ChatDemo/XMPP/Extensions/XEP-0202/XMPPTime.h
#import <Foundation/Foundation.h>
#import "XMPP.h"

#define _XMPP_TIME_H

@class XMPPIDTracker;
@protocol XMPPTimeDelegate;


@interface XMPPTime : XMPPModule
{
	BOOL respondsToQueries;
	XMPPIDTracker *queryTracker;
}

/**
 * Whether or not the module should respond to incoming time queries.
 * It you create multiple instances of this module, only one instance should respond to queries.
 * 
 * It is recommended you set this (if needed) before you activate the module.
 * The default value is YES.
**/
@property (readwrite) BOOL respondsToQueries;

/**
 * Send query to the server or a specific JID.
 * The disco module may be used to detect if the target supports this XEP.
 * 
 * The returned string is the queryID (the elementID of the query that was sent).
 * In other words:
 * 
 * SEND: <iq id="<returned_string>" type="get" .../>
 * RECV: <iq id="<returned_string>" type="result" .../>
 * 
 * This may be helpful if you are sending multiple simultaneous queries to the same target.
**/
- (NSString *)sendQueryToServer;
- (NSString *)sendQueryToServerWithTimeout:(NSTimeInterval)timeout;
- (NSString *)sendQueryToJID:(XMPPJID *)jid;
- (NSString *)sendQueryToJID:(XMPPJID *)jid withTimeout:(NSTimeInterval)timeout;

/**
 * Extracts the utc date from the given response/time element,
 * and returns an NSDate representation of the time in the local time zone.
 * Since the returned date is in the local time zone, it is suitable for presentation.
**/
+ (NSDate *)dateFromResponse:(XMPPIQ *)iq;

/**
 * Extracts the time zone offset from the given response/time element.
**/
+ (NSTimeZone *)timeZoneOffsetFromResponse:(XMPPIQ *)iq;

/**
 * Given the returned time response from a remote party, and the approximate round trip time,
 * calculates the difference between our clock and the remote party's clock.
 * 
 * This is NOT a reference to the difference in time zones.
 * Time zone differences generally shouldn't matter as xmpp standards mandate the use of UTC.
 * 
 * Rather this is the difference between our UTC time, and the remote party's UTC time.
 * If the two clocks are not synchronized, then the result represents the approximate difference.
 * 
 * If our clock is earlier than the remote clock, then the result will be negative.
 * If our clock is ahead of the remote clock, then the result will be positive.
 * 
 * If you later receive a timestamp from the remote party, you could add the diff.
 * For example:
 * 
 * myTime = [givenTimeFromRemoteParty dateByAddingTimeInterval:diff];
**/
+ (NSTimeInterval)approximateTimeDifferenceFromResponse:(XMPPIQ *)iq andRTT:(NSTimeInterval)rtt;

/**
 * Creates and returns a time element.
**/
+ (NSXMLElement *)timeElement;
+ (NSXMLElement *)timeElementFromDate:(NSDate *)date;

@end

@protocol XMPPTimeDelegate
@optional

- (void)xmppTime:(XMPPTime *)sender didReceiveResponse:(XMPPIQ *)iq withRTT:(NSTimeInterval)rtt;
- (void)xmppTime:(XMPPTime *)sender didNotReceiveResponse:(NSString *)queryID dueToTimeout:(NSTimeInterval)timeout;

// Note: If the xmpp stream is disconnected, no delegate methods will be called, and outstanding queries are forgotten.

@end
