/*
 * The routines in this file move the cursor around on the screen. They
 * compute a new value for the cursor, then adjust ".". The display code
 * always updates the cursor location, so only moves between lines, or
 * functions that adjust the top line in the window and invalidate the
 * framing, are hard.
 */
#include        <stdio.h>
#include        "ueed.h"

/*
 * Move the cursor to the
 * beginning of the current line.
 * Trivial.
 */
gotobol(f, n)
{
        curwp->w_doto  = 0;
        return (TRUE);
}

/*
 * Move the cursor backwards by "n" characters. If "n" is less than zero call
 * "forwchar" to actually do the move. Otherwise compute the new cursor
 * location. Error if you try and move out of the buffer. Set the flag if the
 * line pointer for dot changes.
 */
backchar(f, n)
register int    n;
{
        register LINE   *lp;

        if (n < 0)
                return (forwchar(f, -n));
        while (n--) {
                if (curwp->w_doto == 0) {
                        if ((lp=lback(curwp->w_dotp)) == curbp->b_linep)
                                return (FALSE);
                        curwp->w_dotp  = lp;
                        curwp->w_doto  = llength(lp);
                        curwp->w_flag |= WFMOVE;
                } else
                        curwp->w_doto--;
        }
        return (TRUE);
}

/*
 * Move the cursor to the end of the current line. Trivial. No errors.
 */
gotoeol(f, n)
{
        curwp->w_doto  = llength(curwp->w_dotp);
        return (TRUE);
}

/*
 * Move the cursor forwwards by "n" characters. If "n" is less than zero call
 * "backchar" to actually do the move. Otherwise compute the new cursor
 * location, and move ".". Error if you try and move off the end of the
 * buffer. Set the flag if the line pointer for dot changes.
 */
forwchar(f, n)
register int    n;
{
        if (n < 0)
                return (backchar(f, -n));
        while (n--) {
                if (curwp->w_doto == llength(curwp->w_dotp)) {
                        if (curwp->w_dotp == curbp->b_linep)
                                return (FALSE);
                        curwp->w_dotp  = lforw(curwp->w_dotp);
                        curwp->w_doto  = 0;
                        curwp->w_flag |= WFMOVE;
                } else
                        curwp->w_doto++;
        }
        return (TRUE);
}

/*
 * Goto the beginning of the buffer. Massive adjustment of dot. This is
 * considered to be hard motion; it really isn't if the original value of dot
 * is the same as the new value of dot. Normally bound to "M-<".
 */
gotobob(f, n)
{
        curwp->w_dotp  = lforw(curbp->b_linep);
        curwp->w_doto  = 0;
        curwp->w_flag |= WFHARD;
        return (TRUE);
}

/*
 * Move to the end of the buffer. Dot is always put at the end of the file
 * (ZJ). The standard screen code does most of the hard parts of update.
 * Bound to "M->".
 */
gotoeob(f, n)
{
        curwp->w_dotp  = curbp->b_linep;
        curwp->w_doto  = 0;
        curwp->w_flag |= WFHARD;
        return (TRUE);
}

/*
 * Move forward by full lines. If the number of lines to move is less than
 * zero, call the backward line function to actually do it. The last command
 * controls how the goal column is set. Bound to "C-N". No errors are
 * possible.
 */
forwline(f, n)
{
        register LINE   *dlp;

        if (n < 0)
                return (backline(f, -n));
        if ((lastflag&CFCPCN) == 0)             /* Reset goal if last   */
                curgoal = curcol;               /* not C-P or C-N       */
        thisflag |= CFCPCN;
        dlp = curwp->w_dotp;
        while (n-- && dlp!=curbp->b_linep)
                dlp = lforw(dlp);
        curwp->w_dotp  = dlp;
        curwp->w_doto  = getgoal(dlp);
        curwp->w_flag |= WFMOVE;
        return (TRUE);
}

/*
 * This function is like "forwline", but goes backwards. The scheme is exactly
 * the same. Check for arguments that are less than zero and call your
 * alternate. Figure out the new line and call "movedot" to perform the
 * motion. No errors are possible. Bound to "C-P".
 */
backline(f, n)
{
        register LINE   *dlp;

        if (n < 0)
                return (forwline(f, -n));
        if ((lastflag&CFCPCN) == 0)             /* Reset goal if the    */
                curgoal = curcol;               /* last isn't C-P, C-N  */
        thisflag |= CFCPCN;
        dlp = curwp->w_dotp;
        while (n-- && lback(dlp)!=curbp->b_linep)
                dlp = lback(dlp);
        curwp->w_dotp  = dlp;
        curwp->w_doto  = getgoal(dlp);
        curwp->w_flag |= WFMOVE;
        return (TRUE);
}

/*
 * This routine, given a pointer to a LINE, and the current cursor goal
 * column, return the best choice for the offset. The offset is returned.
 * Used by "C-N" and "C-P".
 */
getgoal(dlp)
register LINE   *dlp;
{
        register int    c;
        register int    col;
        register int    newcol;
        register int    dbo;

        col = 0;
        dbo = 0;
        while (dbo != llength(dlp)) {
                c = lgetc(dlp, dbo);
                newcol = col;
                if (c == '\t')
                        newcol |= 0x07;
                else if (c<0x20 || c==0x7F)
                        ++newcol;
                ++newcol;
                if (newcol > curgoal)
                        break;
                col = newcol;
                ++dbo;
        }
        return (dbo);
}

/*
 * Scroll forward by a specified number of lines, or by a full page if no
 * argument. Bound to "C-V". The "2" in the arithmetic on the window size is
 * the overlap; this value is the default overlap value in ITS EMACS. Because
 * this zaps the top line in the display window, we have to do a hard update.
 */
forwpage(f, n)
register int    n;
{
        register LINE   *lp;

        if (f == FALSE) {
                n = curwp->w_ntrows - 2;        /* Default scroll.      */
                if (n <= 0)                     /* Forget the overlap   */
                        n = 1;                  /* if tiny window.      */
        } else if (n < 0)
                return (backpage(f, -n));
#ifdef CVMVAS
        else                                    /* Convert from pages   */
                n *= curwp->w_ntrows;           /* to lines.            */
#endif
        lp = curwp->w_linep;
        while (n-- && lp!=curbp->b_linep)
                lp = lforw(lp);
        curwp->w_linep = lp;
        curwp->w_dotp  = lp;
        curwp->w_doto  = 0;
        curwp->w_flag |= WFHARD;
        return (TRUE);
}

/*
 * This command is like "forwpage", but it goes backwards. The "2", like
 * above, is the overlap between the two windows. The value is from the ITS
 * EMACS manual. Bound to "M-V". We do a hard update for exactly the same
 * reason.
 */
backpage(f, n)
register int    n;
{
        register LINE   *lp;

        if (f == FALSE) {
                n = curwp->w_ntrows - 2;        /* Default scroll.      */
                if (n <= 0)                     /* Don't blow up if the */
                        n = 1;                  /* window is tiny.      */
        } else if (n < 0)
                return (forwpage(f, -n));
#ifdef CVMVAS
        else                                    /* Convert from pages   */
                n *= curwp->w_ntrows;           /* to lines.            */
#endif
        lp = curwp->w_linep;
        while (n-- && lback(lp)!=curbp->b_linep)
                lp = lback(lp);
        curwp->w_linep = lp;
        curwp->w_dotp  = lp;
        curwp->w_doto  = 0;
        curwp->w_flag |= WFHARD;
        return (TRUE);
}

/*
 * Set the mark in the current window to the value of "." in the window. No
 * errors are possible. Bound to "M-.".
 */
setmark(f, n)
{
        curwp->w_markp = curwp->w_dotp;
        curwp->w_marko = curwp->w_doto;
        mlwrite("[Mark set]");
        return (TRUE);
}

/*
 * Swap the values of "." and "mark" in the current window. This is pretty
 * easy, bacause all of the hard work gets done by the standard routine
 * that moves the mark about. The only possible error is "no mark". Bound to
 * "C-X C-X".
 */
swapmark(f, n)
{
        register LINE   *odotp;
        register int    odoto;

        if (curwp->w_markp == NULL) {
                mlwrite("No mark in this window");
                return (FALSE);
        }
        odotp = curwp->w_dotp;
        odoto = curwp->w_doto;
        curwp->w_dotp  = curwp->w_markp;
        curwp->w_doto  = curwp->w_marko;
        curwp->w_markp = odotp;
        curwp->w_marko = odoto;
        curwp->w_flag |= WFMOVE;
        return (TRUE);
}