/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#import "ProtoRPC.h"

#if GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS
#import <Protobuf/GPBProtocolBuffers.h>
#else
#import <GPBProtocolBuffers.h>
#endif
#import <GRPCClient/GRPCCall.h>
#import <RxLibrary/GRXWriteable.h>
#import <RxLibrary/GRXWriter+Transformations.h>

/**
  * Generate an NSError object that represents a failure in parsing a proto class.
  */
static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsingError) {
  NSDictionary *info = @{
                         NSLocalizedDescriptionKey : @"Unable to parse response from the server",
                         NSLocalizedRecoverySuggestionErrorKey :
                           @"If this RPC is idempotent, retry "
                         @"with exponential backoff. Otherwise, query the server status before "
                         @"retrying.",
                         NSUnderlyingErrorKey : parsingError,
                         @"Expected class" : expectedClass,
                         @"Received value" : proto,
                         };
  // TODO(jcanizales): Use kGRPCErrorDomain and GRPCErrorCodeInternal when they're public.
  return [NSError errorWithDomain:@"io.grpc" code:13 userInfo:info];
}

@implementation GRPCUnaryProtoCall {
  GRPCStreamingProtoCall *_call;
}

- (instancetype)initWithRequestOptions:(GRPCRequestOptions *)requestOptions
                               message:(GPBMessage *)message
                       responseHandler:(id<GRPCProtoResponseHandler>)handler
                           callOptions:(GRPCCallOptions *_Nullable)callOptions
                         responseClass:(Class)responseClass {
  if ((self = [super init])) {
    _call = [[GRPCStreamingProtoCall alloc] initWithRequestOptions:requestOptions
                                                   responseHandler:handler
                                                       callOptions:callOptions
                                                     responseClass:responseClass];
    [_call writeMessage:message];
    [_call finish];
  }
  return self;
}

- (void)cancel {
  [_call cancel];
  _call = nil;
}

@end

@interface GRPCStreamingProtoCall ()<GRPCResponseHandler>

@end

@implementation GRPCStreamingProtoCall {
  GRPCRequestOptions *_requestOptions;
  id<GRPCProtoResponseHandler> _handler;
  GRPCCallOptions *_callOptions;
  Class _responseClass;

  GRPCCall2 *_call;
  dispatch_queue_t _dispatchQueue;
  /**
    * Flags that the call has been canceled. When this is true, pending initial metadata and message
    * should not be issued to \a _handler. This ivar must be accessed with lock to self.
    */
  BOOL _canceled;
}

- (instancetype)initWithRequestOptions:(GRPCRequestOptions *)requestOptions
                       responseHandler:(id<GRPCProtoResponseHandler>)handler
                           callOptions:(GRPCCallOptions *_Nullable)callOptions
                         responseClass:(Class)responseClass {
  if (requestOptions.host.length == 0 || requestOptions.path.length == 0) {
    [NSException raise:NSInvalidArgumentException format:@"Neither host nor path can be nil."];
  }
  if (requestOptions.safety > GRPCCallSafetyCacheableRequest) {
    [NSException raise:NSInvalidArgumentException format:@"Invalid call safety value."];
  }
  if (handler == nil) {
    [NSException raise:NSInvalidArgumentException format:@"Response handler required."];
  }

  if ((self = [super init])) {
    _requestOptions = [requestOptions copy];
    _handler = handler;
    _callOptions = [callOptions copy];
    _responseClass = responseClass;
    if (@available(iOS 8.0, *)) {
      _dispatchQueue = dispatch_queue_create(
          NULL,
          dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_DEFAULT, -1));
    } else {
      _dispatchQueue = dispatch_queue_create(nil, DISPATCH_QUEUE_SERIAL);
    }
    dispatch_set_target_queue(handler.dispatchQueue, _dispatchQueue);
    _canceled = NO;

    [self start];
  }
  return self;
}

- (void)start {
  _call = [[GRPCCall2 alloc] initWithRequestOptions:_requestOptions
                                    responseHandler:self
                                        callOptions:_callOptions];
  [_call start];
}

- (void)cancel {
  dispatch_async(_dispatchQueue, ^{
    if (self->_call) {
      [self->_call cancel];
      self->_call = nil;
    }
    if (self->_handler) {
      @synchronized(self) {
        self->_canceled = YES;
      }
      id<GRPCProtoResponseHandler> handler = self->_handler;
      if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
        dispatch_async(handler.dispatchQueue, ^{
          [handler closedWithTrailingMetadata:nil
                                        error:[NSError errorWithDomain:kGRPCErrorDomain
                                                                  code:GRPCErrorCodeCancelled
                                                              userInfo:@{
                                                                NSLocalizedDescriptionKey :
                                                                    @"Canceled by app"
                                                              }]];
        });
      }
      self->_handler = nil;
    }
  });
}

- (void)writeMessage:(GPBMessage *)message {
  if (![message isKindOfClass:[GPBMessage class]]) {
    [NSException raise:NSInvalidArgumentException format:@"Data must be a valid protobuf type."];
  }

  dispatch_async(_dispatchQueue, ^{
    if (_call) {
      [_call writeData:[message data]];
    }
  });
}

- (void)finish {
  dispatch_async(_dispatchQueue, ^{
    if (_call) {
      [_call finish];
      _call = nil;
    }
  });
}

- (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata {
  if (_handler && initialMetadata != nil) {
    __block id<GRPCResponseHandler> handler = _handler;
    if ([handler respondsToSelector:@selector(initialMetadata:)]) {
      dispatch_async(handler.dispatchQueue, ^{
        // Do not issue initial metadata if the call is already canceled.
        __block BOOL canceled = NO;
        @synchronized(self) {
          canceled = self->_canceled;
        }
        if (!canceled) {
          [handler receivedInitialMetadata:initialMetadata];
        }
      });
    }
  }
}

- (void)receivedRawMessage:(NSData *_Nullable)message {
  if (_handler && message != nil) {
    __block id<GRPCProtoResponseHandler> handler = _handler;
    NSError *error = nil;
    GPBMessage *parsed = [_responseClass parseFromData:message error:&error];
    if (parsed) {
      if ([handler respondsToSelector:@selector(receivedProtoMessage:)]) {
        dispatch_async(handler.dispatchQueue, ^{
          // Do not issue message if the call is already canceled.
          __block BOOL canceled = NO;
          @synchronized(self) {
            canceled = self->_canceled;
          }
          if (!canceled) {
            [handler receivedProtoMessage:parsed];
          }
        });
      }
    } else {
      if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
        dispatch_async(handler.dispatchQueue, ^{
          [handler closedWithTrailingMetadata:nil error:ErrorForBadProto(message, _responseClass, error)];
        });
      }
      _handler = nil;
      [_call cancel];
      _call = nil;
    }
  }
}

- (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                             error:(NSError *_Nullable)error {
  if (_handler) {
    id<GRPCProtoResponseHandler> handler = _handler;
    if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
      dispatch_async(handler.dispatchQueue, ^{
        [handler closedWithTrailingMetadata:trailingMetadata error:error];
      });
    }
    _handler = nil;
  }
  [_call cancel];
  _call = nil;
}

- (dispatch_queue_t)dispatchQueue {
  return _dispatchQueue;
}

@end

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-implementations"
@implementation ProtoRPC {
#pragma clang diagnostic pop
  id<GRXWriteable> _responseWriteable;
}

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-designated-initializers"
- (instancetype)initWithHost:(NSString *)host
                        path:(NSString *)path
              requestsWriter:(GRXWriter *)requestsWriter {
  [NSException raise:NSInvalidArgumentException
              format:@"Please use ProtoRPC's designated initializer instead."];
  return nil;
}
#pragma clang diagnostic pop

// Designated initializer
- (instancetype)initWithHost:(NSString *)host
                      method:(GRPCProtoMethod *)method
              requestsWriter:(GRXWriter *)requestsWriter
               responseClass:(Class)responseClass
          responsesWriteable:(id<GRXWriteable>)responsesWriteable {
  // Because we can't tell the type system to constrain the class, we need to check at runtime:
  if (![responseClass respondsToSelector:@selector(parseFromData:error:)]) {
    [NSException raise:NSInvalidArgumentException
                format:@"A protobuf class to parse the responses must be provided."];
  }
  // A writer that serializes the proto messages to send.
  GRXWriter *bytesWriter = [requestsWriter map:^id(GPBMessage *proto) {
    if (![proto isKindOfClass:[GPBMessage class]]) {
      [NSException raise:NSInvalidArgumentException
                  format:@"Request must be a proto message: %@", proto];
    }
    return [proto data];
  }];
  if ((self = [super initWithHost:host path:method.HTTPPath requestsWriter:bytesWriter])) {
    __weak ProtoRPC *weakSelf = self;

    // A writeable that parses the proto messages received.
    _responseWriteable = [[GRXWriteable alloc] initWithValueHandler:^(NSData *value) {
      // TODO(jcanizales): This is done in the main thread, and needs to happen in another thread.
      NSError *error = nil;
      id parsed = [responseClass parseFromData:value error:&error];
      if (parsed) {
        [responsesWriteable writeValue:parsed];
      } else {
        [weakSelf finishWithError:ErrorForBadProto(value, responseClass, error)];
      }
    }
        completionHandler:^(NSError *errorOrNil) {
          [responsesWriteable writesFinishedWithError:errorOrNil];
        }];
  }
  return self;
}

- (void)start {
  [self startWithWriteable:_responseWriteable];
}

- (void)startWithWriteable:(id<GRXWriteable>)writeable {
  [super startWithWriteable:writeable];
  // Break retain cycles.
  _responseWriteable = nil;
}
@end

@implementation GRPCProtoCall

@end