/*

    File:       QCommandConnection.h

    Contains:   Manages a single TCP connection for sending and receiving commands.

    Written by: DTS

    Copyright:  Copyright (c) 2011 Apple Inc. All Rights Reserved.

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                The Apple Software is provided by Apple on an "AS IS" basis. 

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*/

#import <Foundation/Foundation.h>

// QCommandConnection is a general purpose class for managing a command-oriented 

// network connection.

// 

// The class is run loop based and must be called from a single thread. 

// Specifically, the -open and -close methods add and remove run loop sources 

// to the current thread's run loop, and it's that thread that calls the 

// delegate callbacks.

@protocol QCommandConnectionDelegate;

@interface QCommandConnection : NSObject

- (id)initWithInputStream:(NSInputStream *)inputStream outputStream:(NSOutputStream *)outputStream;

    // Creates the command connection to run over the supplied streams.  

    // You can set other configuration parameters, like the buffer capacities, 

    // before calling -open on the connection.

// properties set on init

@property (nonatomic, retain, readonly ) NSInputStream *            inputStream;

@property (nonatomic, retain, readonly ) NSOutputStream *           outputStream;

// properties that must be configured before -open

@property (nonatomic, assign, readwrite) NSUInteger                 inputBufferCapacity;            // default is 0, meaning chose a reasonable default

@property (nonatomic, assign, readwrite) NSUInteger                 outputBufferCapacity;           // default is 0, meaning chose a reasonable default

// You must open or remove run loop modes before opening the connection

- (void)addRunLoopMode:(NSString *)modeToAdd;

- (void)removeRunLoopMode:(NSString *)modeToRemove;

@property (nonatomic, copy,   readonly ) NSSet *                    runLoopModes;                   // contains NSDefaultRunLoopMode by default

// properties that can be set at any time

@property (nonatomic, assign, readwrite) id<QCommandConnectionDelegate>    delegate;

@property (nonatomic, copy,   readwrite) NSString *                 name;                           // for debugging

// properties that change as the result of other actions

@property (nonatomic, assign, readonly ) BOOL                       isOpen;

@property (nonatomic, copy,   readwrite) NSError *                  error;

// actions

- (void)open;

    // Opens the connection.  It's not legal to call this if the connection has 

    // already been opened.  If the open fails, this calls the 

    // -connection:willCloseWithError: delegate method.

- (void)close;

    // Closes the connection.  It is safe to call this even if -open has not called, 

    // or the connection has already closed.  Will not call -connection:willCloseWithError: 

    // delegate method (that method is only called if the connection closes by 

    // itself).

- (void)closeWithError:(NSError *)error;

    // Closes the connection with the specified error (nil to indicate an end of file), 

    // much like what happens if the connection tears (or ends).  This is primarily for 

    // subclasses and delegates.  It is safe to call this even if -open has not called, 

    // or the connection has already closed.  This /will/ end up calling the 

    // -connection:willCloseWithError: delegate method.

- (void)sendCommand:(NSData *)command;

    // Sends the specified command down the connection.  Note that there's no send-side 

    // flow control here.  If the connection stops sending data, eventually the buffer 

    // space will fill up and connection will tear.

@end

@protocol QCommandConnectionDelegate <NSObject>

@optional

- (void)connection:(QCommandConnection *)connection willCloseWithError:(NSError *)error;

    // Called when the connection fails to open or closes badly (error is not nil), or if 

    // there's an EOF (error is nil).

- (NSUInteger)connection:(QCommandConnection *)connection parseCommandData:(NSData *)commandData;

    // Called when data arrives on the connection.  The delegate is expected to parse the 

    // data to see if there's a complete command present.  If so, it should consume the 

    // command and return the number of bytes consumed.  If not, it should return 0 

    // and will be called again when the next chunk of data arrives.

    //

    // It is more efficient if the delegate parses out multiple commands in one call, 

    // but that is not strictly necessary.

    //

    // If the delegate detects some sort of failure it is reasonable for it to force 

    // the connection to close by calling -closeWithError:.

    //

    // If the delegate does not implement this method, any data arriving on the input stream 

    // will cause the connection to fail with kQCommandConnectionInputUnexpectedError.

- (void)connection:(QCommandConnection *)connection logWithFormat:(NSString *)format arguments:(va_list)argList;

    // Called to log connection activity.

@end

// The following methods are exported for the benefit of subclasses.  Specifically, 

// they allow subclasses to see the delegate methods without actually being the 

// delegate.  The default implementation of these routines just calls the 

// delegate callback, if any.

@interface QCommandConnection (ForSubclassOverride)

- (void)willCloseWithError:(NSError *)error;

- (NSUInteger)parseCommandData:(NSData *)commandData;

- (void)logWithFormat:(NSString *)format arguments:(va_list)argList;

@end

// The following methods are exported for the benefit of subclasses.

@interface QCommandConnection (ForSubclassUse)

- (void)logWithFormat:(NSString *)format, ...;

    // This allows subclasses to log things to the connection delegate.

+ (NSError *)errorWithCode:(NSInteger)code;

    // This allows subclasses to construct errors in the kQCommandConnectionErrorDomain.

@end

// Most connection errors come from NSStream, but some are generated internally.

extern NSString * kQCommandConnectionErrorDomain;

enum {

    kQCommandConnectionOutputBufferFullError = 1, 

    kQCommandConnectionInputBufferFullError = 2,

    kQCommandConnectionOutputCommandTooLongError = 3,

    kQCommandConnectionInputUnexpectedError = 4, 

    kQCommandConnectionInputCommandTooLongError = 5, 

    kQCommandConnectionInputCommandMalformedError = 6       // for the benefit of our subclasses

};