Add -c flag to specify list of config files

- Environment variable also accepts comma-separated list
  - Overwrites cli arguments

.gitignore

@@ -9,3 +9,8 @@ spaceapid
 
 # Saved state
 spaceapid-state.json
+
+# Config shards
+credentials.json
+dynamic.json
+response.json

config/config.go

@@ -3,10 +3,12 @@ package config
 import (
 	"bytes"
 	"encoding/json"
+	"flag"
+	"fmt"
 	"log"
 	"os"
-	"path/filepath"
 	"slices"
+	"strings"
 
 	"gitlab.hamburg.ccc.de/ccchh/spaceapid/types"
 )
@@ -15,36 +17,73 @@ const (
 	envConfigPath = "CONFIG_PATH"
 )
 
-// getConfigPath gets the spaceapid configuration from the respective environment variables
-func getConfigPath() string {
-	// JSON template path
+type pathsT []string
+
+func (p *pathsT) String() string {
+	return fmt.Sprint(*p)
+}
+
+func (p *pathsT) Set(s string) error {
+	*p = make(pathsT, 0)
+	for _, path := range strings.Split(s, ",") {
+		*p = append(*p, path)
+	}
+	return nil
+}
+
+var (
+	flagConfigPaths pathsT
+)
+
+func init() {
+	flag.Var(&flagConfigPaths, "c", "Comma-separated list of config file paths. Parsed in order of appearance. Values get overwritten by files parsed later.")
+}
+
+func getConfigPaths() (paths pathsT) {
+	// Get paths from env variable and if env var present override cli flags
 	configPath, ok := os.LookupEnv(envConfigPath)
-	if !ok || configPath == "" {
-		log.Fatalln("Could not retrieve", envConfigPath, "env variable or variable is empty")
+	if ok {
+		if configPath == "" {
+			log.Fatalln("Env variable", envConfigPath, "is present but empty.")
+		}
+		_ = flagConfigPaths.Set(configPath)
 	}
-	// Save as absolute path
-	absConfigPath, err := filepath.Abs(configPath)
-	if err != nil {
-		log.Fatalln("Failed converting", configPath, "to absolute path:", err)
+
+	for _, path := range flagConfigPaths {
+		_, err := os.Stat(path)
+		if err != nil {
+			log.Fatalln("Config file", path, "doesn't exist or is not accessible, error:", err)
+		}
+		paths = append(paths, path)
 	}
-	return absConfigPath
+
+	// If paths is still empty we are missing something
+	if len(paths) == 0 {
+		log.Fatalln("Neither the env variable nor cli flag was specified, we are missing a config file.")
+	}
+	return
 }
 
 // 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)
-	}
+	log.Println("Parsing configuration files")
 
-	// 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)
+	paths := getConfigPaths()
+	log.Println(paths)
+	for _, path := range paths {
+		// Read file
+		file, err := os.ReadFile(path)
+		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

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"log"
 	"net/http"
@@ -15,7 +16,22 @@ import (
 	"gitlab.hamburg.ccc.de/ccchh/spaceapid/util"
 )
 
+var (
+	flagHelp bool
+)
+
+func init() {
+	flag.BoolVar(&flagHelp, "h", false, "Print help output")
+}
+
 func main() {
+	flag.Parse()
+
+	if flagHelp {
+		flag.PrintDefaults()
+		os.Exit(0)
+	}
+
 	// Get spaceapid configuration
 	conf := config.ParseConfiguration()