/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#import "RCTLocationObserver.h"

#import <CoreLocation/CLError.h>
#import <CoreLocation/CLLocationManager.h>
#import <CoreLocation/CLLocationManagerDelegate.h>

#import "RCTAssert.h"
#import "RCTBridge.h"
#import "RCTConvert.h"
#import "RCTEventDispatcher.h"
#import "RCTLog.h"

typedef NS_ENUM(NSInteger, RCTPositionErrorCode) {
  RCTPositionErrorDenied = 1,
  RCTPositionErrorUnavailable,
  RCTPositionErrorTimeout,
};

#define RCT_DEFAULT_LOCATION_ACCURACY kCLLocationAccuracyHundredMeters

typedef struct {
  NSTimeInterval timeout;
  NSTimeInterval maximumAge;
  CLLocationAccuracy accuracy;
} RCTLocationOptions;

static RCTLocationOptions RCTLocationOptionsWithJSON(id json)
{
  NSDictionary *options = [RCTConvert NSDictionary:json];
  return (RCTLocationOptions){
    .timeout = [RCTConvert NSTimeInterval:options[@"timeout"]] ?: INFINITY,
    .maximumAge = [RCTConvert NSTimeInterval:options[@"maximumAge"]] ?: INFINITY,
    .accuracy = [RCTConvert BOOL:options[@"enableHighAccuracy"]] ? kCLLocationAccuracyBest : RCT_DEFAULT_LOCATION_ACCURACY
  };
}

static NSDictionary *RCTPositionError(RCTPositionErrorCode code, NSString *msg /* nil for default */)
{
  if (!msg) {
    switch (code) {
      case RCTPositionErrorDenied:
        msg = @"User denied access to location services.";
        break;
      case RCTPositionErrorUnavailable:
        msg = @"Unable to retrieve location.";
        break;
      case RCTPositionErrorTimeout:
        msg = @"The location request timed out.";
        break;
    }
  }

  return @{
    @"code": @(code),
    @"message": msg,
    @"PERMISSION_DENIED": @(RCTPositionErrorDenied),
    @"POSITION_UNAVAILABLE": @(RCTPositionErrorUnavailable),
    @"TIMEOUT": @(RCTPositionErrorTimeout)
  };
}

@interface RCTLocationRequest : NSObject

@property (nonatomic, copy) RCTResponseSenderBlock successBlock;
@property (nonatomic, copy) RCTResponseSenderBlock errorBlock;
@property (nonatomic, assign) RCTLocationOptions options;
@property (nonatomic, strong) NSTimer *timeoutTimer;

@end

@implementation RCTLocationRequest

- (void)dealloc
{
  [_timeoutTimer invalidate];
}

@end

@interface RCTLocationObserver () <CLLocationManagerDelegate>

@end

@implementation RCTLocationObserver
{
  CLLocationManager *_locationManager;
  NSDictionary *_lastLocationEvent;
  NSMutableArray *_pendingRequests;
  BOOL _observingLocation;
  RCTLocationOptions _observerOptions;
}

RCT_EXPORT_MODULE()

@synthesize bridge = _bridge;

#pragma mark - Lifecycle

- (instancetype)init
{
  if ((self = [super init])) {

    _locationManager = [[CLLocationManager alloc] init];
    _locationManager.distanceFilter = RCT_DEFAULT_LOCATION_ACCURACY;
    _locationManager.delegate = self;

    _pendingRequests = [[NSMutableArray alloc] init];
  }
  return self;
}

- (void)dealloc
{
  [_locationManager stopUpdatingLocation];
}

#pragma mark - Private API

- (void)beginLocationUpdates
{
  // Request location access permission
  if ([_locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
    [_locationManager requestWhenInUseAuthorization];
  }

  // Start observing location
  [_locationManager startUpdatingLocation];
}

#pragma mark - Timeout handler

- (void)timeout:(NSTimer *)timer
{
  RCTLocationRequest *request = timer.userInfo;
  NSString *message = [NSString stringWithFormat: @"Unable to fetch location within %zds.", (NSInteger)(timer.timeInterval * 1000.0)];
  request.errorBlock(@[RCTPositionError(RCTPositionErrorTimeout, message)]);
  [_pendingRequests removeObject:request];

  // Stop updating if no pending requests
  if (_pendingRequests.count == 0 && !_observingLocation) {
    [_locationManager stopUpdatingLocation];
  }
}

#pragma mark - Public API

RCT_EXPORT_METHOD(startObserving:(NSDictionary *)optionsJSON)
{
  [self checkLocationConfig];

  dispatch_async(dispatch_get_main_queue(), ^{

    // Select best options
    _observerOptions = RCTLocationOptionsWithJSON(optionsJSON);
    for (RCTLocationRequest *request in _pendingRequests) {
      _observerOptions.accuracy = MIN(_observerOptions.accuracy, request.options.accuracy);
    }

    _locationManager.desiredAccuracy = _observerOptions.accuracy;
    [self beginLocationUpdates];
    _observingLocation = YES;

  });
}

RCT_EXPORT_METHOD(stopObserving)
{
  dispatch_async(dispatch_get_main_queue(), ^{

    // Stop observing
    _observingLocation = NO;

    // Stop updating if no pending requests
    if (_pendingRequests.count == 0) {
      [_locationManager stopUpdatingLocation];
    }

  });
}

RCT_EXPORT_METHOD(getCurrentPosition:(NSDictionary *)optionsJSON
                  withSuccessCallback:(RCTResponseSenderBlock)successBlock
                  errorCallback:(RCTResponseSenderBlock)errorBlock)
{
  [self checkLocationConfig];

  if (!successBlock) {
    RCTLogError(@"%@.getCurrentPosition called with nil success parameter.", [self class]);
    return;
  }

  dispatch_async(dispatch_get_main_queue(), ^{

    if (![CLLocationManager locationServicesEnabled]) {
      if (errorBlock) {
        errorBlock(@[
          RCTPositionError(RCTPositionErrorUnavailable, @"Location services disabled.")
        ]);
        return;
      }
    }

    if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusDenied) {
      if (errorBlock) {
        errorBlock(@[
          RCTPositionError(RCTPositionErrorDenied, nil)
        ]);
        return;
      }
    }

    // Get options
    RCTLocationOptions options = RCTLocationOptionsWithJSON(optionsJSON);

    // Check if previous recorded location exists and is good enough
    if (_lastLocationEvent &&
        CFAbsoluteTimeGetCurrent() - [RCTConvert NSTimeInterval:_lastLocationEvent[@"timestamp"]] < options.maximumAge &&
        [_lastLocationEvent[@"coords"][@"accuracy"] doubleValue] >= options.accuracy) {

      // Call success block with most recent known location
      successBlock(@[_lastLocationEvent]);
      return;
    }

    // Create request
    RCTLocationRequest *request = [[RCTLocationRequest alloc] init];
    request.successBlock = successBlock;
    request.errorBlock = errorBlock ?: ^(NSArray *args){};
    request.options = options;
    request.timeoutTimer = [NSTimer scheduledTimerWithTimeInterval:options.timeout
                                                            target:self
                                                          selector:@selector(timeout:)
                                                          userInfo:request
                                                           repeats:NO];
    [_pendingRequests addObject:request];

    // Configure location manager and begin updating location
    _locationManager.desiredAccuracy = MIN(_locationManager.desiredAccuracy, options.accuracy);
    [self beginLocationUpdates];

  });
}

#pragma mark - CLLocationManagerDelegate

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
  // Create event
  CLLocation *location = [locations lastObject];
  _lastLocationEvent = @{
    @"coords": @{
      @"latitude": @(location.coordinate.latitude),
      @"longitude": @(location.coordinate.longitude),
      @"altitude": @(location.altitude),
      @"accuracy": @(location.horizontalAccuracy),
      @"altitudeAccuracy": @(location.verticalAccuracy),
      @"heading": @(location.course),
      @"speed": @(location.speed),
    },
    @"timestamp": @(CFAbsoluteTimeGetCurrent() * 1000.0) // in ms
  };

  // Send event
  if (_observingLocation) {
    [_bridge.eventDispatcher sendDeviceEventWithName:@"geolocationDidChange"
                                                body:_lastLocationEvent];
  }

  // Fire all queued callbacks
  for (RCTLocationRequest *request in _pendingRequests) {
    request.successBlock(@[_lastLocationEvent]);
  }
  [_pendingRequests removeAllObjects];

  // Stop updating if not not observing
  if (!_observingLocation) {
    [_locationManager stopUpdatingLocation];
  }

  // Reset location accuracy
  _locationManager.desiredAccuracy = RCT_DEFAULT_LOCATION_ACCURACY;
}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
  // Check error type
  NSDictionary *jsError = nil;
  switch (error.code) {
    case kCLErrorDenied:
      jsError = RCTPositionError(RCTPositionErrorDenied, nil);
      break;
    case kCLErrorNetwork:
      jsError = RCTPositionError(RCTPositionErrorUnavailable, @"Unable to retrieve location due to a network failure");
      break;
    case kCLErrorLocationUnknown:
    default:
      jsError = RCTPositionError(RCTPositionErrorUnavailable, nil);
      break;
  }

  // Send event
  if (_observingLocation) {
    [_bridge.eventDispatcher sendDeviceEventWithName:@"geolocationError"
                                                body:jsError];
  }

  // Fire all queued error callbacks
  for (RCTLocationRequest *request in _pendingRequests) {
    request.errorBlock(@[jsError]);
  }
  [_pendingRequests removeAllObjects];

  // Reset location accuracy
  _locationManager.desiredAccuracy = RCT_DEFAULT_LOCATION_ACCURACY;
}

- (void)checkLocationConfig
{
  if (![[NSBundle mainBundle] objectForInfoDictionaryKey:@"NSLocationWhenInUseUsageDescription"]) {
    RCTLogError(@"NSLocationWhenInUseUsageDescription key must be present in Info.plist to use geolocation.");
  }
}

@end
