/**
 * This module provides helper functions for working with Confluent Schema Registry.
 * It handles schema registration, serialization, and deserialization of messages
 * using various schema formats (AVRO, JSON, PROTOBUF).
 */
import { Deserializer, SchemaRegistryClient, SerdeType, Serializer } from "@confluentinc/schemaregistry";
/**
 * Supported schema types for Confluent Schema Registry.
 * AVRO: Apache Avro binary format with schema evolution support
 * JSON: JSON Schema format with validation
 * PROTOBUF: Protocol Buffers format with backward compatibility
 */
export type SchemaType = "AVRO" | "JSON" | "PROTOBUF";
/**
 * Common options for schema registry operations.
 * These options control how schemas are registered and used for serialization.
 */
export interface SchemaRegistryOptions {
    useSchemaRegistry?: boolean;
    schemaType?: SchemaType;
    schema?: string;
    subject?: string;
    normalize?: boolean;
}
/**
 * Options for message serialization/deserialization.
 * Includes the message payload and schema registry configuration.
 */
export type MessageOptions = {
    message: Buffer | object | string;
    useSchemaRegistry?: boolean;
    schemaType?: SchemaType;
    schema?: string;
    subject?: string;
    normalize?: boolean;
};
/**
 * Result of checking if a schema is needed for a message.
 * Can indicate:
 * - A schema is needed and provides the latest schema details
 * - No schema exists and needs to be provided
 * - No schema action is needed
 */
export type SchemaCheckResult = {
    type: "schema-needed";
    latestSchema: string;
    subject: string;
    schemaType: string;
} | {
    type: "no-schema";
    subject: string;
} | null;
/**
 * Creates and returns the appropriate serializer instance based on schema type.
 * The serializer is configured to use either a specific schema ID or the latest version.
 *
 * @param schemaType - The type of schema (AVRO, JSON, PROTOBUF)
 * @param registry - The schema registry client instance
 * @param serdeType - Whether this is for key or value serialization
 * @param schemaId - Optional schema ID to use for serialization
 * @returns The appropriate Serializer instance
 * @throws Error if the schema type is unknown or unsupported
 */
export declare function getSerializer(schemaType: SchemaType | undefined, registry: SchemaRegistryClient, serdeType: SerdeType, schemaId?: number): Serializer;
/**
 * Creates and returns the appropriate deserializer instance based on schema type.
 * The deserializer is configured to handle schema evolution and compatibility.
 *
 * @param schemaType - The type of schema (AVRO, JSON, PROTOBUF)
 * @param registry - The schema registry client instance
 * @param serdeType - Whether this is for key or value deserialization
 * @returns The appropriate Deserializer instance
 * @throws Error if the schema type is unknown or unsupported
 */
export declare function getDeserializer(schemaType: SchemaType | undefined, registry: SchemaRegistryClient, serdeType: SerdeType): Deserializer;
/**
 * Checks if a schema is needed for the given message options.
 * This function determines if:
 * 1. A schema is already registered and should be used
 * 2. No schema exists and needs to be provided
 * 3. No schema action is needed
 *
 * @param topicName - The Kafka topic name
 * @param options - The message options including schema, type, and payload
 * @param serdeType - Whether this is for key or value serialization
 * @param registry - The schema registry client instance (if used)
 * @returns An object describing the schema state, or null if no schema action is needed
 */
export declare function checkSchemaNeeded(topicName: string, options: MessageOptions, serdeType: SerdeType, registry: SchemaRegistryClient | undefined): Promise<SchemaCheckResult>;
/**
 * Fetches the latest schema string and schema type for a given subject from the schema registry.
 * Handles 404 errors gracefully by returning null when no schema exists.
 *
 * @param registry - The schema registry client instance
 * @param subject - The subject to look up in the registry
 * @returns An object with the latest schema string and schema type, or null if not found
 * @throws Error if there's an unexpected error from the registry
 */
export declare function getLatestSchemaIfExists(registry: SchemaRegistryClient, subject: string): Promise<{
    schema: string;
    schemaType: SchemaType;
} | null>;
/**
 * Serializes a message using the provided options and schema registry configuration.
 * This function:
 * 1. Registers the schema if provided
 * 2. Validates the message type
 * 3. Creates the appropriate serializer
 * 4. Serializes the message
 *
 * @param topicName - The Kafka topic name
 * @param options - The message options including schema, type, and payload
 * @param serdeType - Whether this is for key or value serialization
 * @param registry - The schema registry client instance (if used)
 * @returns The serialized message as a Buffer or string
 * @throws Error if serialization fails, schema registration fails, or message type is invalid
 */
export declare function serializeMessage(topicName: string, options: MessageOptions, serdeType: SerdeType, registry: SchemaRegistryClient | undefined): Promise<Buffer | string>;
/**
 * Deserializes a message using Schema Registry.
 * This function:
 * 1. Creates the appropriate deserializer
 * 2. Deserializes the message using the schema from the registry
 *
 * @param topic - The Kafka topic name
 * @param message - The message buffer to deserialize
 * @param schemaType - The schema type (AVRO, JSON, PROTOBUF)
 * @param registry - The schema registry client
 * @param serdeType - Whether this is key or value
 * @returns The deserialized object
 * @throws Error if deserialization fails
 */
export declare function deserializeMessage(topic: string, message: Buffer, schemaType: SchemaType, registry: SchemaRegistryClient, serdeType: SerdeType): Promise<unknown>;
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