/*
 * kmscon - VT Emulator
 *
 * Copyright (c) 2011 David Herrmann <dh.herrmann@googlemail.com>
 * Copyright (c) 2011 University of Tuebingen
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Virtual Terminal Emulator
 * This is a vt100 implementation. It is written from scratch. It uses the
 * console subsystem as output and is tightly bound to it.
 */

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <X11/keysym.h>

#include "console.h"
#include "input.h"
#include "log.h"
#include "unicode.h"
#include "vte.h"

/* Input parser states */
enum parser_state {
	STATE_NORMAL,		/* normal mode */
	STATE_ESC,		/* starting escape sequence */
	STATE_CSI,		/* Control Sequence Introducer */
	STATE_OTHER,		/* other known but unimpl escp seqs */
};

/* maximum CSI parameters */
#define CSI_ARG_MAX 15

/* CSI flags */
#define CSI_START	0x01 /* no arg has been parsed yet */
#define CSI_QUESTION	0x02 /* ? flag */
#define CSI_BANG	0x04 /* ! flag */

struct kmscon_vte {
	unsigned long ref;
	struct kmscon_symbol_table *st;
	struct kmscon_console *con;

	const char *kbd_sym;
	struct kmscon_utf8_mach *mach;

	struct {
		unsigned int state;
		unsigned int csi_flags;
		unsigned int csi_argc;
		unsigned int csi_argv[CSI_ARG_MAX];
	} parser;
};

int kmscon_vte_new(struct kmscon_vte **out, struct kmscon_symbol_table *st)
{
	struct kmscon_vte *vte;
	int ret;

	if (!out)
		return -EINVAL;

	log_debug("vte: new vte object\n");

	vte = malloc(sizeof(*vte));
	if (!vte)
		return -ENOMEM;

	memset(vte, 0, sizeof(*vte));
	vte->ref = 1;
	vte->st = st;

	ret = kmscon_utf8_mach_new(&vte->mach);
	if (ret)
		goto err_free;

	kmscon_symbol_table_ref(vte->st);
	*out = vte;
	return 0;

err_free:
	free(vte);
	return ret;
}

void kmscon_vte_ref(struct kmscon_vte *vte)
{
	if (!vte)
		return;

	vte->ref++;
}

void kmscon_vte_unref(struct kmscon_vte *vte)
{
	if (!vte || !vte->ref)
		return;

	if (--vte->ref)
		return;

	kmscon_console_unref(vte->con);
	kmscon_utf8_mach_free(vte->mach);
	kmscon_symbol_free_u8(vte->kbd_sym);
	kmscon_symbol_table_unref(vte->st);
	free(vte);
	log_debug("vte: destroying vte object\n");
}

void kmscon_vte_bind(struct kmscon_vte *vte, struct kmscon_console *con)
{
	if (!vte)
		return;

	kmscon_console_unref(vte->con);
	vte->con = con;
	kmscon_console_ref(vte->con);
}

static void parse_control(struct kmscon_vte *vte, uint32_t ctrl)
{
	switch (ctrl) {
		case 0x00: /* NUL */
			/* Ignore on input */
			break;
		case 0x05: /* ENQ */
			/* Transmit answerback message */
			break;
		case 0x07: /* BEL */
			/* Sound bell tone */
			break;
		case 0x08: /* BS */
			/* Move cursor one position left */
			break;
		case 0x09: /* HT */
			/* Move to next tab stop or end of line */
			break;
		case 0x0a: /* LF */
			/* Line feed or newline (CR/NL mode) */
			kmscon_console_newline(vte->con);
			break;
		case 0x0b: /* VT */
		case 0x0c: /* FF */
			/* Line feed */
			kmscon_console_move_down(vte->con, 1, true);
			break;
		case 0x0d: /* CR */
			/* Move cursor to left margin */
			kmscon_console_move_line_home(vte->con);
			break;
		case 0x0e: /* SO */
			/* Invoke G1 character set */
			break;
		case 0x0f: /* SI */
			/* Select G0 character set */
			break;
		case 0x11: /* XON */
			/* Resume transmission */
			break;
		case 0x13: /* XOFF */
			/* Stop transmission */
			break;
		case 0x18: /* CAN */
		case 0x1a: /* SUB */
			/* Discard current escape sequence and show err-sym */
			break;
		case 0x1b: /* ESC */
			/* Invokes an escape sequence */
			vte->parser.state = STATE_ESC;
			break;
		case 0x7f: /* DEL */
			/* Ignored on input */
			break;
	}
}

static void parse_csi(struct kmscon_vte *vte, uint32_t val)
{
	int new;
	unsigned int num;

	if (vte->parser.csi_flags & CSI_START) {
		switch (val) {
			case '?':
				vte->parser.csi_flags |= CSI_QUESTION;
				return;
			case '!':
				vte->parser.csi_flags |= CSI_BANG;
				return;
			default:
				vte->parser.csi_flags &= ~CSI_START;
		}
	}

	if (val == ';') {
		if (vte->parser.csi_argc < CSI_ARG_MAX)
			vte->parser.csi_argc++;
		return;
	}

	if (val >= '0' && val <= '9') {
		if (vte->parser.csi_argc >= CSI_ARG_MAX)
			return;

		new = vte->parser.csi_argv[vte->parser.csi_argc];
		new *= 10;
		new += val - '0';

		/* avoid integer overflows */
		if (new > vte->parser.csi_argv[vte->parser.csi_argc])
			vte->parser.csi_argv[vte->parser.csi_argc] = new;

		return;
	}

	vte->parser.csi_argc++;
	vte->parser.state = STATE_NORMAL;

	switch (val) {
		case 'A':
			num = vte->parser.csi_argv[0];
			if (!num)
				num = 1;
			kmscon_console_move_up(vte->con, num, false);
			break;
		case 'B':
			num = vte->parser.csi_argv[0];
			if (!num)
				num = 1;
			kmscon_console_move_down(vte->con, num, false);
			break;
		case 'C':
			num = vte->parser.csi_argv[0];
			if (!num)
				num = 1;
			kmscon_console_move_right(vte->con, num);
			break;
		case 'D':
			num = vte->parser.csi_argv[0];
			if (!num)
				num = 1;
			kmscon_console_move_left(vte->con, num);
			break;
		case 'J':
			if (vte->parser.csi_argc < 1 ||
						vte->parser.csi_argv[0] == 0)
				kmscon_console_erase_cursor_to_screen(vte->con);
			else if (vte->parser.csi_argv[0] == 1)
				kmscon_console_erase_screen_to_cursor(vte->con);
			else if (vte->parser.csi_argv[0] == 2)
				kmscon_console_erase_screen(vte->con);
			break;
		case 'K':
			if (vte->parser.csi_argc < 1 ||
						vte->parser.csi_argv[0] == 0)
				kmscon_console_erase_cursor_to_end(vte->con);
			else if (vte->parser.csi_argv[0] == 1)
				kmscon_console_erase_home_to_cursor(vte->con);
			else if (vte->parser.csi_argv[0] == 2)
				kmscon_console_erase_current_line(vte->con);
			break;
		default:
			log_debug("vte: unhandled CSI sequence\n");
	}
}

static void parse_other(struct kmscon_vte *vte, uint32_t val)
{
	/* TODO: make this more sophisticated */
	vte->parser.state = STATE_NORMAL;
}

static void parse_esc(struct kmscon_vte *vte, uint32_t val)
{
	switch (val) {
		case '[': /* CSI */
			vte->parser.state = STATE_CSI;
			vte->parser.csi_flags = CSI_START;
			vte->parser.csi_argc = 0;
			memset(vte->parser.csi_argv, 0,
						sizeof(vte->parser.csi_argv));
			break;
		case 'P': /* DCS */
		case ']': /* OCS */
		case '^': /* PM */
		case '_': /* APC */
		case '#': /* special */
		case '(': /* G0 */
		case ')': /* G1 */
		case '%': /* charset */
		default:
			vte->parser.state = STATE_OTHER;
			break;
	}
}

static void parse_input(struct kmscon_vte *vte, uint32_t val)
{
	kmscon_symbol_t sym;

	if (val < 0x20) {
		parse_control(vte, val);
		return;
	}

	switch (vte->parser.state) {
		case STATE_ESC:
			parse_esc(vte, val);
			return;
		case STATE_CSI:
			parse_csi(vte, val);
			return;
		case STATE_OTHER:
			parse_other(vte, val);
			return;
	}

	sym = kmscon_symbol_make(val);
	kmscon_console_write(vte->con, sym);
}

void kmscon_vte_input(struct kmscon_vte *vte, const char *u8, size_t len)
{
	int state, i;
	uint32_t ucs4;

	if (!vte || !vte->con)
		return;

	for (i = 0; i < len; ++i) {
		state = kmscon_utf8_mach_feed(vte->mach, u8[i]);
		if (state == KMSCON_UTF8_ACCEPT ||
				state == KMSCON_UTF8_REJECT) {
			ucs4 = kmscon_utf8_mach_get(vte->mach);
			parse_input(vte, ucs4);
		}
	}
}

int kmscon_vte_handle_keyboard(struct kmscon_vte *vte,
	const struct kmscon_input_event *ev, const char **u8, size_t *len)
{
	kmscon_symbol_t sym;

	switch (ev->keysym) {
		case XK_BackSpace:
			*u8 = "\x08";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Tab:
		case XK_KP_Tab:
			*u8 = "\x09";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Linefeed:
			*u8 = "\x0a";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Clear:
			*u8 = "\x0b";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Pause:
			*u8 = "\x13";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Scroll_Lock:
			/* TODO: do we need scroll lock impl.? */
			*u8 = "\x14";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Sys_Req:
			*u8 = "\x15";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Escape:
			*u8 = "\x1b";
			*len = 1;
			return KMSCON_VTE_SEND;
		case XK_Return:
		case XK_KP_Enter:
			/* TODO: im CR/LF mode send \x0d\x0a */
			*u8 = "\x0d";
			*len = 1;
			return KMSCON_VTE_SEND;
	}

	if (ev->unicode != KMSCON_INPUT_INVALID) {
		kmscon_symbol_free_u8(vte->kbd_sym);
		sym = kmscon_symbol_make(ev->unicode);
		vte->kbd_sym = kmscon_symbol_get_u8(vte->st, sym, len);
		*u8 = vte->kbd_sym;
		return KMSCON_VTE_SEND;
	}

	return KMSCON_VTE_DROP;
}