//
// Copyright 2010-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License").
// You may not use this file except in compliance with the License.
// A copy of the License is located at
//
// http://aws.amazon.com/apache2.0
//
// or in the "license" file accompanying this file. This file 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 "AWSCocoaLumberjack.h"
#import "AWSMQTTDecoder.h"

@interface AWSMQTTDecoder() {
        NSInputStream*  stream;
        UInt8           header;
        UInt32          length;
        UInt32          lengthMultiplier;
        NSMutableData*  dataBuffer;
    
}

@end

@implementation AWSMQTTDecoder

int maxLengthMultiplier = 128 * 128 * 128;

- (id)initWithStream:(NSInputStream*)aStream
{
    _status = AWSMQTTDecoderStatusInitializing;
    stream = aStream;
    [stream setDelegate:self];
    return self;
}

- (void)open {
    AWSDDLogDebug(@"opening decoder stream.");
    [stream setDelegate:self];
    [stream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [stream open];
}

- (void)close {
    AWSDDLogDebug(@"closing decoder stream.");
    [stream setDelegate:nil];
    [stream close];
    stream = nil;
}

- (void)stream:(NSStream*)sender handleEvent:(NSStreamEvent)eventCode {
    AWSDDLogVerbose(@"%s [Line %d] EventCode:%lu, status:%lu, stream: %@, Thread: %@",
                    __PRETTY_FUNCTION__,
                    __LINE__,
                    (unsigned long)eventCode,
                    (unsigned long)_status,
                    sender,
                    [NSThread currentThread]);

    if (stream == nil) {
        return;
    }

    switch (eventCode) {
        case NSStreamEventOpenCompleted:
            _status = AWSMQTTDecoderStatusDecodingHeader;
            length = 0;
            lengthMultiplier = 1;
            break;
        case NSStreamEventHasBytesAvailable:
            if (_status == AWSMQTTDecoderStatusDecodingHeader) {
                NSInteger n = [stream read:&header maxLength:1];
                if (n == -1) {
                    _status = AWSMQTTDecoderStatusConnectionError;
                    [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionError];
                }
                else if (n == 1) {
                    length = 0;
                    lengthMultiplier = 1;
                    _status = AWSMQTTDecoderStatusDecodingLength;
                }
            }
            while (_status == AWSMQTTDecoderStatusDecodingLength) {
                UInt8 digit;
                NSInteger n = [stream read:&digit maxLength:1];
                if (n == -1) {
                    _status = AWSMQTTDecoderStatusConnectionError;
                    [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionError];
                    break;
                }
                else if (n == 0) {
                    break;
                }
                length += (digit & 0x7f) * lengthMultiplier;
                if ((digit & 0x80) == 0x00) {
                    dataBuffer = [NSMutableData dataWithCapacity:length];
                    _status = AWSMQTTDecoderStatusDecodingData;
                }
                else {
                    lengthMultiplier *= 128;
                    if (lengthMultiplier > maxLengthMultiplier) {
                        AWSDDLogError(@"Malformed Remaining Length");
                        _status = AWSMQTTDecoderStatusConnectionError;
                        lengthMultiplier = 1;
                        length = 0;
                        [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionError];
                        break;
                    }
                }
            }
            if (_status == AWSMQTTDecoderStatusDecodingData) {
                if (length > 0) {
                    NSInteger n, toRead;
                    UInt8 buffer[768];
                    toRead = length - [dataBuffer length];
                    if (toRead > sizeof buffer) {
                        toRead = sizeof buffer;
                    }
                    n = [stream read:buffer maxLength:toRead];
                    if (n == -1) {
                        _status = AWSMQTTDecoderStatusConnectionError;
                        [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionError];
                    }
                    else {
                        [dataBuffer appendBytes:buffer length:n];
                    }
                }
                if ([dataBuffer length] == length) {
                    AWSMQTTMessage* msg;
                    UInt8 type, qos;
                    BOOL isDuplicate, retainFlag;
                    type = (header >> 4) & 0x0f;
                    isDuplicate = NO;
                    if ((header & 0x08) == 0x08) {
                        isDuplicate = YES;
                    }
                    // XXX qos > 2
                    qos = (header >> 1) & 0x03;
                    retainFlag = NO;
                    if ((header & 0x01) == 0x01) {
                        retainFlag = YES;
                    }
                    msg = [[AWSMQTTMessage alloc] initWithType:type
                                                           qos:qos
                                                    retainFlag:retainFlag
                                                       dupFlag:isDuplicate
                                                          data:dataBuffer];
                    [_delegate decoder:self newMessage:msg];
                    dataBuffer = nil;
                    _status = AWSMQTTDecoderStatusDecodingHeader;
                }
            }
            break;
        case NSStreamEventEndEncountered:
            _status = AWSMQTTDecoderStatusConnectionClosed;
            [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionClosed];
            break;
        case NSStreamEventErrorOccurred:
            _status = AWSMQTTDecoderStatusConnectionError;
            [_delegate decoder:self handleEvent:AWSMQTTDecoderEventConnectionError];
            break;
        default:
            AWSDDLogDebug(@"unhandled event code");
            break;
    }
}

@end