#include <u.h>
#include <libc.h>
#include <draw.h>
#include <mouse.h>
#include <frame.h>

int frdelete(Frame* f, ulong p0, ulong p1) {
  Point pt0, pt1, ppt0;
  Frbox* b;
  int n0, n1, n, w0;
  ulong cn1;
  Rectangle r;
  int nn0;
  Image* col;

  if (p0 >= f->nchars || p0 == p1 || f->b == nil)
    return 0;
  if (p1 > f->nchars)
    p1 = f->nchars;
  n0 = _frfindbox(f, 0, 0, p0);
  if (n0 == f->nbox)
    drawerror(f->display, "off end in frdelete");
  n1 = _frfindbox(f, n0, p0, p1);
  pt0 = _frptofcharnb(f, p0, n0);
  pt1 = frptofchar(f, p1);
  if (f->p0 == f->p1)
    frtick(f, frptofchar(f, f->p0), 0);
  nn0 = n0;
  ppt0 = pt0;
  _frfreebox(f, n0, n1 - 1);
  f->modified = 1;

  /*
   * Invariants:
   *  - pt0 points to beginning, pt1 points to end
   *  - n0 is box containing beginning of stuff being deleted
   *  - n1, b are box containing beginning of stuff to be kept after deletion
   *  - cn1 is char position of n1
   *  - f->p0 and f->p1 are not adjusted until after all deletion is done
   */
  b = &f->box[n1];
  cn1 = p1;
  while (pt1.x != pt0.x && n1 < f->nbox) {
    _frcklinewrap0(f, &pt0, b);
    _frcklinewrap(f, &pt1, b);
    n = _frcanfit(f, pt0, b);
    if (n == 0)
      drawerror(f->display, "_frcanfit==0");
    r.min = pt0;
    r.max = pt0;
    r.max.y += f->font->height;
    if (b->nrune > 0) {
      w0 = b->wid;
      if (n != b->nrune) {
        _frsplitbox(f, n1, n);
        b = &f->box[n1];
      }
      r.max.x += b->wid;
      draw(f->b, r, f->b, nil, pt1);
      cn1 += b->nrune;

      /* blank remainder of line */
      r.min.x = r.max.x;
      r.max.x += w0 - b->wid;
      if (r.max.x > f->r.max.x)
        r.max.x = f->r.max.x;
      draw(f->b, r, f->cols[BACK], nil, r.min);
    } else {
      r.max.x += _frnewwid0(f, pt0, b);
      if (r.max.x > f->r.max.x)
        r.max.x = f->r.max.x;
      col = f->cols[BACK];
      if (f->p0 <= cn1 && cn1 < f->p1)
        col = f->cols[HIGH];
      draw(f->b, r, col, nil, pt0);
      cn1++;
    }
    _fradvance(f, &pt1, b);
    pt0.x += _frnewwid(f, pt0, b);
    f->box[n0++] = f->box[n1++];
    b++;
  }
  if (n1 == f->nbox && pt0.x != pt1.x) /* deleting last thing in window; must
                                          clean up */
    frselectpaint(f, pt0, pt1, f->cols[BACK]);
  if (pt1.y != pt0.y) {
    Point pt2;

    pt2 = _frptofcharptb(f, 32767, pt1, n1);
    if (pt2.y > f->r.max.y)
      drawerror(f->display, "frptofchar in frdelete");
    if (n1 < f->nbox) {
      int q0, q1, q2;

      q0 = pt0.y + f->font->height;
      q1 = pt1.y + f->font->height;
      q2 = pt2.y + f->font->height;
      if (q2 > f->r.max.y)
        q2 = f->r.max.y;
      draw(
        f->b,
        Rect(pt0.x, pt0.y, pt0.x + (f->r.max.x - pt1.x), q0),
        f->b,
        nil,
        pt1);
      draw(
        f->b,
        Rect(f->r.min.x, q0, f->r.max.x, q0 + (q2 - q1)),
        f->b,
        nil,
        Pt(f->r.min.x, q1));
      frselectpaint(f, Pt(pt2.x, pt2.y - (pt1.y - pt0.y)), pt2, f->cols[BACK]);
    } else
      frselectpaint(f, pt0, pt2, f->cols[BACK]);
  }
  _frclosebox(f, n0, n1 - 1);
  if (
    nn0 > 0 && f->box[nn0 - 1].nrune >= 0 &&
    ppt0.x - f->box[nn0 - 1].wid >= (int)f->r.min.x) {
    --nn0;
    ppt0.x -= f->box[nn0].wid;
  }
  _frclean(f, ppt0, nn0, n0 < f->nbox - 1 ? n0 + 1 : n0);
  if (f->p1 > p1)
    f->p1 -= p1 - p0;
  else if (f->p1 > p0)
    f->p1 = p0;
  if (f->p0 > p1)
    f->p0 -= p1 - p0;
  else if (f->p0 > p0)
    f->p0 = p0;
  f->nchars -= p1 - p0;
  if (f->p0 == f->p1)
    frtick(f, frptofchar(f, f->p0), 1);
  pt0 = frptofchar(f, f->nchars);
  n = f->nlines;
  f->nlines = (pt0.y - f->r.min.y) / f->font->height + (pt0.x > f->r.min.x);
  return n - f->nlines;
}