Implement version update checking feature

cmd/lib/installer/installer.go

@@ -0,0 +1,117 @@
+package installer
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// InstallMethod represents how stacktodate was installed
+type InstallMethod int
+
+const (
+	Unknown InstallMethod = iota
+	Homebrew
+	Binary
+)
+
+// String returns a string representation of the install method
+func (m InstallMethod) String() string {
+	switch m {
+	case Homebrew:
+		return "homebrew"
+	case Binary:
+		return "binary"
+	default:
+		return "unknown"
+	}
+}
+
+// DetectInstallMethod attempts to determine how stacktodate was installed
+func DetectInstallMethod() InstallMethod {
+	// Try to detect Homebrew installation first
+	if IsHomebrew() {
+		return Homebrew
+	}
+
+	// Default to binary download
+	return Binary
+}
+
+// IsHomebrew checks if stacktodate was installed via Homebrew
+func IsHomebrew() bool {
+	// Method 1: Check executable path for Homebrew-specific directories
+	executable, err := os.Executable()
+	if err == nil {
+		if isHomebrewPath(executable) {
+			return true
+		}
+	}
+
+	// Method 2: Verify with brew command (silent check)
+	if isBrewInstalled() {
+		return true
+	}
+
+	return false
+}
+
+// isHomebrewPath checks if the executable path looks like a Homebrew installation
+func isHomebrewPath(execPath string) bool {
+	// Common Homebrew paths
+	homebrewPatterns := []string{
+		"/Cellar/stacktodate/",           // Intel Macs, Linux
+		"/opt/homebrew/Cellar/stacktodate", // Apple Silicon Macs
+		"/opt/homebrew/bin/stacktodate",
+		"/usr/local/bin/stacktodate",
+		"/usr/local/Cellar/stacktodate/",
+	}
+
+	for _, pattern := range homebrewPatterns {
+		if strings.Contains(execPath, pattern) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// isBrewInstalled checks if the brew command recognizes stacktodate
+func isBrewInstalled() bool {
+	// Run: brew list stacktodate
+	// This will succeed (exit code 0) if stacktodate is installed via Homebrew
+	cmd := exec.Command("brew", "list", "stacktodate")
+
+	// Redirect output to /dev/null (we don't need the output)
+	cmd.Stdout = nil
+	cmd.Stderr = nil
+
+	// Silent execution - we only care about the exit code
+	return cmd.Run() == nil
+}
+
+// GetUpgradeInstructions returns the appropriate upgrade instructions based on install method
+func GetUpgradeInstructions(method InstallMethod, version string) string {
+	switch method {
+	case Homebrew:
+		return "Upgrade: brew upgrade stacktodate"
+
+	case Binary:
+		return fmt.Sprintf("Download: https://github.com/stacktodate/stacktodate-cli/releases/tag/%s", version)
+
+	default:
+		return fmt.Sprintf("Visit: https://github.com/stacktodate/stacktodate-cli/releases/tag/%s", version)
+	}
+}
+
+// GetInstallerDownloadURL returns the download URL appropriate for the install method
+func GetInstallerDownloadURL(method InstallMethod) string {
+	switch method {
+	case Homebrew:
+		return "https://github.com/stacktodate/homebrew-stacktodate"
+
+	default:
+		return "https://github.com/stacktodate/stacktodate-cli/releases/latest"
+	}
+}

cmd/lib/installer/installer_test.go

@@ -0,0 +1,101 @@
+package installer
+
+import (
+	"testing"
+)
+
+func TestInstallMethodString(t *testing.T) {
+	tests := []struct {
+		method   InstallMethod
+		expected string
+	}{
+		{Homebrew, "homebrew"},
+		{Binary, "binary"},
+		{Unknown, "unknown"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.expected, func(t *testing.T) {
+			if got := tt.method.String(); got != tt.expected {
+				t.Fatalf("expected %s, got %s", tt.expected, got)
+			}
+		})
+	}
+}
+
+func TestIsHomebrewPath(t *testing.T) {
+	tests := []struct {
+		name     string
+		path     string
+		expected bool
+	}{
+		{"Intel Mac Cellar", "/usr/local/Cellar/stacktodate/0.2.0/bin/stacktodate", true},
+		{"Apple Silicon", "/opt/homebrew/Cellar/stacktodate/0.2.0/bin/stacktodate", true},
+		{"Apple Silicon bin", "/opt/homebrew/bin/stacktodate", true},
+		{"Standard usr local bin", "/usr/local/bin/stacktodate", true},
+		{"Binary download", "/Users/username/Downloads/stacktodate", false},
+		{"Build from source", "/Users/username/projects/stacktodate-cli/stacktodate", false},
+		{"Go workspace", "/home/user/go/bin/stacktodate", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isHomebrewPath(tt.path); got != tt.expected {
+				t.Fatalf("expected %v, got %v for path %s", tt.expected, got, tt.path)
+			}
+		})
+	}
+}
+
+func TestGetUpgradeInstructions(t *testing.T) {
+	tests := []struct {
+		name     string
+		method   InstallMethod
+		version  string
+		expected string
+	}{
+		{"Homebrew", Homebrew, "v0.3.0", "Upgrade: brew upgrade stacktodate"},
+		{"Homebrew without v", Homebrew, "0.3.0", "Upgrade: brew upgrade stacktodate"},
+		{"Binary with v", Binary, "v0.3.0", "Download: https://github.com/stacktodate/stacktodate-cli/releases/tag/v0.3.0"},
+		{"Binary without v", Binary, "0.3.0", "Download: https://github.com/stacktodate/stacktodate-cli/releases/tag/0.3.0"},
+		{"Unknown", Unknown, "v0.3.0", "Visit: https://github.com/stacktodate/stacktodate-cli/releases/tag/v0.3.0"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := GetUpgradeInstructions(tt.method, tt.version); got != tt.expected {
+				t.Fatalf("expected %q, got %q", tt.expected, got)
+			}
+		})
+	}
+}
+
+func TestGetInstallerDownloadURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		method   InstallMethod
+		expected string
+	}{
+		{"Homebrew", Homebrew, "https://github.com/stacktodate/homebrew-stacktodate"},
+		{"Binary", Binary, "https://github.com/stacktodate/stacktodate-cli/releases/latest"},
+		{"Unknown", Unknown, "https://github.com/stacktodate/stacktodate-cli/releases/latest"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := GetInstallerDownloadURL(tt.method); got != tt.expected {
+				t.Fatalf("expected %q, got %q", tt.expected, got)
+			}
+		})
+	}
+}
+
+func TestDetectInstallMethod(t *testing.T) {
+	// This test just verifies the function runs without panic
+	// Actual detection result depends on environment
+	method := DetectInstallMethod()
+
+	if method != Homebrew && method != Binary && method != Unknown {
+		t.Fatalf("unexpected install method: %v", method)
+	}
+}