieve the latest release and parses
+// the response into a releaseInfo struct.
+//
+// Returns a pointer to a releaseInfo struct and nil error on success.
+// On failure, it returns nil and an error indicating what went wrong.
+func getLatestRelease() (*releaseInfo, error) {
+	resp, err := http.Get(fmt.Sprintf("https://api.github.com/repos/%s/releases/latest", githubRepo))
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GitHub API response status: %s", resp.Status)
+	}
+
+	var release releaseInfo
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return nil, err
+	}
+
+	return &release, nil
+}
+
+// UpdateApplication checks the GitHub repository for a newer release of the application.
+// If a newer release is found, it downloads the corresponding binary for the current
+// platform and architecture, replaces the current executable with the downloaded binary,
+// and restarts the application.
+//
+// Returns nil if the application is up to date or the update is successfully applied.
+// If an error occurs during the update process, it returns a non-nil error.
+func UpdateApplication() error {
+	release, err := getLatestRelease()
+	if err != nil {
+		return fmt.Errorf("error fetching latest release: %w", err)
+	}
+
+	if release.TagName == currentVersion {
+		fmt.Println("No update available.")
+		return nil
+	}
+
+	tempFileName, err := downloadAndUpdate(release)
+	if err != nil {
+		return err
+	}
+
+	if err := applyUpdate(tempFileName); err != nil {
+		return err
+	}
+
+	restartApplication()
+	return nil
+}
+
+// downloadAndUpdate handles the downloading and updating of the application.
+// It returns the name of the downloaded file or an error.
+func downloadAndUpdate(release *releaseInfo) (string, error) {
+	fmt.Printf("Update available: %s\n", release.TagName)
+	fmt.Println("Downloading update...")
+
+	assetURL, err := findMatchingAsset(release)
+	if err != nil {
+		return "", err
+	}
+
+	tempFileName, err := downloadAsset(assetURL)
+	if err != nil {
+		return "", err
+	}
+
+	fmt.Println("Update downloaded.")
+	return tempFileName, nil
+}
+
+// findMatchingAsset finds and returns the URL of the asset that matches the current platform.
+func findMatchingAsset(release *releaseInfo) (string, error) {
+	for _, asset := range release.Assets {
+		if asset.Name == fmt.Sprintf("ChatGPT-Next-Web-Session-Exporter-%s-%s", runtime.GOOS, runtime.GOARCH) {
+			return asset.BrowserDownloadURL, nil
+		}
+	}
+	return "", fmt.Errorf("no binary for the current platform")
+}
+
+// downloadAsset downloads the asset from the given URL and writes it to a temporary file.
+// It returns the name of the temporary file or an error.
+func downloadAsset(assetURL string) (string, error) {
+	resp, err := http.Get(assetURL)
+	if err != nil {
+		return "", fmt.Errorf("error downloading update: %w", err)
+	}
+	defer resp.Body.Close()
+
+	out, err := os.CreateTemp("", "ChatGPT-Next-Web-Session-Exporter-update-*")
+	if err != nil {
+		return "", fmt.Errorf("error creating temp file: %w", err)
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return out.Name(), nil
+}
+
+// applyUpdate applies the update by replacing the current binary with the new one.
+// It takes the name of the temporary file containing the new binary as an argument.
+func applyUpdate(tempFileName string) error {
+	// Replace the current binary with the new one
+	if err := os.Rename(tempFileName, "ChatGPT-Next-Web-Session-Exporter"); err != nil {
+		return fmt.Errorf("error replacing binary: %w", err)
+	}
+	return nil
+}
+
+// restartApplication restarts the application.
+func restartApplication() {
+	fmt.Println("Update applied. Restarting application...")
+	cmd := exec.Command("ChatGPT-Next-Web-Session-Exporter")
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Start(); err != nil {
+		fmt.Fprintf(os.Stderr, "error restarting application: %v", err)
+		return
+	}
+
+	// Exit the current process
+	os.Exit(0)
+}