feat: add flag decoder (candidate)

internal/utils/decoders/flags_decoder.go

@@ -0,0 +1,55 @@
+package decoders
+
+import (
+	"strings"
+	"tinyauth/internal/config"
+	"tinyauth/internal/utils"
+
+	"github.com/traefik/paerser/parser"
+)
+
+func DecodeFlags(flags map[string]string) (config.Providers, error) {
+	// Normalize flags (sorry to whoever has to read this)
+	// --providers-client1-client-id -> tinyauth.providers.client1.clientId
+	normalized := make(map[string]string)
+	for k, v := range flags {
+		newKey := ""
+
+		nk := strings.TrimPrefix(k, "--")
+		parts := strings.SplitN(nk, "-", 4)
+
+		for i, part := range parts {
+			if i == 3 {
+				subParts := strings.Split(part, "-")
+				for j, subPart := range subParts {
+					if j == 0 {
+						newKey += "." + subPart
+					} else {
+						newKey += utils.Capitalize(subPart)
+					}
+				}
+				continue
+			}
+			if i == 0 {
+				newKey += part
+				continue
+			}
+			newKey += "." + part
+		}
+
+		newKey = "tinyauth." + newKey
+		normalized[newKey] = v
+
+	}
+
+	// Decode
+	var providers config.Providers
+
+	err := parser.Decode(normalized, &providers, "tinyauth", "tinyauth.providers")
+
+	if err != nil {
+		return config.Providers{}, err
+	}
+
+	return providers, nil
+}