/**
 * @file kernel/vfs/tty.c
 * @brief PTY driver.
 *
 * @copyright
 * This file is part of ToaruOS and is released under the terms
 * of the NCSA / University of Illinois License - see LICENSE.md
 * Copyright (C) 2013-2021 K. Lange
 */
#include <stddef.h>
#include <errno.h>
#include <kernel/vfs.h>
#include <kernel/pipe.h>
#include <kernel/string.h>
#include <kernel/printf.h>
#include <kernel/ringbuffer.h>
#include <kernel/pty.h>
#include <kernel/hashmap.h>
#include <kernel/process.h>
#include <kernel/signal.h>
#include <kernel/time.h>
#include <sys/ioctl.h>
#include <sys/termios.h>
#include <sys/signal_defs.h>

#define TTY_BUFFER_SIZE 4096

#define MIN(a,b) ((a) < (b) ? (a) : (b))
extern void ptr_validate(void * ptr, const char * syscall);
#define validate(o) ptr_validate(o,"ioctl")

static int _pty_counter = 0;
static hashmap_t * _pty_index = NULL;
static fs_node_t * _pty_dir = NULL;
static fs_node_t * _dev_tty = NULL;

static void pty_write_in(pty_t * pty, uint8_t c) {
	ring_buffer_write(pty->in, 1, &c);
}

static void pty_write_out(pty_t * pty, uint8_t c) {
	ring_buffer_write(pty->out, 1, &c);
}

#define IN(character)   pty->write_in(pty, (uint8_t)character)
#define OUT(character)  pty->write_out(pty, (uint8_t)character)

static void dump_input_buffer(pty_t * pty) {
	char * c = pty->canon_buffer;
	while (pty->canon_buflen > 0) {
		IN(*c);
		pty->canon_buflen--;
		c++;
	}
}

static void clear_input_buffer(pty_t * pty) {
	pty->canon_buflen = 0;
	pty->canon_buffer[0] = '\0';
}

#define output_process_slave tty_output_process_slave
#define output_process tty_output_process
#define input_process tty_input_process

void tty_output_process_slave(pty_t * pty, uint8_t c) {
	if (c == '\n' && (pty->tios.c_oflag & ONLCR)) {
		c = '\n';
		OUT(c);
		c = '\r';
		OUT(c);
		return;
	}

	if (c == '\r' && (pty->tios.c_oflag & ONLRET)) {
		return;
	}

	if (c >= 'a' && c <= 'z' && (pty->tios.c_oflag & OLCUC)) {
		c = c + 'a' - 'A';
		OUT(c);
		return;
	}

	OUT(c);
}

void tty_output_process(pty_t * pty, uint8_t c) {
	output_process_slave(pty, c);
}

static int is_control(int c) {
	return c < ' ' || c == 0x7F;
}

static void erase_one(pty_t * pty, int erase) {
	if (pty->canon_buflen > 0) {
		/* How many do we backspace? */
		int vwidth = 1;
		pty->canon_buflen--;
		if (is_control(pty->canon_buffer[pty->canon_buflen])) {
			/* Erase ^@ */
			vwidth = 2;
		}
		pty->canon_buffer[pty->canon_buflen] = '\0';
		if (pty->tios.c_lflag & ECHO) {
			if (erase) {
				for (int i = 0; i < vwidth; ++i) {
					output_process(pty, '\010');
					output_process(pty, ' ');
					output_process(pty, '\010');
				}
			}
		}
	}
}

void tty_input_process(pty_t * pty, uint8_t c) {
	if (pty->next_is_verbatim) {
		pty->next_is_verbatim = 0;
		if (pty->canon_buflen < pty->canon_bufsize) {
			pty->canon_buffer[pty->canon_buflen] = c;
			pty->canon_buflen++;
		}
		if (pty->tios.c_lflag & ECHO) {
			if (is_control(c)) {
				output_process(pty, '^');
				output_process(pty, ('@'+c) % 128);
			} else {
				output_process(pty, c);
			}
		}
		return;
	}
	if (pty->tios.c_lflag & ISIG) {
		int sig = -1;
		if (c == pty->tios.c_cc[VINTR]) {
			sig = SIGINT;
		} else if (c == pty->tios.c_cc[VQUIT]) {
			sig = SIGQUIT;
		} else if (c == pty->tios.c_cc[VSUSP]) {
			sig = SIGTSTP;
		}
		/* VSUSP */
		if (sig != -1) {
			if (pty->tios.c_lflag & ECHO) {
				output_process(pty, '^');
				output_process(pty, ('@' + c) % 128);
				output_process(pty, '\n');
			}
			clear_input_buffer(pty);
			if (pty->fg_proc) {
				group_send_signal(pty->fg_proc, sig, 1);
			}
			return;
		}
	}
#if 0
	if (pty->tios.c_lflag & IXON ) {
		/* VSTOP, VSTART */
	}
#endif

	/* ISTRIP: Strip eighth bit */
	if (pty->tios.c_iflag & ISTRIP) {
		c &= 0x7F;
	}

	/* IGNCR: Ignore carriage return. */
	if ((pty->tios.c_iflag & IGNCR) && c == '\r') {
		return;
	}

	if ((pty->tios.c_iflag & INLCR) && c == '\n') {
		/* INLCR: Translate NL to CR. */
		c = '\r';
	} else if ((pty->tios.c_iflag & ICRNL) && c == '\r') {
		/* ICRNL: Convert carriage return. */
		c = '\n';
	}

	if (pty->tios.c_lflag & ICANON) {

		if (c == pty->tios.c_cc[VLNEXT] && (pty->tios.c_lflag & IEXTEN)) {
			pty->next_is_verbatim = 1;
			output_process(pty, '^');
			output_process(pty, '\010');
			return;
		}

		if (c == pty->tios.c_cc[VKILL]) {
			while (pty->canon_buflen > 0) {
				erase_one(pty, pty->tios.c_lflag & ECHOK);
			}
			if ((pty->tios.c_lflag & ECHO) && ! (pty->tios.c_lflag & ECHOK)) {
				output_process(pty, '^');
				output_process(pty, ('@' + c) % 128);
			}
			return;
		}
		if (c == pty->tios.c_cc[VERASE]) {
			/* Backspace */
			erase_one(pty, pty->tios.c_lflag & ECHOE);
			if ((pty->tios.c_lflag & ECHO) && ! (pty->tios.c_lflag & ECHOE)) {
				output_process(pty, '^');
				output_process(pty, ('@' + c) % 128);
			}
			return;
		}
		if (c == pty->tios.c_cc[VWERASE] && (pty->tios.c_lflag & IEXTEN)) {
			while (pty->canon_buflen && pty->canon_buffer[pty->canon_buflen-1] == ' ') {
				erase_one(pty, pty->tios.c_lflag & ECHOE);
			}
			while (pty->canon_buflen && pty->canon_buffer[pty->canon_buflen-1] != ' ') {
				erase_one(pty, pty->tios.c_lflag & ECHOE);
			}
			if ((pty->tios.c_lflag & ECHO) && ! (pty->tios.c_lflag & ECHOE)) {
				output_process(pty, '^');
				output_process(pty, ('@' + c) % 128);
			}
			return;
		}
		if (c == pty->tios.c_cc[VEOF]) {
			if (pty->canon_buflen) {
				dump_input_buffer(pty);
			} else {
				ring_buffer_interrupt(pty->in);
			}
			return;
		}

		if (pty->canon_buflen < pty->canon_bufsize) {
			pty->canon_buffer[pty->canon_buflen] = c;
			pty->canon_buflen++;
		}
		if (pty->tios.c_lflag & ECHO) {
			if (is_control(c) && c != '\n') {
				output_process(pty, '^');
				output_process(pty, ('@' + c) % 128);
			} else {
				output_process(pty, c);
			}
		}
		if (c == '\n' || (pty->tios.c_cc[VEOL] && c == pty->tios.c_cc[VEOL])) {
			if (!(pty->tios.c_lflag & ECHO) && (pty->tios.c_lflag & ECHONL)) {
				output_process(pty, c);
			}
			pty->canon_buffer[pty->canon_buflen-1] = c;
			dump_input_buffer(pty);
			return;
		}
		return;
	} else if (pty->tios.c_lflag & ECHO) {
		output_process(pty, c);
	}
	IN(c);
}

static void tty_fill_name(pty_t * pty, char * out) {
	((char*)out)[0] = '\0';
	snprintf((char*)out, 100, "/dev/pts/%zd", pty->name);
}

int pty_ioctl(pty_t * pty, unsigned long request, void * argp) {
	switch (request) {
		case IOCTLDTYPE:
			/*
			 * This is a special toaru-specific call to get a simple
			 * integer that describes the kind of device this is.
			 * It's more specific than just "character device" or "file",
			 * but for here we just need to say we're a TTY.
			 */
			return IOCTL_DTYPE_TTY;
		case IOCTLTTYNAME:
			if (!argp) return -EINVAL;
			validate(argp);
			pty->fill_name(pty, argp);
			return 0;
		case IOCTLTTYLOGIN:
			/* Set the user id of the login user */
			if (this_core->current_process->user != 0) return -EPERM;
			if (!argp) return -EINVAL;
			validate(argp);
			pty->slave->uid = *(int*)argp;
			pty->master->uid = *(int*)argp;
			return 0;
		case TIOCSWINSZ:
			if (!argp) return -EINVAL;
			validate(argp);
			memcpy(&pty->size, argp, sizeof(struct winsize));
			if (pty->fg_proc) {
				group_send_signal(pty->fg_proc, SIGWINCH, 1);
			}
			return 0;
		case TIOCGWINSZ:
			if (!argp) return -EINVAL;
			validate(argp);
			memcpy(argp, &pty->size, sizeof(struct winsize));
			return 0;
		case TCGETS:
			if (!argp) return -EINVAL;
			validate(argp);
			memcpy(argp, &pty->tios, sizeof(struct termios));
			return 0;
		case TIOCSPGRP:
			if (!argp) return -EINVAL;
			validate(argp);
			pty->fg_proc = *(pid_t *)argp;
			return 0;
		case TIOCGPGRP:
			if (!argp) return -EINVAL;
			validate(argp);
			*(pid_t *)argp = pty->fg_proc;
			return 0;
		case TCSETS:
		case TCSETSW:
		case TCSETSF:
			if (!argp) return -EINVAL;
			validate(argp);
			if (!(((struct termios *)argp)->c_lflag & ICANON) && (pty->tios.c_lflag & ICANON)) {
				/* Switch out of canonical mode, the dump the input buffer */
				dump_input_buffer(pty);
			}
			memcpy(&pty->tios, argp, sizeof(struct termios));
			return 0;
		default:
			return -EINVAL;
	}
}

ssize_t  read_pty_master(fs_node_t * node, off_t offset, size_t size, uint8_t *buffer) {
	pty_t * pty = (pty_t *)node->device;

	/* Standard pipe read */
	return ring_buffer_read(pty->out, size, buffer);
}
ssize_t write_pty_master(fs_node_t * node, off_t offset, size_t size, uint8_t *buffer) {
	pty_t * pty = (pty_t *)node->device;

	size_t l = 0;
	for (uint8_t * c = buffer; l < size; ++c, ++l) {
		input_process(pty, *c);
	}

	return l;
}
void      open_pty_master(fs_node_t * node, unsigned int flags) {
	return;
}
void     close_pty_master(fs_node_t * node) {
	return;
}

ssize_t read_pty_slave(fs_node_t * node, off_t offset, size_t size, uint8_t *buffer) {
	pty_t * pty = (pty_t *)node->device;

	if (pty->tios.c_lflag & ICANON) {
		return ring_buffer_read(pty->in, size, buffer);
	} else {
		if (pty->tios.c_cc[VMIN] == 0) {
			return ring_buffer_read(pty->in, MIN(size, ring_buffer_unread(pty->in)), buffer);
		} else {
			return ring_buffer_read(pty->in, MIN(pty->tios.c_cc[VMIN], size), buffer);
		}
	}
}

ssize_t write_pty_slave(fs_node_t * node, off_t offset, size_t size, uint8_t *buffer) {
	pty_t * pty = (pty_t *)node->device;

	size_t l = 0;
	for (uint8_t * c = buffer; l < size; ++c, ++l) {
		output_process_slave(pty, *c);
	}

	return l;
}
void      open_pty_slave(fs_node_t * node, unsigned int flags) {
	return;
}
void     close_pty_slave(fs_node_t * node) {
	pty_t * pty = (pty_t *)node->device;

	if (pty->name) {
		hashmap_remove(_pty_index, (void*)pty->name);
	}

	return;
}

/*
 * These are separate functions just in case I ever feel the need to do
 * things differently in the slave or master.
 */
int ioctl_pty_master(fs_node_t * node, unsigned long request, void * argp) {
	pty_t * pty = (pty_t *)node->device;
	return pty_ioctl(pty, request, argp);
}

int ioctl_pty_slave(fs_node_t * node, unsigned long request, void * argp) {
	pty_t * pty = (pty_t *)node->device;
	return pty_ioctl(pty, request, argp);
}

int pty_available_input(fs_node_t * node) {
	pty_t * pty = (pty_t *)node->device;
	return ring_buffer_unread(pty->in);
}

int pty_available_output(fs_node_t * node) {
	pty_t * pty = (pty_t *)node->device;
	return ring_buffer_unread(pty->out);
}

static int check_pty_master(fs_node_t * node) {
	pty_t * pty = (pty_t *)node->device;
	if (ring_buffer_unread(pty->out) > 0) {
		return 0;
	}
	return 1;
}

static int check_pty_slave(fs_node_t * node) {
	pty_t * pty = (pty_t *)node->device;
	if (ring_buffer_unread(pty->in) > 0) {
		return 0;
	}
	return 1;
}

static int wait_pty_master(fs_node_t * node, void * process) {
	pty_t * pty = (pty_t *)node->device;
	ring_buffer_select_wait(pty->out, process);
	return 0;
}

static int wait_pty_slave(fs_node_t * node, void * process) {
	pty_t * pty = (pty_t *)node->device;
	ring_buffer_select_wait(pty->in, process);
	return 0;
}

fs_node_t * pty_master_create(pty_t * pty) {
	fs_node_t * fnode = malloc(sizeof(fs_node_t));
	memset(fnode, 0x00, sizeof(fs_node_t));

	fnode->name[0] = '\0';
	snprintf(fnode->name, 100, "pty master");
	fnode->uid   = this_core->current_process->user;
	fnode->gid   = this_core->current_process->user_group;
	fnode->mask  = 0666;
	fnode->flags = FS_PIPE;
	fnode->read  =  read_pty_master;
	fnode->write = write_pty_master;
	fnode->open  =  open_pty_master;
	fnode->close = close_pty_master;
	fnode->selectcheck = check_pty_master;
	fnode->selectwait  = wait_pty_master;
	fnode->readdir = NULL;
	fnode->finddir = NULL;
	fnode->ioctl = ioctl_pty_master;
	fnode->get_size = pty_available_output;
	fnode->ctime   = now();
	fnode->mtime   = now();
	fnode->atime   = now();

	fnode->device = pty;

	return fnode;
}

fs_node_t * pty_slave_create(pty_t * pty) {
	fs_node_t * fnode = malloc(sizeof(fs_node_t));
	memset(fnode, 0x00, sizeof(fs_node_t));

	fnode->name[0] = '\0';
	snprintf(fnode->name, 100, "pty slave");
	fnode->uid   = this_core->current_process->user;
	fnode->gid   = this_core->current_process->user_group;
	fnode->mask  = 0620;
	fnode->flags = FS_CHARDEVICE;
	fnode->read  =  read_pty_slave;
	fnode->write = write_pty_slave;
	fnode->open  =  open_pty_slave;
	fnode->close = close_pty_slave;
	fnode->selectcheck = check_pty_slave;
	fnode->selectwait  = wait_pty_slave;
	fnode->readdir = NULL;
	fnode->finddir = NULL;
	fnode->ioctl = ioctl_pty_slave;
	fnode->get_size = pty_available_input;
	fnode->ctime   = now();
	fnode->mtime   = now();
	fnode->atime   = now();

	fnode->device = pty;

	return fnode;
}

static int isatty(fs_node_t * node) {
	if (!node) return 0;
	if (!node->ioctl) return 0;
	return ioctl_fs(node, IOCTLDTYPE, NULL) == IOCTL_DTYPE_TTY;
}

static ssize_t readlink_dev_tty(fs_node_t * node, char * buf, size_t size) {
	pty_t * pty = NULL;

	for (unsigned int i = 0; i < ((this_core->current_process->fds->length < 3) ? this_core->current_process->fds->length : 3); ++i) {
		if (isatty(this_core->current_process->fds->entries[i])) {
			pty = (pty_t *)this_core->current_process->fds->entries[i]->device;
			break;
		}
	}

	char tmp[30];
	size_t req;
	if (!pty) {
		snprintf(tmp, 100, "/dev/null");
	} else {
		pty->fill_name(pty, tmp);
	}

	req = strlen(tmp) + 1;

	if (size < req) {
		memcpy(buf, tmp, size);
		buf[size-1] = '\0';
		return size-1;
	}

	if (size > req) size = req;

	memcpy(buf, tmp, size);
	return size-1;
}

static fs_node_t * create_dev_tty(void) {
	fs_node_t * fnode = malloc(sizeof(fs_node_t));
	memset(fnode, 0x00, sizeof(fs_node_t));
	fnode->inode = 0;
	strcpy(fnode->name, "tty");
	fnode->mask = 0777;
	fnode->uid  = 0;
	fnode->gid  = 0;
	fnode->flags   = FS_FILE | FS_SYMLINK;
	fnode->readlink = readlink_dev_tty;
	fnode->length  = 1;
	fnode->nlink   = 1;
	fnode->ctime   = now();
	fnode->mtime   = now();
	fnode->atime   = now();
	return fnode;
}

static struct dirent * readdir_pty(fs_node_t *node, unsigned long index) {
	if (index == 0) {
		struct dirent * out = malloc(sizeof(struct dirent));
		memset(out, 0x00, sizeof(struct dirent));
		out->d_ino = 0;
		strcpy(out->d_name, ".");
		return out;
	}

	if (index == 1) {
		struct dirent * out = malloc(sizeof(struct dirent));
		memset(out, 0x00, sizeof(struct dirent));
		out->d_ino = 0;
		strcpy(out->d_name, "..");
		return out;
	}

	index -= 2;

	pty_t * out_pty = NULL;
	list_t * values = hashmap_values(_pty_index);
	foreach(node, values) {
		if (index == 0) {
			out_pty = node->value;
			break;
		}
		index--;
	}
	list_free(values);

	if (out_pty) {
		struct dirent * out = malloc(sizeof(struct dirent));
		memset(out, 0x00, sizeof(struct dirent));
		out->d_ino = out_pty->name;
		out->d_name[0] = '\0';
		snprintf(out->d_name, 100, "%zd", out_pty->name);
		return out;
	} else {
		return NULL;
	}
}

static fs_node_t * finddir_pty(fs_node_t * node, char * name) {
	if (!name) return NULL;
	if (strlen(name) < 1) return NULL;

	intptr_t c = 0;
	for (intptr_t i = 0; name[i]; ++i) {
		if (name[i] < '0' || name[i] > '9') {
			return NULL;
		}
		c = c * 10 + name[i] - '0';
	}

	pty_t * _pty = hashmap_get(_pty_index, (void*)c);

	if (!_pty) {
		return NULL;
	}

	return _pty->slave;
}

static fs_node_t * create_pty_dir(void) {
	fs_node_t * fnode = malloc(sizeof(fs_node_t));
	memset(fnode, 0x00, sizeof(fs_node_t));
	fnode->inode = 0;
	strcpy(fnode->name, "pty");
	fnode->mask = 0555;
	fnode->uid  = 0;
	fnode->gid  = 0;
	fnode->flags   = FS_DIRECTORY;
	fnode->read    = NULL;
	fnode->write   = NULL;
	fnode->open    = NULL;
	fnode->close   = NULL;
	fnode->readdir = readdir_pty;
	fnode->finddir = finddir_pty;
	fnode->nlink   = 1;
	fnode->ctime   = now();
	fnode->mtime   = now();
	fnode->atime   = now();
	return fnode;
}

void pty_install(void) {
	_pty_index = hashmap_create_int(10);
	_pty_dir   = create_pty_dir();
	_dev_tty   = create_dev_tty();

	vfs_mount("/dev/pts", _pty_dir);
	vfs_mount("/dev/tty", _dev_tty);
}

pty_t * pty_new(struct winsize * size, int index) {

	if (!_pty_index) {
		pty_install();
	}

	pty_t * pty = malloc(sizeof(pty_t));

	pty->next_is_verbatim = 0;

	/* stdin linkage; characters from terminal → PTY slave */
	pty->in  = ring_buffer_create(TTY_BUFFER_SIZE);
	pty->out = ring_buffer_create(TTY_BUFFER_SIZE);

	/* Master endpoint - writes go to stdin, reads come from stdout */
	pty->master = pty_master_create(pty);

	/* Slave endpoint, reads come from stdin, writes go to stdout */
	pty->slave  = pty_slave_create(pty);

	/* tty name */
	pty->name      = index;
	pty->fill_name = tty_fill_name;

	pty->write_in = pty_write_in;
	pty->write_out = pty_write_out;

	if (index) {
		hashmap_set(_pty_index, (void*)pty->name, pty);
	}

	if (size) {
		memcpy(&pty->size, size, sizeof(struct winsize));
	} else {
		/* Sane defaults */
		pty->size.ws_row = 25;
		pty->size.ws_col = 80;
	}

	/* Controlling and foreground processes are set to 0 by default */
	pty->ct_proc = 0;
	pty->fg_proc = 0;

	pty->tios.c_iflag = ICRNL | BRKINT;
	pty->tios.c_oflag = ONLCR | OPOST;
	pty->tios.c_lflag = ECHO | ECHOE | ECHOK | ICANON | ISIG | IEXTEN;
	pty->tios.c_cflag = CREAD | CS8;
	pty->tios.c_cc[VEOF]   =  4; /* ^D */
	pty->tios.c_cc[VEOL]   =  0; /* Not set */
	pty->tios.c_cc[VERASE] = 0x7f; /* ^? */
	pty->tios.c_cc[VINTR]  =  3; /* ^C */
	pty->tios.c_cc[VKILL]  = 21; /* ^U */
	pty->tios.c_cc[VMIN]   =  1;
	pty->tios.c_cc[VQUIT]  = 28; /* ^\ */
	pty->tios.c_cc[VSTART] = 17; /* ^Q */
	pty->tios.c_cc[VSTOP]  = 19; /* ^S */
	pty->tios.c_cc[VSUSP] = 26; /* ^Z */
	pty->tios.c_cc[VTIME]  =  0;
	pty->tios.c_cc[VLNEXT] = 22; /* ^V */
	pty->tios.c_cc[VWERASE] = 23; /* ^W */

	pty->canon_buffer  = malloc(TTY_BUFFER_SIZE);
	pty->canon_bufsize = TTY_BUFFER_SIZE-2;
	pty->canon_buflen  = 0;

	return pty;
}

int pty_create(void *size, fs_node_t ** fs_master, fs_node_t ** fs_slave) {
	pty_t * pty = pty_new(size, ++_pty_counter);

	*fs_master = pty->master;
	*fs_slave  = pty->slave;

	return 0;
}