Initial commit.

internal/version/checker.go

@@ -0,0 +1,159 @@
+// Package version provides version checking against GitHub releases.
+package version
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+)
+
+const (
+	// githubReleasesURL is the GitHub API endpoint for latest release
+	githubReleasesURL = "https://api.github.com/repos/%s/%s/releases/latest"
+	// requestTimeout is the timeout for HTTP requests
+	requestTimeout = 5 * time.Second
+)
+
+// ReleaseInfo contains information about a GitHub release
+type ReleaseInfo struct {
+	TagName string `json:"tag_name"`
+	HTMLURL string `json:"html_url"`
+	Name    string `json:"name"`
+}
+
+// UpdateInfo contains information about an available update
+type UpdateInfo struct {
+	CurrentVersion string
+	LatestVersion  string
+	ReleaseURL     string
+	ReleaseName    string
+}
+
+// Checker checks for new versions on GitHub
+type Checker struct {
+	owner   string
+	repo    string
+	current string
+	client  *http.Client
+}
+
+// NewChecker creates a new version checker
+func NewChecker(owner, repo, currentVersion string) *Checker {
+	return &Checker{
+		owner:   owner,
+		repo:    repo,
+		current: normalizeVersion(currentVersion),
+		client: &http.Client{
+			Timeout: requestTimeout,
+		},
+	}
+}
+
+// CheckForUpdate checks if a newer version is available.
+// Returns nil if current version is up to date or if check fails.
+// This is designed to fail silently - network errors should not impact the user.
+func (c *Checker) CheckForUpdate(ctx context.Context) *UpdateInfo {
+	release, err := c.fetchLatestRelease(ctx)
+	if err != nil {
+		return nil
+	}
+
+	latestVersion := normalizeVersion(release.TagName)
+	if isNewerVersion(latestVersion, c.current) {
+		return &UpdateInfo{
+			CurrentVersion: c.current,
+			LatestVersion:  latestVersion,
+			ReleaseURL:     release.HTMLURL,
+			ReleaseName:    release.Name,
+		}
+	}
+
+	return nil
+}
+
+// fetchLatestRelease fetches the latest release info from GitHub API
+func (c *Checker) fetchLatestRelease(ctx context.Context) (*ReleaseInfo, error) {
+	url := fmt.Sprintf(githubReleasesURL, c.owner, c.repo)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("Accept", "application/vnd.github.v3+json")
+	req.Header.Set("User-Agent", "lolcathost-version-checker")
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GitHub API returned status %d", resp.StatusCode)
+	}
+
+	var release ReleaseInfo
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return nil, err
+	}
+
+	return &release, nil
+}
+
+// normalizeVersion removes 'v' or 'V' prefix and trims whitespace
+func normalizeVersion(v string) string {
+	v = strings.TrimSpace(v)
+	v = strings.TrimPrefix(v, "v")
+	v = strings.TrimPrefix(v, "V")
+	return v
+}
+
+// isNewerVersion compares two semver-like versions.
+// Returns true if latest is newer than current.
+func isNewerVersion(latest, current string) bool {
+	latestParts := parseVersion(latest)
+	currentParts := parseVersion(current)
+
+	// Compare each part
+	for i := 0; i < len(latestParts) && i < len(currentParts); i++ {
+		if latestParts[i] > currentParts[i] {
+			return true
+		}
+		if latestParts[i] < currentParts[i] {
+			return false
+		}
+	}
+
+	// If all compared parts are equal, longer version is newer
+	// e.g., 1.0.1 > 1.0
+	return len(latestParts) > len(currentParts)
+}
+
+// parseVersion splits a version string into numeric parts
+func parseVersion(v string) []int {
+	// Remove any suffix like -beta, -rc1, etc.
+	if idx := strings.IndexAny(v, "-+"); idx != -1 {
+		v = v[:idx]
+	}
+
+	parts := strings.Split(v, ".")
+	result := make([]int, 0, len(parts))
+
+	for _, p := range parts {
+		var num int
+		fmt.Sscanf(p, "%d", &num)
+		result = append(result, num)
+	}
+
+	return result
+}
+
+// FormatUpdateMessage formats a user-friendly update notification
+func (u *UpdateInfo) FormatUpdateMessage() string {
+	return fmt.Sprintf("New version available: %s (current: %s) - %s",
+		u.LatestVersion, u.CurrentVersion, u.ReleaseURL)
+}