/* $OpenBSD$ */

/*
 * Copyright (c) 2020 Anindya Mukherjee <anindya49@hotmail.com>
 *
 * 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 INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "tmux.h"

/* Initialise virtual cursor. */
void
grid_reader_start(struct grid_reader *gr, struct grid *gd, u_int cx, u_int cy)
{
	gr->gd = gd;
	gr->cx = cx;
	gr->cy = cy;
}

/* Get cursor position from reader. */
void
grid_reader_get_cursor(struct grid_reader *gr, u_int *cx, u_int *cy)
{
	*cx = gr->cx;
	*cy = gr->cy;
}

/* Get length of line containing the cursor. */
u_int
grid_reader_line_length(struct grid_reader *gr)
{
	return (grid_line_length(gr->gd, gr->cy));
}

/* Move cursor forward one position. */
void
grid_reader_cursor_right(struct grid_reader *gr, int wrap, int all)
{
	u_int			px;
	struct grid_cell	gc;

	if (all)
		px = gr->gd->sx;
	else
		px = grid_reader_line_length(gr);

	if (wrap && gr->cx >= px && gr->cy < gr->gd->hsize + gr->gd->sy - 1) {
		grid_reader_cursor_start_of_line(gr, 0);
		grid_reader_cursor_down(gr);
	} else if (gr->cx < px) {
		gr->cx++;
		while (gr->cx < px) {
			grid_get_cell(gr->gd, gr->cx, gr->cy, &gc);
			if (~gc.flags & GRID_FLAG_PADDING)
				break;
			gr->cx++;
		}
	}
}

/* Move cursor back one position. */
void
grid_reader_cursor_left(struct grid_reader *gr)
{
	struct grid_cell	gc;

	while (gr->cx > 0) {
		grid_get_cell(gr->gd, gr->cx, gr->cy, &gc);
		if (~gc.flags & GRID_FLAG_PADDING)
			break;
		gr->cx--;
	}
	if (gr->cx == 0 && gr->cy > 0) {
		grid_reader_cursor_up(gr);
		grid_reader_cursor_end_of_line(gr, 0, 0);
	} else if (gr->cx > 0)
		gr->cx--;
}

/* Move cursor down one line. */
void
grid_reader_cursor_down(struct grid_reader *gr)
{
	struct grid_cell	gc;

	if (gr->cy < gr->gd->hsize + gr->gd->sy - 1)
		gr->cy++;
	while (gr->cx > 0) {
		grid_get_cell(gr->gd, gr->cx, gr->cy, &gc);
		if (~gc.flags & GRID_FLAG_PADDING)
			break;
		gr->cx--;
	}
}

/* Move cursor up one line. */
void
grid_reader_cursor_up(struct grid_reader *gr)
{
	struct grid_cell	gc;

	if (gr->cy > 0)
		gr->cy--;
	while (gr->cx > 0) {
		grid_get_cell(gr->gd, gr->cx, gr->cy, &gc);
		if (~gc.flags & GRID_FLAG_PADDING)
			break;
		gr->cx--;
	}
}

/* Move cursor to the start of the line. */
void
grid_reader_cursor_start_of_line(struct grid_reader *gr, int wrap)
{
	if (wrap) {
		while (gr->cy > 0 &&
		    grid_get_line(gr->gd, gr->cy - 1)->flags &
		        GRID_LINE_WRAPPED)
			gr->cy--;
	}
	gr->cx = 0;
}

/* Move cursor to the end of the line. */
void
grid_reader_cursor_end_of_line(struct grid_reader *gr, int wrap, int all)
{
	u_int	yy;

	if (wrap) {
		yy = gr->gd->hsize + gr->gd->sy - 1;
		while (gr->cy < yy && grid_get_line(gr->gd, gr->cy)->flags &
		    GRID_LINE_WRAPPED)
			gr->cy++;
	}
	if (all)
		gr->cx = gr->gd->sx;
	else
		gr->cx = grid_reader_line_length(gr);
}

/* Check if character under cursor is in set. */
int
grid_reader_in_set(struct grid_reader *gr, const char *set)
{
	struct grid_cell	gc;

	grid_get_cell(gr->gd, gr->cx, gr->cy, &gc);
	if (gc.flags & GRID_FLAG_PADDING)
		return (0);
	return (utf8_cstrhas(set, &gc.data));
}

/* Move cursor to the start of the next word. */
void
grid_reader_cursor_next_word(struct grid_reader *gr, const char *separators)
{
	u_int	xx, yy;
	int expected = 0;

	/* Do not break up wrapped words. */
	if (grid_get_line(gr->gd, gr->cy)->flags & GRID_LINE_WRAPPED)
		xx = grid_reader_line_length(gr) - 1;
	else
		xx = grid_reader_line_length(gr);
	yy = gr->gd->hsize + gr->gd->sy - 1;

	/*
	 * If we started inside a word, skip over word characters. Then skip
	 * over separators till the next word.
	 *
	 * expected is initially set to 0 for the former and then 1 for the
	 * latter. It is finally set to 0 when the beginning of the next word is
	 * found.
	 */
	do {
		while (gr->cx > xx ||
		    grid_reader_in_set(gr, separators) == expected) {
			/* Move down if we are past the end of the line. */
			if (gr->cx > xx) {
				if (gr->cy == yy)
					return;
				grid_reader_cursor_start_of_line(gr, 0);
				grid_reader_cursor_down(gr);

				if (grid_get_line(gr->gd, gr->cy)->flags &
				    GRID_LINE_WRAPPED)
					xx = grid_reader_line_length(gr) - 1;
				else
					xx = grid_reader_line_length(gr);
			} else
				gr->cx++;
		}
		expected = !expected;
	} while (expected == 1);
}

/* Move cursor to the end of the next word. */
void
grid_reader_cursor_next_word_end(struct grid_reader *gr, const char *separators)
{
	u_int	xx, yy;
	int	expected = 1;

	/* Do not break up wrapped words. */
	if (grid_get_line(gr->gd, gr->cy)->flags & GRID_LINE_WRAPPED)
		xx = grid_reader_line_length(gr) - 1;
	else
		xx = grid_reader_line_length(gr);
	yy = gr->gd->hsize + gr->gd->sy - 1;

	/*
	 * If we started on a separator, skip over separators. Then skip over
	 * word characters till the next separator.
	 *
	 * expected is initially set to 1 for the former and then 1 for the
	 * latter. It is finally set to 1 when the end of the next word is
	 * found.
	 */
	do {
		while (gr->cx > xx ||
		    grid_reader_in_set(gr, separators) == expected) {
			/* Move down if we are past the end of the line. */
			if (gr->cx > xx) {
				if (gr->cy == yy)
					return;
				grid_reader_cursor_start_of_line(gr, 0);
				grid_reader_cursor_down(gr);

				if (grid_get_line(gr->gd, gr->cy)->flags &
				    GRID_LINE_WRAPPED)
					xx = grid_reader_line_length(gr) - 1;
				else
					xx = grid_reader_line_length(gr);
			} else
				gr->cx++;
		}
		expected = !expected;
	} while (expected == 0);
}

/* Move to the previous place where a word begins. */
void
grid_reader_cursor_previous_word(struct grid_reader *gr, const char *separators,
    int already)
{
	int	oldx, oldy, r;

	/* Move back to the previous word character. */
	if (already || grid_reader_in_set(gr, separators)) {
		for (;;) {
			if (gr->cx > 0) {
				gr->cx--;
				if (!grid_reader_in_set(gr, separators))
					break;
			} else {
				if (gr->cy == 0)
					return;
				grid_reader_cursor_up(gr);
				grid_reader_cursor_end_of_line(gr, 0, 0);

				/* Stop if separator at EOL. */
				if (gr->cx > 0) {
					oldx = gr->cx;
					gr->cx--;
					r = grid_reader_in_set(gr, separators);
					gr->cx = oldx;
					if (r)
						break;
				}
			}
		}
	}

	/* Move back to the beginning of this word. */
	do {
		oldx = gr->cx;
		oldy = gr->cy;
		if (gr->cx == 0) {
			if (gr->cy == 0 ||
			  ~grid_get_line(gr->gd, gr->cy - 1)->flags &
			  GRID_LINE_WRAPPED)
				break;
			grid_reader_cursor_up(gr);
			grid_reader_cursor_end_of_line(gr, 0, 0);
		}
		if (gr->cx > 0)
			gr->cx--;
	} while (!grid_reader_in_set(gr, separators));
	gr->cx = oldx;
	gr->cy = oldy;
}