add ai feature

internal/ai/config.go

@@ -0,0 +1,41 @@
+package ai
+
+import (
+	"errors"
+	"fmt"
+	"os"
+)
+
+var apiKeyEnvVars = []string{
+	"GOOGLE_API_KEY",
+	"GEMINI_API_KEY",
+	"RENAMER_AI_KEY",
+}
+
+// Credentials encapsulates the values required to authenticate with the AI provider.
+type Credentials struct {
+	APIKey string
+}
+
+// LoadCredentials returns the AI credentials sourced from environment variables.
+func LoadCredentials() (Credentials, error) {
+	for _, env := range apiKeyEnvVars {
+		if key, ok := os.LookupEnv(env); ok && key != "" {
+			return Credentials{APIKey: key}, nil
+		}
+	}
+	return Credentials{}, errors.New("AI provider key missing; set GOOGLE_API_KEY (recommended), GEMINI_API_KEY, or RENAMER_AI_KEY")
+}
+
+// MaskedCredentials returns a redacted view of the credentials for logging purposes.
+func MaskedCredentials(creds Credentials) string {
+	if creds.APIKey == "" {
+		return "(empty)"
+	}
+
+	if len(creds.APIKey) <= 6 {
+		return "***"
+	}
+
+	return fmt.Sprintf("%s***", creds.APIKey[:3])
+}