Refactor 1/2 + new stuff

* Refactor CLI
* Add config:print command
* Add diagnose command
* Allow including other files in config
* Watch for file changes and automatically restart server

internal/glance/main.go

@@ -2,45 +2,120 @@ package glance
 
 import (
 	"fmt"
-	"os"
+	"log"
 )
 
 func Main() int {
-	options, err := ParseCliOptions()
+	options, err := parseCliOptions()
 
 	if err != nil {
 		fmt.Println(err)
 		return 1
 	}
 
-	configFile, err := os.Open(options.ConfigPath)
-
-	if err != nil {
-		fmt.Printf("failed opening config file: %v\n", err)
-		return 1
-	}
-
-	config, err := NewConfigFromYml(configFile)
-	configFile.Close()
-
-	if err != nil {
-		fmt.Printf("failed parsing config file: %v\n", err)
-		return 1
-	}
-
-	if options.Intent == CliIntentServe {
-		app, err := NewApplication(config)
-
+	switch options.intent {
+	case cliIntentServe:
+		if err := serveApp(options.configPath); err != nil {
+			fmt.Println(err)
+			return 1
+		}
+	case cliIntentConfigValidate:
+		contents, _, err := parseYAMLIncludes(options.configPath)
 		if err != nil {
-			fmt.Printf("failed creating application: %v\n", err)
+			fmt.Printf("failed to parse config file: %v\n", err)
 			return 1
 		}
 
-		if err := app.Serve(); err != nil {
-			fmt.Printf("http server error: %v\n", err)
+		if _, err := newConfigFromYAML(contents); err != nil {
+			fmt.Printf("config file is invalid: %v\n", err)
 			return 1
 		}
+	case cliIntentConfigPrint:
+		contents, _, err := parseYAMLIncludes(options.configPath)
+		if err != nil {
+			fmt.Printf("failed to parse config file: %v\n", err)
+			return 1
+		}
+
+		fmt.Println(string(contents))
+	case cliIntentDiagnose:
+		runDiagnostic()
 	}
 
 	return 0
 }
+
+func serveApp(configPath string) error {
+	exitChannel := make(chan struct{})
+	// the onChange method gets called at most once per 500ms due to debouncing so we shouldn't
+	// need to use atomic.Bool here unless newConfigFromYAML is very slow for some reason
+	hadValidConfigOnStartup := false
+	var stopServer func() error
+
+	onChange := func(newContents []byte) {
+		if stopServer != nil {
+			log.Println("Config file changed, attempting to restart server")
+		}
+
+		config, err := newConfigFromYAML(newContents)
+		if err != nil {
+			log.Printf("Config file is invalid: %v", err)
+
+			if !hadValidConfigOnStartup {
+				close(exitChannel)
+			}
+
+			return
+		} else if !hadValidConfigOnStartup {
+			hadValidConfigOnStartup = true
+		}
+
+		app := newApplication(config)
+
+		if stopServer != nil {
+			if err := stopServer(); err != nil {
+				log.Printf("Error while trying to stop server: %v", err)
+			}
+		}
+
+		go func() {
+			var startServer func() error
+			startServer, stopServer = app.Server()
+
+			if err := startServer(); err != nil {
+				log.Printf("Failed to start server: %v", err)
+			}
+		}()
+	}
+
+	onErr := func(err error) {
+		log.Printf("Error watching config files: %v", err)
+	}
+
+	configContents, configIncludes, err := parseYAMLIncludes(configPath)
+	if err != nil {
+		return fmt.Errorf("failed to parse config file: %w", err)
+	}
+
+	stopWatching, err := configFilesWatcher(configPath, configContents, configIncludes, onChange, onErr)
+	if err == nil {
+		defer stopWatching()
+	} else {
+		log.Printf("Error starting file watcher, config file changes will require a manual restart. (%v)", err)
+
+		config, err := newConfigFromYAML(configContents)
+		if err != nil {
+			return fmt.Errorf("could not parse config file: %w", err)
+		}
+
+		app := newApplication(config)
+
+		startServer, _ := app.Server()
+		if err := startServer(); err != nil {
+			return fmt.Errorf("failed to start server: %w", err)
+		}
+	}
+
+	<-exitChannel
+	return nil
+}