/*
This software is part of libcsdr, a set of simple DSP routines for 
Software Defined Radio.

Copyright (c) 2014, Andras Retzler <randras@sdr.hu>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the copyright holder nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL ANDRAS RETZLER BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "ddcd.h"


#define SOFTWARE_NAME "ddcd"
#define MSG_START SOFTWARE_NAME ": "

int host_port = 0;
char host_address[100] = "127.0.0.1";
int decimation = 0;
float transition_bw = 0.05;
int bufsize = 1024;
int bufsizeall;
int pipe_max_size;
char ddc_method_str[100] = "td";
ddc_method_t ddc_method;
pid_t main_dsp_proc;
pid_t pgrp;
int input_pipe = STDIN_FILENO; //can be stdin, or the stdout of main_subprocess

char* buf;

int set_nonblocking(int fd)
{
	int flagtmp;
	if((flagtmp = fcntl(fd, F_GETFL))!=-1)
		if((flagtmp = fcntl(fd, F_SETFL, flagtmp|O_NONBLOCK))!=-1)
			return 0;
	return 1;
}

int proc_exists(pid_t pid)
{
	if(pid==0 || pid==1) return 1;
	return kill(pid, 0) != -1;
}

void sig_handler(int signo)
{	
	if(pgrp!=1 && pgrp!=0) //I just want to make sure that we cannot kill init or sched
		killpg(pgrp, signo);
	fprintf(stderr, MSG_START "signal caught, exiting ddcd...\n");
	fflush(stderr);
	exit(0);
}

client_t* this_client;

int main(int argc, char* argv[])
{
	int c;
	fd_set select_fds;
	
	for(;;)
	{
		int option_index = 0;
		static struct option long_options[] = {
		   {"port",       required_argument, 0,  'p' },
		   {"address",    required_argument, 0,  'a' },
		   {"decimation", required_argument, 0,  'd' },
		   {"bufsize", 	  required_argument, 0,  'b' },
	       {"method", 	  required_argument, 0,  'm' },
	       {"transition", required_argument, 0,  't' }
		};
		c = getopt_long(argc, argv, "p:a:d:b:", long_options, &option_index);
		if(c==-1) break;
		switch (c) 
		{
		case 'a':
			host_address[100-1]=0;
			strncpy(host_address,optarg,100-1);
			break;
		case 'p':
			host_port=atoi(optarg);
			break;
		case 'd':
			decimation=atoi(optarg);
			break;
		case 'b':
			bufsize=atoi(optarg);
			break;
		case 'm':
			host_address[100-1]=0;
			strncpy(ddc_method_str,optarg,100-1);
			break;
		case 't':
			sscanf(optarg,"%g",&transition_bw);
			break;
		case 0:
		case '?':
		case ':':
		default:;
		}
	}
	
	if(!decimation) print_exit(MSG_START "missing required command line argument, --decimation.\n");
	if(!host_port) print_exit(MSG_START "missing required command line argument, --port.\n");
	if(decimation<0) print_exit(MSG_START "invalid value for --decimation (should be >0).\n");
	if(decimation==1) fprintf(stderr, MSG_START "decimation = 1, just copying raw samples.\n");
	if(transition_bw<0||transition_bw>0.5) print_exit(MSG_START "invalid value for --transition (should be between 0 and 0.5).\n");
	
	if(!strcmp(ddc_method_str,"td")) 
	{
		ddc_method = M_TD; 
		fprintf(stderr, MSG_START "method is M_TD (default).\n");
	}
	else if (!strcmp(ddc_method_str,"fastddc")) 
	{
		ddc_method = M_FASTDDC; 
		fprintf(stderr, MSG_START "method is M_FASTDDC.\n");
	}
	else print_exit(MSG_START "invalid parameter given to --method.\n");

	//set signals
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = sig_handler;
	sigaction(SIGKILL, &sa, NULL);
	sigaction(SIGQUIT, &sa, NULL);
	sigaction(SIGHUP, &sa, NULL);
	prctl(PR_SET_PDEATHSIG, SIGHUP); //get a signal when parent exits

	struct sockaddr_in addr_host;
    int listen_socket;
	std::vector<client_t*> clients;
	clients.reserve(100);
    listen_socket=socket(AF_INET,SOCK_STREAM,0);

	int sockopt = 1;
	if( setsockopt(listen_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&sockopt, sizeof(sockopt)) == -1 )
		error_exit(MSG_START "cannot set SO_REUSEADDR");  //the best description on SO_REUSEADDR ever: http://stackoverflow.com/a/14388707/3182453

    memset(&addr_host,'0',sizeof(addr_host));
    addr_host.sin_family=AF_INET;
    addr_host.sin_port=htons(host_port);
	addr_host.sin_addr.s_addr = INADDR_ANY;

    if( (addr_host.sin_addr.s_addr=inet_addr(host_address)) == INADDR_NONE ) 
		error_exit(MSG_START "invalid host address");

	if( bind(listen_socket, (struct sockaddr*) &addr_host, sizeof(addr_host)) < 0 )
		error_exit(MSG_START "cannot bind() address to the socket");

	if( listen(listen_socket, 10) == -1 )
		error_exit(MSG_START "cannot listen() on socket");

	fprintf(stderr,MSG_START "listening on %s:%d\n", inet_ntoa(addr_host.sin_addr), host_port);

	struct sockaddr_in addr_cli;
	socklen_t addr_cli_len = sizeof(addr_cli);
	int new_socket;

	bufsizeall = bufsize*sizeof(char);
	buf = (char*)malloc(bufsizeall);

	FILE* tempfile = fopen("/proc/sys/fs/pipe-max-size","r");
	if(!tempfile)
	{
		perror(MSG_START "cannot read /proc/sys/fs/pipe-max-size");
	}
	else
	{
		char pipe_max_size_str[100];
		int tfread = fread(pipe_max_size_str, 1, 100, tempfile);
		pipe_max_size_str[tfread]='\0';
		pipe_max_size = atoi(pipe_max_size_str);
		//fprintf(stderr, MSG_START "note: pipe_max_size = %d\n", pipe_max_size);
		//if(pipe_max_size>4096 && fcntl(STDIN_FILENO, F_SETPIPE_SZ, pipe_max_size)==-1)
		//	perror("failed to fcntl(STDIN_FILENO, F_SETPIPE_SZ, ...)");
	}

	//We'll see if it is a good idea:
	setpgrp();
	pgrp = getpgrp();

	//Start DSP subprocess from the main process if required
	char main_subprocess_cmd_buf[500];
	pid_t main_subprocess_pid = 0;

	int pipe_m2s_ctl[2];	//main to subprocess :: control channel
	int pipe_s2m[2];		//subprocess to main

	if(pipe(pipe_m2s_ctl)) error_exit(MSG_START "couldn't create pipe_m2s_ctl");
	if(pipe(pipe_s2m)) error_exit(MSG_START "couldn't create pipe_s2m");

	if(decimation!=1)
	{
		switch(ddc_method)
		{
		case M_TD:
			break;
		case M_FASTDDC:
			sprintf(main_subprocess_cmd_buf, subprocess_args_fastddc_1, decimation, transition_bw);
			fprintf(stderr, MSG_START "starting main_subprocess_cmd: %s\n", main_subprocess_cmd_buf);
			close(STDIN_FILENO); // redirect stdin to the stdin of the subprocess 
			main_subprocess_pid = run_subprocess( main_subprocess_cmd_buf, 0, pipe_s2m );
			break;
		}
	}

	int highfd = 0; 
	FD_ZERO(&select_fds);
	FD_SET(listen_socket, &select_fds);
	maxfd(&highfd, listen_socket);
	if(main_subprocess_pid) input_pipe = pipe_s2m[1]; //else STDIN_FILENO
	FD_SET(input_pipe, &select_fds);
	maxfd(&highfd, input_pipe);

	//Set stdin and listen_socket to non-blocking 
	if(set_nonblocking(input_pipe) || set_nonblocking(listen_socket)) //don't do it before subprocess fork!
		error_exit(MSG_START "cannot set_nonblocking()");

	for(;;)
	{
		//Let's wait until there is any new data to read, or any new connection!
		select(highfd, &select_fds, NULL, NULL, NULL);

		//Is there a new client connection?
		if( (new_socket = accept(listen_socket, (struct sockaddr*)&addr_cli, &addr_cli_len)) != -1)
		{ 
			this_client = new client_t;
			this_client->error = 0;
			memcpy(&this_client->addr, &addr_cli, sizeof(this_client->addr));
			this_client->socket = new_socket;
			if(pipe(this_client->pipefd) == -1)
			{ 
				perror(MSG_START "cannot open new pipe() for the client");
				continue;
			}
			if(fcntl(this_client->pipefd[1], F_SETPIPE_SZ, pipe_max_size) == -1)
				perror("failed to F_SETPIPE_SZ for the client pipe");
			if(this_client->pid = fork())
			{
				//We're the parent
				set_nonblocking(this_client->pipefd[1]);
				clients.push_back(this_client);
				fprintf(stderr, MSG_START "client pid: %d\n", this_client->pid);
			}
			else
			{
				//We're the client
				client();
				return 1;
			}
		}

		int retval = read(input_pipe, buf, bufsizeall);
		if(retval==0)
		{
			//end of input stream, close clients and exit
		}
		else if(retval != -1)
		{
			for (int i=0; i<clients.size(); i++)
			{
				if(write(clients[i]->pipefd[1], buf, retval)==-1)
				{
					
					if(!clients[i]->error) 
					{
						print_client(clients[i], "lost buffer, failed to write pipe.");
						clients[i]->error=1;
					}
					//fprintf(stderr, MSG_START "errno is %d\n", errno); //usually 11
					//int wpstatus;
					//int wpresult = waitpid(clients[i]->pid, &wpstatus, WNOHANG);
					//fprintf(stderr, MSG_START "pid is %d\n",clients[i]->pid);
					//perror("somethings wrong");
					//if(wpresult == -1) print_client(clients[i], "error while waitpid()!");
					//else if(wpresult == 0) 
					waitpid(clients[i]->pid, NULL, WNOHANG);
					if(!proc_exists(clients[i]->pid))
					{
						//Client exited!
						print_client(clients[i], "closing client from main process.");
						close(clients[i]->pipefd[1]);
						close(clients[i]->socket);
						delete clients[i];
						clients.erase(clients.begin()+i);
						print_client(clients[i], "done closing client from main process.");
					}
				}
				else  { if(clients[i]->error) print_client(clients[i], "pipe okay again."); clients[i]->error=0; }
			}
		}
		//TODO: at the end, server closes pipefd[1] for client
		//
	}

	return 0; 
}

pid_t run_subprocess(char* cmd, int* pipe_in, int* pipe_out)
{
	pid_t pid = fork();
	if(pid < 0) return 0; //fork failed
	if(pid == 0)
	{
		//We're the subprocess
		if(fcntl(pipe_in[1], F_SETPIPE_SZ, pipe_max_size) == -1) perror("Failed to F_SETPIPE_SZ in run_subprocess()");
		if(pipe_in)
		{
			close(pipe_in[1]);
			dup2(pipe_in[0], STDIN_FILENO);
		}
		if(pipe_out)
		{
			close(pipe_out[0]);
			dup2(pipe_out[1], STDOUT_FILENO);
		}
		execl("/bin/bash","bash","-c",cmd, NULL);
		error_exit(MSG_START "run_subprocess failed to execute command");
	}
	else return pid;
}

void print_client(client_t* client, const char* what)
{
	fprintf(stderr,MSG_START "(client %s:%d) %s\n", inet_ntoa(client->addr.sin_addr), client->addr.sin_port, what);
}

void client_cleanup()
{
	close(this_client->pipefd[0]);
}

void client()
{
	print_client(this_client, "client process forked.");
	for(;;)
	{
		read(this_client->pipefd[0],buf,bufsizeall);
		if(send(this_client->socket,buf,bufsizeall,0)==-1)
		{
			print_client(this_client, "client process is exiting.");
			exit(0);
		}
	}	
}

void error_exit(const char* why)
{
	perror(why);
	exit(1);
}

void print_exit(const char* why)
{
	fprintf(stderr, "%s", why);
	exit(1);
}

void maxfd(int* maxfd, int fd)
{
	if(fd>*maxfd) *maxfd=fd+1; 
}