First implementation of new config format

- Functionally equivalent to old version at present
- Temperature and Humidity sensors not handled yet
- Moved HTTP handlers around

config/config.go

@@ -1,11 +1,54 @@
 package config
 
-// Configuration represents the settings needed to configure spaceapid
-type Configuration struct {
-	// The HTTP BasicAuth username for door status updates
-	BAUsername string
-	// The HTTP BasicAuth password for door status updates
-	BAPassword string
-	// The path to the JSON with initial values
-	TemplatePath string
+import (
+	"bytes"
+	"encoding/json"
+	"log"
+	"os"
+	"path/filepath"
+	"slices"
+)
+
+const (
+	envConfigPath = "CONFIG_PATH"
+)
+
+// getConfigPath gets the spaceapid configuration from the respective environment variables
+func getConfigPath() string {
+	// JSON template path
+	configPath, ok := os.LookupEnv(envConfigPath)
+	if !ok || configPath == "" {
+		log.Fatalln("Could not retrieve", envConfigPath, "env variable or variable is empty")
+	}
+	// Save as absolute path
+	absConfigPath, err := filepath.Abs(configPath)
+	if err != nil {
+		log.Fatalln("Failed converting", configPath, "to absolute path:", err)
+	}
+	return absConfigPath
+}
+
+// ParseConfiguration returns the config from file
+func ParseConfiguration() (conf SpaceapidConfig) {
+	log.Println("Parsing configuration file")
+	// Read file
+	file, err := os.ReadFile(getConfigPath())
+	if err != nil {
+		log.Fatalln("Failed reading file:", err)
+	}
+
+	// Parse JSON
+	dec := json.NewDecoder(bytes.NewReader(file))
+	dec.DisallowUnknownFields()
+	err = dec.Decode(&conf)
+	if err != nil {
+		log.Fatalln("Could not parse spaceapid config file:", err)
+	}
+
+	// Check if compatible with v14
+	if !slices.Contains(conf.Response.APICompatibility, "14") {
+		log.Fatalln("Provided file doesn't specify compatibility with API version 14")
+	}
+
+	return
 }