//
// FILE: srt_client.h
//
// Description: this file contains client states' definition, some important data structures
// and the client SRT socket interface definitions. You need to implement all these interfaces
//
// Date: April 18, 2008
//       April 21, 2008 **Added more detailed description of prototypes fixed ambiguities** ATC
//       April 26, 2008 ** Added GBN and send buffer function descriptions **
//       May 1, 2009    ** Clarified that srt_client_send is non blocking ** ATC
//

#ifndef SRTCLIENT_H
#define SRTCLIENT_H

#include <pthread.h>
#include "../common/seg.h"

//client states used in FSM
#define	CLOSED 1
#define	SYNSENT 2
#define	CONNECTED 3
#define	FINWAIT 4

//unit to store segments in send buffer linked list.
typedef struct segBuf {
        seg_t seg;
        unsigned int sentTime;
        struct segBuf* next;
} segBuf_t;


//client transport control block. the client side of a SRT connection uses this data structure to keep track of the connection information.   
typedef struct client_tcb {
	unsigned int svr_nodeID;        //node ID of server, similar as IP address, currently unused
	unsigned int svr_portNum;       //port number of server
	unsigned int client_nodeID;     //node ID of client, similar as IP address, currently unused
	unsigned int client_portNum;    //port number of client
	unsigned int state;     	//state of client
	unsigned int next_seqNum;       //next sequence number to be used by new segment 
	pthread_mutex_t* bufMutex;      //send buffer mutex
	segBuf_t* sendBufHead;          //head of send buffer
	segBuf_t* sendBufunSent;        //first unsent segment in send buffer
	segBuf_t* sendBufTail;          //tail of send buffer
	unsigned int unAck_segNum;      //number of sent-but-not-Acked segments
} client_tcb_t;



//
//
//  SRT socket API for the client side application. 
//  ===================================
//
//  In what follows, we provide the prototype definition for each call and limited pseudo code representation
//  of the function. This is not meant to be comprehensive - more a guideline. 
// 
//  You are free to design the code as you wish.
//
//  NOTE: When designing all functions you should consider all possible states of the FSM using
//  a switch statement (see the Lab4 assignment for an example). Typically, the FSM has to be
// in a certain state determined by the design of the FSM to carry out a certain action. 
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

void srt_client_init(int conn);

// This function initializes the TCB table marking all entries NULL. It also initializes 
// a global variable for the overlay TCP socket descriptor ``conn'' used as input parameter
// for snp_sendseg and snp_recvseg. Finally, the function starts the seghandler thread to 
// handle the incoming segments. There is only one seghandler for the client side which
// handles call connections for the client.
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

int srt_client_sock(unsigned int client_port);

// This function looks up the client TCB table to find the first NULL entry, and creates
// a new TCB entry using malloc() for that entry. All fields in the TCB are initialized 
// e.g., TCB state is set to CLOSED and the client port set to the function call parameter 
// client port.  The TCB table entry index should be returned as the new socket ID to the client 
// and be used to identify the connection on the client side. If no entry in the TC table  
// is available the function returns -1.
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

int srt_client_connect(int socked, unsigned int server_port);

// This function is used to connect to the server. It takes the socket ID and the 
// server's port number as input parameters. The socket ID is used to find the TCB entry.  
// This function sets up the TCB's server port number and a SYN segment to send to
// the server using snp_sendseg(). After the SYN segment is sent, a timer is started. 
// If no SYNACK is received after SYNSEG_TIMEOUT timeout, then the SYN is 
// retransmitted. If SYNACK is received, return 1. Otherwise, if the number of SYNs 
// sent > SYN_MAX_RETRY,  transition to CLOSED state and return -1.
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

int srt_client_send(int sockfd, void* data, unsigned int length);

// Send data to a srt server. This function should use the SRT socket ID to find the TCP entry. 
// It creates segBufs using the given data and append them to send linked list. 
// If the send buffer is empty before insertion, a thread called sendbuf_timer 
// should be started to poll the send buffer every SENDBUF_POLLING_INTERVAL time
// to check if a timeout event should occur. If the function completes successfully, 
// it returns 1. Otherwise, it returns -1. srt_client_send is a non-blocking function call.
// Because user data is fragmented into fixed sized SRT segments there may be
// multiple segBufs queued to the send link list for a single srt_client_send call.
// If the call is successful the data is queued on the TCB send linked list and
// depending on the condition of the sliding window the data will either be
// trasmitted over the network or queued waiting to be transmitted. 
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

int srt_client_disconnect(int sockfd);

// This function is used to disconnect from the server. It takes the socket ID as 
// an input parameter. The socket ID is used to find the TCB entry in the TCB table.  
// This function sends a FIN segment to the server. After the FIN segment is sent
// the state should transition to FINWAIT and a timer started. If the 
// state == CLOSED after the timeout the FINACK was successfully received. Else,
// if after a number of retries FIN_MAX_RETRY the state is still FINWAIT then
// the state transitions to CLOSED and -1 is returned.


//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

int srt_client_close(int sockfd);

// This function calls free() to free the TCB entry. It marks that entry in TCB as NULL
// and returns 1 if succeeded (i.e., was in the right state to complete a close) and -1 
// if fails (i.e., in the wrong state).
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//

void *seghandler(void* arg);

// This is a thread  started by srt_client_init(). It handles all the incoming 
// segments from the server. The design of seghanlder is an infinite loop that calls snp_recvseg(). If
// snp_recvseg() fails then the overlay connection is closed and the thread is terminated. Depending
// on the state of the connection when a segment is received  (based on the incoming segment) various
// actions are taken. See the client FSM for more details.
//
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


void* sendBuf_timer(void* clienttcb);

// This thread continuously polls send buffer to trigger timeout events
// It should always be running when the send buffer is not empty
// If the current time -  first sent-but-unAcked segment's sent time > DATA_TIMEOUT, a timeout event occurs
// When timeout, resend all sent-but-unAcked segments
// When the send buffer is empty, this thread terminates
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#endif