Read configuration from flags and reply with configured name step-1

Signed-off-by: Mel <einebeere@gmail.com>

2 files changed, 77 insertions, 3 deletions

diff --git a/application/cmd/specimen/cfg/config.go b/application/cmd/specimen/cfg/config.go
new file mode 100644
index 0000000..713ad96
--- /dev/null
+++ b/application/cmd/specimen/cfg/config.go
@@ -0,0 +1,65 @@
+package cfg
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+)
+
+type Config struct {
+	Port    int
+	Address string
+
+	// since the server will be restarted when the name file changes,
+	// we can read the file directly after parsing the arguments,
+	// and pass the name to the server. no need to pass the path to the server.
+	Name string
+}
+
+func ParseFromArguments() (Config, error) {
+	c := Config{}
+	var namePath string
+
+	defineFlags(&c, &namePath)
+	flag.Parse()
+
+	if err := validateAndSet(&c, namePath); err != nil {
+		return Config{}, err
+	}
+
+	return c, nil
+}
+
+func defineFlags(c *Config, namePath *string) {
+	flag.IntVar(&c.Port, "port", 4444, "port to listen on")
+	flag.StringVar(&c.Address, "address", "127.0.0.1", "address to listen on")
+	flag.StringVar(namePath, "name", "", "path to the name file")
+}
+
+func validateAndSet(c *Config, namePath string) error {
+	if c.Port < 1 || c.Port > 65535 {
+		return errors.New("port is out of range")
+	}
+
+	if namePath == "" {
+		return errors.New("name file path is required")
+	}
+
+	file, err := os.Open(namePath)
+	if err != nil {
+		return fmt.Errorf("failed to open the name file. %w", err)
+	}
+
+	name := make([]byte, 1024)
+	n, err := file.Read(name)
+	if err != nil {
+		return fmt.Errorf("failed to read the name file. %w", err)
+	}
+
+	fmt.Printf("read %d bytes from the name file\n", n)
+	fmt.Printf("name: %s\n", string(name[:n]))
+
+	c.Name = string(name[:n])
+	return nil
+}
diff --git a/application/cmd/specimen/main.go b/application/cmd/specimen/main.go
index cf7ff36..9b3cc03 100644
--- a/application/cmd/specimen/main.go
+++ b/application/cmd/specimen/main.go
@@ -2,11 +2,13 @@ package main
 
 import (
 	"context"
+	"flag"
 	"log/slog"
 	"os"
 	"os/signal"
 	"time"
 
+	"git.rnrd.eu/specimen/cmd/specimen/cfg"
 	"git.rnrd.eu/specimen/pkg/specimen"
 	"git.rnrd.eu/specimen/pkg/util"
 )
@@ -17,13 +19,20 @@ func main() {
 	ctx := context.Background()
 	logger := createLogger()
 
-	if err := start(ctx, logger); err != nil {
+	config, err := cfg.ParseFromArguments()
+	if err != nil {
+		logger.Error("argument error!", util.SlogErr(err))
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	if err := start(ctx, logger, config); err != nil {
 		logger.Error("failed to start the specimen application :(", util.SlogErr(err))
 		os.Exit(1)
 	}
 }
 
-func start(ctx context.Context, logger *slog.Logger) error {
+func start(ctx context.Context, logger *slog.Logger, config cfg.Config) error {
 	// listen for SIGINT (or others on other systems, but who cares about those.. :3)
 	ctx, cancel := signal.NotifyContext(ctx, os.Interrupt)
 	defer cancel()
@@ -31,7 +40,7 @@ func start(ctx context.Context, logger *slog.Logger) error {
 	logger.Info("starting the specimen application!", slog.String("version", version))
 
 	// start the specimen server!
-	server := specimen.NewServer(logger)
+	server := specimen.NewServer(logger, config)
 	go server.Start(ctx)
 
 	// listen for signals to gracefully shutdown the server