add mana core

packages/shared-errors/src/errors/credit-error.ts

@@ -0,0 +1,35 @@
+import { ErrorCode } from '../types/error-codes';
+import { AppError } from './app-error';
+
+/**
+ * Error for insufficient credits/mana.
+ * HTTP Status: 402 Payment Required
+ *
+ * @example
+ * ```typescript
+ * return err(new CreditError(100, 50, 'story_generation'));
+ * // Message: "Insufficient credits. Required: 100, Available: 50"
+ * ```
+ */
+export class CreditError extends AppError {
+  /** Credits required for the operation */
+  readonly requiredCredits: number;
+
+  /** Credits currently available */
+  readonly availableCredits: number;
+
+  constructor(
+    requiredCredits: number,
+    availableCredits: number,
+    operation?: string
+  ) {
+    super({
+      code: ErrorCode.INSUFFICIENT_CREDITS,
+      message: `Insufficient credits. Required: ${requiredCredits}, Available: ${availableCredits}`,
+      context: { requiredCredits, availableCredits, operation },
+    });
+    this.name = 'CreditError';
+    this.requiredCredits = requiredCredits;
+    this.availableCredits = availableCredits;
+  }
+}