watchdog: migrate to Cobra and Viper for config management; search /etc for configs

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I65dbf466cb030dccc7025585d6282bd26a6a6964

cmd/watchdog/main.go

@@ -1,15 +1,92 @@
 package watchdog
 
 import (
-	"flag"
-	"log"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+	"notashelf.dev/watchdog/internal/config"
 )
 
-func Main() {
-	configPath := flag.String("config", "config.yaml", "path to config file")
-	flag.Parse()
+var (
+	cfgFile string
+	cfg     *config.Config
+)
 
-	if err := Run(*configPath); err != nil {
-		log.Fatalf("Error: %v", err)
+var rootCmd = &cobra.Command{
+	Use:   "watchdog",
+	Short: "Privacy-first web analytics with Prometheus metrics",
+	Long:  `Watchdog is a lightweight, privacy-first analytics system that aggregates web traffic data.`,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return Run(cfg)
+	},
+}
+
+func init() {
+	cobra.OnInitialize(initConfig)
+
+	rootCmd.PersistentFlags().
+		StringVar(&cfgFile, "config", "", "config file (default: config.yaml)")
+	rootCmd.PersistentFlags().String("listen-addr", "", "server listen address (overrides config)")
+	rootCmd.PersistentFlags().String("metrics-path", "", "metrics endpoint path (overrides config)")
+	rootCmd.PersistentFlags().
+		String("ingestion-path", "", "ingestion endpoint path (overrides config)")
+
+	// Bind flags to viper
+	viper.BindPFlag("server.listen_addr", rootCmd.PersistentFlags().Lookup("listen-addr"))
+	viper.BindPFlag("server.metrics_path", rootCmd.PersistentFlags().Lookup("metrics-path"))
+	viper.BindPFlag("server.ingestion_path", rootCmd.PersistentFlags().Lookup("ingestion-path"))
+}
+
+func initConfig() {
+	if cfgFile != "" {
+		// Use config file from the flag
+		viper.SetConfigFile(cfgFile)
+	} else {
+		// Search for config in current directory
+		viper.AddConfigPath(".")
+		viper.AddConfigPath("/etc/watchdog")
+		viper.SetConfigName("config")
+		viper.SetConfigType("yaml")
+	}
+
+	// Environment variables
+	viper.SetEnvPrefix("WATCHDOG")
+	viper.AutomaticEnv()
+	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+
+	// Read config file
+	if err := viper.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+			fmt.Fprintf(
+				os.Stderr,
+				"Config file not found, using defaults and environment variables\n",
+			)
+		} else {
+			fmt.Fprintf(os.Stderr, "Error reading config file: %v\n", err)
+			os.Exit(1)
+		}
+	}
+
+	// Unmarshal into config struct
+	cfg = &config.Config{}
+	if err := viper.Unmarshal(cfg); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to parse config: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Validate config
+	if err := cfg.Validate(); err != nil {
+		fmt.Fprintf(os.Stderr, "Config validation failed: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func Main() {
+	if err := rootCmd.Execute(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
 	}
 }

cmd/watchdog/root.go

@@ -21,13 +21,7 @@ import (
 	"notashelf.dev/watchdog/internal/normalize"
 )
 
-func Run(configPath string) error {
-	// Load configuration
-	cfg, err := config.Load(configPath)
-	if err != nil {
-		return fmt.Errorf("failed to load config: %w", err)
-	}
-
+func Run(cfg *config.Config) error {
 	log.Printf("Loaded config for domains: %v", cfg.Site.Domains)
 
 	// Initialize components
@@ -35,7 +29,7 @@ func Run(configPath string) error {
 	pathRegistry := aggregate.NewPathRegistry(cfg.Limits.MaxPaths)
 	refRegistry := normalize.NewReferrerRegistry(cfg.Limits.MaxSources)
 	eventRegistry := aggregate.NewCustomEventRegistry(cfg.Limits.MaxCustomEvents)
-	metricsAgg := aggregate.NewMetricsAggregator(pathRegistry, eventRegistry, *cfg)
+	metricsAgg := aggregate.NewMetricsAggregator(pathRegistry, eventRegistry, cfg)
 
 	// HLL state persistence is handled automatically if salt_rotation is configured
 	if cfg.Site.SaltRotation != "" {
@@ -48,7 +42,7 @@ func Run(configPath string) error {
 
 	// Create HTTP handlers
 	ingestionHandler := api.NewIngestionHandler(
-		*cfg,
+		cfg,
 		pathNormalizer,
 		pathRegistry,
 		refRegistry,