iOS日历中的日程生成VCalendar 2.0（.vcs）格式的字符串和解析

// 获取 VCalendar2.0 的格式字符串
+ (NSString *)getVCalendar20StrWithEvents:(NSArray<EKEvent *> *)events {
    NSString *vcalendar = [NSString stringWithFormat:@"X-SIZE:%lu\n", (unsigned long)events.count];
    
    //版本头
    vcalendar = [vcalendar stringByAppendingString:@"BEGIN:VCALENDAR\nVERSION:2.0\nPRODID:-//STKJ//iOS//EN\n"];
    
    NSString *formatterStr = @"yyyyMMdd HHmmss";
    NSDate *currentDate = [[NSDate alloc] init];
    NSString *currentDateStr = [NSDate stringFromDate:currentDate andFormatterString:formatterStr];
    currentDateStr = [currentDateStr stringByReplacingOccurrencesOfString:@" " withString:@"T"];
    currentDateStr = [currentDateStr stringByAppendingString:@"Z"];
   vcalendar = [vcalendar stringByAppendingFormat:@"BEGIN:VTIMEZONE\nTZID:UTC\nBEGIN:STANDARD\nDTSTART:%@\nTZOFFSETFROM:+0800\nTZOFFSETTO:+0800\nEND:STANDARD\nBEGIN:DAYLIGHT\nDTSTART:%@\nTZOFFSETFROM:+0800\nTZOFFSETTO:+0800\nEND:DAYLIGHT\nEND:VTIMEZONE\n", currentDateStr, currentDateStr];
    
    for(CFIndex i = 0; i < events.count; i++) {
        EKEvent *event = events[i];
        NSString *title = event.title;
        title = title == nil ? @"" : title;
        NSString *notes = event.notes;
        notes = notes == nil ? @"" : notes;
//        NSString *location = event.location;
        NSURL *url = event.URL;
//        NSDate *lastModifiedDate = event.lastModifiedDate;
//        NSDate *creationDate = event.creationDate;
        NSDate *startDate = event.startDate;
        startDate = startDate == nil ? [[NSDate alloc] init] : startDate;
        NSDate *endDate = event.endDate;
        endDate = endDate == nil ? [[NSDate alloc] init] : endDate;
//        NSTimeZone *timeZone = event.timeZone;
        
        // 编码
        title = [NSString URLencode:title stringEncoding:NSUTF8StringEncoding];
        title = [title stringByReplacingOccurrencesOfString:@"%" withString:@"="];
        notes = [NSString URLencode:notes stringEncoding:NSUTF8StringEncoding];
        notes = [notes stringByReplacingOccurrencesOfString:@"%" withString:@"="];
        
        // 开始时间
        NSString *startDateStr = [NSDate stringFromDate:startDate andFormatterString:formatterStr];
        startDateStr = [startDateStr stringByReplacingOccurrencesOfString:@" " withString:@"T"];
        startDateStr = [startDateStr stringByAppendingString:@"Z"];
        // 结束时间
        NSString *endDateStr = [NSDate stringFromDate:endDate andFormatterString:formatterStr];
        endDateStr = [endDateStr stringByReplacingOccurrencesOfString:@" " withString:@"T"];
        endDateStr = [endDateStr stringByAppendingString:@"Z"];
        vcalendar = [vcalendar stringByAppendingFormat:@"BEGIN:VEVENT\nDESCRIPTION;ENCODING=QUOTED-PRINTABLE;CHARSET=UTF-8:%@\nDTEND:%@\nDTSTAMP:%@\nX-ALLDAY:0\nDTSTART:%@\n", title, endDateStr, startDateStr, startDateStr];
        
        // url
        if (url != nil) {
            vcalendar = [vcalendar stringByAppendingFormat:@"UID: %@\n", url.absoluteString];
        }
        
        // 笔记
        if (event.hasNotes) {
            vcalendar = [vcalendar stringByAppendingFormat:@"SUMMARY;ENCODING=QUOTED-PRINTABLE;CHARSET=UTF-8:%@\nX-ALLDAY:0\nSTATUS:CONFIRMED\n", notes];
        }
        
        // 是否有提醒
        if (event.hasAlarms) {
            for (EKAlarm *alarm in event.alarms) {
                if (alarm != nil) {
                    vcalendar = [vcalendar stringByAppendingFormat:@"BEGIN:VALARM\nACTION:AUDIO\nTRIGGER:-PT10M\nEND:VALARM\n"];
                }
            }
                
        }
        
        if (event.hasAttendees) {
            
        }
        
        if (event.hasRecurrenceRules) {
            
        }
        
        vcalendar = [vcalendar stringByAppendingFormat:@"END:VEVENT\n"];
    }
    vcalendar = [vcalendar stringByAppendingString:@"END:VCALENDAR"];
    
    return vcalendar;
}

// 解析 VCalendar2.0 的格式字符串
+ (NSArray<EKEvent *> *)parseVCalendar20StrWithEvents:(NSString *)vcalendarStr andEventStore:(EKEventStore *)store {
    NSString *SeparatedStr1 = @":";
    NSString *SeparatedStr2 = @"\n";
    BOOL isIn = false;
    
    // head data
    NSInteger count = 0;
    NSInteger index = 0;
    NSString *timeCode = @"UTC";
    NSString *tzoffsetFrom = @"";
    
    NSArray *lines = [vcalendarStr componentsSeparatedByString:SeparatedStr2];
    // 获取count
    if (lines.count > 0) {
        if ([lines[0] hasPrefix:@"X-SIZE"]) {
            NSArray *dataArray = [lines[0] componentsSeparatedByString:SeparatedStr1];
            count = [dataArray[1] integerValue];
        } else {
            NSLog(@"缺少X-SIZE字段");
            return nil;
        }
    } else {
        NSLog(@"字符中没有换行或为空");
        return nil;
    }
    
    // 创建事件
    NSMutableArray<EKEvent *> *eventsArray = [[NSMutableArray alloc] initWithCapacity:count];
    for (int i = 0; i < count; i++) {
        EKEvent *event = [EKEvent eventWithEventStore:store];
        [eventsArray addObject:event];
    }
    
    for(NSString* line in lines) {
        if ([line hasPrefix:@"BEGIN:VCALENDAR"]) {
            NSLog(@"parse start");
        } else if ([line hasPrefix:@"END:VCALENDAR"]) {
            NSLog(@"parse end");
        } else if ([line hasPrefix:@"TZID"]) {
            NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
            timeCode = dataArray[1];
        } else if ([line hasPrefix:@"TZOFFSETFROM"]) {
            NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
            tzoffsetFrom = dataArray[1];
        } else if (isIn || [line hasPrefix:@"BEGIN:VEVENT"]) {
            isIn = true; // 进入位
            
            EKEvent *event = [eventsArray objectAtIndex:index];
            if ([line hasPrefix:@"SUMMARY"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                // 解码
                NSString *text = [dataArray[1] stringByReplacingOccurrencesOfString:@"=" withString:@"%"];
                text = [NSString URLdecode:text stringEncoding:NSUTF8StringEncoding];
                
                event.title = text;
            } else if ([line hasPrefix:@"DTEND"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                event.endDate = [NSDate dateWithTZString:dataArray[1] andTZID:timeCode andTZOffset:tzoffsetFrom];
            } else if ([line hasPrefix:@"DTSTART"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                event.startDate = [NSDate dateWithTZString:dataArray[1] andTZID:timeCode andTZOffset:tzoffsetFrom];
            } else if ([line hasPrefix:@"URL"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                event.URL = [NSURL URLWithString:dataArray[1]];
            } else if ([line hasPrefix:@"LCOATION"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                event.location = dataArray[1];
            } else if ([line hasPrefix:@"DESCRIPTION"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                // 解码
                NSString *text = [dataArray[1] stringByReplacingOccurrencesOfString:@"=" withString:@"%"];
                text = [NSString URLdecode:text stringEncoding:NSUTF8StringEncoding];
                
                event.notes = text;
            } else if ([line hasPrefix:@"X-ALLDAY"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                event.allDay = [dataArray[1] isEqual:@"0"] ? false : true;
            } else if ([line hasPrefix:@"TRIGGER"]) {
                NSArray *dataArray = [line componentsSeparatedByString:SeparatedStr1];
                NSString *countMinutes = [NSString stringRangeOfStringWithStart:@"PT" andEnd:@"M" andDealStr:dataArray[1]];
                EKAlarm *alarm = [EKAlarm alarmWithRelativeOffset:[countMinutes integerValue] * -60];
                [event addAlarm:alarm];
            }
            
            // 退出位
            if ([line hasPrefix:@"END:VEVENT"]) {
                [event setCalendar:[store defaultCalendarForNewEvents]];
                isIn = false;
                index++;
            }
        }
    }

    return eventsArray;
}