#define _LINUX_SOURCE 1
#include <sys/syscall.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/swap.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>
#include <tcl.h>

#include <linux/sockios.h>
#include <linux/route.h>
#include <linux/if.h>
#include <linux/if_arp.h>
#include <linux/if_bridge.h>

#endif
#ifndef MNT_EXPIRE
#define MNT_EXPIRE 4
#endif
#ifndef MS_MOVE
#define MS_MOVE 8192
#endif

/* Simple macros */
#ifndef MAX
#define MAX(a, b) (((a) < (b)) ? (b) : (a))
#endif
#ifndef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif

/* User environment, for execve */
extern char **environ;

/* Re-implement these if needed */
#ifdef SYS_init_module
static int init_module(void *val, unsigned long len, const char *args) {

	if (sock_v6 != -1) {
		close(sock_v6);
	}

	return(retval);
}

static int tclsystem_tsmf_start_svc(ClientData cd, Tcl_Interp *interp, int objc, Tcl_Obj *CONST objv[]) {
	Tcl_Obj *filename_obj, *env_obj, *logfile_obj, **env_entry_objv;
	pid_t child, child_pgid = -1;
	ssize_t read_ret;
	time_t currtime;
	char *argv[3], *envv[512];
	char *logfile, *filename;
	char logmsg[2048];
	int pipe_ret, setsid_ret, execve_ret, tcl_ret;
	int null_fd, log_fd, tmp_fd, max_fd;
	int env_entry_objc;
	int fds[2], fd;
	int status;
	int idx;

	/* 1. Parse arguments */
	/* 1.a. Ensure the correct number of arguments were passed */
	if (objc != 9) {
		Tcl_SetObjResult(interp, Tcl_NewStringObj("wrong # args: should be \"::system::syscall::tsmf_start_svc sri filename logfile env cwd umask user group\"", -1));

		return(TCL_ERROR);
	}

	/* 1.b. Identify Tcl_Objs to use for each argument */
	filename_obj = objv[2];
	logfile_obj = objv[3];
	env_obj = objv[4];

	/* 1.c. Store string arguments */
	filename = Tcl_GetString(filename_obj);
	logfile = Tcl_GetString(logfile_obj);

	/* 1.d. Process environment */
	tcl_ret = Tcl_ListObjGetElements(interp, env_obj, &env_entry_objc, &env_entry_objv);
	if (tcl_ret != TCL_OK) {
		return(tcl_ret);
	}

	for (idx = 0; idx < MIN(env_entry_objc, sizeof(envv) / sizeof(envv[0]) - 1); idx++) {
		envv[idx] = Tcl_GetString(env_entry_objv[idx]);
	}
	envv[idx] = NULL;

	/* 2. Create a pipe for communication between the processes */
	pipe_ret = pipe(fds);
	if (pipe_ret != 0) {
		Tcl_SetObjResult(interp, Tcl_NewStringObj("pipe failed", -1));

		return(TCL_ERROR);
	}

	/* 3. Fork into a new process */
	child = fork();
	if (child == ((pid_t) -1)) {
		Tcl_SetObjResult(interp, Tcl_NewStringObj("fork failed", -1));

		return(TCL_ERROR);
	}

	if (child != 0) {
		/* 4.parent. Get PGID from child */
		/* 4.parent.a. Close write end of pipe -- we are read-only */
		close(fds[1]);
		fd = fds[0];

		/* 4.parent.b. Read process group ID of child from pipe */
		read_ret = read(fd, &child_pgid, sizeof(child_pgid));

		/* 4.parent.c. Close read end of pipe */
		close(fd);

		/* 4.parent.d. Verify read was meaningful */
		if (read_ret != sizeof(child_pgid)) {
			Tcl_SetObjResult(interp, Tcl_NewStringObj("failed to communicate with started service", -1));

			return(TCL_ERROR);
		}

		/* 4.parent.e. If the PGID given is actually an error, return error */
		if (child_pgid == ((pid_t) -1)) {
			Tcl_SetObjResult(interp, Tcl_NewStringObj("service failed to start", -1));

			return(TCL_ERROR);
		}

		/* 4.parent.f. Return PGID to Tcl */
		Tcl_SetObjResult(interp, Tcl_NewWideIntObj((Tcl_WideInt) child_pgid));

		return(TCL_OK);
	}

	/* 4.child.a. Close read end of pipe -- we only write to it */
	close(fds[0]);
	fd = fds[1];

	/* 5. Create a new session */
	setsid_ret = setsid();
	if (setsid_ret == ((pid_t) -1)) {
		write(fd, &child_pgid, sizeof(child_pgid));

		_exit(0);
	}

	/* 6. Setup environment */
	/* 6.a. Set umask */
	/* XXX: TODO */
	umask(022);

	/* 6.b. Set working directory */
	/* XXX: TODO */
	chdir("/");

	/* 6.c. Open log file for stderr and stdout */
	log_fd = open(logfile, O_WRONLY | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

	/* 6.d. Open "/dev/null" for stdin */
	null_fd = open("/dev/null", O_RDONLY);
	if (null_fd < 0 || log_fd <0) {
		write(fd, &child_pgid, sizeof(child_pgid));

		_exit(0);
	}

	/* 6.e. Redirect stdin, stdout, and stderr to null, logs */
	dup2(null_fd, STDIN_FILENO);
	dup2(log_fd, STDOUT_FILENO);
	dup2(log_fd, STDERR_FILENO);

	close(null_fd);
	close(log_fd);

	/* 6.f. Close stray file descriptors */
	max_fd = MAX(MAX(MAX(1024, STDIN_FILENO), STDOUT_FILENO), STDERR_FILENO);
	for (tmp_fd = 0; tmp_fd < max_fd; tmp_fd++) {
		if (tmp_fd == STDIN_FILENO || tmp_fd == STDOUT_FILENO || tmp_fd == STDERR_FILENO) {
			continue;
		}

		if (tmp_fd == fd) {
			continue;
		}

		close(tmp_fd);
	}

	/* 6.g. Switch to appropriate user/group */
	/* 6.g.i. Group */
	/* XXX: TODO */

	/* 6.g.ii. User */
	/* XXX: TODO */

	/* 7. Create a new process to actually spawn the process */
	child = fork();
	if (child == ((pid_t) -1)) {
		write(fd, &child_pgid, sizeof(child_pgid));

		_exit(0);
	}

	if (child != 0) {
		/* 7.parent.a. Wait for child process to terminate and collect status */
		waitpid(child, &status, 0);

		/* 7.parent.b. Set PGID (if successful, -1 otherwise) to pass back to TSMF */
		if (status == 0) {
			child_pgid = getpgid(getpid());
		}
		write(fd, &child_pgid, sizeof(child_pgid));

		close(fd);

		/* 7.parent.c. Write log of result */
		/* Note: We avoid ANSI I/O here in case there is already something in the buffer */
		currtime = time(NULL);
		strftime(logmsg, sizeof(logmsg), "[ %b %e %H:%M:%S ", localtime(&currtime));
		write(STDERR_FILENO, logmsg, strlen(logmsg));

		snprintf(logmsg, sizeof(logmsg), "Method \"start\" exited with status %i ]\n", WEXITSTATUS(status));
		write(STDERR_FILENO, logmsg, strlen(logmsg));

		_exit(0);
	}
	
	/* 7.child.a. Close channel to parent */
	close(fd);

	/* 8. Log attempt to run start method */
	currtime = time(NULL);
	strftime(logmsg, sizeof(logmsg), "[ %b %e %H:%M:%S ", localtime(&currtime));
	write(STDERR_FILENO, logmsg, strlen(logmsg));

	snprintf(logmsg, sizeof(logmsg), "Executing start method (\"%s\") ]\n", filename);
	write(STDERR_FILENO, logmsg, strlen(logmsg));

	/* 9. execve() new image */
	argv[0] = filename;
	argv[1] = "start";
	argv[2] = NULL;
	execve_ret = execve(filename, argv, envv);

	/* 10. Abort if something has gone wrong */
	_exit(execve_ret);
}

int System_Init(Tcl_Interp *interp) {
#ifdef USE_TCL_STUBS
	const char *tclInitStubs_ret;

	/* Initialize Stubs */
	tclInitStubs_ret = Tcl_InitStubs(interp, "8.4", 0);

	/* Network related commands */
	Tcl_CreateObjCommand(interp, "::system::syscall::ifconfig", tclsystem_ifconfig, NULL, NULL);
	Tcl_CreateObjCommand(interp, "::system::syscall::route", tclsystem_route, NULL, NULL);
	Tcl_CreateObjCommand(interp, "::system::syscall::brctl", tclsystem_brctl, NULL, NULL);
	Tcl_CreateObjCommand(interp, "::system::syscall::vconfig", tclsystem_vconfig, NULL, NULL);

	/* Service (TSMF) related commands */
	Tcl_CreateObjCommand(interp, "::system::syscall::tsmf_start_svc", tclsystem_tsmf_start_svc, NULL, NULL);

	/* Internal functions */
	Tcl_CreateObjCommand(interp, "::system::internal::hash", tclsystem_internalproc_simplehash, NULL, NULL);

	/* Define constants */
	/** Create parent namespace **/
	Tcl_CreateNamespace(interp, "::system::const", NULL, NULL);