#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include <pthread.h>

/* XXX Umpfh.
   Python.h defines a typedef destructor, which conflicts with pthread.h.
   So Python.h must be included after pthread.h. */

#include <Python.h>

#ifndef PORT
#define PORT 4000
#endif

extern int optind;
extern char *optarg;
extern int getopt();

struct workorder {
	int conn;
	struct sockaddr_in addr;
};

/* Forward */
static void init_python(void);
static void usage(void);
static void oprogname(void);
static void main_thread(int);
static void create_thread(int, struct sockaddr_in *);
static void *service_thread(struct workorder *);
static void run_interpreter(FILE *, FILE *);
static int run_command(char *, PyObject *);

static char *progname = "pysvr";

main(int argc, char **argv)
{
	int port = PORT;
	int c;

	if (argc > 0 && argv[0] != NULL && argv[0][0] != '\0')
		progname = argv[0];

	while ((c = getopt(argc, argv, "")) != EOF) {
		switch (c) {
		default:
			usage();
		}
	}

	if (optind < argc) {
		if (optind+1 < argc) {
			oprogname();
			fprintf(stderr, "too many arguments\n");
			usage();
		}
		port = atoi(argv[optind]);
		if (port <= 0) {
			fprintf(stderr, "bad port (%s)\n", argv[optind]);
			usage();
		}
	}

	main_thread(port);

	fprintf(stderr, "Bye.\n");

	exit(0);
}

static char usage_line[] = "usage: %s [port]\n";

static void
usage()
{
	fprintf(stderr, usage_line, progname);
	exit(2);
}

static void
main_thread(int port)
{
	int sock;
	struct sockaddr_in addr;

	sock = socket(PF_INET, SOCK_STREAM, 0);
	if (sock < 0) {
		oprogname();
		perror("can't create socket");
		exit(1);
	}

	memset(&addr, '\0', sizeof addr);
	addr.sin_family = AF_INET;
	addr.sin_port = htons(port);
	addr.sin_addr.s_addr = 0L;
	if (bind(sock, (struct sockaddr *)&addr, sizeof addr) < 0) {
		oprogname();
		perror("can't bind socket to address");
		exit(1);
	}

	if (listen(sock, 5) < 0) {
		oprogname();
		perror("can't listen on socket");
		exit(1);
	}

	fprintf(stderr, "Listening on port %d...\n", port);

	for (;;) {
		struct sockaddr_in clientaddr;
		int conn, size;

		conn = accept(sock, (struct sockaddr *) &clientaddr, &size);
		if (conn < 0) {
			oprogname();
			perror("can't accept connection from socket");
			exit(1);
		}

		create_thread(conn, &clientaddr);
	}
}

static void
create_thread(int conn, struct sockaddr_in *addr)
{
	struct workorder *work;
	pthread_t tdata;

	work = malloc(sizeof(struct workorder));
	if (work == NULL) {
		oprogname();
		fprintf(stderr, "out of memory for thread.\n");
		close(conn);
		return;
	}
	work->conn = conn;
	work->addr = *addr;

	init_python();

	if (pthread_create(&tdata, NULL, (void *)service_thread, work) < 0) {
		oprogname();
		perror("can't create new thread");
		close(conn);
		return;
	}

	if (pthread_detach(tdata) < 0) {
		oprogname();
		perror("can't detach from thread");
	}
}

static PyThreadState *the_tstate;
static PyInterpreterState *the_interp;
static PyObject *the_builtins;

static void
init_python()
{
	if (the_interp)
		return;
	Py_Initialize(); /* Initialize the interpreter */
	the_builtins = PyEval_GetBuiltins(); /* Get __builtins__ */
	PyEval_InitThreads(); /* Create and acquire the interpreter lock */
	the_tstate = PyEval_SaveThread(); /* Release lock & get thread state */
	the_interp = the_tstate->interpreter_state; /* Get interp state */
}

static void *
service_thread(struct workorder *work)
{
	FILE *input, *output;

	fprintf(stderr, "Start thread for connection %d.\n", work->conn);

	input = fdopen(work->conn, "r");
	if (input == NULL) {
		oprogname();
		perror("can't create input stream");
		goto done;
	}

	output = fdopen(work->conn, "w");
	if (output == NULL) {
		oprogname();
		perror("can't create output stream");
		fclose(input);
		goto done;
	}

	setvbuf(input, NULL, _IONBF, 0);
	setvbuf(output, NULL, _IONBF, 0);

	run_interpreter(input, output);

	fclose(input);
	fclose(output);

  done:
	fprintf(stderr, "End thread for connection %d.\n", work->conn);
	close(work->conn);
	free(work);
}

static void
oprogname()
{
	int save = errno;
	fprintf(stderr, "%s: ", progname);
	errno = save;
}

static void
run_interpreter(FILE *input, FILE *output)
{
	PyThreadState *tstate;
	PyObject *new_stdin, *new_stdout;
	PyObject *old_stdin, *old_stdout, *old_stderr;
	PyObject *globals;
	char buffer[1000];
	char *p, *q;
	int n, end;

	tstate = PyThreadState_New(the_interp);
	PyEval_AcquireThread(tstate);

	globals = PyDict_New();
	PyDict_SetItemString(globals, "__builtins__", the_builtins);

	new_stdin = PyFile_FromFile(input, "<socket-in>", "r", NULL);
	new_stdout = PyFile_FromFile(output, "<socket-out>", "w", NULL);

	old_stdin = PySys_GetObject("stdin");
	old_stdout = PySys_GetObject("stdout");
	old_stderr = PySys_GetObject("stderr");

	for (n = 1; !PyErr_Occurred(); n++) {
		Py_BEGIN_ALLOW_THREADS
		fprintf(output, "%d> ", n);
		p = fgets(buffer, sizeof buffer, input);
		Py_END_ALLOW_THREADS

		if (p == NULL)
			break;
		if (p[0] == '\377' && p[1] == '\354')
			break;

		q = strrchr(p, '\r');
		if (q && q[1] == '\n' && q[2] == '\0') {
			*q++ = '\n';
			*q++ = '\0';
		}

		while (*p && isspace(*p))
			p++;
		if (p[0] == '#' || p[0] == '\0')
			continue;

		PySys_SetObject("stdin", new_stdin);
		PySys_SetObject("stdout", new_stdout);
		PySys_SetObject("stderr", new_stdout);

		end = run_command(buffer, globals);
		if (end < 0)
			PyErr_Print();

		PySys_SetObject("stdin", old_stdin);
		PySys_SetObject("stdout", old_stdout);
		PySys_SetObject("stderr", old_stderr);

		if (end)
			break;
	}

	Py_XDECREF(globals);
	Py_XDECREF(new_stdin);
	Py_XDECREF(new_stdout);

	PyEval_ReleaseThread(tstate);
	PyThreadState_Delete(tstate);

	fprintf(output, "Goodbye!\n");
}

static int
run_command(char *buffer, PyObject *globals)
{
	PyObject *m, *d, *v;
	v = PyRun_String(buffer, Py_single_input, globals, globals);
	if (v == NULL) {
		if (PyErr_Occurred() == PyExc_SystemExit) {
			PyErr_Clear();
			return 1;
		}
		PyErr_Print();
		return 0;
	}
	Py_DECREF(v);
	return 0;
}