/*
 * Copyright (C) 1984-2012  Mark Nudelman
 * Modified for use with illumos by Garrett D'Amore.
 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information, see the README file.
 */

/*
 * Routines to decode user commands.
 *
 * This is all table driven.
 * A command table is a sequence of command descriptors.
 * Each command descriptor is a sequence of bytes with the following format:
 *	<c1><c2>...<cN><0><action>
 * The characters c1,c2,...,cN are the command string; that is,
 * the characters which the user must type.
 * It is terminated by a null <0> byte.
 * The byte after the null byte is the action code associated
 * with the command string.
 * If an action byte is OR-ed with A_EXTRA, this indicates
 * that the option byte is followed by an extra string.
 *
 * There may be many command tables.
 * The first (default) table is built-in.
 * Other tables are read in from "lesskey" files.
 * All the tables are linked together and are searched in order.
 */

#include "cmd.h"
#include "less.h"
#include "lesskey.h"

extern int erase_char, erase2_char, kill_char;
extern int secure, less_is_more;

#define	SK(k) \
	SK_SPECIAL_KEY, (k), 6, 1, 1, 1
/*
 * Command table is ordered roughly according to expected
 * frequency of use, so the common commands are near the beginning.
 */

static unsigned char cmdtable[] =
{
	'\r', 0,			A_F_LINE,
	'\n', 0,			A_F_LINE,
	'e', 0,				A_F_LINE,
	'j', 0,				A_F_LINE,
	SK(SK_DOWN_ARROW), 0,		A_F_LINE,
	CONTROL('E'), 0,		A_F_LINE,
	CONTROL('N'), 0,		A_F_LINE,
	'k', 0,				A_B_LINE,
	'y', 0,				A_B_LINE,
	CONTROL('Y'), 0,		A_B_LINE,
	SK(SK_CONTROL_K), 0,		A_B_LINE,
	CONTROL('P'), 0,		A_B_LINE,
	SK(SK_UP_ARROW), 0,		A_B_LINE,
	'J', 0,				A_FF_LINE,
	'K', 0,				A_BF_LINE,
	'Y', 0,				A_BF_LINE,
	'd', 0,				A_F_SCROLL,
	CONTROL('D'), 0,		A_F_SCROLL,
	'u', 0,				A_B_SCROLL,
	CONTROL('U'), 0,		A_B_SCROLL,
	' ', 0,				A_F_SCREEN,
	'f', 0,				A_F_SCREEN,
	CONTROL('F'), 0,		A_F_SCREEN,
	CONTROL('V'), 0,		A_F_SCREEN,
	SK(SK_PAGE_DOWN), 0,		A_F_SCREEN,
	'b', 0,				A_B_SCREEN,
	CONTROL('B'), 0,		A_B_SCREEN,
	ESC, 'v', 0,			A_B_SCREEN,
	SK(SK_PAGE_UP), 0,		A_B_SCREEN,
	'z', 0,				A_F_WINDOW,
	'w', 0,				A_B_WINDOW,
	ESC, ' ', 0,			A_FF_SCREEN,
	'F', 0,				A_F_FOREVER,
	ESC, 'F', 0,			A_F_UNTIL_HILITE,
	'R', 0,				A_FREPAINT,
	'r', 0,				A_REPAINT,
	CONTROL('R'), 0,		A_REPAINT,
	CONTROL('L'), 0,		A_REPAINT,
	ESC, 'u', 0,			A_UNDO_SEARCH,
	'g', 0,				A_GOLINE,
	SK(SK_HOME), 0,			A_GOLINE,
	'<', 0,				A_GOLINE,
	ESC, '<', 0,			A_GOLINE,
	'p', 0,				A_PERCENT,
	'%', 0,				A_PERCENT,
	ESC, '[', 0,			A_LSHIFT,
	ESC, ']', 0,			A_RSHIFT,
	ESC, '(', 0,			A_LSHIFT,
	ESC, ')', 0,			A_RSHIFT,
	SK(SK_RIGHT_ARROW), 0,		A_RSHIFT,
	SK(SK_LEFT_ARROW), 0,		A_LSHIFT,
	'{', 0,				A_F_BRACKET|A_EXTRA,	'{', '}', 0,
	'}', 0,				A_B_BRACKET|A_EXTRA,	'{', '}', 0,
	'(', 0,				A_F_BRACKET|A_EXTRA,	'(', ')', 0,
	')', 0,				A_B_BRACKET|A_EXTRA,	'(', ')', 0,
	'[', 0,				A_F_BRACKET|A_EXTRA,	'[', ']', 0,
	']', 0,				A_B_BRACKET|A_EXTRA,	'[', ']', 0,
	ESC, CONTROL('F'), 0,		A_F_BRACKET,
	ESC, CONTROL('B'), 0,		A_B_BRACKET,
	'G', 0,				A_GOEND,
	ESC, '>', 0,			A_GOEND,
	'>', 0,				A_GOEND,
	SK(SK_END), 0,			A_GOEND,
	'P', 0,				A_GOPOS,

	'0', 0,				A_DIGIT,
	'1', 0,				A_DIGIT,
	'2', 0,				A_DIGIT,
	'3', 0,				A_DIGIT,
	'4', 0,				A_DIGIT,
	'5', 0,				A_DIGIT,
	'6', 0,				A_DIGIT,
	'7', 0,				A_DIGIT,
	'8', 0,				A_DIGIT,
	'9', 0,				A_DIGIT,
	'.', 0,				A_DIGIT,

	'=', 0,				A_STAT,
	CONTROL('G'), 0,		A_STAT,
	':', 'f', 0,			A_STAT,
	'/', 0,				A_F_SEARCH,
	'?', 0,				A_B_SEARCH,
	ESC, '/', 0,			A_F_SEARCH|A_EXTRA,	'*', 0,
	ESC, '?', 0,			A_B_SEARCH|A_EXTRA,	'*', 0,
	'n', 0,				A_AGAIN_SEARCH,
	ESC, 'n', 0,			A_T_AGAIN_SEARCH,
	'N', 0,				A_REVERSE_SEARCH,
	ESC, 'N', 0,			A_T_REVERSE_SEARCH,
	'&', 0,				A_FILTER,
	'm', 0,				A_SETMARK,
	'\'', 0,			A_GOMARK,
	CONTROL('X'), CONTROL('X'), 0,	A_GOMARK,
	'E', 0,				A_EXAMINE,
	':', 'e', 0,			A_EXAMINE,
	CONTROL('X'), CONTROL('V'), 0,	A_EXAMINE,
	':', 'n', 0,			A_NEXT_FILE,
	':', 'p', 0,			A_PREV_FILE,
	't', 0,				A_NEXT_TAG,
	'T', 0,				A_PREV_TAG,
	':', 'x', 0,			A_INDEX_FILE,
	':', 'd', 0,			A_REMOVE_FILE,
	':', 't', 0,			A_OPT_TOGGLE|A_EXTRA,	't', 0,
	'|', 0,				A_PIPE,
	'v', 0,				A_VISUAL,
	'+', 0,				A_FIRSTCMD,

	'H', 0,				A_HELP,
	'h', 0,				A_HELP,
	SK(SK_F1), 0,			A_HELP,
	'V', 0,				A_VERSION,
	'q', 0,				A_QUIT,
	'Q', 0,				A_QUIT,
	':', 'q', 0,			A_QUIT,
	':', 'Q', 0,			A_QUIT,
	'Z', 'Z', 0,			A_QUIT
};

static unsigned char lesstable[] = {
	'-', 0,				A_OPT_TOGGLE,
	's', 0,				A_OPT_TOGGLE|A_EXTRA,	'o', 0,
	'_', 0,				A_DISP_OPTION
};

static unsigned char moretable[] = {
	's', 0,				A_F_SKIP
};

static unsigned char edittable[] =
{
	'\t', 0,			EC_F_COMPLETE,	/* TAB */
	'\17', 0,			EC_B_COMPLETE,	/* BACKTAB */
	SK(SK_BACKTAB), 0,		EC_B_COMPLETE,	/* BACKTAB */
	ESC, '\t', 0,			EC_B_COMPLETE,	/* ESC TAB */
	CONTROL('L'), 0,		EC_EXPAND,	/* CTRL-L */
	CONTROL('V'), 0,		EC_LITERAL,	/* BACKSLASH */
	CONTROL('A'), 0,		EC_LITERAL,	/* BACKSLASH */
	ESC, 'l', 0,			EC_RIGHT,	/* ESC l */
	SK(SK_RIGHT_ARROW), 0,		EC_RIGHT,	/* RIGHTARROW */
	ESC, 'h', 0,			EC_LEFT,	/* ESC h */
	SK(SK_LEFT_ARROW), 0,		EC_LEFT,	/* LEFTARROW */
	ESC, 'b', 0,			EC_W_LEFT,	/* ESC b */
	ESC, SK(SK_LEFT_ARROW), 0,	EC_W_LEFT,	/* ESC LEFTARROW */
	SK(SK_CTL_LEFT_ARROW), 0,	EC_W_LEFT,	/* CTRL-LEFTARROW */
	ESC, 'w', 0,			EC_W_RIGHT,	/* ESC w */
	ESC, SK(SK_RIGHT_ARROW), 0,	EC_W_RIGHT,	/* ESC RIGHTARROW */
	SK(SK_CTL_RIGHT_ARROW), 0,	EC_W_RIGHT,	/* CTRL-RIGHTARROW */
	ESC, 'i', 0,			EC_INSERT,	/* ESC i */
	SK(SK_INSERT), 0,		EC_INSERT,	/* INSERT */
	ESC, 'x', 0,			EC_DELETE,	/* ESC x */
	SK(SK_DELETE), 0,		EC_DELETE,	/* DELETE */
	ESC, 'X', 0,			EC_W_DELETE,	/* ESC X */
	ESC, SK(SK_DELETE), 0,		EC_W_DELETE,	/* ESC DELETE */
	SK(SK_CTL_DELETE), 0,		EC_W_DELETE,	/* CTRL-DELETE */
	SK(SK_CTL_BACKSPACE), 0,	EC_W_BACKSPACE, /* CTRL-BACKSPACE */
	ESC, '\b', 0,			EC_W_BACKSPACE,	/* ESC BACKSPACE */
	ESC, '0', 0,			EC_HOME,	/* ESC 0 */
	SK(SK_HOME), 0,			EC_HOME,	/* HOME */
	ESC, '$', 0,			EC_END,		/* ESC $ */
	SK(SK_END), 0,			EC_END,		/* END */
	ESC, 'k', 0,			EC_UP,		/* ESC k */
	SK(SK_UP_ARROW), 0,		EC_UP,		/* UPARROW */
	ESC, 'j', 0,			EC_DOWN,	/* ESC j */
	SK(SK_DOWN_ARROW), 0,		EC_DOWN,	/* DOWNARROW */
	CONTROL('G'), 0,		EC_ABORT,	/* CTRL-G */
};

/*
 * Structure to support a list of command tables.
 */
struct tablelist {
	struct tablelist *t_next;
	char *t_start;
	char *t_end;
};

/*
 * List of command tables and list of line-edit tables.
 */
static struct tablelist *list_fcmd_tables = NULL;
static struct tablelist *list_ecmd_tables = NULL;
static struct tablelist *list_var_tables = NULL;
static struct tablelist *list_sysvar_tables = NULL;


/*
 * Expand special key abbreviations in a command table.
 */
static void
expand_special_keys(char *table, int len)
{
	char *fm;
	char *to;
	int a;
	char *repl;
	int klen;

	for (fm = table;  fm < table + len; ) {
		/*
		 * Rewrite each command in the table with any
		 * special key abbreviations expanded.
		 */
		for (to = fm;  *fm != '\0'; ) {
			if (*fm != SK_SPECIAL_KEY) {
				*to++ = *fm++;
				continue;
			}
			/*
			 * After SK_SPECIAL_KEY, next byte is the type
			 * of special key (one of the SK_* contants),
			 * and the byte after that is the number of bytes,
			 * N, reserved by the abbreviation (including the
			 * SK_SPECIAL_KEY and key type bytes).
			 * Replace all N bytes with the actual bytes
			 * output by the special key on this terminal.
			 */
			repl = special_key_str(fm[1]);
			klen = fm[2] & 0377;
			fm += klen;
			if (repl == NULL || strlen(repl) > klen)
				repl = "\377";
			while (*repl != '\0')
				*to++ = *repl++;
		}
		*to++ = '\0';
		/*
		 * Fill any unused bytes between end of command and
		 * the action byte with A_SKIP.
		 */
		while (to <= fm)
			*to++ = A_SKIP;
		fm++;
		a = *fm++ & 0377;
		if (a & A_EXTRA) {
			while (*fm++ != '\0')
				continue;
		}
	}
}

/*
 * Initialize the command lists.
 */
void
init_cmds(void)
{
	/*
	 * Add the default command tables.
	 */
	add_fcmd_table((char *)cmdtable, sizeof (cmdtable));
	add_ecmd_table((char *)edittable, sizeof (edittable));
	if (less_is_more) {
		add_fcmd_table((char *)moretable, sizeof (moretable));
		return;
	} else {
		add_fcmd_table((char *)lesstable, sizeof (lesstable));
	}

	/*
	 * Try to add the tables in the system lesskey file.
	 */
	add_hometable("LESSKEY_SYSTEM", LESSKEYFILE_SYS, 1);
	/*
	 * Try to add the tables in the standard lesskey file "$HOME/.less".
	 */
	add_hometable("LESSKEY", LESSKEYFILE, 0);
}

/*
 * Add a command table.
 */
static int
add_cmd_table(struct tablelist **tlist, char *buf, int len)
{
	struct tablelist *t;

	if (len == 0)
		return (0);
	/*
	 * Allocate a tablelist structure, initialize it,
	 * and link it into the list of tables.
	 */
	if ((t = calloc(1, sizeof (struct tablelist))) == NULL) {
		return (-1);
	}
	expand_special_keys(buf, len);
	t->t_start = buf;
	t->t_end = buf + len;
	t->t_next = *tlist;
	*tlist = t;
	return (0);
}

/*
 * Add a command table.
 */
void
add_fcmd_table(char *buf, int len)
{
	if (add_cmd_table(&list_fcmd_tables, buf, len) < 0)
		error("Warning: some commands disabled", NULL);
}

/*
 * Add an editing command table.
 */
void
add_ecmd_table(char *buf, int len)
{
	if (add_cmd_table(&list_ecmd_tables, buf, len) < 0)
		error("Warning: some edit commands disabled", NULL);
}

/*
 * Add an environment variable table.
 */
static void
add_var_table(struct tablelist **tlist, char *buf, int len)
{
	if (add_cmd_table(tlist, buf, len) < 0)
		error("Warning: environment variables from "
		    "lesskey file unavailable", NULL);
}

/*
 * Search a single command table for the command string in cmd.
 */
static int
cmd_search(const char *cmd, char *table, char *endtable, char **sp)
{
	char *p;
	const char *q;
	int a;

	*sp = NULL;
	for (p = table, q = cmd;  p < endtable;  p++, q++) {
		if (*p == *q) {
			/*
			 * Current characters match.
			 * If we're at the end of the string, we've found it.
			 * Return the action code, which is the character
			 * after the null at the end of the string
			 * in the command table.
			 */
			if (*p == '\0') {
				a = *++p & 0377;
				while (a == A_SKIP)
					a = *++p & 0377;
				if (a == A_END_LIST) {
					/*
					 * We get here only if the original
					 * cmd string passed in was empty ("").
					 * I don't think that can happen,
					 * but just in case ...
					 */
					return (A_UINVALID);
				}
				/*
				 * Check for an "extra" string.
				 */
				if (a & A_EXTRA) {
					*sp = ++p;
					a &= ~A_EXTRA;
				}
				return (a);
			}
		} else if (*q == '\0') {
			/*
			 * Hit the end of the user's command,
			 * but not the end of the string in the command table.
			 * The user's command is incomplete.
			 */
			return (A_PREFIX);
		} else {
			/*
			 * Not a match.
			 * Skip ahead to the next command in the
			 * command table, and reset the pointer
			 * to the beginning of the user's command.
			 */
			if (*p == '\0' && p[1] == A_END_LIST) {
				/*
				 * A_END_LIST is a special marker that tells
				 * us to abort the cmd search.
				 */
				return (A_UINVALID);
			}
			while (*p++ != '\0')
				continue;
			while (*p == A_SKIP)
				p++;
			if (*p & A_EXTRA)
				while (*++p != '\0')
					continue;
			q = cmd-1;
		}
	}
	/*
	 * No match found in the entire command table.
	 */
	return (A_INVALID);
}

/*
 * Decode a command character and return the associated action.
 * The "extra" string, if any, is returned in sp.
 */
static int
cmd_decode(struct tablelist *tlist, const char *cmd, char **sp)
{
	struct tablelist *t;
	int action = A_INVALID;

	/*
	 * Search thru all the command tables.
	 * Stop when we find an action which is not A_INVALID.
	 */
	for (t = tlist;  t != NULL;  t = t->t_next) {
		action = cmd_search(cmd, t->t_start, t->t_end, sp);
		if (action != A_INVALID)
			break;
	}
	if (action == A_UINVALID)
		action = A_INVALID;
	return (action);
}

/*
 * Decode a command from the cmdtables list.
 */
int
fcmd_decode(const char *cmd, char **sp)
{
	return (cmd_decode(list_fcmd_tables, cmd, sp));
}

/*
 * Decode a command from the edittables list.
 */
int
ecmd_decode(const char *cmd, char **sp)
{
	return (cmd_decode(list_ecmd_tables, cmd, sp));
}

/*
 * Get the value of an environment variable.
 * Looks first in the lesskey file, then in the real environment.
 */
char *
lgetenv(char *var)
{
	int a;
	char *s;

	/*
	 * Ignore lookups of any LESS* setting when we are more, and ignore
	 * the less key files
	 */
	if (less_is_more) {
		if (strncmp(var, "LESS", 4) == 0) {
			return (NULL);
		}
		return (getenv(var));
	}
	a = cmd_decode(list_var_tables, var, &s);
	if (a == EV_OK)
		return (s);
	s = getenv(var);
	if (s != NULL && *s != '\0')
		return (s);
	a = cmd_decode(list_sysvar_tables, var, &s);
	if (a == EV_OK)
		return (s);
	return (NULL);
}

/*
 * Get an "integer" from a lesskey file.
 * Integers are stored in a funny format:
 * two bytes, low order first, in radix KRADIX.
 */
static int
gint(char **sp)
{
	int n;

	n = *(*sp)++;
	n += *(*sp)++ * KRADIX;
	return (n);
}

/*
 * Process an old (pre-v241) lesskey file.
 */
static int
old_lesskey(char *buf, int len)
{
	/*
	 * Old-style lesskey file.
	 * The file must end with either
	 *	..,cmd,0,action
	 * or	...,cmd,0,action|A_EXTRA,string,0
	 * So the last byte or the second to last byte must be zero.
	 */
	if (buf[len-1] != '\0' && buf[len-2] != '\0')
		return (-1);
	add_fcmd_table(buf, len);
	return (0);
}

/*
 * Process a new (post-v241) lesskey file.
 */
static int
new_lesskey(char *buf, int len, int sysvar)
{
	char *p;
	int c;
	int n;

	/*
	 * New-style lesskey file.
	 * Extract the pieces.
	 */
	if (buf[len-3] != C0_END_LESSKEY_MAGIC ||
	    buf[len-2] != C1_END_LESSKEY_MAGIC ||
	    buf[len-1] != C2_END_LESSKEY_MAGIC)
		return (-1);
	p = buf + 4;
	for (;;) {
		c = *p++;
		switch (c) {
		case CMD_SECTION:
			n = gint(&p);
			add_fcmd_table(p, n);
			p += n;
			break;
		case EDIT_SECTION:
			n = gint(&p);
			add_ecmd_table(p, n);
			p += n;
			break;
		case VAR_SECTION:
			n = gint(&p);
			add_var_table((sysvar) ?
			    &list_sysvar_tables : &list_var_tables, p, n);
			p += n;
			break;
		case END_SECTION:
			return (0);
		default:
			/*
			 * Unrecognized section type.
			 */
			return (-1);
		}
	}
}

/*
 * Set up a user command table, based on a "lesskey" file.
 */
int
lesskey(char *filename, int sysvar)
{
	char *buf;
	off_t len;
	long n;
	int f;

	if (secure)
		return (1);
	/*
	 * Try to open the lesskey file.
	 */
	filename = shell_unquote(filename);
	f = open(filename, O_RDONLY);
	free(filename);
	if (f < 0)
		return (1);

	/*
	 * Read the file into a buffer.
	 * We first figure out the size of the file and allocate space for it.
	 * {{ Minimal error checking is done here.
	 *    A garbage .less file will produce strange results.
	 *    To avoid a large amount of error checking code here, we
	 *    rely on the lesskey program to generate a good .less file. }}
	 */
	len = filesize(f);
	if (len == -1 || len < 3) {
		/*
		 * Bad file (valid file must have at least 3 chars).
		 */
		(void) close(f);
		return (-1);
	}
	if ((buf = calloc((int)len, sizeof (char))) == NULL) {
		(void) close(f);
		return (-1);
	}
	if (lseek(f, (off_t)0, SEEK_SET) == (off_t)-1) {
		free(buf);
		(void) close(f);
		return (-1);
	}
	n = read(f, buf, (unsigned int) len);
	close(f);
	if (n != len) {
		free(buf);
		return (-1);
	}

	/*
	 * Figure out if this is an old-style (before version 241)
	 * or new-style lesskey file format.
	 */
	if (buf[0] != C0_LESSKEY_MAGIC || buf[1] != C1_LESSKEY_MAGIC ||
	    buf[2] != C2_LESSKEY_MAGIC || buf[3] != C3_LESSKEY_MAGIC)
		return (old_lesskey(buf, (int)len));
	return (new_lesskey(buf, (int)len, sysvar));
}

/*
 * Add the standard lesskey file "$HOME/.less"
 */
void
add_hometable(char *envname, char *def_filename, int sysvar)
{
	char *filename;
	PARG parg;

	if (envname != NULL && (filename = lgetenv(envname)) != NULL)
		filename = estrdup(filename);
	else if (sysvar)
		filename = estrdup(def_filename);
	else
		filename = homefile(def_filename);
	if (filename == NULL)
		return;
	if (lesskey(filename, sysvar) < 0) {
		parg.p_string = filename;
		error("Cannot use lesskey file \"%s\"", &parg);
	}
	free(filename);
}

/*
 * See if a char is a special line-editing command.
 */
int
editchar(int c, int flags)
{
	int action;
	int nch;
	char *s;
	char usercmd[MAX_CMDLEN+1];

	/*
	 * An editing character could actually be a sequence of characters;
	 * for example, an escape sequence sent by pressing the uparrow key.
	 * To match the editing string, we use the command decoder
	 * but give it the edit-commands command table
	 * This table is constructed to match the user's keyboard.
	 */
	if (c == erase_char || c == erase2_char)
		return (EC_BACKSPACE);
	if (c == kill_char)
		return (EC_LINEKILL);

	/*
	 * Collect characters in a buffer.
	 * Start with the one we have, and get more if we need them.
	 */
	nch = 0;
	do {
		if (nch > 0)
			c = getcc();
		usercmd[nch] = (char)c;
		usercmd[nch+1] = '\0';
		nch++;
		action = ecmd_decode(usercmd, &s);
	} while (action == A_PREFIX);

	if (flags & EC_NORIGHTLEFT) {
		switch (action) {
		case EC_RIGHT:
		case EC_LEFT:
			action = A_INVALID;
			break;
		}
	}
	if (flags & EC_NOHISTORY) {
		/*
		 * The caller says there is no history list.
		 * Reject any history-manipulation action.
		 */
		switch (action) {
		case EC_UP:
		case EC_DOWN:
			action = A_INVALID;
			break;
		}
	}
	if (flags & EC_NOCOMPLETE) {
		/*
		 * The caller says we don't want any filename completion cmds.
		 * Reject them.
		 */
		switch (action) {
		case EC_F_COMPLETE:
		case EC_B_COMPLETE:
		case EC_EXPAND:
			action = A_INVALID;
			break;
		}
	}
	if ((flags & EC_PEEK) || action == A_INVALID) {
		/*
		 * We're just peeking, or we didn't understand the command.
		 * Unget all the characters we read in the loop above.
		 * This does NOT include the original character that was
		 * passed in as a parameter.
		 */
		while (nch > 1) {
			ungetcc(usercmd[--nch]);
		}
	} else {
		if (s != NULL)
			ungetsc(s);
	}
	return (action);
}