/*
 *  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, fd, file_size, bytes_read;
static int begin_reached = 1, end_reached, 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)
{
        int i, x, y, cur_x, cur_y, fpos, key = 0;
        int passed_end;
        WINDOW *dialog, *text;

        /* 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);
        wattrset(text, dialog_attr);
        wbkgdset(text, dialog_attr & A_COLOR);

        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);
        wbkgdset(dialog, dialog_attr & A_COLOR);
        waddch(dialog, ACS_RTEE);

        print_title(dialog, title, width);

        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;

        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));

        /* Clear 'residue' of previous line */
#if OLD_NCURSES
        {
                int i;
                int y, x;

                getyx(win, y, x);
                for (i = 0; i < width - x; i++)
                        waddch(win, ' ');
        }
#else
        wclrtoeol(win);
#endif
}

/*
 * 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)
{
        int i = 0, fpos;
        static char line[MAX_LEN + 1];

        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);
        wbkgdset(win, position_indicator_attr & A_COLOR);
        percent = !file_size ?
            100 : ((fpos - bytes_read + page - buf) * 100) / file_size;
        wmove(win, height - 3, width - 9);
        wprintw(win, "(%3d%%)", percent);
}