Implement passing user configuration

This allows overwriting values of the default configuration with custom
ones.

4 files changed, 45 insertions, 2 deletions

diff --git a/config.go b/config.go
index 7d3cab8..dfea550 100644
--- a/config.go
+++ b/config.go
@@ -7,6 +7,7 @@ import (
 	"log"
 	"net"
 	"net/url"
+	"os"
 	"regexp"
 	"strconv"
 	"time"
@@ -120,7 +121,21 @@ func (sc *StartupConfig) FromJSON(data []byte) error {
 	return nil
 }
 
-func GetStartupConfig() StartupConfig {
+func (sc *StartupConfig) FromFile(path string) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Errorf("Failed to read config file '%s': %w", path, err)
+	}
+
+	err = sc.FromJSON(data)
+	if err != nil {
+		return fmt.Errorf("Could not parse config file '%s': %w", path, err)
+	}
+
+	return nil
+}
+
+func GetStartupConfig(path string) StartupConfig {
 	config := StartupConfig{}
 
 	err := config.FromJSON(defaultConfig)
@@ -128,5 +143,14 @@ func GetStartupConfig() StartupConfig {
 		log.Fatalf("Could not parse default config: %v", err)
 	}
 
+	if path != "" {
+		log.Printf("Config path: %s", path)
+
+		err = config.FromFile(path)
+		if err != nil {
+			log.Fatalf("Failed to read configuration: %v", err)
+		}
+	}
+
 	return config
 }
diff --git a/flags.go b/flags.go
new file mode 100644
index 0000000..11a79c6
--- /dev/null
+++ b/flags.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"flag"
+)
+
+type Flags struct {
+	ConfigPath string
+}
+
+func (f *Flags) FromArgs() {
+	flag.StringVar(&f.ConfigPath, "config", "", "path to configuration file")
+
+	flag.Parse()
+}
diff --git a/main.go b/main.go
index 128720f..f06d525 100644
--- a/main.go
+++ b/main.go
@@ -11,7 +11,10 @@ func main() {
 	log.Println("+++ Started Sia server +++")
 	defer log.Println("--- Stopped Sia server ---")
 
-	config := GetStartupConfig()
+	flags := Flags{}
+	flags.FromArgs()
+
+	config := GetStartupConfig(flags.ConfigPath)
 
 	tx := make(chan MQTTMessage)
 
diff --git a/meson.build b/meson.build
index 0917410..7436494 100644
--- a/meson.build
+++ b/meson.build
@@ -9,6 +9,7 @@ sia_server = custom_target(
     meson.current_source_dir() / 'mqtt.go',
     meson.current_source_dir() / 'homematic.go',
     meson.current_source_dir() / 'config.go',
+    meson.current_source_dir() / 'flags.go',
   ],
   output : 'sia-server',
   command : [