/*
 *
 * Copyright 2016, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
#if SWIFT_PACKAGE
  import CgRPC
#endif
import Foundation // for String.Encoding

/// A gRPC request handler
public class Handler {
  /// Pointer to underlying C representation
  var h: UnsafeMutableRawPointer!

  /// Completion queue for handler response operations
  var completionQueue: CompletionQueue

  /// Metadata received with the request
  public var requestMetadata: Metadata

  /// Initializes a Handler
  ///
  /// - Parameter h: the underlying C representation
  init(h:UnsafeMutableRawPointer!) {
    self.h = h;
    self.requestMetadata = Metadata()
    self.completionQueue = CompletionQueue(cq:cgrpc_handler_get_completion_queue(h))
  }

  deinit {
    cgrpc_handler_destroy(self.h)
  }

  /// Gets the host name sent with the request
  ///
  /// - Returns: the host name sent with the request
  public func host() -> String {
    return String(cString:cgrpc_handler_host(h), encoding:String.Encoding.utf8)!;
  }

  /// Gets the method name sent with the request
  ///
  /// - Returns: the method name sent with the request
  public func method() -> String {
    return String(cString:cgrpc_handler_method(h), encoding:String.Encoding.utf8)!;
  }

  /// Gets the caller identity associated with the request
  ///
  /// - Returns: a string representing the caller address
  public func caller() -> String {
    return String(cString:cgrpc_handler_call_peer(h), encoding:String.Encoding.utf8)!;
  }

  /// Creates a call object associated with the handler
  ///
  /// - Returns: a Call object that can be used to respond to the request
  func call() -> Call {
    return Call(call: cgrpc_handler_get_call(h), owned:false)
  }

  /// Request a call for the handler
  ///
  /// Fills the handler properties with information about the received request
  /// 
  /// - Returns: a grpc_call_error indicating the result of requesting the call
  func requestCall(tag: Int) -> grpc_call_error {
    return cgrpc_handler_request_call(h, requestMetadata.array, tag)
  }

  /// Receive the message sent with a call
  ///
  /// - Returns: a tuple containing status codes and a message (if available)
  public func receiveMessage(initialMetadata: Metadata) -> (grpc_call_error, grpc_completion_type, ByteBuffer?) {

    let operation_sendInitialMetadata = Operation_SendInitialMetadata(metadata:initialMetadata);
    let operation_receiveMessage = Operation_ReceiveMessage()

    let operations: [Operation] = [
      operation_sendInitialMetadata,
      operation_receiveMessage
    ]

    let call = self.call()
    let call_error = call.performOperations(operations:operations, tag:222)
    if call_error != GRPC_CALL_OK {
      return (call_error, GRPC_OP_COMPLETE, nil)
    }

    let call_status = completionQueue.waitForCompletion(timeout:5.0)
    if (call_status == GRPC_OP_COMPLETE) {
      return (GRPC_CALL_OK, GRPC_OP_COMPLETE, operation_receiveMessage.message())
    } else {
      return (GRPC_CALL_OK, call_status, nil)
    }
  }

  /// Sends the response to a request
  ///
  /// - Parameter message: the message to send
  /// - Returns: a tuple containing status codes
  public func sendResponse(message: ByteBuffer,
                           trailingMetadata: Metadata) -> (grpc_call_error, grpc_completion_type) {
    let operation_receiveCloseOnServer = Operation_ReceiveCloseOnServer();
    let operation_sendStatusFromServer = Operation_SendStatusFromServer(status:0,
                                                                        statusDetails:"OK",
                                                                        metadata:trailingMetadata)
    let operation_sendMessage = Operation_SendMessage(message:message)

    let operations: [Operation] = [
      operation_receiveCloseOnServer,
      operation_sendStatusFromServer,
      operation_sendMessage
    ]

    let call = self.call()
    let call_error = call.performOperations(operations:operations, tag:333)
    if call_error != GRPC_CALL_OK {
      return (call_error, GRPC_OP_COMPLETE)
    }
    let call_status = completionQueue.waitForCompletion(timeout:5.0)
    return (GRPC_CALL_OK, call_status)
  }
}