/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2019 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/**
 * Marlin Firmware -- G26 - Mesh Validation Tool
 */

#include "../../inc/MarlinConfig.h"

#if ENABLED(G26_MESH_VALIDATION)

#define G26_OK false
#define G26_ERR true

#include "../../gcode/gcode.h"
#include "../../feature/bedlevel/bedlevel.h"

#include "../../Marlin.h"
#include "../../module/planner.h"
#include "../../module/stepper.h"
#include "../../module/motion.h"
#include "../../module/tool_change.h"
#include "../../module/temperature.h"
#include "../../lcd/ultralcd.h"

#define EXTRUSION_MULTIPLIER 1.0
#define RETRACTION_MULTIPLIER 1.0
#define PRIME_LENGTH 10.0
#define OOZE_AMOUNT 0.3

#define INTERSECTION_CIRCLE_RADIUS 5
#define CROSSHAIRS_SIZE 3

#ifndef G26_XY_FEEDRATE
  #define G26_XY_FEEDRATE (PLANNER_XY_FEEDRATE() / 3.0)
#endif

#if CROSSHAIRS_SIZE >= INTERSECTION_CIRCLE_RADIUS
  #error "CROSSHAIRS_SIZE must be less than INTERSECTION_CIRCLE_RADIUS."
#endif

#define G26_OK false
#define G26_ERR true

#if ENABLED(ARC_SUPPORT)
  void plan_arc(const float (&cart)[XYZE], const float (&offset)[2], const uint8_t clockwise);
#endif

/**
 *   G26 Mesh Validation Tool
 *
 *   G26 is a Mesh Validation Tool intended to provide support for the Marlin Unified Bed Leveling System.
 *   In order to fully utilize and benefit from the Marlin Unified Bed Leveling System an accurate Mesh must
 *   be defined. G29 is designed to allow the user to quickly validate the correctness of her Mesh. It will
 *   first heat the bed and nozzle. It will then print lines and circles along the Mesh Cell boundaries and
 *   the intersections of those lines (respectively).
 *
 *   This action allows the user to immediately see where the Mesh is properly defined and where it needs to
 *   be edited. The command will generate the Mesh lines closest to the nozzle's starting position. Alternatively
 *   the user can specify the X and Y position of interest with command parameters. This allows the user to
 *   focus on a particular area of the Mesh where attention is needed.
 *
 *   B #  Bed         Set the Bed Temperature. If not specified, a default of 60 C. will be assumed.
 *
 *   C    Current     When searching for Mesh Intersection points to draw, use the current nozzle location
 *                    as the base for any distance comparison.
 *
 *   D    Disable     Disable the Unified Bed Leveling System. In the normal case the user is invoking this
 *                    command to see how well a Mesh as been adjusted to match a print surface. In order to do
 *                    this the Unified Bed Leveling System is turned on by the G26 command. The D parameter
 *                    alters the command's normal behavior and disables the Unified Bed Leveling System even if
 *                    it is on.
 *
 *   H #  Hotend      Set the Nozzle Temperature. If not specified, a default of 205 C. will be assumed.
 *
 *   F #  Filament    Used to specify the diameter of the filament being used. If not specified
 *                    1.75mm filament is assumed. If you are not getting acceptable results by using the
 *                    'correct' numbers, you can scale this number up or down a little bit to change the amount
 *                    of filament that is being extruded during the printing of the various lines on the bed.
 *
 *   K    Keep-On     Keep the heaters turned on at the end of the command.
 *
 *   L #  Layer       Layer height. (Height of nozzle above bed)  If not specified .20mm will be used.
 *
 *   O #  Ooooze      How much your nozzle will Ooooze filament while getting in position to print. This
 *                    is over kill, but using this parameter will let you get the very first 'circle' perfect
 *                    so you have a trophy to peel off of the bed and hang up to show how perfectly you have your
 *                    Mesh calibrated. If not specified, a filament length of .3mm is assumed.
 *
 *   P #  Prime       Prime the nozzle with specified length of filament. If this parameter is not
 *                    given, no prime action will take place. If the parameter specifies an amount, that much
 *                    will be purged before continuing. If no amount is specified the command will start
 *                    purging filament until the user provides an LCD Click and then it will continue with
 *                    printing the Mesh. You can carefully remove the spent filament with a needle nose
 *                    pliers while holding the LCD Click wheel in a depressed state. If you do not have
 *                    an LCD, you must specify a value if you use P.
 *
 *   Q #  Multiplier  Retraction Multiplier. Normally not needed. Retraction defaults to 1.0mm and
 *                    un-retraction is at 1.2mm   These numbers will be scaled by the specified amount
 *
 *   R #  Repeat      Prints the number of patterns given as a parameter, starting at the current location.
 *                    If a parameter isn't given, every point will be printed unless G26 is interrupted.
 *                    This works the same way that the UBL G29 P4 R parameter works.
 *
 *                    NOTE:  If you do not have an LCD, you -must- specify R. This is to ensure that you are
 *                    aware that there's some risk associated with printing without the ability to abort in
 *                    cases where mesh point Z value may be inaccurate. As above, if you do not include a
 *                    parameter, every point will be printed.
 *
 *   S #  Nozzle      Used to control the size of nozzle diameter. If not specified, a .4mm nozzle is assumed.
 *
 *   U #  Random      Randomize the order that the circles are drawn on the bed. The search for the closest
 *                    un-drawn circle is still done. But the distance to the location for each circle has a
 *                    random number of the specified size added to it. Specifying S50 will give an interesting
 *                    deviation from the normal behavior on a 10 x 10 Mesh.
 *
 *   X #  X Coord.    Specify the starting location of the drawing activity.
 *
 *   Y #  Y Coord.    Specify the starting location of the drawing activity.
 */

// External references

// Private functions

static uint16_t circle_flags[16], horizontal_mesh_line_flags[16], vertical_mesh_line_flags[16];
float g26_e_axis_feedrate = 0.025,
      random_deviation = 0.0;

static bool g26_retracted = false; // Track the retracted state of the nozzle so mismatched
                                   // retracts/recovers won't result in a bad state.

float g26_extrusion_multiplier,
      g26_retraction_multiplier,
      g26_layer_height,
      g26_prime_length;

float g26_x_pos = 0, g26_y_pos = 0;

int16_t g26_bed_temp,
        g26_hotend_temp;

int8_t g26_prime_flag;

#if HAS_LCD_MENU

  /**
   * If the LCD is clicked, cancel, wait for release, return true
   */
  bool user_canceled() {
    if (!ui.button_pressed()) return false; // Return if the button isn't pressed
    ui.set_status_P(PSTR("Mesh Validation Stopped."), 99);
    #if HAS_LCD_MENU
      ui.quick_feedback();
    #endif
    ui.wait_for_release();
    return true;
  }

#endif

mesh_index_pair find_closest_circle_to_print(const float &X, const float &Y) {
  float closest = 99999.99;
  mesh_index_pair return_val;

  return_val.x_index = return_val.y_index = -1;

  for (uint8_t i = 0; i < GRID_MAX_POINTS_X; i++) {
    for (uint8_t j = 0; j < GRID_MAX_POINTS_Y; j++) {
      if (!is_bitmap_set(circle_flags, i, j)) {
        const float mx = _GET_MESH_X(i),  // We found a circle that needs to be printed
                    my = _GET_MESH_Y(j);

        // Get the distance to this intersection
        float f = HYPOT(X - mx, Y - my);

        // It is possible that we are being called with the values
        // to let us find the closest circle to the start position.
        // But if this is not the case, add a small weighting to the
        // distance calculation to help it choose a better place to continue.
        f += HYPOT(g26_x_pos - mx, g26_y_pos - my) / 15.0;

        // Add in the specified amount of Random Noise to our search
        if (random_deviation > 1.0)
          f += random(0.0, random_deviation);

        if (f < closest) {
          closest = f;              // We found a closer location that is still
          return_val.x_index = i;   // un-printed  --- save the data for it
          return_val.y_index = j;
          return_val.distance = closest;
        }
      }
    }
  }
  bitmap_set(circle_flags, return_val.x_index, return_val.y_index);   // Mark this location as done.
  return return_val;
}

void G26_line_to_destination(const float &feed_rate) {
  const float save_feedrate = feedrate_mm_s;
  feedrate_mm_s = feed_rate;
  prepare_move_to_destination();  // will ultimately call ubl.line_to_destination_cartesian or ubl.prepare_linear_move_to for UBL_SEGMENTED
  feedrate_mm_s = save_feedrate;
}

void move_to(const float &rx, const float &ry, const float &z, const float &e_delta) {
  float feed_value;
  static float last_z = -999.99;

  bool has_xy_component = (rx != current_position[X_AXIS] || ry != current_position[Y_AXIS]); // Check if X or Y is involved in the movement.

  if (z != last_z) {
    last_z = z;
    feed_value = planner.settings.max_feedrate_mm_s[Z_AXIS]/(2.0);  // Base the feed rate off of the configured Z_AXIS feed rate

    destination[X_AXIS] = current_position[X_AXIS];
    destination[Y_AXIS] = current_position[Y_AXIS];
    destination[Z_AXIS] = z;                          // We know the last_z!=z or we wouldn't be in this block of code.
    destination[E_AXIS] = current_position[E_AXIS];

    G26_line_to_destination(feed_value);
    set_destination_from_current();
  }

  // Check if X or Y is involved in the movement.
  // Yes: a 'normal' movement. No: a retract() or recover()
  feed_value = has_xy_component ? G26_XY_FEEDRATE : planner.settings.max_feedrate_mm_s[E_AXIS] / 1.5;

  destination[X_AXIS] = rx;
  destination[Y_AXIS] = ry;
  destination[E_AXIS] += e_delta;

  G26_line_to_destination(feed_value);
  set_destination_from_current();
}

FORCE_INLINE void move_to(const float (&where)[XYZE], const float &de) { move_to(where[X_AXIS], where[Y_AXIS], where[Z_AXIS], de); }

void retract_filament(const float (&where)[XYZE]) {
  if (!g26_retracted) { // Only retract if we are not already retracted!
    g26_retracted = true;
    move_to(where, -1.0 * g26_retraction_multiplier);
  }
}

void recover_filament(const float (&where)[XYZE]) {
  if (g26_retracted) { // Only un-retract if we are retracted.
    move_to(where, 1.2 * g26_retraction_multiplier);
    g26_retracted = false;
  }
}

/**
 * print_line_from_here_to_there() takes two cartesian coordinates and draws a line from one
 * to the other. But there are really three sets of coordinates involved. The first coordinate
 * is the present location of the nozzle. We don't necessarily want to print from this location.
 * We first need to move the nozzle to the start of line segment where we want to print. Once
 * there, we can use the two coordinates supplied to draw the line.
 *
 * Note:  Although we assume the first set of coordinates is the start of the line and the second
 * set of coordinates is the end of the line, it does not always work out that way. This function
 * optimizes the movement to minimize the travel distance before it can start printing. This saves
 * a lot of time and eliminates a lot of nonsensical movement of the nozzle. However, it does
 * cause a lot of very little short retracement of th nozzle when it draws the very first line
 * segment of a 'circle'. The time this requires is very short and is easily saved by the other
 * cases where the optimization comes into play.
 */
void print_line_from_here_to_there(const float &sx, const float &sy, const float &sz, const float &ex, const float &ey, const float &ez) {
  const float dx_s = current_position[X_AXIS] - sx,   // find our distance from the start of the actual line segment
              dy_s = current_position[Y_AXIS] - sy,
              dist_start = HYPOT2(dx_s, dy_s),        // We don't need to do a sqrt(), we can compare the distance^2
                                                      // to save computation time
              dx_e = current_position[X_AXIS] - ex,   // find our distance from the end of the actual line segment
              dy_e = current_position[Y_AXIS] - ey,
              dist_end = HYPOT2(dx_e, dy_e),

              line_length = HYPOT(ex - sx, ey - sy);

  // If the end point of the line is closer to the nozzle, flip the direction,
  // moving from the end to the start. On very small lines the optimization isn't worth it.
  if (dist_end < dist_start && (INTERSECTION_CIRCLE_RADIUS) < ABS(line_length))
    return print_line_from_here_to_there(ex, ey, ez, sx, sy, sz);

  // Decide whether to retract & bump

  if (dist_start > 2.0) {
    retract_filament(destination);
    //todo:  parameterize the bump height with a define
    move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] + 0.500, 0.0);  // Z bump to minimize scraping
    move_to(sx, sy, sz + 0.500, 0.0); // Get to the starting point with no extrusion while bumped
  }

  move_to(sx, sy, sz, 0.0); // Get to the starting point with no extrusion / un-Z bump

  const float e_pos_delta = line_length * g26_e_axis_feedrate * g26_extrusion_multiplier;

  recover_filament(destination);
  move_to(ex, ey, ez, e_pos_delta);  // Get to the ending point with an appropriate amount of extrusion
}

inline bool look_for_lines_to_connect() {
  float sx, sy, ex, ey;

  for (uint8_t i = 0; i < GRID_MAX_POINTS_X; i++) {
    for (uint8_t j = 0; j < GRID_MAX_POINTS_Y; j++) {

      #if HAS_LCD_MENU
        if (user_canceled()) return true;
      #endif

      if (i < GRID_MAX_POINTS_X) { // Can't connect to anything to the right than GRID_MAX_POINTS_X.
                                   // Already a half circle at the edge of the bed.

        if (is_bitmap_set(circle_flags, i, j) && is_bitmap_set(circle_flags, i + 1, j)) { // check if we can do a line to the left
          if (!is_bitmap_set(horizontal_mesh_line_flags, i, j)) {
            // Two circles need a horizontal line to connect them
            sx = _GET_MESH_X(  i  ) + (INTERSECTION_CIRCLE_RADIUS - (CROSSHAIRS_SIZE)); // right edge
            ex = _GET_MESH_X(i + 1) - (INTERSECTION_CIRCLE_RADIUS - (CROSSHAIRS_SIZE)); // left edge

            sx = constrain(sx, X_MIN_POS + 1, X_MAX_POS - 1);
            sy = ey = constrain(_GET_MESH_Y(j), Y_MIN_POS + 1, Y_MAX_POS - 1);
            ex = constrain(ex, X_MIN_POS + 1, X_MAX_POS - 1);

            if (position_is_reachable(sx, sy) && position_is_reachable(ex, ey))
              print_line_from_here_to_there(sx, sy, g26_layer_height, ex, ey, g26_layer_height);

            bitmap_set(horizontal_mesh_line_flags, i, j); // Mark done, even if skipped
          }
        }

        if (j < GRID_MAX_POINTS_Y) {  // Can't connect to anything further back than GRID_MAX_POINTS_Y.
                                      // Already a half circle at the edge of the bed.

          if (is_bitmap_set(circle_flags, i, j) && is_bitmap_set(circle_flags, i, j + 1)) { // check if we can do a line straight down
            if (!is_bitmap_set( vertical_mesh_line_flags, i, j)) {
              // Two circles that need a vertical line to connect them
              sy = _GET_MESH_Y(  j  ) + (INTERSECTION_CIRCLE_RADIUS - (CROSSHAIRS_SIZE)); // top edge
              ey = _GET_MESH_Y(j + 1) - (INTERSECTION_CIRCLE_RADIUS - (CROSSHAIRS_SIZE)); // bottom edge

              sx = ex = constrain(_GET_MESH_X(i), X_MIN_POS + 1, X_MAX_POS - 1);
              sy = constrain(sy, Y_MIN_POS + 1, Y_MAX_POS - 1);
              ey = constrain(ey, Y_MIN_POS + 1, Y_MAX_POS - 1);

              if (position_is_reachable(sx, sy) && position_is_reachable(ex, ey))
                print_line_from_here_to_there(sx, sy, g26_layer_height, ex, ey, g26_layer_height);

              bitmap_set(vertical_mesh_line_flags, i, j); // Mark done, even if skipped
            }
          }
        }
      }
    }
  }
  return false;
}

/**
 * Turn on the bed and nozzle heat and
 * wait for them to get up to temperature.
 */
inline bool turn_on_heaters() {

  SERIAL_ECHOLNPGM("Waiting for heatup.");

  #if HAS_HEATED_BED

    if (g26_bed_temp > 25) {
      #if ENABLED(ULTRA_LCD)
        ui.set_status_P(PSTR("G26 Heating Bed."), 99);
        ui.quick_feedback();
        #if HAS_LCD_MENU
          ui.capture();
        #endif
      #endif
      thermalManager.setTargetBed(g26_bed_temp);

      // Wait for the temperature to stabilize
      if (!thermalManager.wait_for_bed(true
          #if G26_CLICK_CAN_CANCEL
            , true
          #endif
        )
      ) return G26_ERR;
    }

  #endif // HAS_HEATED_BED

  // Start heating the active nozzle
  #if ENABLED(ULTRA_LCD)
    ui.set_status_P(PSTR("G26 Heating Nozzle."), 99);
    ui.quick_feedback();
  #endif
  thermalManager.setTargetHotend(g26_hotend_temp, active_extruder);

  // Wait for the temperature to stabilize
  if (!thermalManager.wait_for_hotend(active_extruder, true
      #if G26_CLICK_CAN_CANCEL
        , true
      #endif
    )
  ) return G26_ERR;

  #if ENABLED(ULTRA_LCD)
    ui.reset_status();
    ui.quick_feedback();
  #endif

  return G26_OK;
}

/**
 * Prime the nozzle if needed. Return true on error.
 */
inline bool prime_nozzle() {

  #if HAS_LCD_MENU
    #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
      float Total_Prime = 0.0;
    #endif

    if (g26_prime_flag == -1) {  // The user wants to control how much filament gets purged

      ui.capture();
      ui.set_status_P(PSTR("User-Controlled Prime"), 99);
      ui.chirp();

      set_destination_from_current();

      recover_filament(destination); // Make sure G26 doesn't think the filament is retracted().

      while (!ui.button_pressed()) {
        ui.chirp();
        destination[E_AXIS] += 0.25;
        #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
          Total_Prime += 0.25;
          if (Total_Prime >= EXTRUDE_MAXLENGTH) return G26_ERR;
        #endif
        G26_line_to_destination(planner.settings.max_feedrate_mm_s[E_AXIS] / 15.0);
        set_destination_from_current();
        planner.synchronize();    // Without this synchronize, the purge is more consistent,
                                  // but because the planner has a buffer, we won't be able
                                  // to stop as quickly. So we put up with the less smooth
                                  // action to give the user a more responsive 'Stop'.
      }

      ui.wait_for_release();

      ui.set_status_P(PSTR("Done Priming"), 99);
      ui.quick_feedback();
      ui.release();
    }
    else
  #endif
  {
    #if ENABLED(ULTRA_LCD)
      ui.set_status_P(PSTR("Fixed Length Prime."), 99);
      ui.quick_feedback();
    #endif
    set_destination_from_current();
    destination[E_AXIS] += g26_prime_length;
    G26_line_to_destination(planner.settings.max_feedrate_mm_s[E_AXIS] / 15.0);
    set_destination_from_current();
    retract_filament(destination);
  }

  return G26_OK;
}

float valid_trig_angle(float d) {
  while (d > 360.0) d -= 360.0;
  while (d < 0.0) d += 360.0;
  return d;
}

/**
 * G26: Mesh Validation Pattern generation.
 *
 * Used to interactively edit the mesh by placing the
 * nozzle in a problem area and doing a G29 P4 R command.
 *
 * Parameters:
 *
 *  B  Bed Temperature
 *  C  Continue from the Closest mesh point
 *  D  Disable leveling before starting
 *  F  Filament diameter
 *  H  Hotend Temperature
 *  K  Keep heaters on when completed
 *  L  Layer Height
 *  O  Ooze extrusion length
 *  P  Prime length
 *  Q  Retraction multiplier
 *  R  Repetitions (number of grid points)
 *  S  Nozzle Size (diameter) in mm
 *  T  Tool index to change to, if included
 *  U  Random deviation (50 if no value given)
 *  X  X position
 *  Y  Y position
 */
void GcodeSuite::G26() {
  SERIAL_ECHOLNPGM("G26 starting...");

  // Don't allow Mesh Validation without homing first,
  // or if the parameter parsing did not go OK, abort
  if (axis_unhomed_error()) return;

  // Change the tool first, if specified
  if (parser.seenval('T')) tool_change(parser.value_int());

  g26_extrusion_multiplier    = EXTRUSION_MULTIPLIER;
  g26_retraction_multiplier   = RETRACTION_MULTIPLIER;
  g26_layer_height            = MESH_TEST_LAYER_HEIGHT;
  g26_prime_length            = PRIME_LENGTH;
  g26_bed_temp                = MESH_TEST_BED_TEMP;
  g26_hotend_temp             = MESH_TEST_HOTEND_TEMP;
  g26_prime_flag              = 0;

  float g26_nozzle            = MESH_TEST_NOZZLE_SIZE,
        g26_filament_diameter = DEFAULT_NOMINAL_FILAMENT_DIA,
        g26_ooze_amount       = parser.linearval('O', OOZE_AMOUNT);

  bool g26_continue_with_closest = parser.boolval('C'),
       g26_keep_heaters_on       = parser.boolval('K');

  #if HAS_HEATED_BED
    if (parser.seenval('B')) {
      g26_bed_temp = parser.value_celsius();
      if (g26_bed_temp && !WITHIN(g26_bed_temp, 40, (BED_MAXTEMP - 10))) {
        SERIAL_ECHOLNPAIR("?Specified bed temperature not plausible (40-", int(BED_MAXTEMP - 10), "C).");
        return;
      }
    }
  #endif

  if (parser.seenval('L')) {
    g26_layer_height = parser.value_linear_units();
    if (!WITHIN(g26_layer_height, 0.0, 2.0)) {
      SERIAL_ECHOLNPGM("?Specified layer height not plausible.");
      return;
    }
  }

  if (parser.seen('Q')) {
    if (parser.has_value()) {
      g26_retraction_multiplier = parser.value_float();
      if (!WITHIN(g26_retraction_multiplier, 0.05, 15.0)) {
        SERIAL_ECHOLNPGM("?Specified Retraction Multiplier not plausible.");
        return;
      }
    }
    else {
      SERIAL_ECHOLNPGM("?Retraction Multiplier must be specified.");
      return;
    }
  }

  if (parser.seenval('S')) {
    g26_nozzle = parser.value_float();
    if (!WITHIN(g26_nozzle, 0.1, 2.0)) {
      SERIAL_ECHOLNPGM("?Specified nozzle size not plausible.");
      return;
    }
  }

  if (parser.seen('P')) {
    if (!parser.has_value()) {
      #if HAS_LCD_MENU
        g26_prime_flag = -1;
      #else
        SERIAL_ECHOLNPGM("?Prime length must be specified when not using an LCD.");
        return;
      #endif
    }
    else {
      g26_prime_flag++;
      g26_prime_length = parser.value_linear_units();
      if (!WITHIN(g26_prime_length, 0.0, 25.0)) {
        SERIAL_ECHOLNPGM("?Specified prime length not plausible.");
        return;
      }
    }
  }

  if (parser.seenval('F')) {
    g26_filament_diameter = parser.value_linear_units();
    if (!WITHIN(g26_filament_diameter, 1.0, 4.0)) {
      SERIAL_ECHOLNPGM("?Specified filament size not plausible.");
      return;
    }
  }
  g26_extrusion_multiplier *= sq(1.75) / sq(g26_filament_diameter); // If we aren't using 1.75mm filament, we need to
                                                                    // scale up or down the length needed to get the
                                                                    // same volume of filament

  g26_extrusion_multiplier *= g26_filament_diameter * sq(g26_nozzle) / sq(0.3); // Scale up by nozzle size

  if (parser.seenval('H')) {
    g26_hotend_temp = parser.value_celsius();
    if (!WITHIN(g26_hotend_temp, 165, (HEATER_0_MAXTEMP - 15))) {
      SERIAL_ECHOLNPGM("?Specified nozzle temperature not plausible.");
      return;
    }
  }

  if (parser.seen('U')) {
    randomSeed(millis());
    // This setting will persist for the next G26
    random_deviation = parser.has_value() ? parser.value_float() : 50.0;
  }

  int16_t g26_repeats;
  #if HAS_LCD_MENU
    g26_repeats = parser.intval('R', GRID_MAX_POINTS + 1);
  #else
    if (!parser.seen('R')) {
      SERIAL_ECHOLNPGM("?(R)epeat must be specified when not using an LCD.");
      return;
    }
    else
      g26_repeats = parser.has_value() ? parser.value_int() : GRID_MAX_POINTS + 1;
  #endif
  if (g26_repeats < 1) {
    SERIAL_ECHOLNPGM("?(R)epeat value not plausible; must be at least 1.");
    return;
  }

  g26_x_pos = parser.seenval('X') ? RAW_X_POSITION(parser.value_linear_units()) : current_position[X_AXIS];
  g26_y_pos = parser.seenval('Y') ? RAW_Y_POSITION(parser.value_linear_units()) : current_position[Y_AXIS];
  if (!position_is_reachable(g26_x_pos, g26_y_pos)) {
    SERIAL_ECHOLNPGM("?Specified X,Y coordinate out of bounds.");
    return;
  }

  /**
   * Wait until all parameters are verified before altering the state!
   */
  set_bed_leveling_enabled(!parser.seen('D'));

  if (current_position[Z_AXIS] < Z_CLEARANCE_BETWEEN_PROBES) {
    do_blocking_move_to_z(Z_CLEARANCE_BETWEEN_PROBES);
    set_current_from_destination();
  }

  #if DISABLED(NO_VOLUMETRICS)
    bool volumetric_was_enabled = parser.volumetric_enabled;
    parser.volumetric_enabled = false;
    planner.calculate_volumetric_multipliers();
  #endif

  if (turn_on_heaters() != G26_OK) goto LEAVE;

  current_position[E_AXIS] = 0.0;
  sync_plan_position_e();

  if (g26_prime_flag && prime_nozzle() != G26_OK) goto LEAVE;

  /**
   *  Bed is preheated
   *
   *  Nozzle is at temperature
   *
   *  Filament is primed!
   *
   *  It's  "Show Time" !!!
   */

  ZERO(circle_flags);
  ZERO(horizontal_mesh_line_flags);
  ZERO(vertical_mesh_line_flags);

  // Move nozzle to the specified height for the first layer
  set_destination_from_current();
  destination[Z_AXIS] = g26_layer_height;
  move_to(destination, 0.0);
  move_to(destination, g26_ooze_amount);

  #if HAS_LCD_MENU
    ui.capture();
  #endif

  #if DISABLED(ARC_SUPPORT)

    /**
     * Pre-generate radius offset values at 30 degree intervals to reduce CPU load.
     */
    #define A_INT 30
    #define _ANGS (360 / A_INT)
    #define A_CNT (_ANGS / 2)
    #define _IND(A) ((A + _ANGS * 8) % _ANGS)
    #define _COS(A) (trig_table[_IND(A) % A_CNT] * (_IND(A) >= A_CNT ? -1 : 1))
    #define _SIN(A) (-_COS((A + A_CNT / 2) % _ANGS))
    #if A_CNT & 1
      #error "A_CNT must be a positive value. Please change A_INT."
    #endif
    float trig_table[A_CNT];
    for (uint8_t i = 0; i < A_CNT; i++)
      trig_table[i] = INTERSECTION_CIRCLE_RADIUS * cos(RADIANS(i * A_INT));

  #endif // !ARC_SUPPORT

  mesh_index_pair location;
  do {
     location = g26_continue_with_closest
      ? find_closest_circle_to_print(current_position[X_AXIS], current_position[Y_AXIS])
      : find_closest_circle_to_print(g26_x_pos, g26_y_pos); // Find the closest Mesh Intersection to where we are now.

    if (location.x_index >= 0 && location.y_index >= 0) {
      const float circle_x = _GET_MESH_X(location.x_index),
                  circle_y = _GET_MESH_Y(location.y_index);

      // If this mesh location is outside the printable_radius, skip it.
      if (!position_is_reachable(circle_x, circle_y)) continue;

      // Determine where to start and end the circle,
      // which is always drawn counter-clockwise.
      const uint8_t xi = location.x_index, yi = location.y_index;
      const bool f = yi == 0, r = xi >= GRID_MAX_POINTS_X - 1, b = yi >= GRID_MAX_POINTS_Y - 1;

      #if ENABLED(ARC_SUPPORT)

        #define ARC_LENGTH(quarters)  (INTERSECTION_CIRCLE_RADIUS * M_PI * (quarters) / 2)
        #define INTERSECTION_CIRCLE_DIAM  ((INTERSECTION_CIRCLE_RADIUS) * 2)
        float sx = circle_x + INTERSECTION_CIRCLE_RADIUS,   // default to full circle
              ex = circle_x + INTERSECTION_CIRCLE_RADIUS,
              sy = circle_y, ey = circle_y,
              arc_length = ARC_LENGTH(4);

        // Figure out where to start and end the arc - we always print counterclockwise
        if (xi == 0) {                             // left edge
          if (!f) { sx = circle_x; sy -= INTERSECTION_CIRCLE_RADIUS; }
          if (!b) { ex = circle_x; ey += INTERSECTION_CIRCLE_RADIUS; }
          arc_length = (f || b) ? ARC_LENGTH(1) : ARC_LENGTH(2);
        }
        else if (r) {                             // right edge
          sx = b ? circle_x - (INTERSECTION_CIRCLE_RADIUS) : circle_x;
          ex = f ? circle_x - (INTERSECTION_CIRCLE_RADIUS) : circle_x;
          sy = b ? circle_y : circle_y + INTERSECTION_CIRCLE_RADIUS;
          ey = f ? circle_y : circle_y - (INTERSECTION_CIRCLE_RADIUS);
          arc_length = (f || b) ? ARC_LENGTH(1) : ARC_LENGTH(2);
        }
        else if (f) {
          ex -= INTERSECTION_CIRCLE_DIAM;
          arc_length = ARC_LENGTH(2);
        }
        else if (b) {
          sx -= INTERSECTION_CIRCLE_DIAM;
          arc_length = ARC_LENGTH(2);
        }

        const float arc_offset[2] = { circle_x - sx, circle_y - sy },
                    dx_s = current_position[X_AXIS] - sx,   // find our distance from the start of the actual circle
                    dy_s = current_position[Y_AXIS] - sy,
                    dist_start = HYPOT2(dx_s, dy_s),
                    endpoint[XYZE] = {
                      ex, ey,
                      g26_layer_height,
                      current_position[E_AXIS] + (arc_length * g26_e_axis_feedrate * g26_extrusion_multiplier)
                    };

        if (dist_start > 2.0) {
          retract_filament(destination);
          //todo:  parameterize the bump height with a define
          move_to(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS] + 0.500, 0.0);  // Z bump to minimize scraping
          move_to(sx, sy, g26_layer_height + 0.500, 0.0); // Get to the starting point with no extrusion while bumped
        }

        move_to(sx, sy, g26_layer_height, 0.0); // Get to the starting point with no extrusion / un-Z bump

        recover_filament(destination);
        const float save_feedrate = feedrate_mm_s;
        feedrate_mm_s = PLANNER_XY_FEEDRATE() / 10.0;

        plan_arc(endpoint, arc_offset, false);  // Draw a counter-clockwise arc
        feedrate_mm_s = save_feedrate;
        set_destination_from_current();
        #if HAS_LCD_MENU
          if (user_canceled()) goto LEAVE; // Check if the user wants to stop the Mesh Validation
        #endif

      #else // !ARC_SUPPORT

        int8_t start_ind = -2, end_ind = 9; // Assume a full circle (from 5:00 to 5:00)
        if (xi == 0) {                      // Left edge? Just right half.
          start_ind = f ? 0 : -3;           //  03:00 to 12:00 for front-left
          end_ind = b ? 0 : 2;              //  06:00 to 03:00 for back-left
        }
        else if (r) {                       // Right edge? Just left half.
          start_ind = b ? 6 : 3;            //  12:00 to 09:00 for front-right
          end_ind = f ? 5 : 8;              //  09:00 to 06:00 for back-right
        }
        else if (f) {                       // Front edge? Just back half.
          start_ind = 0;                    //  03:00
          end_ind = 5;                      //  09:00
        }
        else if (b) {                       // Back edge? Just front half.
          start_ind = 6;                    //  09:00
          end_ind = 11;                     //  03:00
        }

        for (int8_t ind = start_ind; ind <= end_ind; ind++) {

          #if HAS_LCD_MENU
            if (user_canceled()) goto LEAVE;          // Check if the user wants to stop the Mesh Validation
          #endif

          float rx = circle_x + _COS(ind),            // For speed, these are now a lookup table entry
                ry = circle_y + _SIN(ind),
                xe = circle_x + _COS(ind + 1),
                ye = circle_y + _SIN(ind + 1);

          #if IS_KINEMATIC
            // Check to make sure this segment is entirely on the bed, skip if not.
            if (!position_is_reachable(rx, ry) || !position_is_reachable(xe, ye)) continue;
          #else                                               // not, we need to skip
            rx = constrain(rx, X_MIN_POS + 1, X_MAX_POS - 1); // This keeps us from bumping the endstops
            ry = constrain(ry, Y_MIN_POS + 1, Y_MAX_POS - 1);
            xe = constrain(xe, X_MIN_POS + 1, X_MAX_POS - 1);
            ye = constrain(ye, Y_MIN_POS + 1, Y_MAX_POS - 1);
          #endif

          print_line_from_here_to_there(rx, ry, g26_layer_height, xe, ye, g26_layer_height);
          SERIAL_FLUSH();  // Prevent host M105 buffer overrun.
        }

      #endif // !ARC_SUPPORT

      if (look_for_lines_to_connect()) goto LEAVE;
    }

    SERIAL_FLUSH(); // Prevent host M105 buffer overrun.

  } while (--g26_repeats && location.x_index >= 0 && location.y_index >= 0);

  LEAVE:
  ui.set_status_P(PSTR("Leaving G26"), -1);

  retract_filament(destination);
  destination[Z_AXIS] = Z_CLEARANCE_BETWEEN_PROBES;

  move_to(destination, 0); // Raise the nozzle

  destination[X_AXIS] = g26_x_pos;                            // Move back to the starting position
  destination[Y_AXIS] = g26_y_pos;
  //destination[Z_AXIS] = Z_CLEARANCE_BETWEEN_PROBES;         // Keep the nozzle where it is

  move_to(destination, 0);                                    // Move back to the starting position

  #if DISABLED(NO_VOLUMETRICS)
    parser.volumetric_enabled = volumetric_was_enabled;
    planner.calculate_volumetric_multipliers();
  #endif

  #if HAS_LCD_MENU
    ui.release();                                             // Give back control of the LCD
  #endif

  if (!g26_keep_heaters_on) {
    #if HAS_HEATED_BED
      thermalManager.setTargetBed(0);
    #endif
    thermalManager.setTargetHotend(active_extruder, 0);
  }
}

#endif // G26_MESH_VALIDATION
