grpc/src/objective-c/ProtoRPC/ProtoRPC.m

/*
 *
 * Copyright 2015, 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,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */

#import "ProtoRPC.h"

#import <Protobuf/GPBProtocolBuffers.h>
#import <RxLibrary/GRXWriteable.h>
#import <RxLibrary/GRXWriter+Transformations.h>

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 ProtoRPC {
  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:(ProtoMethod *)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