/*  textbox.c -- implements the text box
 *
 *  ORIGINAL AUTHOR: Savio Lam (lam836@cs.cuhk.hk)
 *  MODIFIED FOR LINUX KERNEL CONFIG BY: William Roadcap (roadcap@cfw.com)
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "dialog.h"

static void back_lines(int n);
static void print_page(WINDOW * win, int height, int width);
static void print_line(WINDOW * win, int row, int width);
static char *get_line(void);
static void print_position(WINDOW * win, int height, int width);

static int hscroll = 0, fd, file_size, bytes_read;
static int begin_reached = 1, end_reached = 0, page_length;
static char *buf, *page;

/*
 * Display text from a file in a dialog box.
 */
int dialog_textbox(const char *title, const char *file, int height, int width)
{
    WINDOW *dialog, *text;
    int i, x, y, cur_x, cur_y, fpos, key = 0, passed_end;

    /* Open input file for reading */
    if ((fd = open(file, O_RDONLY)) == -1) {
	endwin();
	fprintf(stderr, "\nCan't open input file in dialog_textbox().\n");
	exit(-1);
    }
    /* Get file size. Actually, 'file_size' is the real file size - 1,
     * since it's only the last byte offset from the beginning */
    if ((file_size = lseek(fd, 0, SEEK_END)) == -1) {
	endwin();
	fprintf(stderr, "\nError getting file size in dialog_textbox().\n");
	exit(-1);
    }
    /* Restore file pointer to beginning of file after getting file size */
    if (lseek(fd, 0, SEEK_SET) == -1) {
	endwin();
	fprintf(stderr, "\nError moving file pointer in dialog_textbox().\n");
	exit(-1);
    }
    /* Allocate space for read buffer */
    if ((buf = malloc(BUF_SIZE + 1)) == NULL) {
	endwin();
	fprintf(stderr, "\nCan't allocate memory in dialog_textbox().\n");
	exit(-1);
    }
    if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
	endwin();
	fprintf(stderr, "\nError reading file in dialog_textbox().\n");
	exit(-1);
    }
    buf[bytes_read] = '\0';	/* mark end of valid data */
    page = buf;			/* page is pointer to start of page to be displayed */

    /* center dialog box on screen */
    x = (COLS - width) / 2;
    y = (LINES - height) / 2;

    draw_shadow(stdscr, y, x, height, width);

    dialog = newwin(height, width, y, x);
    keypad(dialog, TRUE);

    /* Create window for text region, used for scrolling text */
    text = subwin(dialog, height - 4, width - 2, y + 1, x + 1);

    keypad(text, TRUE);

    /* register the new window, along with its borders */
    draw_box(dialog, 0, 0, height, width, dialog_attr, border_attr);

    wattrset(dialog, border_attr);
    mvwaddch(dialog, height - 3, 0, ACS_LTEE);
    for (i = 0; i < width - 2; i++)
	waddch(dialog, ACS_HLINE);
    wattrset(dialog, dialog_attr);
    waddch(dialog, ACS_RTEE);

    if (title != NULL) {
	wattrset(dialog, title_attr);
	mvwaddch(dialog, 0, (width - strlen(title)) / 2 - 1, ' ');
	waddstr(dialog, (char *) title);
	waddch(dialog, ' ');
    }
    print_button(dialog, " Exit ", height - 2, width / 2 - 4, TRUE);
    wnoutrefresh(dialog);
    getyx(dialog, cur_y, cur_x);	/* Save cursor position */

    /* Print first page of text */
    attr_clear(text, height - 4, width - 2, dialog_attr);
    print_page(text, height - 4, width - 2);
    print_position(dialog, height, width);
    wmove(dialog, cur_y, cur_x);	/* Restore cursor position */
    wrefresh(dialog);

    while ((key != ESC) && (key != '\n')) {
	key = wgetch(dialog);
	switch (key) {
	case 'E':		/* Exit */
	case 'e':
	case 'X':
	case 'x':
	    delwin(dialog);
	    free(buf);
	    close(fd);
	    return 0;
	case 'g':		/* First page */
	case KEY_HOME:
	    if (!begin_reached) {
		begin_reached = 1;
		/* First page not in buffer? */
		if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
		    endwin();
		    fprintf(stderr,
			    "\nError moving file pointer in dialog_textbox().\n");
		    exit(-1);
		}
		if (fpos > bytes_read) {	/* Yes, we have to read it in */
		    if (lseek(fd, 0, SEEK_SET) == -1) {
			endwin();
			fprintf(stderr, "\nError moving file pointer in "
				"dialog_textbox().\n");
			exit(-1);
		    }
		    if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
			endwin();
			fprintf(stderr,
				"\nError reading file in dialog_textbox().\n");
			exit(-1);
		    }
		    buf[bytes_read] = '\0';
		}
		page = buf;
		print_page(text, height - 4, width - 2);
		print_position(dialog, height, width);
		wmove(dialog, cur_y, cur_x);	/* Restore cursor position */
		wrefresh(dialog);
	    }
	    break;
	case 'G':		/* Last page */
	case KEY_END:

	    end_reached = 1;
	    /* Last page not in buffer? */
	    if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
		endwin();
		fprintf(stderr,
			"\nError moving file pointer in dialog_textbox().\n");
		exit(-1);
	    }
	    if (fpos < file_size) {	/* Yes, we have to read it in */
		if (lseek(fd, -BUF_SIZE, SEEK_END) == -1) {
		    endwin();
		    fprintf(stderr,
			    "\nError moving file pointer in dialog_textbox().\n");
		    exit(-1);
		}
		if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
		    endwin();
		    fprintf(stderr,
			    "\nError reading file in dialog_textbox().\n");
		    exit(-1);
		}
		buf[bytes_read] = '\0';
	    }
	    page = buf + bytes_read;
	    back_lines(height - 4);
	    print_page(text, height - 4, width - 2);
	    print_position(dialog, height, width);
	    wmove(dialog, cur_y, cur_x);	/* Restore cursor position */
	    wrefresh(dialog);
	    break;
	case 'K':		/* Previous line */
	case 'k':
	case KEY_UP:
	    if (!begin_reached) {
		back_lines(page_length + 1);

		/* We don't call print_page() here but use scrolling to ensure
		 * faster screen update. However, 'end_reached' and
		 * 'page_length' should still be updated, and 'page' should
		 * point to start of next page. This is done by calling
		 * get_line() in the following 'for' loop. */
		scrollok(text, TRUE);
		wscrl(text, -1);	/* Scroll text region down one line */
		scrollok(text, FALSE);
		page_length = 0;
		passed_end = 0;
		for (i = 0; i < height - 4; i++) {
		    if (!i) {
			/* print first line of page */
			print_line(text, 0, width - 2);
			wnoutrefresh(text);
		    } else
			/* Called to update 'end_reached' and 'page' */
			get_line();
		    if (!passed_end)
			page_length++;
		    if (end_reached && !passed_end)
			passed_end = 1;
		}

		print_position(dialog, height, width);
		wmove(dialog, cur_y, cur_x);	/* Restore cursor position */
		wrefresh(dialog);
	    }
	    break;
	case 'B':		/* Previous page */
	case 'b':
	case KEY_PPAGE:
	    if (begin_reached)
		break;
	    back_lines(page_length + height - 4);
	    print_page(text, height - 4, width - 2);
	    print_position(dialog, height, width);
	    wmove(dialog, cur_y, cur_x);
	    wrefresh(dialog);
	    break;
	case 'J':		/* Next line */
	case 'j':
	case KEY_DOWN:
	    if (!end_reached) {
		begin_reached = 0;
		scrollok(text, TRUE);
		scroll(text);	/* Scroll text region up one line */
		scrollok(text, FALSE);
		print_line(text, height - 5, width - 2);
		wnoutrefresh(text);
		print_position(dialog, height, width);
		wmove(dialog, cur_y, cur_x);	/* Restore cursor position */
		wrefresh(dialog);
	    }
	    break;
	case KEY_NPAGE:	/* Next page */
	case ' ':
	    if (end_reached)
		break;

	    begin_reached = 0;
	    print_page(text, height - 4, width - 2);
	    print_position(dialog, height, width);
	    wmove(dialog, cur_y, cur_x);
	    wrefresh(dialog);
	    break;
	case '0':		/* Beginning of line */
	case 'H':		/* Scroll left */
	case 'h':
	case KEY_LEFT:
	    if (hscroll <= 0)
		break;

	    if (key == '0')
		hscroll = 0;
	    else
		hscroll--;
	    /* Reprint current page to scroll horizontally */
	    back_lines(page_length);
	    print_page(text, height - 4, width - 2);
	    wmove(dialog, cur_y, cur_x);
	    wrefresh(dialog);
	    break;
	case 'L':		/* Scroll right */
	case 'l':
	case KEY_RIGHT:
	    if (hscroll >= MAX_LEN)
		break;
	    hscroll++;
	    /* Reprint current page to scroll horizontally */
	    back_lines(page_length);
	    print_page(text, height - 4, width - 2);
	    wmove(dialog, cur_y, cur_x);
	    wrefresh(dialog);
	    break;
	case ESC:
	    break;
	}
    }

    delwin(dialog);
    free(buf);
    close(fd);
    return -1;			/* ESC pressed */
}

/*
 * Go back 'n' lines in text file. Called by dialog_textbox().
 * 'page' will be updated to point to the desired line in 'buf'.
 */
static void back_lines(int n)
{
    int i, fpos;

    begin_reached = 0;
    /* We have to distinguish between end_reached and !end_reached
     * since at end of file, the line is not ended by a '\n'.
     * The code inside 'if' basically does a '--page' to move one
     * character backward so as to skip '\n' of the previous line */
    if (!end_reached) {
	/* Either beginning of buffer or beginning of file reached? */
	if (page == buf) {
	    if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
		endwin();
		fprintf(stderr, "\nError moving file pointer in "
			"back_lines().\n");
		exit(-1);
	    }
	    if (fpos > bytes_read) {	/* Not beginning of file yet */
		/* We've reached beginning of buffer, but not beginning of
		 * file yet, so read previous part of file into buffer.
		 * Note that we only move backward for BUF_SIZE/2 bytes,
		 * but not BUF_SIZE bytes to avoid re-reading again in
		 * print_page() later */
		/* Really possible to move backward BUF_SIZE/2 bytes? */
		if (fpos < BUF_SIZE / 2 + bytes_read) {
		    /* No, move less then */
		    if (lseek(fd, 0, SEEK_SET) == -1) {
			endwin();
			fprintf(stderr, "\nError moving file pointer in "
				"back_lines().\n");
			exit(-1);
		    }
		    page = buf + fpos - bytes_read;
		} else {	/* Move backward BUF_SIZE/2 bytes */
		    if (lseek(fd, -(BUF_SIZE / 2 + bytes_read), SEEK_CUR)
			== -1) {
			endwin();
			fprintf(stderr, "\nError moving file pointer "
				"in back_lines().\n");
			exit(-1);
		    }
		    page = buf + BUF_SIZE / 2;
		}
		if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
		    endwin();
		    fprintf(stderr, "\nError reading file in back_lines().\n");
		    exit(-1);
		}
		buf[bytes_read] = '\0';
	    } else {		/* Beginning of file reached */
		begin_reached = 1;
		return;
	    }
	}
	if (*(--page) != '\n') {	/* '--page' here */
	    /* Something's wrong... */
	    endwin();
	    fprintf(stderr, "\nInternal error in back_lines().\n");
	    exit(-1);
	}
    }
    /* Go back 'n' lines */
    for (i = 0; i < n; i++)
	do {
	    if (page == buf) {
		if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
		    endwin();
		    fprintf(stderr,
			    "\nError moving file pointer in back_lines().\n");
		    exit(-1);
		}
		if (fpos > bytes_read) {
		    /* Really possible to move backward BUF_SIZE/2 bytes? */
		    if (fpos < BUF_SIZE / 2 + bytes_read) {
			/* No, move less then */
			if (lseek(fd, 0, SEEK_SET) == -1) {
			    endwin();
			    fprintf(stderr, "\nError moving file pointer "
				    "in back_lines().\n");
			    exit(-1);
			}
			page = buf + fpos - bytes_read;
		    } else {	/* Move backward BUF_SIZE/2 bytes */
			if (lseek(fd, -(BUF_SIZE / 2 + bytes_read),
				  SEEK_CUR) == -1) {
			    endwin();
			    fprintf(stderr, "\nError moving file pointer"
				    " in back_lines().\n");
			    exit(-1);
			}
			page = buf + BUF_SIZE / 2;
		    }
		    if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
			endwin();
			fprintf(stderr, "\nError reading file in "
				"back_lines().\n");
			exit(-1);
		    }
		    buf[bytes_read] = '\0';
		} else {	/* Beginning of file reached */
		    begin_reached = 1;
		    return;
		}
	    }
	} while (*(--page) != '\n');
    page++;
}

/*
 * Print a new page of text. Called by dialog_textbox().
 */
static void print_page(WINDOW * win, int height, int width)
{
    int i, passed_end = 0;

    page_length = 0;
    for (i = 0; i < height; i++) {
	print_line(win, i, width);
	if (!passed_end)
	    page_length++;
	if (end_reached && !passed_end)
	    passed_end = 1;
    }
    wnoutrefresh(win);
}

/*
 * Print a new line of text. Called by dialog_textbox() and print_page().
 */
static void print_line(WINDOW * win, int row, int width)
{
    char *line;
    int i, y, x;

    line = get_line();
    line += MIN(strlen(line), hscroll);	/* Scroll horizontally */
    wmove(win, row, 0);		/* move cursor to correct line */
    waddch(win, ' ');
    waddnstr(win, line, MIN(strlen(line), width - 2));

    getyx(win, y, x);
    /* Clear 'residue' of previous line */
    for (i = 0; i < width - x; i++)
	waddch(win, ' ');
}

/*
 * Return current line of text. Called by dialog_textbox() and print_line().
 * 'page' should point to start of current line before calling, and will be
 * updated to point to start of next line.
 */
static char *get_line(void)
{
    static char line[MAX_LEN + 1];
    int i = 0, fpos;

    end_reached = 0;
    while (*page != '\n') {
	if (*page == '\0') {
	    /* Either end of file or end of buffer reached */
	    if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
		endwin();
		fprintf(stderr, "\nError moving file pointer in "
			"get_line().\n");
		exit(-1);
	    }
	    if (fpos < file_size) {	/* Not end of file yet */
		/* We've reached end of buffer, but not end of file yet,
		 * so read next part of file into buffer */
		if ((bytes_read = read(fd, buf, BUF_SIZE)) == -1) {
		    endwin();
		    fprintf(stderr, "\nError reading file in get_line().\n");
		    exit(-1);
		}
		buf[bytes_read] = '\0';
		page = buf;
	    } else {
		if (!end_reached)
		    end_reached = 1;
		break;
	    }
	} else if (i < MAX_LEN)
	    line[i++] = *(page++);
	else {
	    /* Truncate lines longer than MAX_LEN characters */
	    if (i == MAX_LEN)
		line[i++] = '\0';
	    page++;
	}
    }
    if (i <= MAX_LEN)
	line[i] = '\0';
    if (!end_reached)
	page++;			/* move pass '\n' */

    return line;
}

/*
 * Print current position
 */
static void print_position(WINDOW * win, int height, int width)
{
    int fpos, percent;

    if ((fpos = lseek(fd, 0, SEEK_CUR)) == -1) {
	endwin();
	fprintf(stderr, "\nError moving file pointer in print_position().\n");
	exit(-1);
    }
    wattrset(win, position_indicator_attr);
    percent = !file_size ?
	100 : ((fpos - bytes_read + page - buf) * 100) / file_size;
    wmove(win, height - 3, width - 9);
    wprintw(win, "(%3d%%)", percent);
}
