/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2001-2002 NaN Holding BV. All rights reserved. */

/** \file
 * \ingroup edcurve
 */

#include "DNA_curve_types.h"
#include "DNA_windowmanager_types.h"

#include "MEM_guardedalloc.h"

#include "BLI_listbase.h"
#include "BLI_math.h"

#include "BKE_context.h"
#include "BKE_curve.h"

#include "DEG_depsgraph.h"

#include "WM_api.h"

#include "ED_curve.h"
#include "ED_screen.h"
#include "ED_select_utils.h"
#include "ED_view3d.h"

#include "BKE_object.h"

#include "curve_intern.h"

#include "RNA_access.h"
#include "RNA_define.h"

#include "float.h"

#define FOREACH_SELECTED_BEZT_BEGIN(bezt, nurbs) \
  LISTBASE_FOREACH (Nurb *, nu, nurbs) { \
    if (nu->type == CU_BEZIER) { \
      for (int i = 0; i < nu->pntsu; i++) { \
        BezTriple *bezt = nu->bezt + i; \
        if (BEZT_ISSEL_ANY(bezt) && !bezt->hide) {

#define FOREACH_SELECTED_BEZT_END \
  } \
  } \
  } \
  BKE_nurb_handles_calc(nu); \
  } \
  ((void)0)

/* Used to scale the default select distance. */
#define SEL_DIST_FACTOR 0.2f

/**
 * Data structure to keep track of details about the cut location
 */
typedef struct CutData {
  /* Index of the last #BezTriple or BPoint before the cut. */
  int bezt_index, bp_index;
  /* Nurb to which the cut belongs to. */
  Nurb *nurb;
  /* Minimum distance to curve from mouse location. */
  float min_dist;
  /* Fraction of segments after which the new point divides the curve segment. */
  float parameter;
  /* Whether the currently identified closest point has any vertices before/after it. */
  bool has_prev, has_next;
  /* Locations of adjacent vertices and cut location. */
  float prev_loc[3], cut_loc[3], next_loc[3];
  /* Mouse location in floats. */
  float mval[2];
} CutData;

/**
 * Data required for segment altering functionality.
 */
typedef struct MoveSegmentData {
  /* Nurb being altered. */
  Nurb *nu;
  /* Index of the #BezTriple before the segment. */
  int bezt_index;
  /* Fraction along the segment at which mouse was pressed. */
  float t;
} MoveSegmentData;

typedef struct CurvePenData {
  MoveSegmentData *msd;
  /* Whether the mouse is clicking and dragging. */
  bool dragging;
  /* Whether a new point was added at the beginning of tool execution. */
  bool new_point;
  /* Whether a segment is being altered by click and drag. */
  bool spline_nearby;
  /* Whether some action was done. Used for select. */
  bool acted;
  /* Whether a point was found underneath the mouse. */
  bool found_point;
  /* Whether multiple selected points should be moved. */
  bool multi_point;
  /* Whether a point has already been selected. */
  bool selection_made;
  /* Whether a shift-click occurred. */
  bool select_multi;

  /* Whether the current handle type of the moved handle is free. */
  bool free_toggle;
  /* Whether the shortcut for moving the adjacent handle is pressed. */
  bool move_adjacent;
  /* Whether the current state of the moved handle is linked. */
  bool link_handles;
  /* Whether the current state of the handle angle is locked. */
  bool lock_angle;
  /* Whether the shortcut for moving the entire point is pressed. */
  bool move_entire;

  /* Data about found point. Used for closing splines. */
  Nurb *nu;
  BezTriple *bezt;
  BPoint *bp;
} CurvePenData;

static const EnumPropertyItem prop_handle_types[] = {
    {HD_AUTO, "AUTO", 0, "Auto", ""},
    {HD_VECT, "VECTOR", 0, "Vector", ""},
    {0, NULL, 0, NULL, NULL},
};

typedef enum eClose_opt {
  OFF = 0,
  ON_PRESS = 1,
  ON_CLICK = 2,
} eClose_opt;

static const EnumPropertyItem prop_close_spline_method[] = {
    {OFF, "OFF", 0, "None", ""},
    {ON_PRESS, "ON_PRESS", 0, "On Press", "Move handles after closing the spline"},
    {ON_CLICK, "ON_CLICK", 0, "On Click", "Spline closes on release if not dragged"},
    {0, NULL, 0, NULL, NULL},
};

static void update_location_for_2d_curve(const ViewContext *vc, float location[3])
{
  Curve *cu = vc->obedit->data;
  if (CU_IS_2D(cu)) {
    const float eps = 1e-6f;

    /* Get the view vector to `location`. */
    float view_dir[3];
    ED_view3d_global_to_vector(vc->rv3d, location, view_dir);

    /* Get the plane. */
    float plane[4];
    /* Only normalize to avoid precision errors. */
    normalize_v3_v3(plane, vc->obedit->obmat[2]);
    plane[3] = -dot_v3v3(plane, vc->obedit->obmat[3]);

    if (fabsf(dot_v3v3(view_dir, plane)) < eps) {
      /* Can't project on an aligned plane. */
    }
    else {
      float lambda;
      if (isect_ray_plane_v3(location, view_dir, plane, &lambda, false)) {
        /* Check if we're behind the viewport */
        float location_test[3];
        madd_v3_v3v3fl(location_test, location, view_dir, lambda);
        if ((vc->rv3d->is_persp == false) ||
            (mul_project_m4_v3_zfac(vc->rv3d->persmat, location_test) > 0.0f)) {
          copy_v3_v3(location, location_test);
        }
      }
    }
  }

  float imat[4][4];
  invert_m4_m4(imat, vc->obedit->obmat);
  mul_m4_v3(imat, location);

  if (CU_IS_2D(cu)) {
    location[2] = 0.0f;
  }
}

static void screenspace_to_worldspace(const ViewContext *vc,
                                      const float pos_2d[2],
                                      const float depth[3],
                                      float r_pos_3d[3])
{
  mul_v3_m4v3(r_pos_3d, vc->obedit->obmat, depth);
  ED_view3d_win_to_3d(vc->v3d, vc->region, r_pos_3d, pos_2d, r_pos_3d);
  update_location_for_2d_curve(vc, r_pos_3d);
}

static void screenspace_to_worldspace_int(const ViewContext *vc,
                                          const int pos_2d[2],
                                          const float depth[3],
                                          float r_pos_3d[3])
{
  const float pos_2d_fl[2] = {UNPACK2(pos_2d)};
  screenspace_to_worldspace(vc, pos_2d_fl, depth, r_pos_3d);
}

static bool worldspace_to_screenspace(const ViewContext *vc,
                                      const float pos_3d[3],
                                      float r_pos_2d[2])
{
  return ED_view3d_project_float_object(
             vc->region, pos_3d, r_pos_2d, V3D_PROJ_RET_CLIP_BB | V3D_PROJ_RET_CLIP_WIN) ==
         V3D_PROJ_RET_OK;
}

static void move_bezt_by_displacement(BezTriple *bezt, const float disp_3d[3])
{
  add_v3_v3(bezt->vec[0], disp_3d);
  add_v3_v3(bezt->vec[1], disp_3d);
  add_v3_v3(bezt->vec[2], disp_3d);
}

/**
 * Move entire control point to given worldspace location.
 */
static void move_bezt_to_location(BezTriple *bezt, const float location[3])
{
  float disp_3d[3];
  sub_v3_v3v3(disp_3d, location, bezt->vec[1]);
  move_bezt_by_displacement(bezt, disp_3d);
}

/**
 * Alter handle types to allow free movement (Set handles to #FREE or #ALIGN).
 */
static void remove_handle_movement_constraints(BezTriple *bezt, const bool f1, const bool f3)
{
  if (f1) {
    if (bezt->h1 == HD_VECT) {
      bezt->h1 = HD_FREE;
    }
    if (bezt->h1 == HD_AUTO) {
      bezt->h1 = HD_ALIGN;
      bezt->h2 = HD_ALIGN;
    }
  }
  if (f3) {
    if (bezt->h2 == HD_VECT) {
      bezt->h2 = HD_FREE;
    }
    if (bezt->h2 == HD_AUTO) {
      bezt->h1 = HD_ALIGN;
      bezt->h2 = HD_ALIGN;
    }
  }
}

static void move_bezt_handle_or_vertex_by_displacement(const ViewContext *vc,
                                                       BezTriple *bezt,
                                                       const int bezt_idx,
                                                       const float disp_2d[2],
                                                       const float distance,
                                                       const bool link_handles,
                                                       const bool lock_angle)
{
  if (lock_angle) {
    float disp_3d[3];
    sub_v3_v3v3(disp_3d, bezt->vec[bezt_idx], bezt->vec[1]);
    normalize_v3_length(disp_3d, distance);
    add_v3_v3v3(bezt->vec[bezt_idx], bezt->vec[1], disp_3d);
  }
  else {
    float pos[2], dst[2];
    worldspace_to_screenspace(vc, bezt->vec[bezt_idx], pos);
    add_v2_v2v2(dst, pos, disp_2d);

    float location[3];
    screenspace_to_worldspace(vc, dst, bezt->vec[bezt_idx], location);
    if (bezt_idx == 1) {
      move_bezt_to_location(bezt, location);
    }
    else {
      copy_v3_v3(bezt->vec[bezt_idx], location);
      if (bezt->h1 == HD_ALIGN && bezt->h2 == HD_ALIGN) {
        /* Move the handle on the opposite side. */
        float handle_vec[3];
        sub_v3_v3v3(handle_vec, bezt->vec[1], location);
        const int other_handle = bezt_idx == 2 ? 0 : 2;
        normalize_v3_length(handle_vec, len_v3v3(bezt->vec[1], bezt->vec[other_handle]));
        add_v3_v3v3(bezt->vec[other_handle], bezt->vec[1], handle_vec);
      }
    }

    if (link_handles) {
      float handle[3];
      sub_v3_v3v3(handle, bezt->vec[1], bezt->vec[bezt_idx]);
      add_v3_v3v3(bezt->vec[(bezt_idx + 2) % 4], bezt->vec[1], handle);
    }
  }
}

static void move_bp_to_location(const ViewContext *vc, BPoint *bp, const float mval[2])
{
  float location[3];
  screenspace_to_worldspace(vc, mval, bp->vec, location);

  copy_v3_v3(bp->vec, location);
}

/**
 * Get the average position of selected points.
 * \param mid_only: Use only the middle point of the three points on a #BezTriple.
 * \param bezt_only: Use only points of Bezier splines.
 */
static bool get_selected_center(const ListBase *nurbs,
                                const bool mid_only,
                                const bool bezt_only,
                                float r_center[3])
{
  int end_count = 0;
  zero_v3(r_center);
  LISTBASE_FOREACH (Nurb *, nu, nurbs) {
    if (nu->type == CU_BEZIER) {
      for (int i = 0; i < nu->pntsu; i++) {
        BezTriple *bezt = nu->bezt + i;
        if (bezt->hide) {
          continue;
        }
        if (mid_only) {
          if (BEZT_ISSEL_ANY(bezt)) {
            add_v3_v3(r_center, bezt->vec[1]);
            end_count++;
          }
        }
        else {
          if (BEZT_ISSEL_IDX(bezt, 1)) {
            add_v3_v3(r_center, bezt->vec[1]);
            end_count++;
          }
          else if (BEZT_ISSEL_IDX(bezt, 0)) {
            add_v3_v3(r_center, bezt->vec[0]);
            end_count++;
          }
          else if (BEZT_ISSEL_IDX(bezt, 2)) {
            add_v3_v3(r_center, bezt->vec[2]);
            end_count++;
          }
        }
      }
    }
    else if (!bezt_only) {
      for (int i = 0; i < nu->pntsu; i++) {
        if (!nu->bp->hide && (nu->bp + i)->f1 & SELECT) {
          add_v3_v3(r_center, (nu->bp + i)->vec);
          end_count++;
        }
      }
    }
  }
  if (end_count) {
    mul_v3_fl(r_center, 1.0f / end_count);
    return true;
  }
  return false;
}

/**
 * Move all selected points by an amount equivalent to the distance moved by mouse.
 */
static void move_all_selected_points(const ViewContext *vc,
                                     const wmEvent *event,
                                     CurvePenData *cpd,
                                     ListBase *nurbs,
                                     const bool bezt_only)
{
  const float mval[2] = {UNPACK2(event->xy)};
  const float prev_mval[2] = {UNPACK2(event->prev_xy)};
  float disp_2d[2];
  sub_v2_v2v2(disp_2d, mval, prev_mval);

  const bool link_handles = cpd->link_handles && !cpd->free_toggle;
  const bool lock_angle = cpd->lock_angle;
  const bool move_entire = cpd->move_entire;

  float distance = 0.0f;
  if (lock_angle) {
    float mval_3d[3], center_mid[3];
    get_selected_center(nurbs, true, true, center_mid);
    screenspace_to_worldspace_int(vc, event->mval, center_mid, mval_3d);
    distance = len_v3v3(center_mid, mval_3d);
  }

  LISTBASE_FOREACH (Nurb *, nu, nurbs) {
    if (nu->type == CU_BEZIER) {
      for (int i = 0; i < nu->pntsu; i++) {
        BezTriple *bezt = nu->bezt + i;
        if (bezt->hide) {
          continue;
        }
        if (BEZT_ISSEL_IDX(bezt, 1) || (move_entire && BEZT_ISSEL_ANY(bezt))) {
          move_bezt_handle_or_vertex_by_displacement(vc, bezt, 1, disp_2d, 0.0f, false, false);
        }
        else {
          remove_handle_movement_constraints(
              bezt, BEZT_ISSEL_IDX(bezt, 0), BEZT_ISSEL_IDX(bezt, 2));
          if (BEZT_ISSEL_IDX(bezt, 0)) {
            move_bezt_handle_or_vertex_by_displacement(
                vc, bezt, 0, disp_2d, distance, link_handles, lock_angle);
          }
          else if (BEZT_ISSEL_IDX(bezt, 2)) {
            move_bezt_handle_or_vertex_by_displacement(
                vc, bezt, 2, disp_2d, distance, link_handles, lock_angle);
          }
        }
      }
      BKE_nurb_handles_calc(nu);
    }
    else if (!bezt_only) {
      for (int i = 0; i < nu->pntsu; i++) {
        BPoint *bp = nu->bp + i;
        if (!bp->hide && (bp->f1 & SELECT)) {
          float pos[2], dst[2];
          worldspace_to_screenspace(vc, bp->vec, pos);
          add_v2_v2v2(dst, pos, disp_2d);
          move_bp_to_location(vc, bp, dst);
        }
      }
    }
  }
}

static int get_nurb_index(const ListBase *nurbs, const Nurb *nurb)
{
  return BLI_findindex(nurbs, nurb);
}

static void delete_nurb(Curve *cu, Nurb *nu)
{
  EditNurb *editnurb = cu->editnurb;
  ListBase *nurbs = &editnurb->nurbs;
  const int nu_index = get_nurb_index(nurbs, nu);
  if (cu->actnu == nu_index) {
    BKE_curve_nurb_vert_active_set(cu, NULL, NULL);
  }

  BLI_remlink(nurbs, nu);
  BKE_nurb_free(nu);
}

static void delete_bezt_from_nurb(const BezTriple *bezt, Nurb *nu, EditNurb *editnurb)
{
  BLI_assert(nu->type == CU_BEZIER);
  const int index = BKE_curve_nurb_vert_index_get(nu, bezt);
  nu->pntsu -= 1;
  memmove(nu->bezt + index, nu->bezt + index + 1, (nu->pntsu - index) * sizeof(BezTriple));
  BKE_curve_editNurb_keyIndex_delCV(editnurb->keyindex, nu->bezt + index);
}

static void delete_bp_from_nurb(const BPoint *bp, Nurb *nu, EditNurb *editnurb)
{
  BLI_assert(nu->type == CU_NURBS || nu->type == CU_POLY);
  const int index = BKE_curve_nurb_vert_index_get(nu, bp);
  nu->pntsu -= 1;
  memmove(nu->bp + index, nu->bp + index + 1, (nu->pntsu - index) * sizeof(BPoint));
  BKE_curve_editNurb_keyIndex_delCV(editnurb->keyindex, nu->bp + index);
}

/**
 * Get closest vertex in all nurbs in given #ListBase to a given point.
 * Returns true if point is found.
 */
static bool get_closest_vertex_to_point_in_nurbs(const ViewContext *vc,
                                                 const ListBase *nurbs,
                                                 const float point[2],
                                                 Nurb **r_nu,
                                                 BezTriple **r_bezt,
                                                 BPoint **r_bp,
                                                 int *r_bezt_idx)
{
  *r_nu = NULL;
  *r_bezt = NULL;
  *r_bp = NULL;

  float min_dist_bezt = FLT_MAX;
  int closest_handle = 0;
  BezTriple *closest_bezt = NULL;
  Nurb *closest_bezt_nu = NULL;

  float min_dist_bp = FLT_MAX;
  BPoint *closest_bp = NULL;
  Nurb *closest_bp_nu = NULL;

  LISTBASE_FOREACH (Nurb *, nu, nurbs) {
    if (nu->type == CU_BEZIER) {
      for (int i = 0; i < nu->pntsu; i++) {
        BezTriple *bezt = &nu->bezt[i];
        float bezt_vec[2];
        int start = 0, end = 3;

        /* Consider handles only if visible. Else only consider the middle point of the triple. */
        int handle_display = vc->v3d->overlay.handle_display;
        if (handle_display == CURVE_HANDLE_NONE ||
            (handle_display == CURVE_HANDLE_SELECTED && !BEZT_ISSEL_ANY(bezt))) {
          start = 1, end = 2;
        }

        /* Loop over each of the 3 points of the #BezTriple and update data of closest bezt. */
        for (int j = start; j < end; j++) {
          if (worldspace_to_screenspace(vc, bezt->vec[j], bezt_vec)) {
            const float dist = len_manhattan_v2v2(bezt_vec, point);
            if (dist < min_dist_bezt) {
              min_dist_bezt = dist;
              closest_bezt = bezt;
              closest_bezt_nu = nu;
              closest_handle = j;
            }
          }
        }
      }
    }
    else {
      for (int i = 0; i < nu->pntsu; i++) {
        BPoint *bp = &nu->bp[i];
        float bp_vec[2];

        /* Update data of closest #BPoint. */
        if (worldspace_to_screenspace(vc, bp->vec, bp_vec)) {
          const float dist = len_manhattan_v2v2(bp_vec, point);
          if (dist < min_dist_bp) {
            min_dist_bp = dist;
            closest_bp = bp;
            closest_bp_nu = nu;
          }
        }
      }
    }
  }

  /* Assign closest data to the returned variables. */
  const float threshold_dist = ED_view3d_select_dist_px() * SEL_DIST_FACTOR;
  if (min_dist_bezt < threshold_dist || min_dist_bp < threshold_dist) {
    if (min_dist_bp < min_dist_bezt) {
      *r_bp = closest_bp;
      *r_nu = closest_bp_nu;
    }
    else {
      *r_bezt = closest_bezt;
      *r_bezt_idx = closest_handle;
      *r_nu = closest_bezt_nu;
    }
    return true;
  }
  return false;
}

/**
 * Interpolate along the Bezier segment by a parameter (between 0 and 1) and get its location.
 */
static void get_bezier_interpolated_point(const BezTriple *bezt1,
                                          const BezTriple *bezt2,
                                          const float parameter,
                                          float r_point[3])
{
  float tmp1[3], tmp2[3], tmp3[3];
  interp_v3_v3v3(tmp1, bezt1->vec[1], bezt1->vec[2], parameter);
  interp_v3_v3v3(tmp2, bezt1->vec[2], bezt2->vec[0], parameter);
  interp_v3_v3v3(tmp3, bezt2->vec[0], bezt2->vec[1], parameter);
  interp_v3_v3v3(tmp1, tmp1, tmp2, parameter);
  interp_v3_v3v3(tmp2, tmp2, tmp3, parameter);
  interp_v3_v3v3(r_point, tmp1, tmp2, parameter);
}

/**
 * Calculate handle positions of added and adjacent control points such that shape is preserved.
 */
static void calculate_new_bezier_point(const float point_prev[3],
                                       float handle_prev[3],
                                       float new_left_handle[3],
                                       float new_right_handle[3],
                                       float handle_next[3],
                                       const float point_next[3],
                                       const float parameter)
{
  float center_point[3];
  interp_v3_v3v3(center_point, handle_prev, handle_next, parameter);
  interp_v3_v3v3(handle_prev, point_prev, handle_prev, parameter);
  interp_v3_v3v3(handle_next, handle_next, point_next, parameter);
  interp_v3_v3v3(new_left_handle, handle_prev, center_point, parameter);
  interp_v3_v3v3(new_right_handle, center_point, handle_next, parameter);
}

static bool is_cyclic(const Nurb *nu)
{
  return nu->flagu & CU_NURB_CYCLIC;
}

/**
 * Insert a #BezTriple to a nurb at the location specified by `data`.
 */
static void insert_bezt_to_nurb(Nurb *nu, const CutData *data, Curve *cu)
{
  EditNurb *editnurb = cu->editnurb;

  BezTriple *new_bezt_array = (BezTriple *)MEM_mallocN((nu->pntsu + 1) * sizeof(BezTriple),
                                                       __func__);
  const int index = data->bezt_index + 1;
  /* Copy all control points before the cut to the new memory. */
  ED_curve_beztcpy(editnurb, new_bezt_array, nu->bezt, index);
  BezTriple *new_bezt = new_bezt_array + index;

  /* Duplicate control point after the cut. */
  ED_curve_beztcpy(editnurb, new_bezt, new_bezt - 1, 1);
  copy_v3_v3(new_bezt->vec[1], data->cut_loc);

  if (index < nu->pntsu) {
    /* Copy all control points after the cut to the new memory. */
    ED_curve_beztcpy(editnurb, new_bezt_array + index + 1, nu->bezt + index, nu->pntsu - index);
  }

  nu->pntsu += 1;
  BKE_curve_nurb_vert_active_set(cu, nu, nu->bezt + index);

  BezTriple *next_bezt;
  if (is_cyclic(nu) && (index == nu->pntsu - 1)) {
    next_bezt = new_bezt_array;
  }
  else {
    next_bezt = new_bezt + 1;
  }

  /* Interpolate radius, tilt, weight */
  new_bezt->tilt = interpf(next_bezt->tilt, (new_bezt - 1)->tilt, data->parameter);
  new_bezt->radius = interpf(next_bezt->radius, (new_bezt - 1)->radius, data->parameter);
  new_bezt->weight = interpf(next_bezt->weight, (new_bezt - 1)->weight, data->parameter);

  new_bezt->h1 = new_bezt->h2 = HD_ALIGN;

  calculate_new_bezier_point((new_bezt - 1)->vec[1],
                             (new_bezt - 1)->vec[2],
                             new_bezt->vec[0],
                             new_bezt->vec[2],
                             next_bezt->vec[0],
                             next_bezt->vec[1],
                             data->parameter);

  MEM_freeN(nu->bezt);
  nu->bezt = new_bezt_array;
  ED_curve_deselect_all(editnurb);
  BKE_nurb_handles_calc(nu);
  BEZT_SEL_ALL(new_bezt);
}

/**
 * Insert a #BPoint to a nurb at the location specified by `op_data`.
 */
static void insert_bp_to_nurb(Nurb *nu, const CutData *data, Curve *cu)
{
  EditNurb *editnurb = cu->editnurb;

  BPoint *new_bp_array = (BPoint *)MEM_mallocN((nu->pntsu + 1) * sizeof(BPoint), __func__);
  const int index = data->bp_index + 1;
  /* Copy all control points before the cut to the new memory. */
  ED_curve_bpcpy(editnurb, new_bp_array, nu->bp, index);
  BPoint *new_bp = new_bp_array + index;

  /* Duplicate control point after the cut. */
  ED_curve_bpcpy(editnurb, new_bp, new_bp - 1, 1);
  copy_v3_v3(new_bp->vec, data->cut_loc);

  if (index < nu->pntsu) {
    /* Copy all control points after the cut to the new memory. */
    ED_curve_bpcpy(editnurb, new_bp_array + index + 1, nu->bp + index, (nu->pntsu - index));
  }

  nu->pntsu += 1;
  BKE_curve_nurb_vert_active_set(cu, nu, nu->bp + index);

  BPoint *next_bp;
  if (is_cyclic(nu) && (index == nu->pntsu - 1)) {
    next_bp = new_bp_array;
  }
  else {
    next_bp = new_bp + 1;
  }

  /* Interpolate radius, tilt, weight */
  new_bp->tilt = interpf(next_bp->tilt, (new_bp - 1)->tilt, data->parameter);
  new_bp->radius = interpf(next_bp->radius, (new_bp - 1)->radius, data->parameter);
  new_bp->weight = interpf(next_bp->weight, (new_bp - 1)->weight, data->parameter);

  MEM_freeN(nu->bp);
  nu->bp = new_bp_array;
  ED_curve_deselect_all(editnurb);
  BKE_nurb_knot_calc_u(nu);
  new_bp->f1 |= SELECT;
}

/**
 * Update r_min_dist, r_min_i, and r_param based on the edge and the external point.
 * \param point: External point
 * \param point1: One end of the edge
 * \param point2: The other end of the edge
 * \param point_idx: Index of the control point out of the points on the Nurb
 * \param resolu_idx: Index of the edge on a Bezier segment (zero for non-Bezier edges)
 * \param r_min_dist: minimum distance from point to edge
 * \param r_min_i: index of closest point on Nurb
 * \param r_param: the fraction along the edge at which the closest point lies
 */
static void get_updated_data_for_edge(const float point[2],
                                      const float point1[2],
                                      const float point2[2],
                                      const int point_idx,
                                      const int resolu_idx,
                                      float *r_min_dist,
                                      int *r_min_i,
                                      float *r_param)
{
  float edge[2], vec1[2], vec2[2];
  sub_v2_v2v2(edge, point1, point2);
  sub_v2_v2v2(vec1, point1, point);
  sub_v2_v2v2(vec2, point, point2);
  const float len_vec1 = len_v2(vec1);
  const float len_vec2 = len_v2(vec2);
  const float dot1 = dot_v2v2(edge, vec1);
  const float dot2 = dot_v2v2(edge, vec2);

  /* Signs of dot products being equal implies that the angles formed with the external point are
   * either both acute or both obtuse, meaning the external point is closer to a point on the edge
   * rather than an endpoint. */
  if ((dot1 > 0) == (dot2 > 0)) {
    const float perp_dist = len_vec1 * sinf(angle_v2v2(vec1, edge));
    if (*r_min_dist > perp_dist) {
      *r_min_dist = perp_dist;
      *r_min_i = point_idx;
      *r_param = resolu_idx + len_vec1 * cos_v2v2v2(point, point1, point2) / len_v2(edge);
    }
  }
  else {
    if (*r_min_dist > len_vec2) {
      *r_min_dist = len_vec2;
      *r_min_i = point_idx;
      *r_param = resolu_idx;
    }
  }
}

/**
 * Update #CutData for a single #Nurb.
 */
static void update_cut_data_for_nurb(
    const ViewContext *vc, CutData *cd, Nurb *nu, const int resolu, const float point[2])
{
  float min_dist = cd->min_dist, param = 0.0f;
  int min_i = 0;
  const int end = is_cyclic(nu) ? nu->pntsu : nu->pntsu - 1;

  if (nu->type == CU_BEZIER) {
    for (int i = 0; i < end; i++) {
      float *points = MEM_mallocN(sizeof(float[3]) * (resolu + 1), __func__);

      const BezTriple *bezt1 = nu->bezt + i;
      const BezTriple *bezt2 = nu->bezt + (i + 1) % nu->pntsu;

      /* Calculate all points on curve. */
      for (int j = 0; j < 3; j++) {
        BKE_curve_forward_diff_bezier(bezt1->vec[1][j],
                                      bezt1->vec[2][j],
                                      bezt2->vec[0][j],
                                      bezt2->vec[1][j],
                                      points + j,
                                      resolu,
                                      sizeof(float[3]));
      }

      float point1[2], point2[2];
      worldspace_to_screenspace(vc, points, point1);
      const float len_vec1 = len_v2v2(point, point1);

      if (min_dist > len_vec1) {
        min_dist = len_vec1;
        min_i = i;
        param = 0;
      }

      for (int j = 0; j < resolu; j++) {
        worldspace_to_screenspace(vc, points + 3 * (j + 1), point2);
        get_updated_data_for_edge(point, point1, point2, i, j, &min_dist, &min_i, &param);
        copy_v2_v2(point1, point2);
      }

      MEM_freeN(points);
    }
    if (cd->min_dist > min_dist) {
      cd->min_dist = min_dist;
      cd->nurb = nu;
      cd->bezt_index = min_i;
      cd->parameter = param / resolu;
    }
  }
  else {
    float point1[2], point2[2];
    worldspace_to_screenspace(vc, nu->bp->vec, point1);
    for (int i = 0; i < end; i++) {
      worldspace_to_screenspace(vc, (nu->bp + (i + 1) % nu->pntsu)->vec, point2);
      get_updated_data_for_edge(point, point1, point2, i, 0, &min_dist, &min_i, &param);
      copy_v2_v2(point1, point2);
    }

    if (cd->min_dist > min_dist) {
      cd->min_dist = min_dist;
      cd->nurb = nu;
      cd->bp_index = min_i;
      cd->parameter = param;
    }
  }
}

/* Update #CutData for all the Nurbs in the curve. */
static bool update_cut_data_for_all_nurbs(const ViewContext *vc,
                                          const ListBase *nurbs,
                                          const float point[2],
                                          const float sel_dist,
                                          CutData *cd)
{
  cd->min_dist = FLT_MAX;
  LISTBASE_FOREACH (Nurb *, nu, nurbs) {
    update_cut_data_for_nurb(vc, cd, nu, nu->resolu, point);
  }

  return cd->min_dist < sel_dist;
}

static CutData init_cut_data(const wmEvent *event)
{
  CutData cd = {.bezt_index = 0,
                .bp_index = 0,
                .min_dist = FLT_MAX,
                .parameter = 0.5f,
                .has_prev = false,
                .has_next = false,
                .mval[0] = event->mval[0],
                .mval[1] = event->mval[1]};
  return cd;
}

static bool insert_point_to_segment(const ViewContext *vc, const wmEvent *event)
{
  Curve *cu = vc->obedit->data;
  CutData cd = init_cut_data(event);
  const float mval[2] = {UNPACK2(event->mval)};
  const float threshold_dist_px = ED_view3d_select_dist_px() * SEL_DIST_FACTOR;
  const bool near_spline = update_cut_data_for_all_nurbs(
      vc, BKE_curve_editNurbs_get(cu), mval, threshold_dist_px, &cd);

  if (near_spline && !cd.nurb->hide) {
    Nurb *nu = cd.nurb;
    if (nu->type == CU_BEZIER) {
      cd.min_dist = FLT_MAX;
      /* Update cut data at a higher resolution for better accuracy. */
      update_cut_data_for_nurb(vc, &cd, cd.nurb, 25, mval);

      get_bezier_interpolated_point(&nu->bezt[cd.bezt_index],
                                    &nu->bezt[(cd.bezt_index + 1) % (nu->pntsu)],
                                    cd.parameter,
                                    cd.cut_loc);

      insert_bezt_to_nurb(nu, &cd, cu);
    }
    else {
      interp_v2_v2v2(cd.cut_loc,
                     (nu->bp + cd.bp_index)->vec,
                     (nu->bp + (cd.bp_index + 1) % nu->pntsu)->vec,
                     cd.parameter);
      insert_bp_to_nurb(nu, &cd, cu);
    }
    return true;
  }

  return false;
}

/**
 * Get the first selected point from the curve. If more than one selected point is found,
 * define and return only the first detected nu.
 */
static void get_first_selected_point(
    Curve *cu, View3D *v3d, Nurb **r_nu, BezTriple **r_bezt, BPoint **r_bp)
{
  ListBase *nurbs = &cu->editnurb->nurbs;
  BezTriple *bezt;
  BPoint *bp;
  int a;

  *r_nu = NULL;
  *r_bezt = NULL;
  *r_bp = NULL;

  LISTBASE_FOREACH (Nurb *, nu, nurbs) {
    if (nu->type == CU_BEZIER) {
      bezt = nu->bezt;
      a = nu->pntsu;
      while (a--) {
        if (BEZT_ISSEL_ANY_HIDDENHANDLES(v3d, bezt)) {
          if (*r_bezt || *r_bp) {
            *r_bp = NULL;
            *r_bezt = NULL;
            return;
          }
          *r_bezt = bezt;
          *r_nu = nu;
        }
        bezt++;
      }
    }
    else {
      bp = nu->bp;
      a = nu->pntsu * nu->pntsv;
      while (a--) {
        if (bp->f1 & SELECT) {
          if (*r_bezt || *r_bp) {
            *r_bp = NULL;
            *r_bezt = NULL;
            return;
          }
          *r_bp = bp;
          *r_nu = nu;
        }
        bp++;
      }
    }
  }
}

static void extrude_vertices_from_selected_endpoints(EditNurb *editnurb,
                                                     ListBase *nurbs,
                                                     Curve *cu,
                                                     const float disp_3d[3])
{
  int nu_index = 0;
  LISTBASE_FOREACH (Nurb *, nu1, nurbs) {
    if (nu1->type == CU_BEZIER) {
      BezTriple *last_bezt = nu1->bezt + nu1->pntsu - 1;
      const bool first_sel = BEZT_ISSEL_ANY(nu1->bezt);
      const bool last_sel = BEZT_ISSEL_ANY(last_bezt) && nu1->pntsu > 1;
      if (first_sel) {
        if (last_sel) {
          BezTriple *new_bezt = (BezTriple *)MEM_mallocN((nu1->pntsu + 2) * sizeof(BezTriple),
                                                         __func__);
          ED_curve_beztcpy(editnurb, new_bezt, nu1->bezt, 1);
          ED_curve_beztcpy(editnurb, new_bezt + nu1->pntsu + 1, last_bezt, 1);
          BEZT_DESEL_ALL(nu1->bezt);
          BEZT_DESEL_ALL(last_bezt);
          ED_curve_beztcpy(editnurb, new_bezt + 1, nu1->bezt, nu1->pntsu);

          move_bezt_by_displacement(new_bezt, disp_3d);
          move_bezt_by_displacement(new_bezt + nu1->pntsu + 1, disp_3d);
          MEM_freeN(nu1->bezt);
          nu1->bezt = new_bezt;
          nu1->pntsu += 2;
        }
        else {
          BezTriple *new_bezt = (BezTriple *)MEM_mallocN((nu1->pntsu + 1) * sizeof(BezTriple),
                                                         __func__);
          ED_curve_beztcpy(editnurb, new_bezt, nu1->bezt, 1);
          BEZT_DESEL_ALL(nu1->bezt);
          ED_curve_beztcpy(editnurb, new_bezt + 1, nu1->bezt, nu1->pntsu);
          move_bezt_by_displacement(new_bezt, disp_3d);
          MEM_freeN(nu1->bezt);
          nu1->bezt = new_bezt;
          nu1->pntsu++;
        }
        cu->actnu = nu_index;
        cu->actvert = 0;
      }
      else if (last_sel) {
        BezTriple *new_bezt = (BezTriple *)MEM_mallocN((nu1->pntsu + 1) * sizeof(BezTriple),
                                                       __func__);
        ED_curve_beztcpy(editnurb, new_bezt + nu1->pntsu, last_bezt, 1);
        BEZT_DESEL_ALL(last_bezt);
        ED_curve_beztcpy(editnurb, new_bezt, nu1->bezt, nu1->pntsu);
        move_bezt_by_displacement(new_bezt + nu1->pntsu, disp_3d);
        MEM_freeN(nu1->bezt);
        nu1->bezt = new_bezt;
        nu1->pntsu++;
        cu->actnu = nu_index;
        cu->actvert = nu1->pntsu - 1;
      }
    }
    else {
      BPoint *last_bp = nu1->bp + nu1->pntsu - 1;
      const bool first_sel = nu1->bp->f1 & SELECT;
      const bool last_sel = last_bp->f1 & SELECT && nu1->pntsu > 1;
      if (first_sel) {
        if (last_sel) {
          BPoint *new_bp = (BPoint *)MEM_mallocN((nu1->pntsu + 2) * sizeof(BPoint), __func__);
          ED_curve_bpcpy(editnurb, new_bp, nu1->bp, 1);
          ED_curve_bpcpy(editnurb, new_bp + nu1->pntsu + 1, last_bp, 1);
          nu1->bp->f1 &= ~SELECT;
          last_bp->f1 &= ~SELECT;
          ED_curve_bpcpy(editnurb, new_bp + 1, nu1->bp, nu1->pntsu);
          add_v3_v3(new_bp->vec, disp_3d);
          add_v3_v3((new_bp + nu1->pntsu + 1)->vec, disp_3d);
          MEM_freeN(nu1->bp);
          nu1->bp = new_bp;
          nu1->pntsu += 2;
        }
        else {
          BPoint *new_bp = (BPoint *)MEM_mallocN((nu1->pntsu + 1) * sizeof(BPoint), __func__);
          ED_curve_bpcpy(editnurb, new_bp, nu1->bp, 1);
          nu1->bp->f1 &= ~SELECT;
          ED_curve_bpcpy(editnurb, new_bp + 1, nu1->bp, nu1->pntsu);
          add_v3_v3(new_bp->vec, disp_3d);
          MEM_freeN(nu1->bp);
          nu1->bp = new_bp;
          nu1->pntsu++;
        }
        BKE_nurb_knot_calc_u(nu1);
        cu->actnu = nu_index;
        cu->actvert = 0;
      }
      else if (last_sel) {
        BPoint *new_bp = (BPoint *)MEM_mallocN((nu1->pntsu + 1) * sizeof(BPoint), __func__);
        ED_curve_bpcpy(editnurb, new_bp, nu1->bp, nu1->pntsu);
        ED_curve_bpcpy(editnurb, new_bp + nu1->pntsu, last_bp, 1);
        last_bp->f1 &= ~SELECT;
        ED_curve_bpcpy(editnurb, new_bp, nu1->bp, nu1->pntsu);
        add_v3_v3((new_bp + nu1->pntsu)->vec, disp_3d);
        MEM_freeN(nu1->bp);
        nu1->bp = new_bp;
        nu1->pntsu++;
        BKE_nurb_knot_calc_u(nu1);
        cu->actnu = nu_index;
        cu->actvert = nu1->pntsu - 1;
      }
      BKE_curve_nurb_vert_active_validate(cu);
    }
    nu_index++;
  }
}

/**
 * Deselect all vertices that are not endpoints.
 */
static void deselect_all_center_vertices(ListBase *nurbs)
{
  LISTBASE_FOREACH (Nurb *, nu1, nurbs) {
    if (nu1->pntsu > 1) {
      int start, end;
      if (is_cyclic(nu1)) {
        start = 0;
        end = nu1->pntsu;
      }
      else {
        start = 1;
        end = nu1->pntsu - 1;
      }
      for (int i = start; i < end; i++) {
        if (nu1->type == CU_BEZIER) {
          BEZT_DESEL_ALL(nu1->bezt + i);
        }
        else {
          (nu1->bp + i)->f1 &= ~SELECT;
        }
      }
    }
  }
}

static bool is_last_bezt(const Nurb *nu, const BezTriple *bezt)
{
  return nu->pntsu > 1 && nu->bezt + nu->pntsu - 1 == bezt && !is_cyclic(nu);
}

/**
 * Add new vertices connected to the selected vertices.
 */
static void extrude_points_from_selected_vertices(const ViewContext *vc,
                                                  const wmEvent *event,
                                                  const int extrude_handle)
{
  Curve *cu = vc->obedit->data;
  ListBase *nurbs = BKE_curve_editNurbs_get(cu);
  float center[3] = {0.0f, 0.0f, 0.0f};
  deselect_all_center_vertices(nurbs);
  bool sel_exists = get_selected_center(nurbs, true, false, center);

  float location[3];
  if (sel_exists) {
    mul_v3_m4v3(location, vc->obedit->obmat, center);
  }
  else {
    copy_v3_v3(location, vc->scene->cursor.location);
  }

  ED_view3d_win_to_3d_int(vc->v3d, vc->region, location, event->mval, location);

  update_location_for_2d_curve(vc, location);
  EditNurb *editnurb = cu->editnurb;

  if (sel_exists) {
    float disp_3d[3];
    sub_v3_v3v3(disp_3d, location, center);
    /* Reimplemenented due to unexpected behavior for extrusion of 2-point spline. */
    extrude_vertices_from_selected_endpoints(editnurb, nurbs, cu, disp_3d);
  }
  else {
    Nurb *old_last_nu = editnurb->nurbs.last;
    ed_editcurve_addvert(cu, editnurb, vc->v3d, location);
    Nurb *new_last_nu = editnurb->nurbs.last;

    if (old_last_nu != new_last_nu) {
      BKE_curve_nurb_vert_active_set(cu,
                                     new_last_nu,
                                     new_last_nu->bezt ? (const void *)new_last_nu->bezt :
                                                         (const void *)new_last_nu->bp);
      new_last_nu->flagu = ~CU_NURB_CYCLIC;
    }
  }

  FOREACH_SELECTED_BEZT_BEGIN (bezt, &cu->editnurb->nurbs) {
    if (bezt) {
      bezt->h1 = extrude_handle;
      bezt->h2 = extrude_handle;
    }
  }
  FOREACH_SELECTED_BEZT_END;
}

/**
 * Check if a spline segment is nearby.
 */
static bool is_spline_nearby(ViewContext *vc,
                             struct wmOperator *op,
                             const wmEvent *event,
                             const float sel_dist)
{
  Curve *cu = vc->obedit->data;
  ListBase *nurbs = BKE_curve_editNurbs_get(cu);
  CutData cd = init_cut_data(event);

  const float mval[2] = {UNPACK2(event->mval)};
  const bool nearby = update_cut_data_for_all_nurbs(vc, nurbs, mval, sel_dist, &cd);

  if (nearby) {
    if (cd.nurb && (cd.nurb->type == CU_BEZIER) && RNA_boolean_get(op->ptr, "move_segment")) {
      MoveSegmentData *seg_data;
      CurvePenData *cpd = (CurvePenData *)(op->customdata);
      cpd->msd = seg_data = MEM_callocN(sizeof(MoveSegmentData), __func__);
      seg_data->bezt_index = cd.bezt_index;
      seg_data->nu = cd.nurb;
      seg_data->t = cd.parameter;
    }
    return true;
  }
  return false;
}

static void move_segment(ViewContext *vc, MoveSegmentData *seg_data, const wmEvent *event)
{
  Nurb *nu = seg_data->nu;
  BezTriple *bezt1 = nu->bezt + seg_data->bezt_index;
  BezTriple *bezt2 = BKE_nurb_bezt_get_next(nu, bezt1);

  int h1 = 2, h2 = 0;
  if (bezt1->hide) {
    if (bezt2->hide) {
      return;
    }
    /*
     * Swap bezt1 and bezt2 in all calculations if only bezt2 is visible.
     * (The first point needs to be visible for the calculations of the second point to be valid)
     */
    BezTriple *temp_bezt = bezt2;
    bezt2 = bezt1;
    bezt1 = temp_bezt;
    h1 = 0, h2 = 2;
  }

  const float t = max_ff(min_ff(seg_data->t, 0.9f), 0.1f);
  const float t_sq = t * t;
  const float t_cu = t_sq * t;
  const float one_minus_t = 1 - t;
  const float one_minus_t_sq = one_minus_t * one_minus_t;
  const float one_minus_t_cu = one_minus_t_sq * one_minus_t;

  float mouse_3d[3];
  float depth[3];
  /* Use the center of the spline segment as depth. */
  get_bezier_interpolated_point(bezt1, bezt2, t, depth);
  screenspace_to_worldspace_int(vc, event->mval, depth, mouse_3d);

  /*
   * Equation of Bezier Curve
   *      => B(t) = (1-t)^3 * P0 + 3(1-t)^2 * t * P1 + 3(1-t) * t^2 * P2 + t^3 * P3
   *
   * Mouse location (Say Pm) should satisfy this equation.
   * Therefore => (1/t - 1) * P1 + P2 = (Pm - (1 - t)^3 * P0 - t^3 * P3) / [3 * (1 - t) * t^2] = k1
   * (in code)
   *
   * Another constraint is required to identify P1 and P2.
   * The constraint used is that the vector between P1 and P2 doesn't change.
   * Therefore => P1 - P2 = k2
   *
   * From the two equations => P1 = t(k1 + k2) and P2 = P1 - K2
   */

  float k1[3];
  const float denom = 3.0f * one_minus_t * t_sq;
  k1[0] = (mouse_3d[0] - one_minus_t_cu * bezt1->vec[1][0] - t_cu * bezt2->vec[1][0]) / denom;
  k1[1] = (mouse_3d[1] - one_minus_t_cu * bezt1->vec[1][1] - t_cu * bezt2->vec[1][1]) / denom;
  k1[2] = (mouse_3d[2] - one_minus_t_cu * bezt1->vec[1][2] - t_cu * bezt2->vec[1][2]) / denom;

  float k2[3];
  sub_v3_v3v3(k2, bezt1->vec[h1], bezt2->vec[h2]);

  if (!bezt1->hide) {
    /* P1 = t(k1 + k2) */
    add_v3_v3v3(bezt1->vec[h1], k1, k2);
    mul_v3_fl(bezt1->vec[h1], t);

    remove_handle_movement_constraints(bezt1, true, true);

    /* Move opposite handle as well if type is align. */
    if (bezt1->h1 == HD_ALIGN) {
      float handle_vec[3];
      sub_v3_v3v3(handle_vec, bezt1->vec[1], bezt1->vec[h1]);
      normalize_v3_length(handle_vec, len_v3v3(bezt1->vec[1], bezt1->vec[h2]));
      add_v3_v3v3(bezt1->vec[h2], bezt1->vec[1], handle_vec);
    }
  }

  if (!bezt2->hide) {
    /* P2 = P1 - K2 */
    sub_v3_v3v3(bezt2->vec[h2], bezt1->vec[h1], k2);

    remove_handle_movement_constraints(bezt2, true, true);

    /* Move opposite handle as well if type is align. */
    if (bezt2->h2 == HD_ALIGN) {
      float handle_vec[3];
      sub_v3_v3v3(handle_vec, bezt2->vec[1], bezt2->vec[h2]);
      normalize_v3_length(handle_vec, len_v3v3(bezt2->vec[1], bezt2->vec[h1]));
      add_v3_v3v3(bezt2->vec[h1], bezt2->vec[1], handle_vec);
    }
  }
}

/**
 * Toggle between #HD_FREE and #HD_ALIGN handles of the given #BezTriple
 */
static void toggle_bezt_free_align_handles(BezTriple *bezt)
{
  if (bezt->h1 != HD_FREE || bezt->h2 != HD_FREE) {
    bezt->h1 = bezt->h2 = HD_FREE;
  }
  else {
    bezt->h1 = bezt->h2 = HD_ALIGN;
  }
}

/**
 * Toggle between #HD_FREE and #HD_ALIGN handles of the all selected #BezTriple
 */
static void toggle_sel_bezt_free_align_handles(ListBase *nurbs)
{
  FOREACH_SELECTED_BEZT_BEGIN (bezt, nurbs) {
    toggle_bezt_free_align_handles(bezt);
  }
  FOREACH_SELECTED_BEZT_END;
}

/**
 * If a point is found under mouse, delete point and return true. Else return false.
 */
static bool delete_point_under_mouse(ViewContext *vc, const wmEvent *event)
{
  BezTriple *bezt = NULL;
  BPoint *bp = NULL;
  Nurb *nu = NULL;
  int temp = 0;
  Curve *cu = vc->obedit->data;
  EditNurb *editnurb = cu->editnurb;
  ListBase *nurbs = BKE_curve_editNurbs_get(cu);
  const float mouse_point[2] = {UNPACK2(event->mval)};

  get_closest_vertex_to_point_in_nurbs(vc, nurbs, mouse_point, &nu, &bezt, &bp, &temp);
  const bool found_point = nu != NULL;

  bool deleted = false;
  if (found_point) {
    ED_curve_deselect_all(cu->editnurb);
    if (nu) {
      if (nu->type == CU_BEZIER) {
        BezTriple *next_bezt = BKE_nurb_bezt_get_next(nu, bezt);
        BezTriple *prev_bezt = BKE_nurb_bezt_get_prev(nu, bezt);
        if (next_bezt && prev_bezt) {
          const int bez_index = BKE_curve_nurb_vert_index_get(nu, bezt);
          const uint span_step[2] = {bez_index, bez_index};
          ed_dissolve_bez_segment(prev_bezt, next_bezt, nu, cu, 1, span_step);
        }
        delete_bezt_from_nurb(bezt, nu, editnurb);
      }
      else {
        delete_bp_from_nurb(bp, nu, editnurb);
      }

      if (nu->pntsu == 0) {
        delete_nurb(cu, nu);
        nu = NULL;
      }
      deleted = true;
      cu->actvert = CU_ACT_NONE;
    }
  }

  if (nu && nu->type == CU_BEZIER) {
    BKE_nurb_handles_calc(nu);
  }

  return deleted;
}

static void move_adjacent_handle(ViewContext *vc, const wmEvent *event, ListBase *nurbs)
{
  FOREACH_SELECTED_BEZT_BEGIN (bezt, nurbs) {
    BezTriple *adj_bezt;
    int bezt_idx;
    if (nu->pntsu == 1) {
      continue;
    }
    if (nu->bezt == bezt) {
      adj_bezt = BKE_nurb_bezt_get_next(nu, bezt);
      bezt_idx = 0;
    }
    else if (nu->bezt + nu->pntsu - 1 == bezt) {
      adj_bezt = BKE_nurb_bezt_get_prev(nu, bezt);
      bezt_idx = 2;
    }
    else {
      if (BEZT_ISSEL_IDX(bezt, 0)) {
        adj_bezt = BKE_nurb_bezt_get_prev(nu, bezt);
        bezt_idx = 2;
      }
      else if (BEZT_ISSEL_IDX(bezt, 2)) {
        adj_bezt = BKE_nurb_bezt_get_next(nu, bezt);
        bezt_idx = 0;
      }
      else {
        continue;
      }
    }
    adj_bezt->h1 = adj_bezt->h2 = HD_FREE;

    int displacement[2];
    sub_v2_v2v2_int(displacement, event->xy, event->prev_xy);
    const float disp_fl[2] = {UNPACK2(displacement)};
    move_bezt_handle_or_vertex_by_displacement(
        vc, adj_bezt, bezt_idx, disp_fl, 0.0f, false, false);
    BKE_nurb_handles_calc(nu);
  }
  FOREACH_SELECTED_BEZT_END;
}

/**
 * Close the spline if endpoints are selected consecutively. Return true if cycle was created.
 */
static bool make_cyclic_if_endpoints(ViewContext *vc,
                                     Nurb *sel_nu,
                                     BezTriple *sel_bezt,
                                     BPoint *sel_bp)
{
  if (sel_bezt || (sel_bp && sel_nu->pntsu > 2)) {
    const bool is_bezt_endpoint = ((sel_nu->type == CU_BEZIER) &&
                                   ELEM(sel_bezt, sel_nu->bezt, sel_nu->bezt + sel_nu->pntsu - 1));
    const bool is_bp_endpoint = ((sel_nu->type != CU_BEZIER) &&
                                 ELEM(sel_bp, sel_nu->bp, sel_nu->bp + sel_nu->pntsu - 1));
    if (!(is_bezt_endpoint || is_bp_endpoint)) {
      return false;
    }

    Nurb *nu = NULL;
    BezTriple *bezt = NULL;
    BPoint *bp = NULL;
    Curve *cu = vc->obedit->data;
    int bezt_idx;
    const float mval_fl[2] = {UNPACK2(vc->mval)};

    get_closest_vertex_to_point_in_nurbs(
        vc, &(cu->editnurb->nurbs), mval_fl, &nu, &bezt, &bp, &bezt_idx);

    if (nu == sel_nu &&
        ((nu->type == CU_BEZIER && bezt != sel_bezt &&
          ELEM(bezt, nu->bezt, nu->bezt + nu->pntsu - 1) && bezt_idx == 1) ||
         (nu->type != CU_BEZIER && bp != sel_bp && ELEM(bp, nu->bp, nu->bp + nu->pntsu - 1)))) {
      View3D *v3d = vc->v3d;
      ListBase *nurbs = object_editcurve_get(vc->obedit);
      curve_toggle_cyclic(v3d, nurbs, 0);
      return true;
    }
  }
  return false;
}

static void init_selected_bezt_handles(ListBase *nurbs)
{
  FOREACH_SELECTED_BEZT_BEGIN (bezt, nurbs) {
    bezt->h1 = bezt->h2 = HD_ALIGN;
    copy_v3_v3(bezt->vec[0], bezt->vec[1]);
    copy_v3_v3(bezt->vec[2], bezt->vec[1]);
    BEZT_DESEL_ALL(bezt);
    BEZT_SEL_IDX(bezt, is_last_bezt(nu, bezt) ? 2 : 0);
  }
  FOREACH_SELECTED_BEZT_END;
}

static void toggle_select_bezt(BezTriple *bezt, const int bezt_idx, Curve *cu, Nurb *nu)
{
  if (bezt_idx == 1) {
    if (BEZT_ISSEL_IDX(bezt, 1)) {
      BEZT_DESEL_ALL(bezt);
    }
    else {
      BEZT_SEL_ALL(bezt);
    }
  }
  else {
    if (BEZT_ISSEL_IDX(bezt, bezt_idx)) {
      BEZT_DESEL_IDX(bezt, bezt_idx);
    }
    else {
      BEZT_SEL_IDX(bezt, bezt_idx);
    }
  }

  if (BEZT_ISSEL_ANY(bezt)) {
    BKE_curve_nurb_vert_active_set(cu, nu, bezt);
  }
}

static void toggle_select_bp(BPoint *bp, Curve *cu, Nurb *nu)
{
  if (bp->f1 & SELECT) {
    bp->f1 &= ~SELECT;
  }
  else {
    bp->f1 |= SELECT;
    BKE_curve_nurb_vert_active_set(cu, nu, bp);
  }
}

static void toggle_handle_types(BezTriple *bezt, int bezt_idx, CurvePenData *cpd)
{
  if (bezt_idx == 0) {
    if (bezt->h1 == HD_VECT) {
      bezt->h1 = bezt->h2 = HD_AUTO;
    }
    else {
      bezt->h1 = HD_VECT;
      if (bezt->h2 != HD_VECT) {
        bezt->h2 = HD_FREE;
      }
    }
    cpd->acted = true;
  }
  else if (bezt_idx == 2) {
    if (bezt->h2 == HD_VECT) {
      bezt->h1 = bezt->h2 = HD_AUTO;
    }
    else {
      bezt->h2 = HD_VECT;
      if (bezt->h1 != HD_VECT) {
        bezt->h1 = HD_FREE;
      }
    }
    cpd->acted = true;
  }
}

static void cycle_handles(BezTriple *bezt)
{
  if (bezt->h1 == HD_AUTO) {
    bezt->h1 = bezt->h2 = HD_VECT;
  }
  else if (bezt->h1 == HD_VECT) {
    bezt->h1 = bezt->h2 = HD_ALIGN;
  }
  else if (bezt->h1 == HD_ALIGN) {
    bezt->h1 = bezt->h2 = HD_FREE;
  }
  else {
    bezt->h1 = bezt->h2 = HD_AUTO;
  }
}

enum {
  PEN_MODAL_FREE_ALIGN_TOGGLE = 1,
  PEN_MODAL_MOVE_ADJACENT,
  PEN_MODAL_MOVE_ENTIRE,
  PEN_MODAL_LINK_HANDLES,
  PEN_MODAL_LOCK_ANGLE
};

wmKeyMap *curve_pen_modal_keymap(wmKeyConfig *keyconf)
{
  static const EnumPropertyItem modal_items[] = {
      {PEN_MODAL_FREE_ALIGN_TOGGLE,
       "FREE_ALIGN_TOGGLE",
       0,
       "Free-Align Toggle",
       "Move handle of newly added point freely"},
      {PEN_MODAL_MOVE_ADJACENT,
       "MOVE_ADJACENT",
       0,
       "Move Adjacent Handle",
       "Move the closer handle of the adjacent vertex"},
      {PEN_MODAL_MOVE_ENTIRE,
       "MOVE_ENTIRE",
       0,
       "Move Entire Point",
       "Move the entire point using its handles"},
      {PEN_MODAL_LINK_HANDLES,
       "LINK_HANDLES",
       0,
       "Link Handles",
       "Mirror the movement of one handle onto the other"},
      {PEN_MODAL_LOCK_ANGLE,
       "LOCK_ANGLE",
       0,
       "Lock Angle",
       "Move the handle along its current angle"},
      {0, NULL, 0, NULL, NULL},
  };

  wmKeyMap *keymap = WM_modalkeymap_find(keyconf, "Curve Pen Modal Map");

  /* This function is called for each space-type, only needs to add map once. */
  if (keymap && keymap->modal_items) {
    return NULL;
  }

  keymap = WM_modalkeymap_ensure(keyconf, "Curve Pen Modal Map", modal_items);

  WM_modalkeymap_assign(keymap, "CURVE_OT_pen");

  return keymap;
}

static int curve_pen_modal(bContext *C, wmOperator *op, const wmEvent *event)
{
  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
  ViewContext vc;
  Object *obedit = CTX_data_edit_object(C);

  ED_view3d_viewcontext_init(C, &vc, depsgraph);
  Curve *cu = vc.obedit->data;
  ListBase *nurbs = &cu->editnurb->nurbs;
  const float threshold_dist_px = ED_view3d_select_dist_px() * SEL_DIST_FACTOR;

  BezTriple *bezt = NULL;
  BPoint *bp = NULL;
  Nurb *nu = NULL;

  const struct SelectPick_Params params = {
      .sel_op = SEL_OP_SET,
      .deselect_all = false,
  };

  int ret = OPERATOR_RUNNING_MODAL;

  /* Distance threshold for mouse clicks to affect the spline or its points */
  const float mval_fl[2] = {UNPACK2(event->mval)};

  const bool extrude_point = RNA_boolean_get(op->ptr, "extrude_point");
  const bool delete_point = RNA_boolean_get(op->ptr, "delete_point");
  const bool insert_point = RNA_boolean_get(op->ptr, "insert_point");
  const bool move_seg = RNA_boolean_get(op->ptr, "move_segment");
  const bool select_point = RNA_boolean_get(op->ptr, "select_point");
  const bool move_point = RNA_boolean_get(op->ptr, "move_point");
  const bool close_spline = RNA_boolean_get(op->ptr, "close_spline");
  const bool toggle_vector = RNA_boolean_get(op->ptr, "toggle_vector");
  const bool cycle_handle_type = RNA_boolean_get(op->ptr, "cycle_handle_type");
  const int close_spline_method = RNA_enum_get(op->ptr, "close_spline_method");
  const int extrude_handle = RNA_enum_get(op->ptr, "extrude_handle");

  CurvePenData *cpd;
  if (op->customdata == NULL) {
    op->customdata = cpd = MEM_callocN(sizeof(CurvePenData), __func__);
  }
  else {
    cpd = (CurvePenData *)(op->customdata);
    cpd->select_multi = event->modifier == KM_SHIFT;
  }

  if (event->type == EVT_MODAL_MAP) {
    if (cpd->msd == NULL) {
      if (event->val == PEN_MODAL_FREE_ALIGN_TOGGLE) {
        toggle_sel_bezt_free_align_handles(nurbs);
        cpd->link_handles = false;
      }
      else if (event->val == PEN_MODAL_LINK_HANDLES) {
        cpd->link_handles = !cpd->link_handles;
        if (cpd->link_handles) {
          move_all_selected_points(&vc, event, cpd, nurbs, false);
        }
      }
      else if (event->val == PEN_MODAL_MOVE_ENTIRE) {
        cpd->move_entire = !cpd->move_entire;
      }
      else if (event->val == PEN_MODAL_MOVE_ADJACENT) {
        cpd->move_adjacent = !cpd->move_adjacent;
      }
      else if (event->val == PEN_MODAL_LOCK_ANGLE) {
        cpd->lock_angle = !cpd->lock_angle;
      }
    }
    else {
      if (event->val == PEN_MODAL_FREE_ALIGN_TOGGLE) {
        BezTriple *bezt1 = cpd->msd->nu->bezt + cpd->msd->bezt_index;
        BezTriple *bezt2 = BKE_nurb_bezt_get_next(cpd->msd->nu, bezt1);
        toggle_bezt_free_align_handles(bezt1);
        toggle_bezt_free_align_handles(bezt2);
      }
    }
  }

  if (ISMOUSE_MOTION(event->type)) {
    /* Check if dragging */
    if (!cpd->dragging && WM_event_drag_test(event, event->prev_press_xy)) {
      cpd->dragging = true;

      if (cpd->new_point) {
        init_selected_bezt_handles(nurbs);
      }
    }

    if (cpd->dragging) {
      if (cpd->spline_nearby && move_seg && cpd->msd != NULL) {
        MoveSegmentData *seg_data = cpd->msd;
        move_segment(&vc, seg_data, event);
        cpd->acted = true;
        if (seg_data->nu && seg_data->nu->type == CU_BEZIER) {
          BKE_nurb_handles_calc(seg_data->nu);
        }
      }
      else if (cpd->move_adjacent) {
        move_adjacent_handle(&vc, event, nurbs);
        cpd->acted = true;
      }
      else if (cpd->new_point || (move_point && !cpd->spline_nearby && cpd->found_point)) {
        /* Move only the bezt handles if it's a new point. */
        move_all_selected_points(&vc, event, cpd, nurbs, cpd->new_point);
        cpd->acted = true;
      }
    }
  }
  else if (ELEM(event->type, LEFTMOUSE)) {
    if (ELEM(event->val, KM_RELEASE, KM_DBL_CLICK)) {
      if (delete_point && !cpd->new_point && !cpd->dragging) {
        if (ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, false, &params)) {
          cpd->acted = delete_point_under_mouse(&vc, event);
        }
      }

      /* Close spline on Click, if enabled. */
      if (!cpd->acted && close_spline && close_spline_method == ON_CLICK && cpd->found_point &&
          !cpd->dragging) {
        if (cpd->nu && !is_cyclic(cpd->nu)) {
          copy_v2_v2_int(vc.mval, event->mval);
          cpd->acted = make_cyclic_if_endpoints(&vc, cpd->nu, cpd->bezt, cpd->bp);
        }
      }

      if (!cpd->acted && (insert_point || extrude_point) && cpd->spline_nearby && !cpd->dragging) {
        if (insert_point) {
          insert_point_to_segment(&vc, event);
          cpd->new_point = true;
          cpd->acted = true;
        }
        else if (extrude_point) {
          extrude_points_from_selected_vertices(&vc, event, extrude_handle);
          cpd->acted = true;
        }
      }

      if (!cpd->acted && toggle_vector) {
        int bezt_idx;
        get_closest_vertex_to_point_in_nurbs(&vc, nurbs, mval_fl, &nu, &bezt, &bp, &bezt_idx);
        if (bezt) {
          if (bezt_idx == 1 && cycle_handle_type) {
            cycle_handles(bezt);
            cpd->acted = true;
          }
          else {
            toggle_handle_types(bezt, bezt_idx, cpd);
          }

          if (nu && nu->type == CU_BEZIER) {
            BKE_nurb_handles_calc(nu);
          }
        }
      }

      if (!cpd->selection_made && !cpd->acted) {
        if (cpd->select_multi) {
          int bezt_idx;
          get_closest_vertex_to_point_in_nurbs(&vc, nurbs, mval_fl, &nu, &bezt, &bp, &bezt_idx);
          if (bezt) {
            toggle_select_bezt(bezt, bezt_idx, cu, nu);
          }
          else if (bp) {
            toggle_select_bp(bp, cu, nu);
          }
          else {
            ED_curve_deselect_all(cu->editnurb);
          }
        }
        else if (select_point) {
          ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, false, &params);
        }
      }

      if (cpd->msd != NULL) {
        MEM_freeN(cpd->msd);
      }
      MEM_freeN(cpd);
      ret = OPERATOR_FINISHED;
    }
  }

  WM_event_add_notifier(C, NC_GEOM | ND_DATA, obedit->data);
  WM_event_add_notifier(C, NC_GEOM | ND_SELECT, obedit->data);
  DEG_id_tag_update(obedit->data, 0);

  return ret;
}

static int curve_pen_invoke(bContext *C, wmOperator *op, const wmEvent *event)
{
  ViewContext vc;
  ED_view3d_viewcontext_init(C, &vc, CTX_data_ensure_evaluated_depsgraph(C));
  Curve *cu = vc.obedit->data;
  ListBase *nurbs = &cu->editnurb->nurbs;

  BezTriple *bezt = NULL;
  BPoint *bp = NULL;
  Nurb *nu = NULL;

  CurvePenData *cpd;
  op->customdata = cpd = MEM_callocN(sizeof(CurvePenData), __func__);

  /* Distance threshold for mouse clicks to affect the spline or its points */
  const float mval_fl[2] = {UNPACK2(event->mval)};
  const float threshold_dist_px = ED_view3d_select_dist_px() * SEL_DIST_FACTOR;

  const bool extrude_point = RNA_boolean_get(op->ptr, "extrude_point");
  const bool insert_point = RNA_boolean_get(op->ptr, "insert_point");
  const bool move_seg = RNA_boolean_get(op->ptr, "move_segment");
  const bool move_point = RNA_boolean_get(op->ptr, "move_point");
  const bool close_spline = RNA_boolean_get(op->ptr, "close_spline");
  const int close_spline_method = RNA_enum_get(op->ptr, "close_spline_method");
  const int extrude_handle = RNA_enum_get(op->ptr, "extrude_handle");

  if (ELEM(event->type, LEFTMOUSE) && ELEM(event->val, KM_PRESS, KM_DBL_CLICK)) {
    /* Get the details of points selected at the start of the operation.
     * Used for closing the spline when endpoints are clicked consecutively and for selecting a
     * single point. */
    get_first_selected_point(cu, vc.v3d, &nu, &bezt, &bp);
    cpd->nu = nu;
    cpd->bezt = bezt;
    cpd->bp = bp;

    /* Get the details of the vertex closest to the mouse at the start of the operation. */
    Nurb *nu1;
    BezTriple *bezt1;
    BPoint *bp1;
    int bezt_idx = 0;
    cpd->found_point = get_closest_vertex_to_point_in_nurbs(
        &vc, nurbs, mval_fl, &nu1, &bezt1, &bp1, &bezt_idx);

    if (move_point && nu1 && !nu1->hide &&
        (bezt || (bezt1 && !BEZT_ISSEL_IDX(bezt1, bezt_idx)) || (bp1 && !(bp1->f1 & SELECT)))) {
      /* Select the closest bezt or bp. */
      ED_curve_deselect_all(cu->editnurb);
      if (bezt1) {
        if (bezt_idx == 1) {
          BEZT_SEL_ALL(bezt1);
        }
        else {
          BEZT_SEL_IDX(bezt1, bezt_idx);
        }
        BKE_curve_nurb_vert_active_set(cu, nu1, bezt1);
      }
      else if (bp1) {
        bp1->f1 |= SELECT;
        BKE_curve_nurb_vert_active_set(cu, nu1, bp1);
      }

      cpd->selection_made = true;
    }
    if (cpd->found_point) {
      /* Close the spline on press. */
      if (close_spline && close_spline_method == ON_PRESS && cpd->nu && !is_cyclic(cpd->nu)) {
        copy_v2_v2_int(vc.mval, event->mval);
        cpd->new_point = cpd->acted = cpd->link_handles = make_cyclic_if_endpoints(
            &vc, cpd->nu, cpd->bezt, cpd->bp);
      }
    }
    else if (!cpd->acted) {
      if (is_spline_nearby(&vc, op, event, threshold_dist_px)) {
        cpd->spline_nearby = true;

        /* If move segment is disabled, then insert point on key press and set
         * "new_point" to true so that the new point's handles can be controlled. */
        if (insert_point && !move_seg) {
          insert_point_to_segment(&vc, event);
          cpd->new_point = cpd->acted = cpd->link_handles = true;
        }
      }
      else if (extrude_point) {
        extrude_points_from_selected_vertices(&vc, event, extrude_handle);
        cpd->new_point = cpd->acted = cpd->link_handles = true;
      }
    }
  }
  WM_event_add_modal_handler(C, op);

  return OPERATOR_RUNNING_MODAL;
}

void CURVE_OT_pen(wmOperatorType *ot)
{
  /* identifiers */
  ot->name = "Curve Pen";
  ot->idname = "CURVE_OT_pen";
  ot->description = "Construct and edit splines";

  /* api callbacks */
  ot->invoke = curve_pen_invoke;
  ot->modal = curve_pen_modal;
  ot->poll = ED_operator_view3d_active;

  /* flags */
  ot->flag = OPTYPE_UNDO;

  /* properties */
  WM_operator_properties_mouse_select(ot);

  RNA_def_boolean(ot->srna,
                  "extrude_point",
                  false,
                  "Extrude Point",
                  "Add a point connected to the last selected point");
  RNA_def_enum(ot->srna,
               "extrude_handle",
               prop_handle_types,
               HD_VECT,
               "Extrude Handle Type",
               "Type of the extruded handle");
  RNA_def_boolean(ot->srna, "delete_point", false, "Delete Point", "Delete an existing point");
  RNA_def_boolean(
      ot->srna, "insert_point", false, "Insert Point", "Insert Point into a curve segment");
  RNA_def_boolean(ot->srna, "move_segment", false, "Move Segment", "Delete an existing point");
  RNA_def_boolean(
      ot->srna, "select_point", false, "Select Point", "Select a point or its handles");
  RNA_def_boolean(ot->srna, "move_point", false, "Move Point", "Move a point or its handles");
  RNA_def_boolean(ot->srna,
                  "close_spline",
                  true,
                  "Close Spline",
                  "Make a spline cyclic by clicking endpoints");
  RNA_def_enum(ot->srna,
               "close_spline_method",
               prop_close_spline_method,
               OFF,
               "Close Spline Method",
               "The condition for close spline to activate");
  RNA_def_boolean(
      ot->srna, "toggle_vector", false, "Toggle Vector", "Toggle between Vector and Auto handles");
  RNA_def_boolean(ot->srna,
                  "cycle_handle_type",
                  false,
                  "Cycle Handle Type",
                  "Cycle between all four handle types");
}