#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "nvim/ascii_defs.h"
#include "nvim/assert_defs.h"
#include "nvim/buffer.h"
#include "nvim/buffer_defs.h"
#include "nvim/change.h"
#include "nvim/charset.h"
#include "nvim/cursor.h"
#include "nvim/drawscreen.h"
#include "nvim/edit.h"
#include "nvim/errors.h"
#include "nvim/eval.h"
#include "nvim/eval/typval_defs.h"
#include "nvim/ex_cmds_defs.h"
#include "nvim/ex_docmd.h"
#include "nvim/extmark.h"
#include "nvim/extmark_defs.h"
#include "nvim/gettext_defs.h"
#include "nvim/globals.h"
#include "nvim/indent.h"
#include "nvim/indent_c.h"
#include "nvim/mark_defs.h"
#include "nvim/mbyte.h"
#include "nvim/mbyte_defs.h"
#include "nvim/memline.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/move.h"
#include "nvim/option.h"
#include "nvim/option_defs.h"
#include "nvim/option_vars.h"
#include "nvim/os/input.h"
#include "nvim/plines.h"
#include "nvim/pos_defs.h"
#include "nvim/regexp.h"
#include "nvim/regexp_defs.h"
#include "nvim/search.h"
#include "nvim/state_defs.h"
#include "nvim/strings.h"
#include "nvim/textformat.h"
#include "nvim/types_defs.h"
#include "nvim/undo.h"
#include "nvim/vim_defs.h"

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "indent.c.generated.h"
#endif

/// Set the integer values corresponding to the string setting of 'vartabstop'.
/// "array" will be set, caller must free it if needed.
///
/// @return  false for an error.
bool tabstop_set(char *var, colnr_T **array)
{
  int valcount = 1;

  if (var[0] == NUL || (var[0] == '0' && var[1] == NUL)) {
    *array = NULL;
    return true;
  }

  for (char *cp = var; *cp != NUL; cp++) {
    if (cp == var || cp[-1] == ',') {
      char *end;

      if (strtol(cp, &end, 10) <= 0) {
        if (cp != end) {
          emsg(_(e_positive));
        } else {
          semsg(_(e_invarg2), cp);
        }
        return false;
      }
    }

    if (ascii_isdigit(*cp)) {
      continue;
    }
    if (cp[0] == ',' && cp > var && cp[-1] != ',' && cp[1] != NUL) {
      valcount++;
      continue;
    }
    semsg(_(e_invarg2), var);
    return false;
  }

  *array = (colnr_T *)xmalloc((unsigned)(valcount + 1) * sizeof(int));
  (*array)[0] = (colnr_T)valcount;

  int t = 1;
  for (char *cp = var; *cp != NUL;) {
    int n = atoi(cp);

    // Catch negative values, overflow and ridiculous big values.
    if (n <= 0 || n > TABSTOP_MAX) {
      semsg(_(e_invarg2), cp);
      XFREE_CLEAR(*array);
      return false;
    }
    (*array)[t++] = n;
    while (*cp != NUL && *cp != ',') {
      cp++;
    }
    if (*cp != NUL) {
      cp++;
    }
  }

  return true;
}

/// Calculate the number of screen spaces a tab will occupy.
/// If "vts" is set then the tab widths are taken from that array,
/// otherwise the value of ts is used.
int tabstop_padding(colnr_T col, OptInt ts_arg, const colnr_T *vts)
  FUNC_ATTR_PURE
{
  OptInt ts = ts_arg == 0 ? 8 : ts_arg;
  colnr_T tabcol = 0;
  int t;
  int padding = 0;

  if (vts == NULL || vts[0] == 0) {
    return (int)(ts - (col % ts));
  }

  const int tabcount = vts[0];

  for (t = 1; t <= tabcount; t++) {
    tabcol += vts[t];
    if (tabcol > col) {
      padding = tabcol - col;
      break;
    }
  }
  if (t > tabcount) {
    padding = vts[tabcount] - ((col - tabcol) % vts[tabcount]);
  }

  return padding;
}

/// Find the size of the tab that covers a particular column.
///
/// If this is being called as part of a shift operation, col is not the cursor
/// column but is the column number to the left of the first non-whitespace
/// character in the line.  If the shift is to the left (left == true), then
/// return the size of the tab interval to the left of the column.
int tabstop_at(colnr_T col, OptInt ts, const colnr_T *vts, bool left)
{
  if (vts == NULL || vts[0] == 0) {
    return (int)ts;
  }

  colnr_T tabcol = 0;  // Column of the tab stop under consideration.
  int t;  // Tabstop index in the list of variable tab stops.
  int tab_size = 0;  // Size of the tab stop interval to the right or left of the col.
  const int tabcount  // Number of tab stops in the list of variable tab stops.
    = vts[0];
  for (t = 1; t <= tabcount; t++) {
    tabcol += vts[t];
    if (tabcol > col) {
      // If shifting left (left == true), and if the column to the left of
      // the first first non-blank character (col) in the line is
      // already to the left of the first tabstop, set the shift amount
      // (tab_size) to just enough to shift the line to the left margin.
      // The value doesn't seem to matter as long as it is at least that
      // distance.
      if (left && (t == 1)) {
        tab_size = col;
      } else {
        tab_size = vts[t - (left ? 1 : 0)];
      }
      break;
    }
  }
  if (t > tabcount) {  // If the value of the index t is beyond the
                       // end of the list, use the tab stop value at
                       // the end of the list.
    tab_size = vts[tabcount];
  }

  return tab_size;
}

/// Find the column on which a tab starts.
colnr_T tabstop_start(colnr_T col, int ts, colnr_T *vts)
{
  colnr_T tabcol = 0;

  if (vts == NULL || vts[0] == 0) {
    return col - col % ts;
  }

  const int tabcount = vts[0];
  for (int t = 1; t <= tabcount; t++) {
    tabcol += vts[t];
    if (tabcol > col) {
      return (tabcol - vts[t]);
    }
  }

  const int excess = (tabcol % vts[tabcount]);
  return col - (col - excess) % vts[tabcount];
}

/// Find the number of tabs and spaces necessary to get from one column
/// to another.
void tabstop_fromto(colnr_T start_col, colnr_T end_col, int ts_arg, const colnr_T *vts, int *ntabs,
                    int *nspcs)
{
  int spaces = end_col - start_col;
  colnr_T tabcol = 0;
  int padding = 0;
  int t;
  int ts = ts_arg == 0 ? (int)curbuf->b_p_ts : ts_arg;
  assert(ts != 0);  // suppress clang "Division by zero"

  if (vts == NULL || vts[0] == 0) {
    int tabs = 0;

    const int initspc = (ts - (start_col % ts));
    if (spaces >= initspc) {
      spaces -= initspc;
      tabs++;
    }
    tabs += (spaces / ts);
    spaces -= ((spaces / ts) * ts);

    *ntabs = tabs;
    *nspcs = spaces;
    return;
  }

  // Find the padding needed to reach the next tabstop.
  const int tabcount = vts[0];
  for (t = 1; t <= tabcount; t++) {
    tabcol += vts[t];
    if (tabcol > start_col) {
      padding = tabcol - start_col;
      break;
    }
  }
  if (t > tabcount) {
    padding = vts[tabcount] - ((start_col - tabcol) % vts[tabcount]);
  }

  // If the space needed is less than the padding no tabs can be used.
  if (spaces < padding) {
    *ntabs = 0;
    *nspcs = spaces;
    return;
  }

  *ntabs = 1;
  spaces -= padding;

  // At least one tab has been used. See if any more will fit.
  while (spaces != 0 && ++t <= tabcount) {
    padding = vts[t];
    if (spaces < padding) {
      *nspcs = spaces;
      return;
    }
    *ntabs += 1;
    spaces -= padding;
  }

  *ntabs += spaces / (int)vts[tabcount];
  *nspcs = spaces % (int)vts[tabcount];
}

/// See if two tabstop arrays contain the same values.
bool tabstop_eq(const colnr_T *ts1, const colnr_T *ts2)
{
  if ((ts1 == 0 && ts2) || (ts1 && ts2 == 0)) {
    return false;
  }
  if (ts1 == ts2) {
    return true;
  }
  if (ts1[0] != ts2[0]) {
    return false;
  }

  for (int t = 1; t <= ts1[0]; t++) {
    if (ts1[t] != ts2[t]) {
      return false;
    }
  }

  return true;
}

/// Copy a tabstop array, allocating space for the new array.
int *tabstop_copy(const int *oldts)
{
  if (oldts == 0) {
    return 0;
  }

  int *newts = xmalloc((unsigned)(oldts[0] + 1) * sizeof(int));
  for (int t = 0; t <= oldts[0]; t++) {
    newts[t] = oldts[t];
  }

  return newts;
}

/// Return a count of the number of tabstops.
int tabstop_count(colnr_T *ts)
{
  return ts != NULL ? (int)ts[0] : 0;
}

/// Return the first tabstop, or 8 if there are no tabstops defined.
int tabstop_first(colnr_T *ts)
{
  return ts != NULL ? (int)ts[1] : 8;
}

/// Return the effective shiftwidth value for current buffer, using the
/// 'tabstop' value when 'shiftwidth' is zero.
int get_sw_value(buf_T *buf)
{
  int result = get_sw_value_col(buf, 0, false);
  return result;
}

/// Idem, using "pos".
int get_sw_value_pos(buf_T *buf, pos_T *pos, bool left)
{
  pos_T save_cursor = curwin->w_cursor;

  curwin->w_cursor = *pos;
  int sw_value = get_sw_value_col(buf, get_nolist_virtcol(), left);
  curwin->w_cursor = save_cursor;
  return sw_value;
}

/// Idem, using the first non-black in the current line.
int get_sw_value_indent(buf_T *buf, bool left)
{
  pos_T pos = curwin->w_cursor;

  pos.col = (colnr_T)getwhitecols_curline();
  return get_sw_value_pos(buf, &pos, left);
}

/// Idem, using virtual column "col".
int get_sw_value_col(buf_T *buf, colnr_T col, bool left)
{
  return buf->b_p_sw ? (int)buf->b_p_sw
                     : tabstop_at(col, buf->b_p_ts, buf->b_p_vts_array, left);
}

/// Return the effective softtabstop value for the current buffer,
/// using the shiftwidth  value when 'softtabstop' is negative.
int get_sts_value(void)
{
  int result = curbuf->b_p_sts < 0 ? get_sw_value(curbuf) : (int)curbuf->b_p_sts;
  return result;
}

/// Count the size (in window cells) of the indent in the current line.
int get_indent(void)
{
  return indent_size_ts(get_cursor_line_ptr(), curbuf->b_p_ts, curbuf->b_p_vts_array);
}

/// Count the size (in window cells) of the indent in line "lnum".
int get_indent_lnum(linenr_T lnum)
{
  return indent_size_ts(ml_get(lnum), curbuf->b_p_ts, curbuf->b_p_vts_array);
}

/// Count the size (in window cells) of the indent in line "lnum" of buffer "buf".
int get_indent_buf(buf_T *buf, linenr_T lnum)
{
  return indent_size_ts(ml_get_buf(buf, lnum), buf->b_p_ts, buf->b_p_vts_array);
}

/// Compute the size of the indent (in window cells) in line "ptr",
/// without tabstops (count tab as ^I or <09>).
int indent_size_no_ts(char const *ptr)
  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
{
  int tab_size = byte2cells(TAB);

  int vcol = 0;
  while (true) {
    char const c = *ptr++;
    if (c == ' ') {
      vcol++;
    } else if (c == TAB) {
      vcol += tab_size;
    } else {
      return vcol;
    }
  }
}

/// Compute the size of the indent (in window cells) in line "ptr",
/// using tabstops
int indent_size_ts(char const *ptr, OptInt ts, colnr_T *vts)
  FUNC_ATTR_NONNULL_ARG(1) FUNC_ATTR_PURE
{
  assert(char2cells(' ') == 1);

  int vcol = 0;
  int tabstop_width, next_tab_vcol;

  if (vts == NULL || vts[0] < 1) {  // tab has fixed width
    // can ts be 0 ? This is from tabstop_padding().
    tabstop_width = (int)(ts == 0 ? 8 : ts);
    next_tab_vcol = tabstop_width;
  } else {  // tab has variable width
    colnr_T *cur_tabstop = vts + 1;
    colnr_T *const last_tabstop = vts + vts[0];

    while (cur_tabstop != last_tabstop) {
      int cur_vcol = vcol;
      vcol += *cur_tabstop++;
      assert(cur_vcol < vcol);

      do {
        char const c = *ptr++;
        if (c == ' ') {
          cur_vcol++;
        } else if (c == TAB) {
          break;
        } else {
          return cur_vcol;
        }
      } while (cur_vcol != vcol);
    }

    tabstop_width = *last_tabstop;
    next_tab_vcol = vcol + tabstop_width;
  }

  assert(tabstop_width != 0);
  while (true) {
    char const c = *ptr++;
    if (c == ' ') {
      vcol++;
      next_tab_vcol += (vcol == next_tab_vcol) ? tabstop_width : 0;
    } else if (c == TAB) {
      vcol = next_tab_vcol;
      next_tab_vcol += tabstop_width;
    } else {
      return vcol;
    }
  }
}

/// Set the indent of the current line.
/// Leaves the cursor on the first non-blank in the line.
/// Caller must take care of undo.
/// "flags":
///  SIN_CHANGED:    call changed_bytes() if the line was changed.
///  SIN_INSERT: insert the indent in front of the line.
///  SIN_UNDO:   save line for undo before changing it.
///  SIN_NOMARK: don't move extmarks (because just after ml_append or something)
///  @param size measured in spaces
///
/// @return  true if the line was changed.
bool set_indent(int size, int flags)
{
  char *newline;
  char *oldline;
  char *s;
  int doit = false;
  int ind_done = 0;  // Measured in spaces.
  int tab_pad;
  bool retval = false;

  // Number of initial whitespace chars when 'et' and 'pi' are both set.
  int orig_char_len = -1;

  // First check if there is anything to do and compute the number of
  // characters needed for the indent.
  int todo = size;
  int ind_len = 0;  // Measured in characters.
  char *p = oldline = get_cursor_line_ptr();

  // Calculate the buffer size for the new indent, and check to see if it
  // isn't already set.
  // If 'expandtab' isn't set: use TABs; if both 'expandtab' and
  // 'preserveindent' are set count the number of characters at the
  // beginning of the line to be copied.
  if (!curbuf->b_p_et || (!(flags & SIN_INSERT) && curbuf->b_p_pi)) {
    int ind_col = 0;
    // If 'preserveindent' is set then reuse as much as possible of
    // the existing indent structure for the new indent.
    if (!(flags & SIN_INSERT) && curbuf->b_p_pi) {
      ind_done = 0;

      // Count as many characters as we can use.
      while (todo > 0 && ascii_iswhite(*p)) {
        if (*p == TAB) {
          tab_pad = tabstop_padding(ind_done,
                                    curbuf->b_p_ts,
                                    curbuf->b_p_vts_array);

          // Stop if this tab will overshoot the target.
          if (todo < tab_pad) {
            break;
          }
          todo -= tab_pad;
          ind_len++;
          ind_done += tab_pad;
        } else {
          todo--;
          ind_len++;
          ind_done++;
        }
        p++;
      }

      // These diverge from this point.
      ind_col = ind_done;
      // Set initial number of whitespace chars to copy if we are
      // preserving indent but expandtab is set.
      if (curbuf->b_p_et) {
        orig_char_len = ind_len;
      }
      // Fill to next tabstop with a tab, if possible.
      tab_pad = tabstop_padding(ind_done,
                                curbuf->b_p_ts,
                                curbuf->b_p_vts_array);
      if ((todo >= tab_pad) && (orig_char_len == -1)) {
        doit = true;
        todo -= tab_pad;
        ind_len++;

        // ind_done += tab_pad;
        ind_col += tab_pad;
      }
    }

    // Count tabs required for indent.
    while (true) {
      tab_pad = tabstop_padding(ind_col, curbuf->b_p_ts, curbuf->b_p_vts_array);
      if (todo < tab_pad) {
        break;
      }
      if (*p != TAB) {
        doit = true;
      } else {
        p++;
      }
      todo -= tab_pad;
      ind_len++;
      ind_col += tab_pad;
    }
  }

  // Count spaces required for indent.
  while (todo > 0) {
    if (*p != ' ') {
      doit = true;
    } else {
      p++;
    }
    todo--;
    ind_len++;

    // ind_done++;
  }

  // Return if the indent is OK already.
  if (!doit && !ascii_iswhite(*p) && !(flags & SIN_INSERT)) {
    return false;
  }

  // Allocate memory for the new line.
  if (flags & SIN_INSERT) {
    p = oldline;
  } else {
    p = skipwhite(p);
  }
  int line_len = (int)strlen(p) + 1;

  // If 'preserveindent' and 'expandtab' are both set keep the original
  // characters and allocate accordingly.  We will fill the rest with spaces
  // after the if (!curbuf->b_p_et) below.
  int skipcols = 0;  // number of columns (in bytes) that were presved
  if (orig_char_len != -1) {
    int newline_size;  // = orig_char_len + size - ind_done + line_len
    STRICT_ADD(orig_char_len, size, &newline_size, int);
    STRICT_SUB(newline_size, ind_done, &newline_size, int);
    STRICT_ADD(newline_size, line_len, &newline_size, int);
    assert(newline_size >= 0);
    newline = xmalloc((size_t)newline_size);
    todo = size - ind_done;

    // Set total length of indent in characters, which may have been
    // undercounted until now.
    ind_len = orig_char_len + todo;
    p = oldline;
    s = newline;
    skipcols = orig_char_len;

    while (orig_char_len > 0) {
      *s++ = *p++;
      orig_char_len--;
    }

    // Skip over any additional white space (useful when newindent is less
    // than old).
    while (ascii_iswhite(*p)) {
      p++;
    }
  } else {
    todo = size;
    assert(ind_len + line_len >= 0);
    size_t newline_size;
    STRICT_ADD(ind_len, line_len, &newline_size, size_t);
    newline = xmalloc(newline_size);
    s = newline;
  }

  // Put the characters in the new line.
  // if 'expandtab' isn't set: use TABs
  if (!curbuf->b_p_et) {
    // If 'preserveindent' is set then reuse as much as possible of
    // the existing indent structure for the new indent.
    if (!(flags & SIN_INSERT) && curbuf->b_p_pi) {
      p = oldline;
      ind_done = 0;

      while (todo > 0 && ascii_iswhite(*p)) {
        if (*p == TAB) {
          tab_pad = tabstop_padding(ind_done,
                                    curbuf->b_p_ts,
                                    curbuf->b_p_vts_array);

          // Stop if this tab will overshoot the target.
          if (todo < tab_pad) {
            break;
          }
          todo -= tab_pad;
          ind_done += tab_pad;
        } else {
          todo--;
          ind_done++;
        }
        *s++ = *p++;
        skipcols++;
      }

      // Fill to next tabstop with a tab, if possible.
      tab_pad = tabstop_padding(ind_done,
                                curbuf->b_p_ts,
                                curbuf->b_p_vts_array);

      if (todo >= tab_pad) {
        *s++ = TAB;
        todo -= tab_pad;
        ind_done += tab_pad;
      }
      p = skipwhite(p);
    }

    while (true) {
      tab_pad = tabstop_padding(ind_done,
                                curbuf->b_p_ts,
                                curbuf->b_p_vts_array);
      if (todo < tab_pad) {
        break;
      }
      *s++ = TAB;
      todo -= tab_pad;
      ind_done += tab_pad;
    }
  }

  while (todo > 0) {
    *s++ = ' ';
    todo--;
  }
  memmove(s, p, (size_t)line_len);

  // Replace the line (unless undo fails).
  if (!(flags & SIN_UNDO) || (u_savesub(curwin->w_cursor.lnum) == OK)) {
    const colnr_T old_offset = (colnr_T)(p - oldline);
    const colnr_T new_offset = (colnr_T)(s - newline);

    // this may free "newline"
    ml_replace(curwin->w_cursor.lnum, newline, false);
    if (!(flags & SIN_NOMARK)) {
      extmark_splice_cols(curbuf,
                          (int)curwin->w_cursor.lnum - 1,
                          skipcols,
                          old_offset - skipcols,
                          new_offset - skipcols,
                          kExtmarkUndo);
    }

    if (flags & SIN_CHANGED) {
      changed_bytes(curwin->w_cursor.lnum, 0);
    }

    // Correct saved cursor position if it is in this line.
    if (saved_cursor.lnum == curwin->w_cursor.lnum) {
      if (saved_cursor.col >= old_offset) {
        // Cursor was after the indent, adjust for the number of
        // bytes added/removed.
        saved_cursor.col += ind_len - old_offset;
      } else if (saved_cursor.col >= new_offset) {
        // Cursor was in the indent, and is now after it, put it back
        // at the start of the indent (replacing spaces with TAB).
        saved_cursor.col = new_offset;
      }
    }
    retval = true;
  } else {
    xfree(newline);
  }
  curwin->w_cursor.col = ind_len;
  return retval;
}

// Return the indent of the current line after a number.  Return -1 if no
// number was found.  Used for 'n' in 'formatoptions': numbered list.
// Since a pattern is used it can actually handle more than numbers.
int get_number_indent(linenr_T lnum)
{
  colnr_T col;
  pos_T pos;
  regmatch_T regmatch;
  int lead_len = 0;  // Length of comment leader.

  if (lnum > curbuf->b_ml.ml_line_count) {
    return -1;
  }
  pos.lnum = 0;

  // In format_lines() (i.e. not insert mode), fo+=q is needed too...
  if ((State & MODE_INSERT) || has_format_option(FO_Q_COMS)) {
    lead_len = get_leader_len(ml_get(lnum), NULL, false, true);
  }
  regmatch.regprog = vim_regcomp(curbuf->b_p_flp, RE_MAGIC);

  if (regmatch.regprog != NULL) {
    regmatch.rm_ic = false;

    // vim_regexec() expects a pointer to a line.  This lets us
    // start matching for the flp beyond any comment leader...
    if (vim_regexec(&regmatch, ml_get(lnum) + lead_len, 0)) {
      pos.lnum = lnum;
      pos.col = (colnr_T)(*regmatch.endp - ml_get(lnum));
      pos.coladd = 0;
    }
    vim_regfree(regmatch.regprog);
  }

  if ((pos.lnum == 0) || (*ml_get_pos(&pos) == NUL)) {
    return -1;
  }
  getvcol(curwin, &pos, &col, NULL, NULL);
  return (int)col;
}

/// Check "briopt" as 'breakindentopt' and update the members of "wp".
/// This is called when 'breakindentopt' is changed and when a window is
/// initialized
///
/// @param briopt  when NULL: use "wp->w_p_briopt"
/// @param wp      when NULL: only check "briopt"
///
/// @return  FAIL for failure, OK otherwise.
bool briopt_check(char *briopt, win_T *wp)
{
  int bri_shift = 0;
  int bri_min = 20;
  bool bri_sbr = false;
  int bri_list = 0;
  int bri_vcol = 0;

  char *p = empty_string_option;
  if (briopt != NULL) {
    p = briopt;
  } else if (wp != NULL) {
    p = wp->w_p_briopt;
  }

  while (*p != NUL) {
    // Note: Keep this in sync with opt_briopt_values.
    if (strncmp(p, "shift:", 6) == 0
        && ((p[6] == '-' && ascii_isdigit(p[7])) || ascii_isdigit(p[6]))) {
      p += 6;
      bri_shift = getdigits_int(&p, true, 0);
    } else if (strncmp(p, "min:", 4) == 0 && ascii_isdigit(p[4])) {
      p += 4;
      bri_min = getdigits_int(&p, true, 0);
    } else if (strncmp(p, "sbr", 3) == 0) {
      p += 3;
      bri_sbr = true;
    } else if (strncmp(p, "list:", 5) == 0) {
      p += 5;
      bri_list = (int)getdigits(&p, false, 0);
    } else if (strncmp(p, "column:", 7) == 0) {
      p += 7;
      bri_vcol = (int)getdigits(&p, false, 0);
    }
    if (*p != ',' && *p != NUL) {
      return false;
    }
    if (*p == ',') {
      p++;
    }
  }

  if (wp == NULL) {
    return OK;
  }

  wp->w_briopt_shift = bri_shift;
  wp->w_briopt_min = bri_min;
  wp->w_briopt_sbr = bri_sbr;
  wp->w_briopt_list = bri_list;
  wp->w_briopt_vcol = bri_vcol;

  return true;
}

// Return appropriate space number for breakindent, taking influencing
// parameters into account. Window must be specified, since it is not
// necessarily always the current one.
int get_breakindent_win(win_T *wp, char *line)
  FUNC_ATTR_NONNULL_ALL
{
  static int prev_indent = 0;  // cached indent value
  static OptInt prev_ts = 0;  // cached tabstop value
  static colnr_T *prev_vts = NULL;  // cached vartabs values
  static int prev_fnum = 0;  // cached buffer number
  static char *prev_line = NULL;  // cached copy of "line"
  static varnumber_T prev_tick = 0;  // changedtick of cached value
  static int prev_list = 0;  // cached list indent
  static int prev_listopt = 0;  // cached w_p_briopt_list value
  static bool prev_no_ts = false;  // cached no_ts value
  static unsigned prev_dy_uhex = 0;   // cached 'display' "uhex" value
  static char *prev_flp = NULL;  // cached formatlistpat value
  int bri = 0;
  // window width minus window margin space, i.e. what rests for text
  const int eff_wwidth = wp->w_width_inner - win_col_off(wp) + win_col_off2(wp);

  // In list mode, if 'listchars' "tab" isn't set, a TAB is displayed as ^I.
  const bool no_ts = wp->w_p_list && wp->w_p_lcs_chars.tab1 == NUL;

  // Used cached indent, unless
  // - buffer changed, or
  // - 'tabstop' changed, or
  // - 'vartabstop' changed, or
  // - buffer was changed, or
  // - 'breakindentopt' "list" changed, or
  // - 'list' or 'listchars' "tab" changed, or
  // - 'display' "uhex" flag changed, or
  // - 'formatlistpat' changed, or
  // - line changed.
  if (prev_fnum != wp->w_buffer->b_fnum
      || prev_ts != wp->w_buffer->b_p_ts
      || prev_vts != wp->w_buffer->b_p_vts_array
      || prev_tick != buf_get_changedtick(wp->w_buffer)
      || prev_listopt != wp->w_briopt_list
      || prev_no_ts != no_ts
      || prev_dy_uhex != (dy_flags & kOptDyFlagUhex)
      || prev_flp == NULL
      || strcmp(prev_flp, get_flp_value(wp->w_buffer)) != 0
      || prev_line == NULL || strcmp(prev_line, line) != 0) {
    prev_fnum = wp->w_buffer->b_fnum;
    xfree(prev_line);
    prev_line = xstrdup(line);
    prev_ts = wp->w_buffer->b_p_ts;
    prev_vts = wp->w_buffer->b_p_vts_array;
    if (wp->w_briopt_vcol == 0) {
      if (no_ts) {
        prev_indent = indent_size_no_ts(line);
      } else {
        prev_indent = indent_size_ts(line, wp->w_buffer->b_p_ts,
                                     wp->w_buffer->b_p_vts_array);
      }
    }
    prev_tick = buf_get_changedtick(wp->w_buffer);
    prev_listopt = wp->w_briopt_list;
    prev_list = 0;
    prev_no_ts = no_ts;
    prev_dy_uhex = (dy_flags & kOptDyFlagUhex);
    xfree(prev_flp);
    prev_flp = xstrdup(get_flp_value(wp->w_buffer));
    // add additional indent for numbered lists
    if (wp->w_briopt_list != 0 && wp->w_briopt_vcol == 0) {
      regmatch_T regmatch = {
        .regprog = vim_regcomp(prev_flp, RE_MAGIC + RE_STRING + RE_AUTO + RE_STRICT),
      };
      if (regmatch.regprog != NULL) {
        regmatch.rm_ic = false;
        if (vim_regexec(&regmatch, line, 0)) {
          if (wp->w_briopt_list > 0) {
            prev_list += wp->w_briopt_list;
          } else {
            char *ptr = *regmatch.startp;
            char *end_ptr = *regmatch.endp;
            int indent = 0;
            // Compute the width of the matched text.
            // Use win_chartabsize() so that TAB size is correct,
            // while wrapping is ignored.
            while (ptr < end_ptr) {
              indent += win_chartabsize(wp, ptr, indent);
              MB_PTR_ADV(ptr);
            }
            prev_indent = indent;
          }
        }
        vim_regfree(regmatch.regprog);
      }
    }
  }
  if (wp->w_briopt_vcol != 0) {
    // column value has priority
    bri = wp->w_briopt_vcol;
    prev_list = 0;
  } else {
    bri = prev_indent + wp->w_briopt_shift;
  }

  // Add offset for number column, if 'n' is in 'cpoptions'
  bri += win_col_off2(wp);

  // add additional indent for numbered lists
  if (wp->w_briopt_list > 0) {
    bri += prev_list;
  }

  // indent minus the length of the showbreak string
  if (wp->w_briopt_sbr) {
    bri -= vim_strsize(get_showbreak_value(wp));
  }

  // never indent past left window margin
  if (bri < 0) {
    bri = 0;
  } else if (bri > eff_wwidth - wp->w_briopt_min) {
    // always leave at least bri_min characters on the left,
    // if text width is sufficient
    bri = (eff_wwidth - wp->w_briopt_min < 0)
          ? 0 : eff_wwidth - wp->w_briopt_min;
  }

  return bri;
}

// When extra == 0: Return true if the cursor is before or on the first
// non-blank in the line.
// When extra == 1: Return true if the cursor is before the first non-blank in
// the line.
bool inindent(int extra)
{
  char *ptr;
  colnr_T col;

  for (col = 0, ptr = get_cursor_line_ptr(); ascii_iswhite(*ptr); col++) {
    ptr++;
  }

  if (col >= curwin->w_cursor.col + extra) {
    return true;
  }
  return false;
}

/// @return  true if the conditions are OK for smart indenting.
bool may_do_si(void)
{
  return curbuf->b_p_si && !curbuf->b_p_cin && *curbuf->b_p_inde == NUL && !p_paste;
}

/// Give a "resulting text too long" error and maybe set got_int.
static void emsg_text_too_long(void)
{
  emsg(_(e_resulting_text_too_long));
  // when not inside a try/catch set got_int to break out of any loop
  if (trylevel == 0) {
    got_int = true;
  }
}

/// ":retab".
void ex_retab(exarg_T *eap)
{
  bool got_tab = false;
  int num_spaces = 0;
  int start_col = 0;                   // For start of white-space string
  int64_t start_vcol = 0;                  // For start of white-space string
  char *new_line = (char *)1;  // init to non-NULL
  colnr_T *new_vts_array = NULL;
  char *new_ts_str;  // string value of tab argument

  linenr_T first_line = 0;              // first changed line
  linenr_T last_line = 0;               // last changed line

  int save_list = curwin->w_p_list;
  curwin->w_p_list = 0;             // don't want list mode here

  new_ts_str = eap->arg;
  if (!tabstop_set(eap->arg, &new_vts_array)) {
    return;
  }
  while (ascii_isdigit(*(eap->arg)) || *(eap->arg) == ',') {
    eap->arg++;
  }

  // This ensures that either new_vts_array and new_ts_str are freshly
  // allocated, or new_vts_array points to an existing array and new_ts_str
  // is null.
  if (new_vts_array == NULL) {
    new_vts_array = curbuf->b_p_vts_array;
    new_ts_str = NULL;
  } else {
    new_ts_str = xmemdupz(new_ts_str, (size_t)(eap->arg - new_ts_str));
  }
  for (linenr_T lnum = eap->line1; !got_int && lnum <= eap->line2; lnum++) {
    char *ptr = ml_get(lnum);
    int col = 0;
    int64_t vcol = 0;
    bool did_undo = false;  // called u_save for current line
    while (true) {
      if (ascii_iswhite(ptr[col])) {
        if (!got_tab && num_spaces == 0) {
          // First consecutive white-space
          start_vcol = vcol;
          start_col = col;
        }
        if (ptr[col] == ' ') {
          num_spaces++;
        } else {
          got_tab = true;
        }
      } else {
        if (got_tab || (eap->forceit && num_spaces > 1)) {
          // Retabulate this string of white-space

          // len is virtual length of white string
          int len = num_spaces = (int)(vcol - start_vcol);
          int num_tabs = 0;
          if (!curbuf->b_p_et) {
            int t, s;

            tabstop_fromto((colnr_T)start_vcol, (colnr_T)vcol,
                           (int)curbuf->b_p_ts, new_vts_array, &t, &s);
            num_tabs = t;
            num_spaces = s;
          }
          if (curbuf->b_p_et || got_tab
              || (num_spaces + num_tabs < len)) {
            if (did_undo == false) {
              did_undo = true;
              if (u_save((linenr_T)(lnum - 1),
                         (linenr_T)(lnum + 1)) == FAIL) {
                new_line = NULL;  // flag out-of-memory
                break;
              }
            }

            // len is actual number of white characters used
            len = num_spaces + num_tabs;
            int old_len = (int)strlen(ptr);
            const int new_len = old_len - col + start_col + len + 1;
            if (new_len <= 0 || new_len >= MAXCOL) {
              emsg_text_too_long();
              break;
            }
            new_line = xmalloc((size_t)new_len);

            if (start_col > 0) {
              memmove(new_line, ptr, (size_t)start_col);
            }
            memmove(new_line + start_col + len,
                    ptr + col, (size_t)old_len - (size_t)col + 1);
            ptr = new_line + start_col;
            for (col = 0; col < len; col++) {
              ptr[col] = (col < num_tabs) ? '\t' : ' ';
            }
            if (ml_replace(lnum, new_line, false) == OK) {
              // "new_line" may have been copied
              new_line = curbuf->b_ml.ml_line_ptr;
              extmark_splice_cols(curbuf, lnum - 1, 0, (colnr_T)old_len,
                                  (colnr_T)new_len - 1, kExtmarkUndo);
            }
            if (first_line == 0) {
              first_line = lnum;
            }
            last_line = lnum;
            ptr = new_line;
            col = start_col + len;
          }
        }
        got_tab = false;
        num_spaces = 0;
      }
      if (ptr[col] == NUL) {
        break;
      }
      vcol += win_chartabsize(curwin, ptr + col, (colnr_T)vcol);
      if (vcol >= MAXCOL) {
        emsg_text_too_long();
        break;
      }
      col += utfc_ptr2len(ptr + col);
    }
    if (new_line == NULL) {                 // out of memory
      break;
    }
    line_breakcheck();
  }
  if (got_int) {
    emsg(_(e_interr));
  }

  // If a single value was given then it can be considered equal to
  // either the value of 'tabstop' or the value of 'vartabstop'.
  if (tabstop_count(curbuf->b_p_vts_array) == 0
      && tabstop_count(new_vts_array) == 1
      && curbuf->b_p_ts == tabstop_first(new_vts_array)) {
    // not changed
  } else if (tabstop_count(curbuf->b_p_vts_array) > 0
             && tabstop_eq(curbuf->b_p_vts_array, new_vts_array)) {
    // not changed
  } else {
    redraw_curbuf_later(UPD_NOT_VALID);
  }
  if (first_line != 0) {
    changed_lines(curbuf, first_line, 0, last_line + 1, 0, true);
  }

  curwin->w_p_list = save_list;         // restore 'list'

  if (new_ts_str != NULL) {  // set the new tabstop
    // If 'vartabstop' is in use or if the value given to retab has more
    // than one tabstop then update 'vartabstop'.
    colnr_T *old_vts_ary = curbuf->b_p_vts_array;

    if (tabstop_count(old_vts_ary) > 0 || tabstop_count(new_vts_array) > 1) {
      set_option_direct(kOptVartabstop, CSTR_AS_OPTVAL(new_ts_str), OPT_LOCAL, 0);
      curbuf->b_p_vts_array = new_vts_array;
      xfree(old_vts_ary);
    } else {
      // 'vartabstop' wasn't in use and a single value was given to
      // retab then update 'tabstop'.
      curbuf->b_p_ts = tabstop_first(new_vts_array);
      xfree(new_vts_array);
    }
    xfree(new_ts_str);
  }
  coladvance(curwin, curwin->w_curswant);

  u_clearline(curbuf);
}

/// Get indent level from 'indentexpr'.
int get_expr_indent(void)
{
  bool use_sandbox = was_set_insecurely(curwin, kOptIndentexpr, OPT_LOCAL);
  const sctx_T save_sctx = current_sctx;

  // Save and restore cursor position and curswant, in case it was changed
  // * via :normal commands.
  pos_T save_pos = curwin->w_cursor;
  colnr_T save_curswant = curwin->w_curswant;
  bool save_set_curswant = curwin->w_set_curswant;
  set_vim_var_nr(VV_LNUM, (varnumber_T)curwin->w_cursor.lnum);

  if (use_sandbox) {
    sandbox++;
  }
  textlock++;
  current_sctx = curbuf->b_p_script_ctx[kBufOptIndentexpr];

  // Need to make a copy, the 'indentexpr' option could be changed while
  // evaluating it.
  char *inde_copy = xstrdup(curbuf->b_p_inde);
  int indent = (int)eval_to_number(inde_copy, true);
  xfree(inde_copy);

  if (use_sandbox) {
    sandbox--;
  }
  textlock--;
  current_sctx = save_sctx;

  // Restore the cursor position so that 'indentexpr' doesn't need to.
  // Pretend to be in Insert mode, allow cursor past end of line for "o"
  // command.
  int save_State = State;
  State = MODE_INSERT;
  curwin->w_cursor = save_pos;
  curwin->w_curswant = save_curswant;
  curwin->w_set_curswant = save_set_curswant;
  check_cursor(curwin);
  State = save_State;

  // Reset did_throw, unless 'debug' has "throw" and inside a try/catch.
  if (did_throw && (vim_strchr(p_debug, 't') == NULL || trylevel == 0)) {
    handle_did_throw();
    did_throw = false;
  }

  // If there is an error, just keep the current indent.
  if (indent < 0) {
    indent = get_indent();
  }

  return indent;
}

// When 'p' is present in 'cpoptions, a Vi compatible method is used.
// The incompatible newer method is quite a bit better at indenting
// code in lisp-like languages than the traditional one; it's still
// mostly heuristics however -- Dirk van Deun, dirk@rave.org

// TODO(unknown):
// Findmatch() should be adapted for lisp, also to make showmatch
// work correctly: now (v5.3) it seems all C/C++ oriented:
// - it does not recognize the #\( and #\) notations as character literals
// - it doesn't know about comments starting with a semicolon
// - it incorrectly interprets '(' as a character literal
// All this messes up get_lisp_indent in some rare cases.
// Update from Sergey Khorev:
// I tried to fix the first two issues.
int get_lisp_indent(void)
{
  pos_T *pos;
  pos_T paren;
  int amount;

  pos_T realpos = curwin->w_cursor;
  curwin->w_cursor.col = 0;

  if ((pos = findmatch(NULL, '(')) == NULL) {
    pos = findmatch(NULL, '[');
  } else {
    paren = *pos;
    pos = findmatch(NULL, '[');

    if ((pos == NULL) || lt(*pos, paren)) {
      pos = &paren;
    }
  }

  if (pos != NULL) {
    // Extra trick: Take the indent of the first previous non-white
    // line that is at the same () level.
    amount = -1;
    int parencount = 0;

    while (--curwin->w_cursor.lnum >= pos->lnum) {
      if (linewhite(curwin->w_cursor.lnum)) {
        continue;
      }

      for (char *that = get_cursor_line_ptr(); *that != NUL; that++) {
        if (*that == ';') {
          while (*(that + 1) != NUL) {
            that++;
          }
          continue;
        }

        if (*that == '\\') {
          if (*(that + 1) != NUL) {
            that++;
          }
          continue;
        }

        if ((*that == '"') && (*(that + 1) != NUL)) {
          while (*++that && *that != '"') {
            // Skipping escaped characters in the string
            if (*that == '\\') {
              if (*++that == NUL) {
                break;
              }
              if (that[1] == NUL) {
                that++;
                break;
              }
            }
          }
          if (*that == NUL) {
            break;
          }
        }
        if ((*that == '(') || (*that == '[')) {
          parencount++;
        } else if ((*that == ')') || (*that == ']')) {
          parencount--;
        }
      }

      if (parencount == 0) {
        amount = get_indent();
        break;
      }
    }

    if (amount == -1) {
      curwin->w_cursor.lnum = pos->lnum;
      curwin->w_cursor.col = pos->col;
      colnr_T col = pos->col;

      char *line = get_cursor_line_ptr();

      CharsizeArg csarg;
      CSType cstype = init_charsize_arg(&csarg, curwin, pos->lnum, line);

      StrCharInfo sci = utf_ptr2StrCharInfo(line);
      amount = 0;
      while (*sci.ptr != NUL && col > 0) {
        amount += win_charsize(cstype, amount, sci.ptr, sci.chr.value, &csarg).width;
        sci = utfc_next(sci);
        col--;
      }
      char *that = sci.ptr;

      // Some keywords require "body" indenting rules (the
      // non-standard-lisp ones are Scheme special forms):
      // (let ((a 1))    instead    (let ((a 1))
      //   (...))       of       (...))
      if (((*that == '(') || (*that == '[')) && lisp_match(that + 1)) {
        amount += 2;
      } else {
        if (*that != NUL) {
          that++;
          amount++;
        }
        colnr_T firsttry = amount;

        while (ascii_iswhite(*that)) {
          amount += win_charsize(cstype, amount, that, (uint8_t)(*that), &csarg).width;
          that++;
        }

        if (*that && (*that != ';')) {
          // Not a comment line.
          // Test *that != '(' to accommodate first let/do
          // argument if it is more than one line.
          if ((*that != '(') && (*that != '[')) {
            firsttry++;
          }

          parencount = 0;

          CharInfo ci = utf_ptr2CharInfo(that);
          if (((ci.value != '"') && (ci.value != '\'') && (ci.value != '#')
               && ((ci.value < '0') || (ci.value > '9')))) {
            int quotecount = 0;
            while (*that && (!ascii_iswhite(ci.value) || quotecount || parencount)) {
              if (ci.value == '"') {
                quotecount = !quotecount;
              }
              if (((ci.value == '(') || (ci.value == '[')) && !quotecount) {
                parencount++;
              }
              if (((ci.value == ')') || (ci.value == ']')) && !quotecount) {
                parencount--;
              }
              if ((ci.value == '\\') && (*(that + 1) != NUL)) {
                amount += win_charsize(cstype, amount, that, ci.value, &csarg).width;
                StrCharInfo next_sci = utfc_next((StrCharInfo){ that, ci });
                that = next_sci.ptr;
                ci = next_sci.chr;
              }

              amount += win_charsize(cstype, amount, that, ci.value, &csarg).width;
              StrCharInfo next_sci = utfc_next((StrCharInfo){ that, ci });
              that = next_sci.ptr;
              ci = next_sci.chr;
            }
          }

          while (ascii_iswhite(*that)) {
            amount += win_charsize(cstype, amount, that, (uint8_t)(*that), &csarg).width;
            that++;
          }

          if (!*that || (*that == ';')) {
            amount = firsttry;
          }
        }
      }
    }
  } else {
    amount = 0;  // No matching '(' or '[' found, use zero indent.
  }
  curwin->w_cursor = realpos;

  return amount;
}

static int lisp_match(char *p)
{
  char buf[512];
  char *word = *curbuf->b_p_lw != NUL ? curbuf->b_p_lw : p_lispwords;

  while (*word != NUL) {
    copy_option_part(&word, buf, sizeof(buf), ",");
    int len = (int)strlen(buf);

    if ((strncmp(buf, p, (size_t)len) == 0) && ascii_iswhite_or_nul(p[len])) {
      return true;
    }
  }
  return false;
}

/// Re-indent the current line, based on the current contents of it and the
/// surrounding lines. Fixing the cursor position seems really easy -- I'm very
/// confused what all the part that handles Control-T is doing that I'm not.
/// "get_the_indent" should be get_c_indent, get_expr_indent or get_lisp_indent.
void fixthisline(IndentGetter get_the_indent)
{
  int amount = get_the_indent();

  if (amount < 0) {
    return;
  }

  change_indent(INDENT_SET, amount, false, true);
  if (linewhite(curwin->w_cursor.lnum)) {
    did_ai = true;  // delete the indent if the line stays empty
  }
}

/// Return true if 'indentexpr' should be used for Lisp indenting.
/// Caller may want to check 'autoindent'.
bool use_indentexpr_for_lisp(void)
{
  return curbuf->b_p_lisp
         && *curbuf->b_p_inde != NUL
         && strcmp(curbuf->b_p_lop, "expr:1") == 0;
}

/// Fix indent for 'lisp' and 'cindent'.
void fix_indent(void)
{
  if (p_paste) {
    return;  // no auto-indenting when 'paste' is set
  }
  if (curbuf->b_p_lisp && curbuf->b_p_ai) {
    if (use_indentexpr_for_lisp()) {
      do_c_expr_indent();
    } else {
      fixthisline(get_lisp_indent);
    }
  } else if (cindent_on()) {
    do_c_expr_indent();
  }
}
