/* $OpenBSD$ */

/*

 * Copyright (c) 2026 Nicholas Marriott <nicholas.marriott@gmail.com>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER

 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING

 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include <sys/types.h>

#include <string.h>

#include "tmux.h"

enum tty_draw_line_state {

  TTY_DRAW_LINE_FIRST,

  TTY_DRAW_LINE_FLUSH,

  TTY_DRAW_LINE_NEW1,

  TTY_DRAW_LINE_NEW2,

  TTY_DRAW_LINE_EMPTY,

  TTY_DRAW_LINE_SAME,

  TTY_DRAW_LINE_DONE

};

static const char* tty_draw_line_states[] = {

  "FIRST",

  "FLUSH",

  "NEW1",

  "NEW2",

  "EMPTY",

  "SAME",

  "DONE"

};

/* Clear part of the line. */

static void

tty_draw_line_clear(struct tty *tty, u_int px, u_int py, u_int nx,

    const struct grid_cell *defaults, u_int bg, int wrapped)

{

  /* Nothing to clear. */

  if (nx == 0)

    return;

  /* If genuine BCE is available, can try escape sequences. */

  if (tty->client->overlay_check == NULL &&

      !wrapped &&

      nx >= 10 &&

      !tty_fake_bce(tty, defaults, bg)) {

    /* Off the end of the line, use EL if available. */

    if (px + nx >= tty->sx && tty_term_has(tty->term, TTYC_EL)) {

      tty_cursor(tty, px, py);

      tty_putcode(tty, TTYC_EL);

      return;

    }

    /* At the start of the line. Use EL1. */

    if (px == 0 && tty_term_has(tty->term, TTYC_EL1)) {

      tty_cursor(tty, px + nx - 1, py);

      tty_putcode(tty, TTYC_EL1);

      return;

    }

    /* Section of line. Use ECH if possible. */

    if (tty_term_has(tty->term, TTYC_ECH)) {

      tty_cursor(tty, px, py);

      tty_putcode_i(tty, TTYC_ECH, nx);

      return;

    }

  }

        /* Couldn't use an escape sequence, use spaces. */

  if (px != 0 || !wrapped)

    tty_cursor(tty, px, py);

  if (nx == 1)

    tty_putc(tty, ' ');

  else if (nx == 2)

    tty_putn(tty, "  ", 2, 2);

  else

    tty_repeat_space(tty, nx);

}

/* Draw a line from screen to tty. */

void

tty_draw_line(struct tty *tty, struct screen *s, u_int px, u_int py, u_int nx,

    u_int atx, u_int aty, const struct grid_cell *defaults,

    struct colour_palette *palette)

{

  struct grid   *gd = s->grid;

  const struct grid_cell  *gcp;

  struct grid_cell   gc, ngc, last;

  struct grid_line  *gl;

  u_int      i, j, last_i, cx, ex, width;

  u_int      cellsize, bg;

  int      flags, empty, wrapped = 0;

  char       buf[1000];

  size_t       len;

  enum tty_draw_line_state current_state, next_state;

  /*

   * py is the line in the screen to draw. px is the start x and nx is

   * the width to draw. atx,aty is the line on the terminal to draw it.

   */

  log_debug("%s: px=%u py=%u nx=%u atx=%u aty=%u", __func__, px, py, nx,

      atx, aty);

  /* There is no point in drawing more than the end of the terminal. */

  if (atx >= tty->sx)

    return;

  if (atx + nx >= tty->sx)

    nx = tty->sx - atx;

  if (nx == 0)

    return;

  /*

   * Clamp the width to cellsize - note this is not cellused, because

   * there may be empty background cells after it (from BCE).

   */

  cellsize = grid_get_line(gd, gd->hsize + py)->cellsize;

  if (screen_size_x(s) > cellsize)

    ex = cellsize;

  else

    ex = screen_size_x(s);

  log_debug("%s: drawing %u-%u,%u (end %u) at %u,%u; defaults: fg=%d, "

      "bg=%d", __func__, px, px + nx, py, ex, atx, aty, defaults->fg,

      defaults->bg);

  /* Turn off cursor while redrawing and reset region and margins. */

  flags = (tty->flags & TTY_NOCURSOR);

  tty->flags |= TTY_NOCURSOR;

  tty_update_mode(tty, tty->mode, s);

  tty_region_off(tty);

  tty_margin_off(tty);

  /* Start with the default cell as the last cell. */

  memcpy(&last, &grid_default_cell, sizeof last);

  last.bg = defaults->bg;

  tty_default_attributes(tty, defaults, palette, 8, s->hyperlinks);

  /*

   * If there is padding at the start, we must have truncated a wide

   * character. Clear it.

   */

  cx = 0;

  for (i = px; i < px + nx; i++) {

    grid_view_get_cell(gd, i, py, &gc);

    if (~gc.flags & GRID_FLAG_PADDING)

      break;

    cx++;

  }

  if (cx != 0) {

    /* Find the previous cell for the background colour. */

    for (i = px + 1; i > 0; i--) {

      grid_view_get_cell(gd, i - 1, py, &gc);

      if (~gc.flags & GRID_FLAG_PADDING)

        break;

    }

    if (i == 0)

      bg = defaults->bg;

    else {

      bg = gc.bg;

      if (gc.flags & GRID_FLAG_SELECTED) {

        memcpy(&ngc, &gc, sizeof ngc);

        if (screen_select_cell(s, &ngc, &gc))

          bg = ngc.bg;

      }

    }

    tty_attributes(tty, &last, defaults, palette, s->hyperlinks);

    log_debug("%s: clearing %u padding cells", __func__, cx);

    tty_draw_line_clear(tty, atx, aty, cx, defaults, bg, 0);

    if (cx == ex)

      goto out;

    atx += cx;

    px += cx;

    nx -= cx;

  }

  /* Did the previous line wrap on to this one? */

  if (py != 0 && atx == 0 && tty->cx >= tty->sx && nx == tty->sx) {

    gl = grid_get_line(gd, gd->hsize + py - 1);

    if (gl->flags & GRID_LINE_WRAPPED)

      wrapped = 1;

  }

  /* Loop over each character in the range. */

  last_i = i = 0;

  len = 0;

  width = 0;

  current_state = TTY_DRAW_LINE_FIRST;

  for (;;) {

    /* Work out the next state. */

    if (i == nx) {

      /*

       * If this is the last cell, we are done. But we need to

       * go through the loop again to flush anything in

       * the buffer.

       */

      empty = 0;

      next_state = TTY_DRAW_LINE_DONE;

      gcp = &grid_default_cell;

    } else {

      if (i > nx)

        fatalx("position %u > width %u", i, nx);

      /* Get the current cell. */

      grid_view_get_cell(gd, px + i, py, &gc);

      /* Update for codeset if needed. */

      gcp = tty_check_codeset(tty, &gc);

      /* And for selection. */

      if (gcp->flags & GRID_FLAG_SELECTED) {

        memcpy(&ngc, gcp, sizeof ngc);

        if (screen_select_cell(s, &ngc, gcp))

          gcp = &ngc;

      }

      /* Work out the the empty width. */

      empty = 0;

      if (px >= ex || i >= ex - px) {

        /* Outside the area being drawn. */

        empty = 1;

      } else if (gcp->data.width > nx - i) {

        /* Wide character that has been truncated. */

        empty = nx - i;

      } else if (gcp->flags & GRID_FLAG_PADDING) {

        /* Orphan padding cell. */

        empty = 1;

      } else if (gcp->bg == last.bg && gcp->attr == 0 &&

          gcp->link == 0) {

        /*

         * No attributes - empty if cleared, tab or

         * space.

         */

        if (gcp->flags & GRID_FLAG_CLEARED)

          empty = 1;

        else if (gcp->flags & GRID_FLAG_TAB)

          empty = gcp->data.width;

        else if (gcp->data.size == 1 &&

            *gcp->data.data == ' ')

          empty = 1;

      }

      /* Work out the next state. */

      if (empty != 0)

        next_state = TTY_DRAW_LINE_EMPTY;

      else if (current_state == TTY_DRAW_LINE_FIRST)

        next_state = TTY_DRAW_LINE_SAME;

      else if (grid_cells_look_equal(gcp, &last)) {

        if (gcp->data.size > (sizeof buf) - len)

          next_state = TTY_DRAW_LINE_FLUSH;

        else

          next_state = TTY_DRAW_LINE_SAME;

      } else if (current_state == TTY_DRAW_LINE_NEW1)

        next_state = TTY_DRAW_LINE_NEW2;

      else

        next_state = TTY_DRAW_LINE_NEW1;

    }

    if (log_get_level() != 0) {

      log_debug("%s: cell %u empty %u, bg %u; state: "

          "current %s, next %s", __func__, px + i, empty,

          gcp->bg, tty_draw_line_states[current_state],

          tty_draw_line_states[next_state]);

    }

    /* If the state has changed, flush any collected data. */

    if (next_state != current_state) {

      if (current_state == TTY_DRAW_LINE_EMPTY) {

        tty_attributes(tty, &last, defaults, palette,

            s->hyperlinks);

        tty_draw_line_clear(tty, atx + last_i, aty,

            i - last_i, defaults, last.bg, wrapped);

        wrapped = 0;

      } else if (next_state != TTY_DRAW_LINE_SAME &&

          len != 0) {

        tty_attributes(tty, &last, defaults, palette,

            s->hyperlinks);

        if (atx + i - width != 0 || !wrapped)

          tty_cursor(tty, atx + i - width, aty);

        if (~last.attr & GRID_ATTR_CHARSET)

          tty_putn(tty, buf, len, width);

        else {

          for (j = 0; j < len; j++)

            tty_putc(tty, buf[j]);

        }

        len = 0;

        width = 0;

        wrapped = 0;

      }

      last_i = i;

    }

    /* Append the cell if it is not empty and not padding. */

    if (next_state != TTY_DRAW_LINE_EMPTY) {

      memcpy(buf + len, gcp->data.data, gcp->data.size);

      len += gcp->data.size;

      width += gcp->data.width;

    }

    /* If this is the last cell, we are done. */

    if (next_state == TTY_DRAW_LINE_DONE)

      break;

    /* Otherwise move to the next. */

    current_state = next_state;

    memcpy(&last, gcp, sizeof last);

    if (empty != 0)

      i += empty;

    else

      i += gcp->data.width;

  }

out:

  tty->flags = (tty->flags & ~TTY_NOCURSOR)|flags;

  tty_update_mode(tty, tty->mode, s);

}