/*

     File: SubtitlesTextReader.m

 Abstract: A class for reading subtitles text, in the form of an NSString. It will turn the text into CMSampleBufferRefs, and extract language code, extended language tag, and other metadata. See subtitles_text_en-US.txt for an example of the subtitles file format this class expects.

  Version: 1.0.1

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 */

#import "SubtitlesTextReader.h"

#import <AVFoundation/AVFoundation.h>

@interface Subtitle : NSObject

+ (instancetype)subtitleWithText:(NSString *)text timeRange:(CMTimeRange)timeRange forced:(BOOL)forced;

- (CMFormatDescriptionRef)copyFormatDescription;

- (CMSampleBufferRef)copySampleBuffer;

@property NSString *text;

@property CMTimeRange timeRange;

@property BOOL forced;

@property CMTextDisplayFlags displayFlags;

@end

@implementation SubtitlesTextReader

{

    NSUInteger _index;

    NSArray *_subtitles;

    BOOL _wantsSDH;

}

- (instancetype)initWithText:(NSString *)text

{

    self = [super init];

    if (self)

    {

        _index = 0;

        if (text)

        {

            NSMutableArray *mutableSubtitles = [NSMutableArray array];

            // Check for a language

            NSRegularExpression *languageExpression = [NSRegularExpression regularExpressionWithPattern:@"language: (.*)" options:0 error:nil];

            NSTextCheckingResult *languageResult = [languageExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])];

            _languageCode = [text substringWithRange:[languageResult rangeAtIndex:1]];

            // Check for an extended language

            NSRegularExpression *extendedLanguageExpression = [NSRegularExpression regularExpressionWithPattern:@"extended language: (.*)" options:0 error:nil];

            NSTextCheckingResult *extendedLanguageResult = [extendedLanguageExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])];

            _extendedLanguageTag = [text substringWithRange:[extendedLanguageResult rangeAtIndex:1]];

            // See if SDH has been requested

            NSRegularExpression *characteristicsExpression = [NSRegularExpression regularExpressionWithPattern:@"characteristics:.*(SDH)" options:NSRegularExpressionCaseInsensitive error:nil];

            NSTextCheckingResult *characteristicsResult = [characteristicsExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])];

            _wantsSDH = ([[text substringWithRange:[characteristicsResult rangeAtIndex:1]] caseInsensitiveCompare:@"SDH"] == NSOrderedSame) ? YES : NO;

            // Find the subtitle time ranges and text

            __block int forcedCount = 0;

            NSRegularExpression *subtitlesExpression = [NSRegularExpression regularExpressionWithPattern:@"(..):(..):(..),(...) --> (..):(..):(..),(...)( !!!)?\n(.*)" options:0 error:nil];

            [subtitlesExpression enumerateMatchesInString:text options:0 range:NSMakeRange(0, [text length]) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {

                // Get the text

                NSString *subtitleText = [text substringWithRange:[result rangeAtIndex:10]];

                // Create the time range

                double startTime = ([[text substringWithRange:[result rangeAtIndex:1]] doubleValue] * 60.0 * 60.0) + ([[text substringWithRange:[result rangeAtIndex:2]] doubleValue] * 60.0) + [[text substringWithRange:[result rangeAtIndex:3]] doubleValue] + ([[text substringWithRange:[result rangeAtIndex:4]] doubleValue] / 1000.0);

                double endTime = ([[text substringWithRange:[result rangeAtIndex:5]] doubleValue] * 60.0 * 60.0) + ([[text substringWithRange:[result rangeAtIndex:6]] doubleValue] * 60.0) + [[text substringWithRange:[result rangeAtIndex:7]] doubleValue] + ([[text substringWithRange:[result rangeAtIndex:8]] doubleValue] / 1000.0);

                CMTimeRange timeRange = CMTimeRangeMake(CMTimeMakeWithSeconds(startTime, 600), CMTimeMakeWithSeconds(endTime - startTime, 600));

                // Is it forced?

                BOOL forced = NO;

                if (([result rangeAtIndex:9].length > 0) && [[text substringWithRange:[result rangeAtIndex:9]] isEqualToString:@" !!!"])

                {

                    forced = YES;

                    forcedCount++;

                }

                // Stash a Subtitle object for later use by -copyNextSampleBuffer

                [mutableSubtitles addObject:[Subtitle subtitleWithText:subtitleText timeRange:timeRange forced:forced]];

            }];

            // Set forced subtitles display flags as appropriate.

            if ([mutableSubtitles count] == forcedCount)

            {

                for (Subtitle *subtitle in mutableSubtitles)

                {

                    subtitle.displayFlags = kCMTextDisplayFlag_forcedSubtitlesPresent | kCMTextDisplayFlag_allSubtitlesForced;

                }

            }

            else if (forcedCount > 0)

            {

                for (Subtitle *subtitle in mutableSubtitles)

                {

                    subtitle.displayFlags = kCMTextDisplayFlag_forcedSubtitlesPresent;

                }

            }

            _subtitles = [mutableSubtitles copy];

        }

    }

    return self;

}

+ (instancetype)subtitlesTextReaderWithText:(NSString *)text

{

    return [[[self class] alloc] initWithText:text];

}

- (CMFormatDescriptionRef)copyFormatDescription

{

    // Take the format description from the first object. They are all the same since the display flag are all the same.

    return [[_subtitles firstObject] copyFormatDescription];

}

- (NSArray *)metadata

{

    NSMutableArray *mutableMetadata = [NSMutableArray array];

    // All subtitles must have the AVMediaCharacteristicTranscribesSpokenDialogForAccessibility characteristic.

    AVMutableMetadataItem *spokenItem = [AVMutableMetadataItem metadataItem];

    [spokenItem setKey:AVMetadataQuickTimeUserDataKeyTaggedCharacteristic];

    [spokenItem setKeySpace:AVMetadataKeySpaceQuickTimeUserData];

    [spokenItem setValue:AVMediaCharacteristicTranscribesSpokenDialogForAccessibility];

    [mutableMetadata addObject:spokenItem];

    if (_wantsSDH)

    {

        // SDH subtitles must also have the AVMediaCharacteristicDescribesMusicAndSoundForAccessibility characteristic.

        AVMutableMetadataItem *describesItem = [AVMutableMetadataItem metadataItem];

        [describesItem setKey:AVMetadataQuickTimeUserDataKeyTaggedCharacteristic];

        [describesItem setKeySpace:AVMetadataKeySpaceQuickTimeUserData];

        [describesItem setValue:AVMediaCharacteristicDescribesMusicAndSoundForAccessibility];

        [mutableMetadata addObject:describesItem];

    }

    return [mutableMetadata copy];

}

- (CMSampleBufferRef)copyNextSampleBuffer

{

    CMSampleBufferRef sampleBuffer = NULL;

    if (_index < _subtitles.count)

    {

        sampleBuffer = [(Subtitle *)_subtitles[_index] copySampleBuffer];

        _index++;

    }

    return sampleBuffer;

}

@end

@implementation Subtitle

+ (instancetype)subtitleWithText:(NSString *)text timeRange:(CMTimeRange)timeRange forced:(BOOL)forced

{

    Subtitle *subtitle = [[Subtitle alloc] init];

    subtitle.text = text;

    subtitle.timeRange = timeRange;

    subtitle.forced = forced;

    return subtitle;

}

- (CMFormatDescriptionRef)copyFormatDescription

{

    // Create a subtitle 3g text format description with extensions

    NSDictionary *extensions = @{(id)kCMTextFormatDescriptionExtension_DisplayFlags : @(self.displayFlags),

                                 (id)kCMTextFormatDescriptionExtension_BackgroundColor : @{

                                         (id)kCMTextFormatDescriptionColor_Red : @0,

                                         (id)kCMTextFormatDescriptionColor_Green : @0,

                                         (id)kCMTextFormatDescriptionColor_Blue : @0,

                                         (id)kCMTextFormatDescriptionColor_Alpha : @255},

                                 (id)kCMTextFormatDescriptionExtension_DefaultTextBox : @{

                                         (id)kCMTextFormatDescriptionRect_Top : @0,

                                         (id)kCMTextFormatDescriptionRect_Left : @0,

                                         (id)kCMTextFormatDescriptionRect_Bottom : @0,

                                         (id)kCMTextFormatDescriptionRect_Right : @0},

                                 (id)kCMTextFormatDescriptionExtension_DefaultStyle : @{

                                         (id)kCMTextFormatDescriptionStyle_StartChar : @0,

                                         (id)kCMTextFormatDescriptionStyle_EndChar : @0,

                                         (id)kCMTextFormatDescriptionStyle_Font : @1,

                                         (id)kCMTextFormatDescriptionStyle_FontFace : @0,

                                         (id)kCMTextFormatDescriptionStyle_ForegroundColor : @{

                                                 (id)kCMTextFormatDescriptionColor_Red : @255,

                                                 (id)kCMTextFormatDescriptionColor_Green : @255,

                                                 (id)kCMTextFormatDescriptionColor_Blue : @255,

                                                 (id)kCMTextFormatDescriptionColor_Alpha : @255},

                                         (id)kCMTextFormatDescriptionStyle_FontSize : @255},

                                 (id)kCMTextFormatDescriptionExtension_HorizontalJustification : @0,

                                 (id)kCMTextFormatDescriptionExtension_VerticalJustification : @0,

                                 (id)kCMTextFormatDescriptionExtension_FontTable : @{@"1" : @"Sans-Serif"}};

    CMFormatDescriptionRef formatDescription;

    CMFormatDescriptionCreate(NULL, kCMMediaType_Subtitle, kCMTextFormatType_3GText, (__bridge CFDictionaryRef)extensions, &formatDescription);

    return formatDescription;

}

- (CMSampleBufferRef)copySampleBuffer

{

    const char *text = self.text.UTF8String;

    // Setup the sample size

    uint16_t textLength = 0;

    size_t sampleSize = 0;

    if (text != NULL)

        textLength = strlen(text); // don't include terminator in the length

    sampleSize = textLength + sizeof(uint16_t);

    if (self.forced)

        sampleSize += (sizeof (uint32_t) * 2); // for the 'frcd' atom

    uint8_t *samplePtr = malloc(sampleSize); // malloc space for length of text, text, and extensions. This variable should be char *, uint8_t *, UInt8 * for byte alignment reasons.

    uint16_t textLengthBigEndian = CFSwapInt16HostToBig(textLength);

    memcpy(samplePtr, &textLengthBigEndian, sizeof(textLengthBigEndian));

    if (textLength)

        memcpy ((samplePtr + sizeof(uint16_t)), text, textLength);

    uint8_t *ptr = samplePtr + sizeof (uint16_t) + textLength;

    if (self.forced)

    {

        // Make room for the forced atom.

        (*(uint32_t *) ptr) = CFSwapInt32HostToBig((sizeof (uint32_t) * 2));

        ptr += sizeof(uint32_t);

        // Set the forced atom.

        (*(uint32_t *) ptr) = CFSwapInt32HostToBig('frcd');

    }

    CMBlockBufferRef dataBuffer;

    CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, samplePtr, sampleSize, kCFAllocatorMalloc, NULL, 0, sampleSize, 0, &dataBuffer);

    CMSampleTimingInfo sampleTiming;

    sampleTiming.duration = self.timeRange.duration;

    sampleTiming.presentationTimeStamp = self.timeRange.start;

    sampleTiming.decodeTimeStamp = kCMTimeInvalid;

    CMFormatDescriptionRef formatDescription = [self copyFormatDescription];

    CMSampleBufferRef sampleBuffer;

    CMSampleBufferCreate(kCFAllocatorDefault, dataBuffer, true, NULL, 0, formatDescription, 1, 1, &sampleTiming, 1, &sampleSize, &sampleBuffer);

    if (formatDescription)

        CFRelease(formatDescription);

    if (dataBuffer)

        CFRelease(dataBuffer);

    return sampleBuffer;

}

@end