/*
 *
 * 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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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#if SWIFT_PACKAGE
  import CgRPC
#endif
import Foundation

/// Singleton class that provides a mutex for synchronizing calls to cgrpc_call_perform()
private class CallLock {
  var mutex : Mutex
  private init() {
    mutex = Mutex()
  }
  static let sharedInstance = CallLock()
}

public typealias CallCompletion = (Int, String?, Data?, Metadata?, Metadata?) -> Void
public typealias SendMessageCompletion = (grpc_call_error) -> Void

/// A gRPC API call
public class Call {

  /// Pointer to underlying C representation
  private var call : UnsafeMutableRawPointer!

  /// Completion queue used for call
  private var completionQueue: CompletionQueue

  /// True if this instance is responsible for deleting the underlying C representation
  private var owned : Bool

  /// A queue of pending messages to send over the call
  private var pendingMessages : Array<Data>

  /// True if a message write operation is underway
  private var writing : Bool

  /// Initializes a Call representation
  ///
  /// - Parameter call: the underlying C representation
  /// - Parameter owned: true if this instance is responsible for deleting the underlying call
  init(call: UnsafeMutableRawPointer, owned: Bool, completionQueue: CompletionQueue) {
    self.call = call
    self.owned = owned
    self.completionQueue = completionQueue
    self.pendingMessages = []
    self.writing = false
  }

  deinit {
    if (owned) {
      cgrpc_call_destroy(call)
    }
  }

  /// Initiate performance of a call without waiting for completion
  ///
  /// - Parameter operations: array of operations to be performed
  /// - Parameter tag: integer tag that will be attached to these operations
  /// - Returns: the result of initiating the call
  func performOperations(operations: OperationGroup,
                         tag: Int64,
                         completionQueue: CompletionQueue)
    -> grpc_call_error {
      let mutex = CallLock.sharedInstance.mutex
      mutex.lock()
      let error = cgrpc_call_perform(call, operations.operations, tag)
      mutex.unlock()
      return error
  }

  /// Performs a nonstreaming gRPC API call
  ///
  /// - Parameter message: a ByteBuffer containing the message to send
  /// - Parameter metadata: metadata to send with the call
  /// - Returns: a CallResponse object containing results of the call
  public func performNonStreamingCall(messageData: Data,
                                      metadata: Metadata,
                                      completion: @escaping CallCompletion) -> grpc_call_error {

    let messageBuffer = ByteBuffer(data:messageData)

    let operation_sendInitialMetadata = Operation_SendInitialMetadata(metadata:metadata);
    let operation_sendMessage = Operation_SendMessage(message:messageBuffer)
    let operation_sendCloseFromClient = Operation_SendCloseFromClient()
    let operation_receiveInitialMetadata = Operation_ReceiveInitialMetadata()
    let operation_receiveStatusOnClient = Operation_ReceiveStatusOnClient()
    let operation_receiveMessage = Operation_ReceiveMessage()

    let group = OperationGroup(call:self,
                               operations:[operation_sendInitialMetadata,
                                           operation_sendMessage,
                                           operation_sendCloseFromClient,
                                           operation_receiveInitialMetadata,
                                           operation_receiveStatusOnClient,
                                           operation_receiveMessage],
                               completion:
      {(success) in
        if success {
          completion(operation_receiveStatusOnClient.status(),
                     operation_receiveStatusOnClient.statusDetails(),
                     operation_receiveMessage.message()?.data(),
                     operation_receiveInitialMetadata.metadata(),
                     operation_receiveStatusOnClient.metadata())
        } else {
          completion(0, nil, nil, nil, nil)
        }
    })

    return self.perform(operations: group)
  }

  // perform a group of operations (used internally)
  private func perform(operations: OperationGroup) -> grpc_call_error {
    self.completionQueue.operationGroups[operations.tag] = operations
    return performOperations(operations:operations,
                             tag:operations.tag,
                             completionQueue: self.completionQueue)
  }

  // start a streaming connection
  public func start(metadata: Metadata) -> grpc_call_error {
    var error : grpc_call_error
    error = self.sendInitialMetadata(metadata: metadata)
    if error != GRPC_CALL_OK {
      return error
    }
    error = self.receiveInitialMetadata()
    if error != GRPC_CALL_OK {
      return error
    }
    return self.receiveStatus()
  }

  // send a message over a streaming connection
  public func sendMessage(data: Data,
                          callback:@escaping SendMessageCompletion = {(error) in })
    -> Void {
    DispatchQueue.main.async {
      if self.writing {
        self.pendingMessages.append(data) // TODO: return something if we can't accept another message
        callback(GRPC_CALL_OK)
      } else {
        self.writing = true
        let error = self.sendWithoutBlocking(data: data)
        callback(error)
      }
    }
  }

  private func sendWithoutBlocking(data: Data) -> grpc_call_error {
    let messageBuffer = ByteBuffer(data:data)
    let operation_sendMessage = Operation_SendMessage(message:messageBuffer)
    let operations = OperationGroup(call:self, operations:[operation_sendMessage])
    { (event) in

      // TODO: if the event failed, shut down

      DispatchQueue.main.async {
        if self.pendingMessages.count > 0 {
          let nextMessage = self.pendingMessages.first!
          self.pendingMessages.removeFirst()
          _ = self.sendWithoutBlocking(data: nextMessage)
        } else {
          self.writing = false
        }
      }
    }
    return self.perform(operations:operations)
  }


  // receive a message over a streaming connection
  public func receiveMessage(callback:@escaping ((Data!) -> Void)) -> grpc_call_error {
    let operation_receiveMessage = Operation_ReceiveMessage()
    let operations = OperationGroup(call:self, operations:[operation_receiveMessage])
    { (event) in
      if let messageBuffer = operation_receiveMessage.message() {
        callback(messageBuffer.data())
      }
    }
    return self.perform(operations:operations)
  }

  // send initial metadata over a streaming connection
  private func sendInitialMetadata(metadata: Metadata) -> grpc_call_error {
    let operation_sendInitialMetadata = Operation_SendInitialMetadata(metadata:metadata);
    let operations = OperationGroup(call:self, operations:[operation_sendInitialMetadata])
    { (success) in
      if (success) {
        print("call successful")
      } else {
        return
      }
    }
    return self.perform(operations:operations)
  }

  // receive initial metadata from a streaming connection
  private func receiveInitialMetadata() -> grpc_call_error {
    let operation_receiveInitialMetadata = Operation_ReceiveInitialMetadata()
    let operations = OperationGroup(call:self, operations:[operation_receiveInitialMetadata])
    { (event) in
      let initialMetadata = operation_receiveInitialMetadata.metadata()
      for j in 0..<initialMetadata.count() {
        print("Received initial metadata -> " + initialMetadata.key(index:j) + " : " + initialMetadata.value(index:j))
      }
    }
    return self.perform(operations:operations)
  }

  // receive status from a streaming connection
  private func receiveStatus() -> grpc_call_error {
    let operation_receiveStatus = Operation_ReceiveStatusOnClient()
    let operations = OperationGroup(call:self,
                                    operations:[operation_receiveStatus])
    { (event) in
      print("status = \(operation_receiveStatus.status()), \(operation_receiveStatus.statusDetails())")
    }
    return self.perform(operations:operations)
  }

  // close a streaming connection
  public func close(completion:@escaping (() -> Void)) -> grpc_call_error {
    let operation_sendCloseFromClient = Operation_SendCloseFromClient()
    let operations = OperationGroup(call:self, operations:[operation_sendCloseFromClient])
    { (event) in
      completion()
    }
    return self.perform(operations:operations)
  }
}