Kordophone/kordophone/Bridge/MBIMUpdateQueue.m

//
//  MBIMUpdateQueue.m
//  kordophoned
//
//  Created by James Magahern on 11/16/18.
//  Copyright © 2018 James Magahern. All rights reserved.
//

#import "MBIMUpdateQueue.h"
#import "IMMessageItem+Encoded.h"
#import "IMChat+Encoded.h"
#import "MBIMHTTPConnection.h"
#import "MBIMURLUtilities.h"

#import <CocoaHTTPServer/GCDAsyncSocket.h>
#import <CocoaHTTPServer/HTTPMessage.h>
#import <CocoaHTTPServer/WebSocket.h>

static const NSUInteger kUpdateItemsCullingLength = 100;

@interface MBIMUpdateItem (/*INTERNAL*/) <WebSocketDelegate>
@property (nonatomic, assign) NSUInteger messageSequenceNumber;
@end

@implementation MBIMUpdateQueue {
    NSUInteger           _messageSequenceNumber;
    dispatch_queue_t     _accessQueue;
    NSMutableArray      *_longPollConsumers;
    
    // Maps message sequence number to update item
    NSMutableDictionary<NSNumber *, MBIMUpdateItem *> *_updateItemHistory;
    
    // WebSocket consumers
    NSMutableDictionary<NSString *, MBIMUpdateConsumer> *_websocketConsumers;
}

+ (instancetype)sharedInstance
{
    static MBIMUpdateQueue *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
    });
    
    return sharedInstance;
}

- (instancetype)init
{
    self = [super init];
    if (self) {
        _accessQueue = dispatch_queue_create("net.buzzert.MBIMUpdateQueue", DISPATCH_QUEUE_SERIAL);
        _messageSequenceNumber = 0;
        _updateItemHistory = [[NSMutableDictionary alloc] init];
        _websocketConsumers = [[NSMutableDictionary alloc] init];
        _longPollConsumers = [[NSMutableArray alloc] init];
    }
    
    return self;
}

- (void)addPollingConsumer:(MBIMUpdateConsumer)consumer withLastSyncedMessageSeq:(NSInteger)messageSeq
{
    if (![self _syncConsumer:consumer fromLastMessageSeq:messageSeq]) {
        __weak NSMutableArray *consumers = _longPollConsumers;
        dispatch_async(_accessQueue, ^{
            [consumers addObject:consumer];
        });
    }
}

- (void)removePollingConsumer:(MBIMUpdateConsumer)consumer
{
    __weak NSMutableArray *consumers = _longPollConsumers;
    dispatch_async(_accessQueue, ^{
        [consumers removeObject:consumer];
    });
}

- (void)enqueueUpdateItem:(MBIMUpdateItem *)item
{
    __weak __auto_type pollingConsumers = _longPollConsumers;
    __weak __auto_type websocketConsumers = _websocketConsumers;
    __weak NSMutableDictionary *updateItemHistory = _updateItemHistory;
    dispatch_async(_accessQueue, ^{
        self->_messageSequenceNumber++;
        item.messageSequenceNumber = self->_messageSequenceNumber;
        
        // Notify polling consumers
        for (MBIMUpdateConsumer consumer in pollingConsumers) {
            consumer(@[ item ]);
        }
        [pollingConsumers removeAllObjects];
        
        // Notify websocket consumers
        for (MBIMUpdateConsumer consumer in [websocketConsumers allValues]) {
            consumer(@[ item ]);
        }
        
        [updateItemHistory setObject:item forKey:@(item.messageSequenceNumber)];
        
        [self _cullUpdateItems];
    });
}

- (WebSocket *)vendUpdateWebSocketConsumerForRequest:(HTTPMessage *)request socket:(GCDAsyncSocket *)gcdSocket
{
    WebSocket *socket = [[WebSocket alloc] initWithRequest:request socket:gcdSocket];
    socket.delegate = self;
    
    MBIMUpdateConsumer consumer = ^(NSArray<MBIMUpdateItem *> *updates) {
        NSMutableArray *encodedUpdates = [NSMutableArray array];
        for (MBIMUpdateItem *item in updates) {
            NSDictionary *updateDict = [item dictionaryRepresentation];
            [encodedUpdates addObject:updateDict];
        }
        
        NSData *data = [NSJSONSerialization dataWithJSONObject:encodedUpdates options:0 error:NULL];
        [socket sendData:data];
    };
    
    NSString *messageSeqString = [[request url] valueForQueryItemWithName:@"seq"];
    [self _syncConsumer:consumer fromLastMessageSeq:(messageSeqString ? [messageSeqString integerValue] : -1)];
    
    __weak __auto_type websocketConsumers = _websocketConsumers;
    dispatch_async(_accessQueue, ^{
        NSString *websocketKey = [socket description];
        [websocketConsumers setObject:consumer forKey:websocketKey];
    });
    
    return socket;
}

- (BOOL)_syncConsumer:(MBIMUpdateConsumer)consumer fromLastMessageSeq:(NSInteger)messageSeq
{
    const BOOL needsSync = (messageSeq >= 0) && messageSeq < self->_messageSequenceNumber;
    if (needsSync) {
        __weak NSMutableDictionary *updateItemHistory = _updateItemHistory;
        dispatch_async(_accessQueue, ^{
            NSMutableArray *batchedUpdates = [NSMutableArray array];
            for (NSUInteger seq = messageSeq + 1; seq <= self->_messageSequenceNumber; seq++) {
                MBIMUpdateItem *item = [updateItemHistory objectForKey:@(seq)];
                if (item) {
                    [batchedUpdates addObject:item];
                }
            }
            
            consumer(batchedUpdates);
        });
    }
    
    return needsSync;
}

- (void)_cullUpdateItems
{
    __weak NSMutableDictionary *updateItemHistory = _updateItemHistory;
    dispatch_async(_accessQueue, ^{
        if ([updateItemHistory count] > kUpdateItemsCullingLength) {
            NSArray *sortedKeys = [[updateItemHistory allKeys] sortedArrayUsingSelector:@selector(compare:)];
            for (NSValue *key in sortedKeys) {
                [updateItemHistory removeObjectForKey:key];
                if ([updateItemHistory count] <= kUpdateItemsCullingLength) {
                    break;
                }
            }
        }
    });
}

#pragma mark - <WebSocketDelegate>

- (void)webSocketDidClose:(WebSocket *)ws
{
    // xxx: not great, but works.
    NSString *websocketKey = [ws description];
    __weak __auto_type websocketConsumers = _websocketConsumers;
    dispatch_async(_accessQueue, ^{
        [websocketConsumers removeObjectForKey:websocketKey];
    });
}

@end

@implementation MBIMUpdateItem
- (NSDictionary *)dictionaryRepresentation
{
    NSMutableDictionary *updateDict = [NSMutableDictionary dictionary];
    updateDict[@"messageSequenceNumber"] = @(self.messageSequenceNumber);
    
    if ([self changedChat]) {
        updateDict[@"conversation"] = [[self changedChat] mbim_dictionaryRepresentation];
    }
    
    if ([self addedMessage]) {
        updateDict[@"message"] = [[self addedMessage] mbim_dictionaryRepresentation];
    }
    
    return updateDict;
}

@end