/* Simple built-in editing commands.

Copyright (C) 1985, 1993-1998, 2001-2023 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 3 of the License, or (at
your option) any later version.

GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */


#include <config.h>

#include "lisp.h"
#include "commands.h"
#include "character.h"
#include "buffer.h"
#include "syntax.h"
#include "keyboard.h"
#include "keymap.h"
#include "frame.h"

static int internal_self_insert (int, EMACS_INT);

/* Add N to point; or subtract N if FORWARD is false.  N defaults to 1.
   Validate the new location.  Return nil.  */
static Lisp_Object
move_point (Lisp_Object n, bool forward)
{
  /* This used to just set point to point + XFIXNUM (n), and then check
     to see if it was within boundaries.  But now that SET_PT can
     potentially do a lot of stuff (calling entering and exiting
     hooks, etcetera), that's not a good approach.  So we validate the
     proposed position, then set point.  */

  EMACS_INT new_point;

  if (NILP (n))
    XSETFASTINT (n, 1);
  else
    CHECK_FIXNUM (n);

  new_point = PT + (forward ? XFIXNUM (n) : - XFIXNUM (n));

  if (new_point < BEGV)
    {
      SET_PT (BEGV);
      xsignal0 (Qbeginning_of_buffer);
    }
  if (new_point > ZV)
    {
      SET_PT (ZV);
      xsignal0 (Qend_of_buffer);
    }

  SET_PT (new_point);
  return Qnil;
}

DEFUN ("forward-char", Fforward_char, Sforward_char, 0, 1, "^p",
       doc: /* Move point N characters forward (backward if N is negative).
On reaching end or beginning of buffer, stop and signal error.
Interactively, N is the numeric prefix argument.
If N is omitted or nil, move point 1 character forward.

Depending on the bidirectional context, the movement may be to the
right or to the left on the screen.  This is in contrast with
\\[right-char], which see.  */)
  (Lisp_Object n)
{
  return move_point (n, 1);
}

DEFUN ("backward-char", Fbackward_char, Sbackward_char, 0, 1, "^p",
       doc: /* Move point N characters backward (forward if N is negative).
On attempt to pass beginning or end of buffer, stop and signal error.
Interactively, N is the numeric prefix argument.
If N is omitted or nil, move point 1 character backward.

Depending on the bidirectional context, the movement may be to the
right or to the left on the screen.  This is in contrast with
\\[left-char], which see.  */)
  (Lisp_Object n)
{
  return move_point (n, 0);
}

DEFUN ("forward-line", Fforward_line, Sforward_line, 0, 1, "^p",
       doc: /* Move N lines forward (backward if N is negative).
Precisely, if point is on line I, move to the start of line I + N
\("start of line" in the logical order).
If there isn't room, go as far as possible (no error).
Interactively, N is the numeric prefix argument and defaults to 1.

Returns the count of lines left to move.  If moving forward,
that is N minus number of lines moved; if backward, N plus number
moved.

Exception: With positive N, a non-empty line at the end of the
buffer, or of its accessible portion, counts as one line
successfully moved (for the return value).  This means that the
function will move point to the end of such a line and will count
it as a line moved across, even though there is no next line to
go to its beginning.  */)
  (Lisp_Object n)
{
  ptrdiff_t opoint = PT, pos, pos_byte, count;
  bool excessive = false;

  if (NILP (n))
    count = 1;
  else
    {
      CHECK_INTEGER (n);
      if (FIXNUMP (n)
	  && -BUF_BYTES_MAX <= XFIXNUM (n) && XFIXNUM (n) <= BUF_BYTES_MAX)
	count = XFIXNUM (n);
      else
	{
	  count = !NILP (Fnatnump (n)) ? BUF_BYTES_MAX : -BUF_BYTES_MAX;
	  excessive = true;
	}
    }

  ptrdiff_t counted = scan_newline_from_point (count, &pos, &pos_byte);

  SET_PT_BOTH (pos, pos_byte);

  ptrdiff_t shortage = count - (count <= 0) - counted;
  if (shortage != 0)
    shortage -= (count <= 0 ? -1
		  : (BEGV < ZV && PT != opoint
		     && FETCH_BYTE (PT_BYTE - 1) != '\n'));
  return (excessive
	  ? CALLN (Fplus, make_fixnum (shortage - count), n)
	  : make_fixnum (shortage));
}

DEFUN ("beginning-of-line", Fbeginning_of_line, Sbeginning_of_line, 0, 1, "^p",
       doc: /* Move point to beginning of current line (in the logical order).
With argument N not nil or 1, move forward N - 1 lines first.
If point reaches the beginning or end of buffer, it stops there.

This function constrains point to the current field unless this moves
point to a different line from the original, unconstrained result.
If N is nil or 1, and a front-sticky field starts at point, the point
does not move.  To ignore field boundaries bind
`inhibit-field-text-motion' to t, or use the `forward-line' function
instead.  For instance, `(forward-line 0)' does the same thing as
`(beginning-of-line)', except that it ignores field boundaries.  */)
  (Lisp_Object n)
{
  if (NILP (n))
    XSETFASTINT (n, 1);
  else
    CHECK_FIXNUM (n);

  SET_PT (XFIXNUM (Fline_beginning_position (n)));

  return Qnil;
}

DEFUN ("end-of-line", Fend_of_line, Send_of_line, 0, 1, "^p",
       doc: /* Move point to end of current line (in the logical order).
With argument N not nil or 1, move forward N - 1 lines first.
If point reaches the beginning or end of buffer, it stops there.
To ignore intangibility, bind `inhibit-point-motion-hooks' to t.

This function constrains point to the current field unless this moves
point to a different line from the original, unconstrained result.  If
N is nil or 1, and a rear-sticky field ends at point, the point does
not move.  To ignore field boundaries bind `inhibit-field-text-motion'
to t.  */)
  (Lisp_Object n)
{
  ptrdiff_t newpos;

  if (NILP (n))
    XSETFASTINT (n, 1);
  else
    CHECK_FIXNUM (n);

  while (1)
    {
      newpos = XFIXNUM (Fline_end_position (n));
      SET_PT (newpos);

      if (PT > newpos
	  && FETCH_BYTE (PT_BYTE - 1) == '\n')
	{
	  /* If we skipped over a newline that follows
	     an invisible intangible run,
	     move back to the last tangible position
	     within the line.  */

	  SET_PT (PT - 1);
	  break;
	}
      else if (PT > newpos && PT < ZV
	       && FETCH_BYTE (PT_BYTE) != '\n')
	/* If we skipped something intangible
	   and now we're not really at eol,
	   keep going.  */
	n = make_fixnum (1);
      else
	break;
    }

  return Qnil;
}

DEFUN ("delete-char", Fdelete_char, Sdelete_char, 1, 2, "p\nP",
       doc: /* Delete the following N characters (previous if N is negative).
Optional second arg KILLFLAG non-nil means kill instead (save in kill ring).
Interactively, N is the prefix arg, and KILLFLAG is set if
N was explicitly specified.

The command `delete-forward-char' is preferable for interactive use, e.g.
because it respects values of `delete-active-region' and `overwrite-mode'.  */)
  (Lisp_Object n, Lisp_Object killflag)
{
  EMACS_INT pos;

  CHECK_FIXNUM (n);

  if (eabs (XFIXNUM (n)) < 2)
    call0 (Qundo_auto_amalgamate);

  pos = PT + XFIXNUM (n);
  if (NILP (killflag))
    {
      if (XFIXNUM (n) < 0)
	{
	  if (pos < BEGV)
	    xsignal0 (Qbeginning_of_buffer);
	  else
	    del_range (pos, PT);
	}
      else
	{
	  if (pos > ZV)
	    xsignal0 (Qend_of_buffer);
	  else
	    del_range (PT, pos);
	}
    }
  else
    {
      call1 (Qkill_forward_chars, n);
    }
  return Qnil;
}

DEFUN ("self-insert-command", Fself_insert_command, Sself_insert_command, 1, 2,
       "(list (prefix-numeric-value current-prefix-arg) last-command-event)",
       doc: /* Insert the character you type.
Whichever character C you type to run this command is inserted.
The numeric prefix argument N says how many times to repeat the insertion.
Before insertion, `expand-abbrev' is executed if the inserted character does
not have word syntax and the previous character in the buffer does.
After insertion, `internal-auto-fill' is called if
`auto-fill-function' is non-nil and if the `auto-fill-chars' table has
a non-nil value for the inserted character.  At the end, it runs
`post-self-insert-hook'.  */)
  (Lisp_Object n, Lisp_Object c)
{
  CHECK_FIXNUM (n);

  /* Backward compatibility.  */
  if (NILP (c))
    c = last_command_event;

  if (XFIXNUM (n) < 0)
    error ("Negative repetition argument %"pI"d", XFIXNUM (n));

  if (XFIXNAT (n) < 2)
    call0 (Qundo_auto_amalgamate);

  /* Barf if the key that invoked this was not a character.  */
  if (!CHARACTERP (c))
    bitch_at_user ();
  else {
    int character = translate_char (Vtranslation_table_for_input,
				    XFIXNUM (c));
    int val = internal_self_insert (character, XFIXNAT (n));
    if (val == 2)
      Fset (Qundo_auto__this_command_amalgamating, Qnil);
    frame_make_pointer_invisible (SELECTED_FRAME ());
  }

  return Qnil;
}

/* Insert N times character C

   If this insertion is suitable for direct output (completely simple),
   return 0.  A value of 1 indicates this *might* not have been simple.
   A value of 2 means this did things that call for an undo boundary.  */

static int
internal_self_insert (int c, EMACS_INT n)
{
  int hairy = 0;
  Lisp_Object tem;
  register enum syntaxcode synt;
  Lisp_Object overwrite;
  /* Length of multi-byte form of C.  */
  int len;
  /* Working buffer and pointer for multi-byte form of C.  */
  unsigned char str[MAX_MULTIBYTE_LENGTH];
  ptrdiff_t chars_to_delete = 0;
  ptrdiff_t spaces_to_insert = 0;

  overwrite = BVAR (current_buffer, overwrite_mode);
  if (!NILP (Vbefore_change_functions) || !NILP (Vafter_change_functions))
    hairy = 1;

  /* At first, get multi-byte form of C in STR.  */
  if (!NILP (BVAR (current_buffer, enable_multibyte_characters)))
    {
      len = CHAR_STRING (c, str);
      if (len == 1)
	/* If C has modifier bits, this makes C an appropriate
           one-byte char.  */
	c = *str;
    }
  else
    {
      str[0] = SINGLE_BYTE_CHAR_P (c) ? c : CHAR_TO_BYTE8 (c);
      len = 1;
    }
  if (!NILP (overwrite)
      && PT < ZV)
    {
      /* In overwrite-mode, we substitute a character at point (C2,
	 hereafter) by C.  For that, we delete C2 in advance.  But,
	 just substituting C2 by C may move a remaining text in the
	 line to the right or to the left, which is not preferable.
	 So we insert more spaces or delete more characters in the
	 following cases: if C is narrower than C2, after deleting C2,
	 we fill columns with spaces, if C is wider than C2, we delete
	 C2 and several characters following C2.  */

      /* This is the character after point.  */
      int c2 = FETCH_CHAR (PT_BYTE);

      int cwidth;

      /* Overwriting in binary-mode always replaces C2 by C.
	 Overwriting in textual-mode doesn't always do that.
	 It inserts newlines in the usual way,
	 and inserts any character at end of line
	 or before a tab if it doesn't use the whole width of the tab.  */
      if (EQ (overwrite, Qoverwrite_mode_binary))
	chars_to_delete = min (n, PTRDIFF_MAX);
      else if (c != '\n' && c2 != '\n'
	       && (cwidth = XFIXNAT (Fchar_width (make_fixnum (c)))) != 0)
	{
	  ptrdiff_t pos = PT;
	  ptrdiff_t pos_byte = PT_BYTE;
	  ptrdiff_t curcol = current_column ();

	  if (n <= (min (MOST_POSITIVE_FIXNUM, PTRDIFF_MAX) - curcol) / cwidth)
	    {
	      /* Column the cursor should be placed at after this insertion.
		 The value should be calculated only when necessary.  */
	      ptrdiff_t target_clm = curcol + n * cwidth;

	      /* The actual cursor position after the trial of moving
		 to column TARGET_CLM.  It is greater than TARGET_CLM
		 if the TARGET_CLM is middle of multi-column
		 character.  In that case, the new point is set after
		 that character.  */
	      ptrdiff_t actual_clm
		= XFIXNAT (Fmove_to_column (make_fixnum (target_clm), Qnil));

	      chars_to_delete = PT - pos;

	      if (actual_clm > target_clm)
		{
		  /* We will delete too many columns.  Let's fill columns
		     by spaces so that the remaining text won't move.  */
		  ptrdiff_t actual = PT_BYTE;
		  actual -= prev_char_len (actual);
		  if (FETCH_BYTE (actual) == '\t')
		    /* Rather than add spaces, let's just keep the tab. */
		    chars_to_delete--;
		  else
		    spaces_to_insert = actual_clm - target_clm;
		}

	      SET_PT_BOTH (pos, pos_byte);
	    }
	}
      hairy = 2;
    }

  synt = SYNTAX (c);

  if (!NILP (BVAR (current_buffer, abbrev_mode))
      && synt != Sword
      && NILP (BVAR (current_buffer, read_only))
      && PT > BEGV
      && (SYNTAX (!NILP (BVAR (current_buffer, enable_multibyte_characters))
		  ? XFIXNAT (Fprevious_char ())
		  : UNIBYTE_TO_CHAR (XFIXNAT (Fprevious_char ())))
	  == Sword))
    {
      modiff_count modiff = MODIFF;
      Lisp_Object sym;

      sym = call0 (Qexpand_abbrev);

      /* If we expanded an abbrev which has a hook,
	 and the hook has a non-nil `no-self-insert' property,
	 return right away--don't really self-insert.  */
      if (SYMBOLP (sym) && ! NILP (sym)
	  && ! NILP (XSYMBOL (sym)->u.s.function)
	  && SYMBOLP (XSYMBOL (sym)->u.s.function))
	{
	  Lisp_Object prop;
	  prop = Fget (XSYMBOL (sym)->u.s.function, intern ("no-self-insert"));
	  if (! NILP (prop))
	    return 1;
	}

      if (MODIFF != modiff)
	hairy = 2;
    }

  if (chars_to_delete)
    {
      int mc = ((NILP (BVAR (current_buffer, enable_multibyte_characters))
		 && SINGLE_BYTE_CHAR_P (c))
		? UNIBYTE_TO_CHAR (c) : c);
      Lisp_Object string = Fmake_string (make_fixnum (n), make_fixnum (mc),
					 Qnil);

      if (spaces_to_insert)
	{
	  tem = Fmake_string (make_fixnum (spaces_to_insert),
			      make_fixnum (' '), Qnil);
	  string = concat2 (string, tem);
	}

      ptrdiff_t to;
      if (ckd_add (&to, PT, chars_to_delete))
	to = PTRDIFF_MAX;
      replace_range (PT, to, string, 1, 1, 1, 0, false);
      Fforward_char (make_fixnum (n));
    }
  else if (n > 1)
    {
      USE_SAFE_ALLOCA;
      char *strn, *p;
      SAFE_NALLOCA (strn, len, n);
      for (p = strn; n > 0; n--, p += len)
	memcpy (p, str, len);
      insert_and_inherit (strn, p - strn);
      SAFE_FREE ();
    }
  else if (n > 0)
    insert_and_inherit ((char *) str, len);

  if ((CHAR_TABLE_P (Vauto_fill_chars)
       ? !NILP (CHAR_TABLE_REF (Vauto_fill_chars, c))
       : (c == ' ' || c == '\n'))
      && !NILP (BVAR (current_buffer, auto_fill_function)))
    {
      Lisp_Object auto_fill_result;

      if (c == '\n')
	/* After inserting a newline, move to previous line and fill
	   that.  Must have the newline in place already so filling and
	   justification, if any, know where the end is going to be.  */
	SET_PT_BOTH (PT - 1, PT_BYTE - 1);
      auto_fill_result = call0 (Qinternal_auto_fill);
      /* Test PT < ZV in case the auto-fill-function is strange.  */
      if (c == '\n' && PT < ZV)
	SET_PT_BOTH (PT + 1, PT_BYTE + 1);
      if (!NILP (auto_fill_result))
	hairy = 2;
    }

  /* Run hooks for electric keys.  */
  run_hook (Qpost_self_insert_hook);

  return hairy;
}

/* module initialization */

void
syms_of_cmds (void)
{
  DEFSYM (Qinternal_auto_fill, "internal-auto-fill");

  DEFSYM (Qundo_auto_amalgamate, "undo-auto-amalgamate");
  DEFSYM (Qundo_auto__this_command_amalgamating,
          "undo-auto--this-command-amalgamating");

  DEFSYM (Qkill_forward_chars, "kill-forward-chars");

  /* A possible value for a buffer's overwrite-mode variable.  */
  DEFSYM (Qoverwrite_mode_binary, "overwrite-mode-binary");

  DEFSYM (Qexpand_abbrev, "expand-abbrev");
  DEFSYM (Qpost_self_insert_hook, "post-self-insert-hook");

  DEFVAR_LISP ("post-self-insert-hook", Vpost_self_insert_hook,
	       doc: /* Hook run at the end of `self-insert-command'.
This is run after inserting the character.  */);
  Vpost_self_insert_hook = Qnil;

  defsubr (&Sforward_char);
  defsubr (&Sbackward_char);
  defsubr (&Sforward_line);
  defsubr (&Sbeginning_of_line);
  defsubr (&Send_of_line);

  defsubr (&Sdelete_char);
  defsubr (&Sself_insert_command);
}