#undef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200112L

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/wait.h>
#include <unistd.h>

#ifdef __linux
#include <pty.h>
#endif

#ifdef __NetBSD__
#include <sys/ioctl.h>
#include <util.h>
#endif

#include "../uxn.h"
#include "console.h"

/*
Copyright (c) 2022-2023 Devine Lu Linvega, Andrew Alderwick

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/

/* process */
static char *fork_args[32];
static int child_mode;
static int pty_fd;
static int to_child_fd[2];
static int from_child_fd[2];
static int saved_in;
static int saved_out;
static pid_t child_pid;
struct winsize ws = {24, 80, 8, 12};

static void
parse_args(Uint8 *d)
{
	Uint8 *port_addr = d + 0x3;
	int addr = PEEK2(port_addr);
	char *pos = (char *)&uxn.ram[addr];
	int i = 0;
	do {
		fork_args[i++] = pos;
		while(*pos != 0) pos++;
		pos++;
	} while(*pos != '\0');
	fork_args[i] = NULL;
}

/* call after we're sure the process has exited */
static void
clean_after_child(void)
{
	child_pid = 0;
	if(child_mode >= 0x80) {
		close(pty_fd);
		dup2(saved_in, 0);
		dup2(saved_out, 1);
	} else {
		if(child_mode & 0x01) {
			close(to_child_fd[1]);
			dup2(saved_out, 1);
		}
		if(child_mode & 0x06) {
			close(from_child_fd[0]);
			dup2(saved_in, 0);
		}
	}
	child_mode = 0;
	saved_in = -1;
	saved_out = -1;
}

int
console_input(Uint8 c, int type)
{
	uxn.dev[0x12] = c;
	uxn.dev[0x17] = type;
	return uxn_eval(PEEK2(&uxn.dev[0x10]));
}

void
console_listen(int i, int argc, char **argv)
{
	for(; i < argc; i++) {
		char *p = argv[i];
		while(*p) console_input(*p++, CONSOLE_ARG);
		console_input('\n', i == argc - 1 ? CONSOLE_END : CONSOLE_EOA);
	}
}

static void
start_fork_pty(Uint8 *d)
{
	int fd = -1;
	pid_t pid = forkpty(&fd, NULL, NULL, NULL);
	if(pid < 0) { /* failure */
		d[0x6] = 0xff;
		fprintf(stderr, "fork failure\n");
	} else if(pid == 0) { /* child */
		setenv("TERM", "ansi", 1);
		execvp(fork_args[0], fork_args);
		d[0x6] = 0xff;
		fprintf(stderr, "exec failure\n");
	} else { /*parent*/
		child_pid = pid;
		pty_fd = fd;
		ioctl(fd, TIOCSWINSZ, &ws);
		saved_in = dup(0);
		saved_out = dup(1);
		dup2(fd, 0);
		dup2(fd, 1);
	}
}

static void
start_fork_pipe(Uint8 *d)
{
	pid_t pid;
	if(child_mode & 0x01) {
		/* parent writes to child's stdin */
		if(pipe(to_child_fd) == -1) {
			d[0x6] = 0xff;
			fprintf(stderr, "pipe error: to child\n");
			return;
		}
	}
	if(child_mode & 0x06) {
		/* parent reads from child's stdout and/or stderr */
		if(pipe(from_child_fd) == -1) {
			d[0x6] = 0xff;
			fprintf(stderr, "pipe error: from child\n");
			return;
		}
	}
	pid = fork();
	if(pid < 0) { /* failure */
		d[0x6] = 0xff;
		fprintf(stderr, "fork failure\n");
	} else if(pid == 0) { /* child */
		if(child_mode & 0x01) {
			dup2(to_child_fd[0], 0);
			close(to_child_fd[1]);
		}
		if(child_mode & 0x06) {
			if(child_mode & 0x02) dup2(from_child_fd[1], 1);
			if(child_mode & 0x04) dup2(from_child_fd[1], 2);
			close(from_child_fd[0]);
		}
		execvp(fork_args[0], fork_args);
		d[0x6] = 0xff;
		fprintf(stderr, "exec failure\n");
	} else { /*parent*/
		child_pid = pid;
		if(child_mode & 0x01) {
			saved_out = dup(1);
			dup2(to_child_fd[1], 1);
			close(to_child_fd[0]);
		}
		if(child_mode & 0x06) {
			saved_in = dup(0);
			dup2(from_child_fd[0], 0);
			close(from_child_fd[1]);
		}
	}
}

static void
kill_child(Uint8 *d, int options)
{
	int wstatus;
	if(child_pid) {
		kill(child_pid, 9);
		if(waitpid(child_pid, &wstatus, options)) {
			d[0x6] = 1;
			d[0x7] = WEXITSTATUS(wstatus);
			clean_after_child();
		}
	}
}

static void
start_fork(Uint8 *d)
{
	fflush(stderr);
	kill_child(d, 0);
	child_mode = d[0x5];
	parse_args(d);
	if(child_mode >= 0x80)
		start_fork_pty(d);
	else
		start_fork_pipe(d);
}

Uint8
console_dei(Uint8 addr)
{
	Uint8 port = addr & 0x0f, *d = &uxn.dev[addr & 0xf0];
	switch(port) {
	case 0x6:
	case 0x7: kill_child(d, WNOHANG);
	}
	return d[port];
}

void
console_deo(Uint8 addr)
{
	FILE *fd;
	switch(addr) {
	case 0x15: /* Console/dead */ start_fork(&uxn.dev[0x10]); break;
	case 0x16: /* Console/exit*/ kill_child(&uxn.dev[0x10], 0); break;
	case 0x18: fd = stdout, fputc(uxn.dev[0x18], fd), fflush(fd); break;
	case 0x19: fd = stderr, fputc(uxn.dev[0x19], fd), fflush(fd); break;
	}
}