Message Patterns

import { applyDecorators, SetMetadata } from "@nestjs/common";
import { MessagePattern, EventPattern } from "@nestjs/microservices";

export const MESSAGE_METADATA_KEY = "message_metadata";

export interface MessageMetadata {
  name: string;
  description?: string;
  version?: string;
  deprecated?: boolean;
}

/**
 * Enhanced message pattern with metadata for documentation.
 * 
 * Usage:
 * @Message("user.create", { description: "Creates a new user" })
 * async createUser(@Payload() data: CreateUserDto) {}
 */
export function Message(pattern: string, metadata?: Omit<MessageMetadata, "name">) {
  return applyDecorators(
    MessagePattern(pattern),
    SetMetadata(MESSAGE_METADATA_KEY, { name: pattern, ...metadata })
  );
}

/**
 * Enhanced event pattern with metadata.
 * Events are fire-and-forget (no response expected).
 * 
 * Usage:
 * @Event("user.created")
 * async onUserCreated(@Payload() data: UserCreatedEvent) {}
 */
export function Event(pattern: string, metadata?: Omit<MessageMetadata, "name">) {
  return applyDecorators(
    EventPattern(pattern),
    SetMetadata(MESSAGE_METADATA_KEY, { name: pattern, ...metadata })
  );
}

/**
 * Versioned message pattern.
 * 
 * Usage:
 * @VersionedMessage("user.create", "v2")
 * async createUserV2(@Payload() data: CreateUserDtoV2) {}
 */
export function VersionedMessage(pattern: string, version: string) {
  const versionedPattern = `${version}.${pattern}`;
  return applyDecorators(
    MessagePattern(versionedPattern),
    SetMetadata(MESSAGE_METADATA_KEY, { name: pattern, version })
  );
}

/**
 * Mark a message handler as deprecated.
 */
export function DeprecatedMessage(pattern: string, replacement?: string) {
  return applyDecorators(
    MessagePattern(pattern),
    SetMetadata(MESSAGE_METADATA_KEY, {
      name: pattern,
      deprecated: true,
      description: replacement ? `Deprecated. Use ${replacement} instead.` : "Deprecated",
    })
  );
}