########################################################################
##
## Copyright (C) 2007-2026 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
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## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <https://www.gnu.org/licenses/>.
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########################################################################

## -*- texinfo -*-
## @deftypefn {} {[@var{c}, @var{hg}] =} __contour__ (@dots{})
## Undocumented internal function.
## @end deftypefn

function [c, hg] = __contour__ (varargin)

  ax = varargin{1};
  zlevel = varargin{2};
  filled = "off";

  linespec.color = "auto";
  linespec.linestyle = "-";
  opts = {};
  i = 3;
  while (i <= length (varargin))
    if (ischar (varargin{i}) || iscellstr (varargin{i}))
      arg = varargin{i};
      if (i < length (varargin))
        if (strcmpi (arg, "fill"))
          filled = varargin{i+1};
          varargin(i:i+1) = [];
          continue;
        elseif (strcmpi (arg, "linecolor"))
          linespec.color = varargin{i+1};
          varargin(i:i+1) = [];
          continue;
        endif
      endif

      [lspec, valid] = __pltopt__ ("__contour__", arg, false);
      if (valid)
        varargin(i) = [];
        if (! isempty (lspec.color))
          linespec.color = lspec.color;
        endif
        if (! isempty (lspec.linestyle))
          linespec.linestyle = lspec.linestyle;
        endif
      else  # unrecognized option, pass unmodified in opts cell array
        if (i >= numel (varargin))
          error ("__contour__: Uneven number of PROP/VAL pairs");
        endif
        opts(end+(1:2)) = varargin(i:i+1);
        varargin(i:i+1) = [];
      endif

    else  # skip numeric arguments
      i += 1;
    endif
  endwhile

  if (length (varargin) < 5)
    z1 = varargin{3};
    x1 = 1 : columns (z1);
    y1 = 1 : rows (z1);
    if (! ismatrix (z1))
      error ("__contour__: Z must be a 2-D matrix");
    endif
  else
    x1 = varargin{3};
    y1 = varargin{4};
    z1 = varargin{5};
    if (! ismatrix (z1) || ! ismatrix (x1) || ! ismatrix (y1))
      error ("__contour__: X, Y, and Z must be matrices");
    endif
    if (isvector (x1))
      if (columns (z1) != length (x1))
        error ("__contour__: size of X must match number of columns in Z");
      endif
    else
      if (! size_equal (x1, z1))
        error ("__contour__: size of X and Z must match");
      endif
    endif
    if (isvector (y1))
      if (rows (z1) != length (y1))
        error ("__contour__: size of Y must match number of rows in Z");
      endif
    else
      if (! size_equal (y1, z1))
        error ("__contour__: size of Y and Z must match");
      endif
    endif
  endif

  if (length (varargin) == 4 || length (varargin) == 6)
    vn = varargin{end};
    vnauto = false;
  else
    vn = 10;
    vnauto = true;
  endif

  if (isscalar (vn))
    ## FIXME: The levels should be determined similarly to {x,y,z}ticks
    ##        so that they aren't set at extremely odd values.
    lvl = linspace (min (z1(! isinf (z1))), max (z1(! isinf (z1))), vn + 2);
    ## Strip off max outlier, min must stay for contourf hole algorithm.
    lvl = lvl(1:end-1);
  else
    lvl = sort (vn);
  endif

  if (strcmpi (filled, "on"))
    if (isvector (x1) || isvector (y1))
      [x1, y1] = meshgrid (x1, y1);
    endif
    [nr, nc] = size (z1);
    x0 = prepad (x1, nc+1, 2 * x1(1, 1) - x1(1, 2), 2);
    x0 = postpad (x0, nc+2, 2 * x1(1, nc) - x1(1, nc - 1), 2);
    x0 = [x0(1, :); x0; x0(1, :)];
    y0 = prepad (y1, nr+1, 2 * y1(1, 1) - y1(2, 1), 1);
    y0 = postpad (y0, nr+2, 2 * y1(nr, 1) - y1(nr - 1, 1));
    y0 = [y0(:, 1), y0, y0(:, 1)];
    z0 = -Inf (nr+2, nc+2);
    z0(2:nr+1, 2:nc+1) = z1;
    [c, lev] = contourc (x0, y0, z0, lvl);
  else
    [c, lev] = contourc (x1, y1, z1, lvl);
  endif

  hg = hggroup (ax, "__appdata__", struct ("__creator__", "__contour__"));
  opts = __add_datasource__ ("__countour__", hg, {"x", "y", "z"}, opts{:});

  addproperty ("xdata", hg, "data", x1);
  addproperty ("ydata", hg, "data", y1);
  addproperty ("zdata", hg, "data", z1);
  addproperty ("contourmatrix", hg, "data", c);

  addlistener (hg, "xdata", @update_data);
  addlistener (hg, "ydata", @update_data);
  addlistener (hg, "zdata", @update_data);
  addlistener (hg, "contourmatrix", @update_data);

  addproperty ("fill", hg, "radio", "on|{off}", filled);

  ## The properties zlevel and zlevelmode don't exist in matlab, but allow the
  ## use of contourgroups with the contour3, meshc, and surfc functions.
  if (isnumeric (zlevel))
    addproperty ("zlevelmode", hg, "radio", "{none}|auto|manual", "manual");
    addproperty ("zlevel", hg, "data", zlevel);
  else
    addproperty ("zlevelmode", hg, "radio", "{none}|auto|manual", zlevel);
    addproperty ("zlevel", hg, "data", 0.);
  endif

  lvlstep = sum (diff (lvl)) / (length (lvl) - 1);

  addproperty ("levellist", hg, "data", lev);
  addproperty ("levelstep", hg, "double", lvlstep);
  if (vnauto)
    addproperty ("levellistmode", hg, "radio", "{auto}|manual", "auto");
    addproperty ("levelstepmode", hg, "radio", "{auto}|manual", "auto");
  elseif (isscalar (vn))
    addproperty ("levellistmode", hg, "radio", "{auto}|manual", "auto");
    addproperty ("levelstepmode", hg, "radio", "{auto}|manual", "manual");
  else
    addproperty ("levellistmode", hg, "radio", "{auto}|manual", "manual");
    addproperty ("levelstepmode", hg, "radio", "{auto}|manual", "auto");
  endif

  addproperty ("labelspacing", hg, "double", 144);
  addproperty ("textlist", hg, "data", lev);
  addproperty ("textlistmode", hg, "radio", "{auto}|manual", "auto");
  addproperty ("textstep", hg, "double", lvlstep);
  addproperty ("textstepmode", hg, "radio", "{auto}|manual", "auto");
  addproperty ("showtext", hg, "radio", "on|{off}", "off");

  addproperty ("linecolor", hg, "color", linespec.color, "{auto}|none");
  addproperty ("linestyle", hg, "linelinestyle", linespec.linestyle);
  addproperty ("linewidth", hg, "linelinewidth", 0.5);

  ## Matlab property just for compatibility (bug #60513).
  addproperty ("facecolor", hg, "patchfacecolor", "none");

  ## Matlab property, although Octave does not implement it.
  addproperty ("hittestarea", hg, "radio", "on|{off}", "off");

  addlistener (hg, "fill", {@update_data, "fill"});

  addlistener (hg, "zlevelmode", @update_zlevel);
  addlistener (hg, "zlevel", @update_zlevel);

  addlistener (hg, "levellist", {@update_data, "levellist"});
  addlistener (hg, "levelstep", {@update_data, "levelstep"});
  addlistener (hg, "levellistmode", @update_data);
  addlistener (hg, "levelstepmode", @update_data);

  addlistener (hg, "labelspacing", @update_text);
  addlistener (hg, "textlist", {@update_text, "textlist"});
  addlistener (hg, "textlistmode", @update_text);
  addlistener (hg, "textstep", {@update_text, "textstep"});
  addlistener (hg, "textstepmode", @update_text);
  addlistener (hg, "showtext", @update_text);

  addlistener (hg, "linecolor", @update_line);
  addlistener (hg, "linestyle", @update_line);
  addlistener (hg, "linewidth", @update_line);

  ## Set axis before adding patches so that each new patch does not trigger
  ## new axis calculation.  No need if mode is already "manual".
  if (all (strcmp (get (ax, {"xlimmode", "ylimmode"}), "auto")))
    axis (ax, [min(x1(:)) max(x1(:)) min(y1(:)) max(y1(:))]);
  endif

  add_patch_children (ax, hg);

  if (! isempty (opts))
    set (hg, opts{:});
  endif

endfunction

function add_patch_children (ca, hg)

  if (isempty (ca))
    ca = gca ();
  endif
  c = get (hg, "contourmatrix");
  lev = get (hg, "levellist");
  fill = get (hg, "fill");
  zlev = get (hg, "zlevel");
  zmode = get (hg, "zlevelmode");
  lc = get (hg, "linecolor");
  lw = get (hg, "linewidth");
  ls = get (hg, "linestyle");
  filled = get (hg, "fill");

  ## Turn off automatic updating of clim while adding patches
  climmode = get (ca, "climmode");
  set (ca, "climmode", "manual");

  if (strcmp (lc, "auto"))
    lc = "flat";
  endif

  if (strcmp (filled, "on"))

    lvl_eps = get_lvl_eps (lev);

    ## Decode contourc output format.
    i = 1;
    ncont = 0;
    while (i < columns (c))
      ncont += 1;
      cont_lev(ncont) = c(1, i);
      cont_len(ncont) = c(2, i);
      cont_idx(ncont) = i+1;
      ii = i + (1:cont_len(ncont));
      cont_area(ncont) = polyarea (c(1, ii), c(2, ii));
      i += cont_len(ncont) + 1;
    endwhile

    ## Handle for each level the case where we have (a) hole(s) in a patch.
    ## Those are to be filled with the color of level below or with the
    ## background color.
    for k = 1:numel (lev)
      lvl_idx = find (abs (cont_lev - lev(k)) < lvl_eps);
      len = numel (lvl_idx);
      if (len > 1)
        mark = false (size (lvl_idx));
        a = 1;
        while (a < len)
          ## take 1st patch
          pa_idx = lvl_idx(a);
          ## get pointer to contour start, and contour length
          curr_ct_idx = cont_idx(pa_idx);
          curr_ct_len = cont_len(pa_idx);
          ## get contour
          curr_ct = c(:, curr_ct_idx:curr_ct_idx+curr_ct_len-1);
          b_vec = (a+1):len;
          next_ct_pt_vec = c(:, cont_idx(lvl_idx(b_vec)));
          in = inpolygon (next_ct_pt_vec(1,:), next_ct_pt_vec(2,:),
                          curr_ct(1, :), curr_ct(2, :));
          mark(b_vec(in)) = ! mark(b_vec(in));
          a += 1;
        endwhile
        if (numel (mark) > 0)
          ## All marked contours describe a hole in a larger contour of
          ## the same level and must be filled with color of level below.
          ma_idx = lvl_idx(mark);
          if (k > 1)
            ## Find color of level below.
            tmp = find (abs (cont_lev - lev(k - 1)) < lvl_eps);
            lvl_bel_idx = tmp(1);
            ## Set color of patches found.
            cont_lev(ma_idx) = cont_lev(lvl_bel_idx);
          else
            ## Set lowest level contour to NaN.
            cont_lev(ma_idx) = NaN;
          endif
        endif
      endif
    endfor

    ## The algorithm can create patches with the size of the plotting
    ## area, we would like to draw only the patch with the highest level.
    del_idx = [];
    max_idx = find (cont_area == max (cont_area));
    if (numel (max_idx) > 1)
      ## delete double entries
      del_idx = max_idx(1:end-1);
      cont_area(del_idx) = cont_lev(del_idx) = [];
      cont_len(del_idx) = cont_idx(del_idx) = [];
    endif

    ## Now we have everything together and can start plotting the patches
    ## beginning with largest area.
    [~, svec] = sort (cont_area);
    len = ncont - numel (del_idx);
    h = [];
    for n = len:-1:1
      idx = svec(n);
      ctmp = c(:, cont_idx(idx):cont_idx(idx) + cont_len(idx) - 1);
      if (all (ctmp(:,1) == ctmp(:,end)))
        ## patch() doesn't need/want closed contour.  It will do it itself.
        ctmp(:,end) = [];
      endif
      if (isnan (cont_lev(idx)))
        fc = get (ca, "color");
        if (strcmp (fc, "none"))
          fc = get (ancestor (ca, "figure"), "color");
        endif
      else
        fc = "flat";
      endif
      h = [h; __go_patch__(ca, "xdata", ctmp(1, :)(:), "ydata", ctmp(2, :)(:),
                           "vertices", ctmp.', "faces", 1:(cont_len(idx)-1),
                           "facevertexcdata", cont_lev(idx), "facecolor", fc,
                           "cdata", cont_lev(idx), "edgecolor", lc,
                           "linestyle", ls, "linewidth", lw,
                           "parent", hg)];
    endfor

    if (min (lev) == max (lev))
      set (ca, "clim", [min(lev)-1, max(lev)+1], "layer", "top");
    else
      set (ca, "clim", [min(lev), max(lev)], "layer", "top");
    endif
  else
    ## Decode contourc output format.
    h = [];
    i = 1;
    while (i < length (c))
      clev = c(1,i);
      clen = c(2,i);

      if (all (c(:,i+1) == c(:,i+clen)))
        p = c(:, i+1:i+clen-1).';
      else
        p = [c(:, i+1:i+clen), NaN(2, 1)].';
      endif

      switch (zmode)
        case "none"
          h = [h; __go_patch__(ca, "xdata", p(:,1), "ydata", p(:,2),
                               "zdata", [],
                               "vertices", p, "faces", 1:rows (p),
                               "facevertexcdata", clev, "facecolor", "none",
                               "cdata", clev, "edgecolor", lc,
                               "linestyle", ls, "linewidth", lw,
                               "parent", hg)];
        case "auto"
          h = [h; __go_patch__(ca, "xdata", p(:,1), "ydata", p(:,2),
                               "zdata", clev * ones (rows (p),1),
                               "vertices", [p, clev * ones(rows(p),1)],
                               "faces", 1:rows (p),
                               "facevertexcdata", clev, "facecolor", "none",
                               "cdata", clev, "edgecolor", lc,
                               "linestyle", ls, "linewidth", lw,
                               "parent", hg)];
        otherwise
          h = [h; __go_patch__(ca, "xdata", p(:,1), "ydata", p(:,2),
                               "zdata", zlev * ones (rows (p), 1),
                               "vertices", [p, zlev * ones(rows(p),1)],
                               "faces", 1:rows (p),
                               "facevertexcdata", clev, "facecolor", "none",
                               "cdata", clev, "edgecolor", lc,
                               "linestyle", ls, "linewidth", lw,
                               "parent", hg)];
      endswitch
      i += clen + 1;
    endwhile
  endif

  set (ca, "climmode", climmode);

endfunction

function update_zlevel (h, ~)

  z = get (h, "zlevel");
  zmode = get (h, "zlevelmode");
  kids = get (h, "children");

  switch (zmode)
    case "none"
      set (kids, "zdata", []);
    case "auto"
      for i = 1 : length (kids)
        set (kids(i), "zdata", get (kids(i), "cdata") .*
             ones (size (get (kids(i), "xdata"))));
      endfor
    otherwise
      for i = 1 : length (kids)
        set (kids(i), "zdata", z .* ones (size (get (kids(i), "xdata"))));
      endfor
  endswitch

endfunction

function update_line (h, ~)

  lc = get (h, "linecolor");
  if (strcmp (lc, "auto"))
    lc = "flat";
  endif
  set (findobj (h, "type", "patch"), "edgecolor", lc,
       "linewidth", get (h, "linewidth"), "linestyle", get (h, "linestyle"));

endfunction

function update_data (h, ~, prop = "")
  persistent recursive = false;

  if (! recursive)
    recursive = true;

    delete (get (h, "children"));

    switch (prop)
      case "levellist"
        set (h, "levellistmode", "manual");
      case "levelstep"
        set (h, "levelstepmode", "manual");
      case "fill"
        ## Switching from filled ('k' linespec) to unfilled, reset linecolor
        if (strcmp (get (h, "fill"), "off"))
          set (h, "linecolor", "auto");
        else
          set (h, "linecolor", "black");
        endif
    endswitch

    if (strcmp (get (h, "levellistmode"), "manual")
        && ! strcmp (prop, "levelstep"))
      lvl = get (h, "levellist");
    elseif (strcmp (get (h, "levelstepmode"), "manual"))
      z = get (h, "zdata");
      lvs = get (h, "levelstep");
      lvl(1) = ceil (min (z(:)) / lvs) * lvs;
      lvl(2) = floor (max (z(:)) / lvs) * lvs;
      if (lvl(1) >= lvl(2))
        lvl = median (z(:));
      else
        lvl = lvl(1) : lvs : lvl(2);
      endif
      set (h, "levellist", lvl, "levellistmode", "auto");
    else
      z = get (h, "zdata");
      ## FIXME: The levels should be determined similarly to {x,y,z}ticks
      ##        so that they aren't set at extremely odd values.
      lvl = linspace (min (z(! isinf (z))), max (z(! isinf (z))), 10 + 2);
      ## Strip off max outlier, min must stay for contourf hole algorithm.
      lvl = lvl(1:end-1);
    endif

    if (strcmp (get (h, "fill"), "on"))
      X = get (h, "xdata");
      Y = get (h, "ydata");
      Z = get (h, "zdata");
      if (isvector (X) || isvector (Y))
        [X, Y] = meshgrid (X, Y);
      endif
      [nr, nc] = size (Z);
      X0 = prepad (X, nc+1, 2 * X(1, 1) - X(1, 2), 2);
      X0 = postpad (X0, nc+2, 2 * X(1, nc) - X(1, nc - 1), 2);
      X0 = [X0(1, :); X0; X0(1, :)];
      Y0 = prepad (Y, nr+1, 2 * Y(1, 1) - Y(2, 1), 1);
      Y0 = postpad (Y0, nr+2, 2 * Y(nr, 1) - Y(nr - 1, 1));
      Y0 = [Y0(:, 1), Y0, Y0(:, 1)];
      Z0 = -Inf (nr+2, nc+2);
      Z0(2:nr+1, 2:nc+1) = Z;
      [c, lev] = contourc (X0, Y0, Z0, lvl);
    else
      [c, lev] = contourc (get (h, "xdata"), get (h, "ydata"),
                           get (h, "zdata"), lvl);
    endif
    set (h, "contourmatrix", c);

    if (strcmp (get (h, "levellistmode"), "manual"))
      ## Do nothing
    elseif (strcmp (get (h, "levelstepmode"), "manual"))
      set (h, "levellist", lev);
    else
      set (h, "levellist", lev);
      lvlstep = sum (diff (lvl)) / (length (lvl) - 1);
      set (h, "levelstep", lvlstep);
    endif

    add_patch_children ([], h);
    update_text (h);
    recursive = false;
  endif

endfunction

function update_text (h, ~, prop = "")
  persistent recursive = false;

  if (! recursive)
    recursive = true;

    delete (findobj (h, "type", "text"));

    switch (prop)
      case "textlist"
        set (h, "textlistmode", "manual");
      case "textstep"
        set (h, "textstepmode", "manual");
    endswitch

    if (strcmp (get (h, "textlistmode"), "manual"))
      lvl = get (h, "textlist");
    elseif (strcmp (get (h, "textstepmode"), "manual"))
      lev = get (h, "levellist");

      lvl_eps = get_lvl_eps (lev);

      stp = get (h, "textstep");
      t = [0, floor(cumsum(diff (lev)) / (abs(stp) - lvl_eps))];
      lvl = lev([true, t(1:end-1) != t(2:end)]);
      set (h, "textlist", lvl);
    else
      lvl = get (h, "levellist");
      set (h, "textlist", lvl, "textstep", get (h, "levelstep"));
    endif

    if (strcmp (get (h, "showtext"), "on"))
      switch (get (h, "zlevelmode"))
        case "manual"
          __clabel__ (get (h, "contourmatrix"), lvl, h,
                      get (h, "labelspacing"), get (h, "zlevel"));
        case "auto"
          __clabel__ (get (h, "contourmatrix"), lvl, h,
                      get (h, "labelspacing"), "auto");
        otherwise
          __clabel__ (get (h, "contourmatrix"), lvl, h,
                      get (h, "labelspacing"), []);
      endswitch
    endif

    recursive = false;
  endif

endfunction

function lvl_eps = get_lvl_eps (lev)

  ## FIXME: is this the right thing to do for this tolerance?  Should
  ## it be an absolute or relative tolerance, or switch from one to the
  ## other depending on the value of lev?
  if (isscalar (lev))
    lvl_eps = abs (lev) * sqrt (eps) + sqrt (eps);
  else
    tmp = min (abs (diff (lev)));
    if (tmp < 10*eps)
      lvl_eps = sqrt (eps);
    else
      lvl_eps = tmp / 1000.0;
    endif
  endif

endfunction
