/*
 *
 * Copyright 2015-2016, 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,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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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.
 *
 */

#import "GRPCChannel.h"

#include <grpc/grpc_security.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/string_util.h>

#import "GRPCCompletionQueue.h"

/**
 * Returns @c grpc_channel_credentials from the specified @c path. If the file at the path could not
 * be read then NULL is returned. If NULL is returned, @c errorPtr may not be NULL if there are
 * details available describing what went wrong.
 */
static grpc_channel_credentials *CertificatesAtPath(NSString *path, NSError **errorPtr) {
  // Files in PEM format can have non-ASCII characters in their comments (e.g. for the name of the
  // issuer). Load them as UTF8 and produce an ASCII equivalent.
  NSString *contentInUTF8 = [NSString stringWithContentsOfFile:path
                                                      encoding:NSUTF8StringEncoding
                                                         error:errorPtr];
  NSData *contentInASCII = [contentInUTF8 dataUsingEncoding:NSASCIIStringEncoding
                                       allowLossyConversion:YES];
  if (!contentInASCII.bytes) {
    // Passing NULL to grpc_ssl_credentials_create produces behavior we don't want, so return.
    return NULL;
  }
  return grpc_ssl_credentials_create(contentInASCII.bytes, NULL, NULL);
}

void freeChannelArgs(grpc_channel_args *channel_args) {
  for (size_t i = 0; i < channel_args->num_args; ++i) {
    grpc_arg *arg = &channel_args->args[i];
    gpr_free(arg->key);
    if (arg->type == GRPC_ARG_STRING) {
      gpr_free(arg->value.string);
    }
  }
  gpr_free(channel_args);
}

/**
 * Allocates a @c grpc_channel_args and populates it with the options specified in the
 * @c dictionary. Keys must be @c NSString. If the value responds to @c @selector(UTF8String) then
 * it will be mapped to @c GRPC_ARG_STRING. If not, it will be mapped to @c GRPC_ARG_INTEGER if the
 * value responds to @c @selector(intValue). Otherwise, an exception will be raised. The caller of
 * this function is responsible for calling @c freeChannelArgs on a non-NULL returned value.
 */
grpc_channel_args * buildChannelArgs(NSDictionary *dictionary) {
  if (!dictionary) {
    return NULL;
  }

  NSArray *keys = [dictionary allKeys];
  NSUInteger argCount = [keys count];

  grpc_channel_args *channelArgs = gpr_malloc(sizeof(grpc_channel_args));
  channelArgs->num_args = argCount;
  channelArgs->args = gpr_malloc(argCount * sizeof(grpc_arg));

  // TODO(kriswuollett) Check that keys adhere to GRPC core library requirements

  for (NSUInteger i = 0; i < argCount; ++i) {
    grpc_arg *arg = &channelArgs->args[i];
    arg->key = gpr_strdup([keys[i] UTF8String]);

    id value = dictionary[keys[i]];
    if ([value respondsToSelector:@selector(UTF8String)]) {
      arg->type = GRPC_ARG_STRING;
      arg->value.string = gpr_strdup([value UTF8String]);
    } else if ([value respondsToSelector:@selector(intValue)]) {
      arg->type = GRPC_ARG_INTEGER;
      arg->value.integer = [value intValue];
    } else {
      [NSException raise:NSInvalidArgumentException
                  format:@"Invalid value type: %@", [value class]];
    }
  }

  return channelArgs;
}

@implementation GRPCChannel {
  // Retain arguments to channel_create because they may not be used on the thread that invoked
  // the channel_create function.
  NSString *_host;
  grpc_channel_args *_channelArgs;
}


- (instancetype)initWithHost:(NSString *)host
                      secure:(BOOL)secure
                 credentials:(struct grpc_channel_credentials *)credentials
                 channelArgs:(NSDictionary *)channelArgs {
  if (!host) {
    [NSException raise:NSInvalidArgumentException format:@"host argument missing"];
  }

  if (secure && !credentials) {
    return nil;
  }

  if (self = [super init]) {
    _channelArgs = buildChannelArgs(channelArgs);
    _host = [host copy];
    if (secure) {
      _unmanagedChannel = grpc_secure_channel_create(credentials, _host.UTF8String, _channelArgs,
                                                     NULL);
    } else {
      _unmanagedChannel = grpc_insecure_channel_create(_host.UTF8String, _channelArgs, NULL);
    }
  }

  return self;
}

- (void)dealloc {
  // TODO(jcanizales): Be sure to add a test with a server that closes the connection prematurely,
  // as in the past that made this call to crash.
  grpc_channel_destroy(_unmanagedChannel);
  freeChannelArgs(_channelArgs);
}

+ (GRPCChannel *)secureChannelWithHost:(NSString *)host {
  return [[GRPCChannel alloc] initWithHost:host secure:YES credentials:NULL channelArgs:NULL];
}

+ (GRPCChannel *)secureChannelWithHost:(NSString *)host
                    pathToCertificates:(NSString *)path
                           channelArgs:(NSDictionary *)channelArgs {
  // Load default SSL certificates once.
  static grpc_channel_credentials *kDefaultCertificates;
  static dispatch_once_t loading;
  dispatch_once(&loading, ^{
    NSString *defaultPath = @"gRPCCertificates.bundle/roots"; // .pem
    // Do not use NSBundle.mainBundle, as it's nil for tests of library projects.
    NSBundle *bundle = [NSBundle bundleForClass:self.class];
    NSString *path = [bundle pathForResource:defaultPath ofType:@"pem"];
    NSError *error;
    kDefaultCertificates = CertificatesAtPath(path, &error);
    NSAssert(kDefaultCertificates, @"Could not read %@/%@.pem. This file, with the root "
             "certificates, is needed to establish secure (TLS) connections. Because the file is "
             "distributed with the gRPC library, this error is usually a sign that the library "
             "wasn't configured correctly for your project. Error: %@",
             bundle.bundlePath, defaultPath, error);
  });

  //TODO(jcanizales): Add NSError** parameter to the initializer.
  grpc_channel_credentials *certificates = path
      ? CertificatesAtPath(path, NULL)
      : kDefaultCertificates;

  return [[GRPCChannel alloc] initWithHost:host
                                    secure:YES
                               credentials:certificates
                               channelArgs:channelArgs];
}


+ (GRPCChannel *)secureChannelWithHost:(NSString *)host
                           credentials:(struct grpc_channel_credentials *)credentials
                           channelArgs:(NSDictionary *)channelArgs {
  return [[GRPCChannel alloc] initWithHost:host
                                    secure:YES
                               credentials:credentials
                               channelArgs:channelArgs];

}

+ (GRPCChannel *)insecureChannelWithHost:(NSString *)host
                             channelArgs:(NSDictionary *)channelArgs {
  return [[GRPCChannel alloc] initWithHost:host
                                    secure:NO
                               credentials:NULL
                               channelArgs:channelArgs];
}

- (grpc_call *)unmanagedCallWithPath:(NSString *)path
                     completionQueue:(GRPCCompletionQueue *)queue {
  return grpc_channel_create_call(_unmanagedChannel,
                                  NULL, GRPC_PROPAGATE_DEFAULTS,
                                  queue.unmanagedQueue,
                                  path.UTF8String,
                                  // Get "host" from "host:port"
                                  // TODO(jcanizales): Use NSURLs throughout, to clarify these.
                                  [_host componentsSeparatedByString:@":"][0].UTF8String,
                                  gpr_inf_future(GPR_CLOCK_REALTIME), NULL);
}

@end