feat(backend): implement task creation and admin web

backend-api/internal/config/config.go

@@ -10,11 +10,13 @@ import (
 )
 
 const (
-	HTTPAddressEnvironment  = "CMROUBAO_HTTP_ADDR"
-	DatabasePathEnvironment = "CMROUBAO_DATABASE_PATH"
+	HTTPAddressEnvironment    = "CMROUBAO_HTTP_ADDR"
+	DatabasePathEnvironment   = "CMROUBAO_DATABASE_PATH"
+	AssetDirectoryEnvironment = "CMROUBAO_ASSET_DIR"
 
-	defaultHTTPAddress  = "127.0.0.1:8080"
-	defaultDatabasePath = "var/cmroubao.db"
+	defaultHTTPAddress    = "127.0.0.1:8080"
+	defaultDatabasePath   = "var/cmroubao.db"
+	defaultAssetDirectory = "var/assets"
 )
 
 type LookupEnvironment func(string) (string, bool)
@@ -22,6 +24,7 @@ type LookupEnvironment func(string) (string, bool)
 type Config struct {
 	HTTPAddress       string
 	DatabasePath      string
+	AssetDirectory    string
 	ReadHeaderTimeout time.Duration
 	ReadTimeout       time.Duration
 	WriteTimeout      time.Duration
@@ -53,9 +56,23 @@ func Load(lookup LookupEnvironment) (Config, error) {
 		return Config{}, err
 	}
 
+	assetDirectory, err := environmentValue(
+		lookup,
+		AssetDirectoryEnvironment,
+		defaultAssetDirectory,
+	)
+	if err != nil {
+		return Config{}, err
+	}
+	assetDirectory, err = validatedAssetDirectory(assetDirectory)
+	if err != nil {
+		return Config{}, err
+	}
+
 	return Config{
 		HTTPAddress:       httpAddress,
 		DatabasePath:      filepath.Clean(databasePath),
+		AssetDirectory:    assetDirectory,
 		ReadHeaderTimeout: 5 * time.Second,
 		ReadTimeout:       15 * time.Second,
 		WriteTimeout:      30 * time.Second,
@@ -65,6 +82,24 @@ func Load(lookup LookupEnvironment) (Config, error) {
 	}, nil
 }
 
+func validatedAssetDirectory(path string) (string, error) {
+	if strings.ContainsRune(path, '\x00') {
+		return "", errors.New(
+			AssetDirectoryEnvironment + " contains an invalid character",
+		)
+	}
+	cleanPath := filepath.Clean(path)
+	volumeRoot := filepath.VolumeName(cleanPath) + string(filepath.Separator)
+	if cleanPath == "." ||
+		cleanPath == string(filepath.Separator) ||
+		cleanPath == volumeRoot {
+		return "", errors.New(
+			AssetDirectoryEnvironment + " must be a dedicated directory",
+		)
+	}
+	return cleanPath, nil
+}
+
 func LoadDatabasePath(lookup LookupEnvironment) (string, error) {
 	databasePath, err := environmentValue(
 		lookup,