/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup edcurve
 */

#include "DNA_object_types.h"
#include "DNA_scene_types.h"

#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_math.h"
#include "BLI_mempool.h"

#include "BKE_context.h"
#include "BKE_curve.h"
#include "BKE_fcurve.h"
#include "BKE_report.h"

#include "DEG_depsgraph.h"

#include "WM_api.h"
#include "WM_types.h"

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

#include "GPU_batch.h"
#include "GPU_batch_presets.h"
#include "GPU_immediate.h"
#include "GPU_immediate_util.h"
#include "GPU_matrix.h"
#include "GPU_state.h"

#include "curve_intern.h"

#include "UI_resources.h"

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

#include "RNA_enum_types.h"

#define USE_SPLINE_FIT

#ifdef USE_SPLINE_FIT
#  include "curve_fit_nd.h"
#endif

/* Distance between input samples */
#define STROKE_SAMPLE_DIST_MIN_PX 1
#define STROKE_SAMPLE_DIST_MAX_PX 3

/* Distance between start/end points to consider cyclic */
#define STROKE_CYCLIC_DIST_PX 8

/* -------------------------------------------------------------------- */
/** \name StrokeElem / #RNA_OperatorStrokeElement Conversion Functions
 * \{ */

struct StrokeElem {
  float mval[2];
  float location_world[3];
  float location_local[3];

  /* surface normal, may be zero'd */
  float normal_world[3];
  float normal_local[3];

  float pressure;
};

struct CurveDrawData {
  short init_event_type;
  short curve_type;

  /* projecting 2D into 3D space */
  struct {
    /* use a plane or project to the surface */
    bool use_plane;
    float plane[4];

    /* use 'rv3d->depths', note that this will become 'damaged' while drawing, but that's OK. */
    bool use_depth;

    /* offset projection by this value */
    bool use_offset;
    float offset[3]; /* world-space */
    float surface_offset;
    bool use_surface_offset_absolute;
  } project;

  /* cursor sampling */
  struct {
    /* use substeps, needed for nicely interpolating depth */
    bool use_substeps;
  } sample;

  struct {
    float min, max, range;
  } radius;

  struct {
    float mouse[2];
    /* Used in case we can't calculate the depth. */
    float location_world[3];

    float location_world_valid[3];

    const struct StrokeElem *selem;
  } prev;

  ViewContext vc;
  ViewDepths *depths;
  enum {
    CURVE_DRAW_IDLE = 0,
    CURVE_DRAW_PAINTING = 1,
  } state;

  /* StrokeElem */
  BLI_mempool *stroke_elem_pool;

  void *draw_handle_view;
};

static float stroke_elem_radius_from_pressure(const struct CurveDrawData *cdd,
                                              const float pressure)
{
  const Curve *cu = cdd->vc.obedit->data;
  return ((pressure * cdd->radius.range) + cdd->radius.min) * cu->bevel_radius;
}

static float stroke_elem_radius(const struct CurveDrawData *cdd, const struct StrokeElem *selem)
{
  return stroke_elem_radius_from_pressure(cdd, selem->pressure);
}

static void stroke_elem_pressure_set(const struct CurveDrawData *cdd,
                                     struct StrokeElem *selem,
                                     float pressure)
{
  if ((cdd->project.surface_offset != 0.0f) && !cdd->project.use_surface_offset_absolute &&
      !is_zero_v3(selem->normal_local)) {
    const float adjust = stroke_elem_radius_from_pressure(cdd, pressure) -
                         stroke_elem_radius_from_pressure(cdd, selem->pressure);
    madd_v3_v3fl(selem->location_local, selem->normal_local, adjust);
    mul_v3_m4v3(selem->location_world, cdd->vc.obedit->obmat, selem->location_local);
  }
  selem->pressure = pressure;
}

static void stroke_elem_interp(struct StrokeElem *selem_out,
                               const struct StrokeElem *selem_a,
                               const struct StrokeElem *selem_b,
                               float t)
{
  interp_v2_v2v2(selem_out->mval, selem_a->mval, selem_b->mval, t);
  interp_v3_v3v3(selem_out->location_world, selem_a->location_world, selem_b->location_world, t);
  interp_v3_v3v3(selem_out->location_local, selem_a->location_local, selem_b->location_local, t);
  selem_out->pressure = interpf(selem_a->pressure, selem_b->pressure, t);
}

/**
 * Sets the depth from #StrokeElem.mval
 */
static bool stroke_elem_project(const struct CurveDrawData *cdd,
                                const int mval_i[2],
                                const float mval_fl[2],
                                float surface_offset,
                                const float radius,
                                float r_location_world[3],
                                float r_normal_world[3])
{
  ARegion *region = cdd->vc.region;

  bool is_location_world_set = false;

  /* project to 'location_world' */
  if (cdd->project.use_plane) {
    /* get the view vector to 'location' */
    if (ED_view3d_win_to_3d_on_plane(
            region, cdd->project.plane, mval_fl, true, r_location_world)) {
      if (r_normal_world) {
        zero_v3(r_normal_world);
      }
      is_location_world_set = true;
    }
  }
  else {
    const ViewDepths *depths = cdd->depths;
    if (depths && ((uint)mval_i[0] < depths->w) && ((uint)mval_i[1] < depths->h)) {
      float depth_fl = 1.0f;
      ED_view3d_depth_read_cached(depths, mval_i, 0, &depth_fl);
      const double depth = (double)depth_fl;
      if ((depth > depths->depth_range[0]) && (depth < depths->depth_range[1])) {
        if (ED_view3d_depth_unproject_v3(region, mval_i, depth, r_location_world)) {
          is_location_world_set = true;
          if (r_normal_world) {
            zero_v3(r_normal_world);
          }

          if (surface_offset != 0.0f) {
            const float offset = cdd->project.use_surface_offset_absolute ? 1.0f : radius;
            float normal[3];
            if (ED_view3d_depth_read_cached_normal(region, depths, mval_i, normal)) {
              madd_v3_v3fl(r_location_world, normal, offset * surface_offset);
              if (r_normal_world) {
                copy_v3_v3(r_normal_world, normal);
              }
            }
          }
        }
      }
    }
  }

  if (is_location_world_set) {
    if (cdd->project.use_offset) {
      add_v3_v3(r_location_world, cdd->project.offset);
    }
  }

  return is_location_world_set;
}

static bool stroke_elem_project_fallback(const struct CurveDrawData *cdd,
                                         const int mval_i[2],
                                         const float mval_fl[2],
                                         const float surface_offset,
                                         const float radius,
                                         const float location_fallback_depth[3],
                                         float r_location_world[3],
                                         float r_location_local[3],
                                         float r_normal_world[3],
                                         float r_normal_local[3])
{
  bool is_depth_found = stroke_elem_project(
      cdd, mval_i, mval_fl, surface_offset, radius, r_location_world, r_normal_world);
  if (is_depth_found == false) {
    ED_view3d_win_to_3d(
        cdd->vc.v3d, cdd->vc.region, location_fallback_depth, mval_fl, r_location_world);
    zero_v3(r_normal_local);
  }
  mul_v3_m4v3(r_location_local, cdd->vc.obedit->imat, r_location_world);

  if (!is_zero_v3(r_normal_world)) {
    copy_v3_v3(r_normal_local, r_normal_world);
    mul_transposed_mat3_m4_v3(cdd->vc.obedit->obmat, r_normal_local);
    normalize_v3(r_normal_local);
  }
  else {
    zero_v3(r_normal_local);
  }

  return is_depth_found;
}

/**
 * \note #StrokeElem.mval & #StrokeElem.pressure must be set first.
 */
static bool stroke_elem_project_fallback_elem(const struct CurveDrawData *cdd,
                                              const float location_fallback_depth[3],
                                              struct StrokeElem *selem)
{
  const int mval_i[2] = {UNPACK2(selem->mval)};
  const float radius = stroke_elem_radius(cdd, selem);
  return stroke_elem_project_fallback(cdd,
                                      mval_i,
                                      selem->mval,
                                      cdd->project.surface_offset,
                                      radius,
                                      location_fallback_depth,
                                      selem->location_world,
                                      selem->location_local,
                                      selem->normal_world,
                                      selem->normal_local);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Operator/Stroke Conversion
 * \{ */

static void curve_draw_stroke_to_operator_elem(wmOperator *op, const struct StrokeElem *selem)
{
  PointerRNA itemptr;
  RNA_collection_add(op->ptr, "stroke", &itemptr);

  RNA_float_set_array(&itemptr, "mouse", selem->mval);
  RNA_float_set_array(&itemptr, "location", selem->location_world);
  RNA_float_set(&itemptr, "pressure", selem->pressure);
}

static void curve_draw_stroke_from_operator_elem(wmOperator *op, PointerRNA *itemptr)
{
  struct CurveDrawData *cdd = op->customdata;

  struct StrokeElem *selem = BLI_mempool_calloc(cdd->stroke_elem_pool);

  RNA_float_get_array(itemptr, "mouse", selem->mval);
  RNA_float_get_array(itemptr, "location", selem->location_world);
  mul_v3_m4v3(selem->location_local, cdd->vc.obedit->imat, selem->location_world);
  selem->pressure = RNA_float_get(itemptr, "pressure");
}

static void curve_draw_stroke_to_operator(wmOperator *op)
{
  struct CurveDrawData *cdd = op->customdata;

  BLI_mempool_iter iter;
  const struct StrokeElem *selem;

  BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
  for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
    curve_draw_stroke_to_operator_elem(op, selem);
  }
}

static void curve_draw_stroke_from_operator(wmOperator *op)
{
  RNA_BEGIN (op->ptr, itemptr, "stroke") {
    curve_draw_stroke_from_operator_elem(op, &itemptr);
  }
  RNA_END;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Operator Callbacks & Helpers
 * \{ */

static void curve_draw_stroke_3d(const struct bContext *UNUSED(C),
                                 ARegion *UNUSED(region),
                                 void *arg)
{
  wmOperator *op = arg;
  struct CurveDrawData *cdd = op->customdata;

  const int stroke_len = BLI_mempool_len(cdd->stroke_elem_pool);

  if (stroke_len == 0) {
    return;
  }

  Object *obedit = cdd->vc.obedit;
  Curve *cu = obedit->data;

  if (cu->bevel_radius > 0.0f) {
    BLI_mempool_iter iter;
    const struct StrokeElem *selem;

    const float location_zero[3] = {0};
    const float *location_prev = location_zero;

    float color[3];
    UI_GetThemeColor3fv(TH_WIRE, color);

    GPUBatch *sphere = GPU_batch_preset_sphere(0);
    GPU_batch_program_set_builtin(sphere, GPU_SHADER_3D_UNIFORM_COLOR);
    GPU_batch_uniform_3fv(sphere, "color", color);

    /* scale to edit-mode space */
    GPU_matrix_push();
    GPU_matrix_mul(obedit->obmat);

    BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
    for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
      GPU_matrix_translate_3f(selem->location_local[0] - location_prev[0],
                              selem->location_local[1] - location_prev[1],
                              selem->location_local[2] - location_prev[2]);

      const float radius = stroke_elem_radius(cdd, selem);

      GPU_matrix_push();
      GPU_matrix_scale_1f(radius);
      GPU_batch_draw(sphere);
      GPU_matrix_pop();

      location_prev = selem->location_local;
    }

    GPU_matrix_pop();
  }

  if (stroke_len > 1) {
    float(*coord_array)[3] = MEM_mallocN(sizeof(*coord_array) * stroke_len, __func__);

    {
      BLI_mempool_iter iter;
      const struct StrokeElem *selem;
      int i;
      BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
      for (selem = BLI_mempool_iterstep(&iter), i = 0; selem;
           selem = BLI_mempool_iterstep(&iter), i++) {
        copy_v3_v3(coord_array[i], selem->location_world);
      }
    }

    {
      GPUVertFormat *format = immVertexFormat();
      uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
      immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);

      GPU_depth_test(GPU_DEPTH_NONE);
      GPU_blend(GPU_BLEND_ALPHA);
      GPU_line_smooth(true);
      GPU_line_width(3.0f);

      imm_cpack(0x0);
      immBegin(GPU_PRIM_LINE_STRIP, stroke_len);
      for (int i = 0; i < stroke_len; i++) {
        immVertex3fv(pos, coord_array[i]);
      }
      immEnd();

      GPU_line_width(1.0f);

      imm_cpack(0xffffffff);
      immBegin(GPU_PRIM_LINE_STRIP, stroke_len);
      for (int i = 0; i < stroke_len; i++) {
        immVertex3fv(pos, coord_array[i]);
      }
      immEnd();

      /* Reset defaults */
      GPU_depth_test(GPU_DEPTH_LESS_EQUAL);
      GPU_blend(GPU_BLEND_NONE);
      GPU_line_smooth(false);

      immUnbindProgram();
    }

    MEM_freeN(coord_array);
  }
}

static void curve_draw_event_add(wmOperator *op, const wmEvent *event)
{
  struct CurveDrawData *cdd = op->customdata;
  Object *obedit = cdd->vc.obedit;

  invert_m4_m4(obedit->imat, obedit->obmat);

  struct StrokeElem *selem = BLI_mempool_calloc(cdd->stroke_elem_pool);

  ARRAY_SET_ITEMS(selem->mval, event->mval[0], event->mval[1]);

  /* handle pressure sensitivity (which is supplied by tablets or otherwise 1.0) */
  selem->pressure = event->tablet.pressure;

  bool is_depth_found = stroke_elem_project_fallback_elem(
      cdd, cdd->prev.location_world_valid, selem);

  if (is_depth_found) {
    /* use the depth if a fallback wasn't used */
    copy_v3_v3(cdd->prev.location_world_valid, selem->location_world);
  }
  copy_v3_v3(cdd->prev.location_world, selem->location_world);

  float len_sq = len_squared_v2v2(cdd->prev.mouse, selem->mval);
  copy_v2_v2(cdd->prev.mouse, selem->mval);

  if (cdd->sample.use_substeps && cdd->prev.selem) {
    const struct StrokeElem selem_target = *selem;
    struct StrokeElem *selem_new_last = selem;
    if (len_sq >= square_f(STROKE_SAMPLE_DIST_MAX_PX)) {
      int n = (int)ceil(sqrt((double)len_sq)) / STROKE_SAMPLE_DIST_MAX_PX;

      for (int i = 1; i < n; i++) {
        struct StrokeElem *selem_new = selem_new_last;
        stroke_elem_interp(selem_new, cdd->prev.selem, &selem_target, (float)i / n);

        const bool is_depth_found_substep = stroke_elem_project_fallback_elem(
            cdd, cdd->prev.location_world_valid, selem_new);
        if (is_depth_found == false) {
          if (is_depth_found_substep) {
            copy_v3_v3(cdd->prev.location_world_valid, selem_new->location_world);
          }
        }

        selem_new_last = BLI_mempool_calloc(cdd->stroke_elem_pool);
      }
    }
    selem = selem_new_last;
    *selem_new_last = selem_target;
  }

  cdd->prev.selem = selem;

  ED_region_tag_redraw(cdd->vc.region);
}

static void curve_draw_event_add_first(wmOperator *op, const wmEvent *event)
{
  struct CurveDrawData *cdd = op->customdata;
  const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

  /* add first point */
  curve_draw_event_add(op, event);

  if ((cps->depth_mode == CURVE_PAINT_PROJECT_SURFACE) && cdd->project.use_depth &&
      (cps->flag & CURVE_PAINT_FLAG_DEPTH_STROKE_ENDPOINTS)) {
    RegionView3D *rv3d = cdd->vc.rv3d;

    cdd->project.use_depth = false;
    cdd->project.use_plane = true;

    float normal[3] = {0.0f};
    if (ELEM(cps->surface_plane,
             CURVE_PAINT_SURFACE_PLANE_NORMAL_VIEW,
             CURVE_PAINT_SURFACE_PLANE_NORMAL_SURFACE)) {
      if (ED_view3d_depth_read_cached_normal(cdd->vc.region, cdd->depths, event->mval, normal)) {
        if (cps->surface_plane == CURVE_PAINT_SURFACE_PLANE_NORMAL_VIEW) {
          float cross_a[3], cross_b[3];
          cross_v3_v3v3(cross_a, rv3d->viewinv[2], normal);
          cross_v3_v3v3(cross_b, normal, cross_a);
          copy_v3_v3(normal, cross_b);
        }
      }
    }

    /* CURVE_PAINT_SURFACE_PLANE_VIEW or fallback */
    if (is_zero_v3(normal)) {
      copy_v3_v3(normal, rv3d->viewinv[2]);
    }

    normalize_v3_v3(cdd->project.plane, normal);
    cdd->project.plane[3] = -dot_v3v3(cdd->project.plane, cdd->prev.location_world_valid);

    /* Special case for when we only have offset applied on the first-hit,
     * the remaining stroke must be offset too. */
    if (cdd->project.surface_offset != 0.0f) {
      const float mval_fl[2] = {UNPACK2(event->mval)};

      float location_no_offset[3];

      if (stroke_elem_project(cdd, event->mval, mval_fl, 0.0f, 0.0f, location_no_offset, NULL)) {
        sub_v3_v3v3(cdd->project.offset, cdd->prev.location_world_valid, location_no_offset);
        if (!is_zero_v3(cdd->project.offset)) {
          cdd->project.use_offset = true;
        }
      }
    }
    /* end special case */
  }

  cdd->init_event_type = event->type;
  cdd->state = CURVE_DRAW_PAINTING;
}

static bool curve_draw_init(bContext *C, wmOperator *op, bool is_invoke)
{
  BLI_assert(op->customdata == NULL);

  struct CurveDrawData *cdd = MEM_callocN(sizeof(*cdd), __func__);
  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);

  if (is_invoke) {
    ED_view3d_viewcontext_init(C, &cdd->vc, depsgraph);
    if (ELEM(NULL, cdd->vc.region, cdd->vc.rv3d, cdd->vc.v3d, cdd->vc.win, cdd->vc.scene)) {
      MEM_freeN(cdd);
      BKE_report(op->reports, RPT_ERROR, "Unable to access 3D viewport");
      return false;
    }
  }
  else {
    cdd->vc.bmain = CTX_data_main(C);
    cdd->vc.depsgraph = depsgraph;
    cdd->vc.scene = CTX_data_scene(C);
    cdd->vc.view_layer = CTX_data_view_layer(C);
    cdd->vc.obedit = CTX_data_edit_object(C);
  }

  op->customdata = cdd;

  const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

  cdd->curve_type = cps->curve_type;

  cdd->radius.min = cps->radius_min;
  cdd->radius.max = cps->radius_max;
  cdd->radius.range = cps->radius_max - cps->radius_min;
  cdd->project.surface_offset = cps->surface_offset;
  cdd->project.use_surface_offset_absolute = (cps->flag &
                                              CURVE_PAINT_FLAG_DEPTH_STROKE_OFFSET_ABS) != 0;

  cdd->stroke_elem_pool = BLI_mempool_create(
      sizeof(struct StrokeElem), 0, 512, BLI_MEMPOOL_ALLOW_ITER);

  return true;
}

static void curve_draw_exit(wmOperator *op)
{
  struct CurveDrawData *cdd = op->customdata;
  if (cdd) {
    if (cdd->draw_handle_view) {
      ED_region_draw_cb_exit(cdd->vc.region->type, cdd->draw_handle_view);
      WM_cursor_modal_restore(cdd->vc.win);
    }

    if (cdd->stroke_elem_pool) {
      BLI_mempool_destroy(cdd->stroke_elem_pool);
    }

    if (cdd->depths) {
      ED_view3d_depths_free(cdd->depths);
    }
    MEM_freeN(cdd);
    op->customdata = NULL;
  }
}

/**
 * Initialize values before calling 'exec' (when running interactively).
 */
static void curve_draw_exec_precalc(wmOperator *op)
{
  struct CurveDrawData *cdd = op->customdata;
  const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;
  PropertyRNA *prop;

  prop = RNA_struct_find_property(op->ptr, "fit_method");
  if (!RNA_property_is_set(op->ptr, prop)) {
    RNA_property_enum_set(op->ptr, prop, cps->fit_method);
  }

  prop = RNA_struct_find_property(op->ptr, "corner_angle");
  if (!RNA_property_is_set(op->ptr, prop)) {
    const float corner_angle = (cps->flag & CURVE_PAINT_FLAG_CORNERS_DETECT) ? cps->corner_angle :
                                                                               (float)M_PI;
    RNA_property_float_set(op->ptr, prop, corner_angle);
  }

  prop = RNA_struct_find_property(op->ptr, "error_threshold");
  if (!RNA_property_is_set(op->ptr, prop)) {

    /* Error isn't set so we'll have to calculate it from the pixel values. */
    BLI_mempool_iter iter;
    const struct StrokeElem *selem, *selem_prev;

    float len_3d = 0.0f, len_2d = 0.0f;
    float scale_px; /* pixel to local space scale */

    int i = 0;
    BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
    selem_prev = BLI_mempool_iterstep(&iter);
    for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter), i++) {
      len_3d += len_v3v3(selem->location_local, selem_prev->location_local);
      len_2d += len_v2v2(selem->mval, selem_prev->mval);
      selem_prev = selem;
    }
    scale_px = ((len_3d > 0.0f) && (len_2d > 0.0f)) ? (len_3d / len_2d) : 0.0f;
    float error_threshold = (cps->error_threshold * U.dpi_fac) * scale_px;
    RNA_property_float_set(op->ptr, prop, error_threshold);
  }

  prop = RNA_struct_find_property(op->ptr, "use_cyclic");
  if (!RNA_property_is_set(op->ptr, prop)) {
    bool use_cyclic = false;

    if (BLI_mempool_len(cdd->stroke_elem_pool) > 2) {
      BLI_mempool_iter iter;
      const struct StrokeElem *selem, *selem_first, *selem_last;

      BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
      selem_first = selem_last = BLI_mempool_iterstep(&iter);
      for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
        selem_last = selem;
      }

      if (len_squared_v2v2(selem_first->mval, selem_last->mval) <=
          square_f(STROKE_CYCLIC_DIST_PX * U.dpi_fac)) {
        use_cyclic = true;
      }
    }

    RNA_property_boolean_set(op->ptr, prop, use_cyclic);
  }

  if ((cps->radius_taper_start != 0.0f) || (cps->radius_taper_end != 0.0f)) {
    /* NOTE: we could try to de-duplicate the length calculations above. */
    const int stroke_len = BLI_mempool_len(cdd->stroke_elem_pool);

    BLI_mempool_iter iter;
    struct StrokeElem *selem, *selem_prev;

    float *lengths = MEM_mallocN(sizeof(float) * stroke_len, __func__);
    struct StrokeElem **selem_array = MEM_mallocN(sizeof(*selem_array) * stroke_len, __func__);
    lengths[0] = 0.0f;

    float len_3d = 0.0f;

    int i = 1;
    BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
    selem_prev = BLI_mempool_iterstep(&iter);
    selem_array[0] = selem_prev;
    for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter), i++) {
      const float len_3d_segment = len_v3v3(selem->location_local, selem_prev->location_local);
      len_3d += len_3d_segment;
      lengths[i] = len_3d;
      selem_array[i] = selem;
      selem_prev = selem;
    }

    if (cps->radius_taper_start != 0.0f) {
      const float len_taper_max = cps->radius_taper_start * len_3d;
      for (i = 0; i < stroke_len && lengths[i] < len_taper_max; i++) {
        const float pressure_new = selem_array[i]->pressure * (lengths[i] / len_taper_max);
        stroke_elem_pressure_set(cdd, selem_array[i], pressure_new);
      }
    }

    if (cps->radius_taper_end != 0.0f) {
      const float len_taper_max = cps->radius_taper_end * len_3d;
      const float len_taper_min = len_3d - len_taper_max;
      for (i = stroke_len - 1; i > 0 && lengths[i] > len_taper_min; i--) {
        const float pressure_new = selem_array[i]->pressure *
                                   ((len_3d - lengths[i]) / len_taper_max);
        stroke_elem_pressure_set(cdd, selem_array[i], pressure_new);
      }
    }

    MEM_freeN(lengths);
    MEM_freeN(selem_array);
  }
}

static int curve_draw_exec(bContext *C, wmOperator *op)
{
  if (op->customdata == NULL) {
    if (!curve_draw_init(C, op, false)) {
      return OPERATOR_CANCELLED;
    }
  }

  struct CurveDrawData *cdd = op->customdata;

  const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;
  Object *obedit = cdd->vc.obedit;
  Curve *cu = obedit->data;
  ListBase *nurblist = object_editcurve_get(obedit);

  int stroke_len = BLI_mempool_len(cdd->stroke_elem_pool);

  const bool is_3d = (cu->flag & CU_3D) != 0;
  invert_m4_m4(obedit->imat, obedit->obmat);

  if (BLI_mempool_len(cdd->stroke_elem_pool) == 0) {
    curve_draw_stroke_from_operator(op);
    stroke_len = BLI_mempool_len(cdd->stroke_elem_pool);
  }

  /* Deselect all existing curves. */
  ED_curve_deselect_all_multi(C);

  const float radius_min = cps->radius_min;
  const float radius_max = cps->radius_max;
  const float radius_range = cps->radius_max - cps->radius_min;

  Nurb *nu = MEM_callocN(sizeof(Nurb), __func__);
  nu->pntsv = 0;
  nu->resolu = cu->resolu;
  nu->resolv = cu->resolv;
  nu->flag |= CU_SMOOTH;

  const bool use_pressure_radius = (cps->flag & CURVE_PAINT_FLAG_PRESSURE_RADIUS) ||
                                   ((cps->radius_taper_start != 0.0f) ||
                                    (cps->radius_taper_end != 0.0f));

  if (cdd->curve_type == CU_BEZIER) {
    nu->type = CU_BEZIER;

#ifdef USE_SPLINE_FIT

    /* Allow to interpolate multiple channels */
    int dims = 3;
    struct {
      int radius;
    } coords_indices;
    coords_indices.radius = use_pressure_radius ? dims++ : -1;

    float *coords = MEM_mallocN(sizeof(*coords) * stroke_len * dims, __func__);

    float *cubic_spline = NULL;
    uint cubic_spline_len = 0;

    /* error in object local space */
    const int fit_method = RNA_enum_get(op->ptr, "fit_method");
    const float error_threshold = RNA_float_get(op->ptr, "error_threshold");
    const float corner_angle = RNA_float_get(op->ptr, "corner_angle");
    const bool use_cyclic = RNA_boolean_get(op->ptr, "use_cyclic");

    {
      BLI_mempool_iter iter;
      const struct StrokeElem *selem;
      float *co = coords;

      BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
      for (selem = BLI_mempool_iterstep(&iter); selem;
           selem = BLI_mempool_iterstep(&iter), co += dims) {
        copy_v3_v3(co, selem->location_local);
        if (coords_indices.radius != -1) {
          co[coords_indices.radius] = selem->pressure;
        }

        /* remove doubles */
        if ((co != coords) && UNLIKELY(memcmp(co, co - dims, sizeof(float) * dims) == 0)) {
          co -= dims;
          stroke_len--;
        }
      }
    }

    uint *corners = NULL;
    uint corners_len = 0;

    if ((fit_method == CURVE_PAINT_FIT_METHOD_SPLIT) && (corner_angle < (float)M_PI)) {
      /* this could be configurable... */
      const float corner_radius_min = error_threshold / 8;
      const float corner_radius_max = error_threshold * 2;
      const uint samples_max = 16;

      curve_fit_corners_detect_fl(coords,
                                  stroke_len,
                                  dims,
                                  corner_radius_min,
                                  corner_radius_max,
                                  samples_max,
                                  corner_angle,
                                  &corners,
                                  &corners_len);
    }

    uint *corners_index = NULL;
    uint corners_index_len = 0;
    uint calc_flag = CURVE_FIT_CALC_HIGH_QUALIY;

    if ((stroke_len > 2) && use_cyclic) {
      calc_flag |= CURVE_FIT_CALC_CYCLIC;
    }

    int result;
    if (fit_method == CURVE_PAINT_FIT_METHOD_REFIT) {
      result = curve_fit_cubic_to_points_refit_fl(coords,
                                                  stroke_len,
                                                  dims,
                                                  error_threshold,
                                                  calc_flag,
                                                  NULL,
                                                  0,
                                                  corner_angle,
                                                  &cubic_spline,
                                                  &cubic_spline_len,
                                                  NULL,
                                                  &corners_index,
                                                  &corners_index_len);
    }
    else {
      result = curve_fit_cubic_to_points_fl(coords,
                                            stroke_len,
                                            dims,
                                            error_threshold,
                                            calc_flag,
                                            corners,
                                            corners_len,
                                            &cubic_spline,
                                            &cubic_spline_len,
                                            NULL,
                                            &corners_index,
                                            &corners_index_len);
    }

    MEM_freeN(coords);
    if (corners) {
      free(corners);
    }

    if (result == 0) {
      nu->pntsu = cubic_spline_len;
      nu->bezt = MEM_callocN(sizeof(BezTriple) * nu->pntsu, __func__);

      float *co = cubic_spline;
      BezTriple *bezt = nu->bezt;
      for (int j = 0; j < cubic_spline_len; j++, bezt++, co += (dims * 3)) {
        const float *handle_l = co + (dims * 0);
        const float *pt = co + (dims * 1);
        const float *handle_r = co + (dims * 2);

        copy_v3_v3(bezt->vec[0], handle_l);
        copy_v3_v3(bezt->vec[1], pt);
        copy_v3_v3(bezt->vec[2], handle_r);

        if (coords_indices.radius != -1) {
          bezt->radius = (pt[coords_indices.radius] * cdd->radius.range) + cdd->radius.min;
        }
        else {
          bezt->radius = radius_max;
        }

        bezt->h1 = bezt->h2 = HD_ALIGN; /* will set to free in second pass */
        bezt->f1 = bezt->f2 = bezt->f3 = SELECT;
      }

      if (corners_index) {
        /* ignore the first and last */
        uint i_start = 0, i_end = corners_index_len;

        if ((corners_index_len >= 2) && (calc_flag & CURVE_FIT_CALC_CYCLIC) == 0) {
          i_start += 1;
          i_end -= 1;
        }

        for (uint i = i_start; i < i_end; i++) {
          bezt = &nu->bezt[corners_index[i]];
          bezt->h1 = bezt->h2 = HD_FREE;
        }
      }

      if (calc_flag & CURVE_FIT_CALC_CYCLIC) {
        nu->flagu |= CU_NURB_CYCLIC;
      }
    }

    if (corners_index) {
      free(corners_index);
    }

    if (cubic_spline) {
      free(cubic_spline);
    }

#else
    nu->pntsu = stroke_len;
    nu->bezt = MEM_callocN(nu->pntsu * sizeof(BezTriple), __func__);

    BezTriple *bezt = nu->bezt;

    {
      BLI_mempool_iter iter;
      const struct StrokeElem *selem;

      BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
      for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
        copy_v3_v3(bezt->vec[1], selem->location_local);
        if (!is_3d) {
          bezt->vec[1][2] = 0.0f;
        }

        if (use_pressure_radius) {
          bezt->radius = selem->pressure;
        }
        else {
          bezt->radius = radius_max;
        }

        bezt->h1 = bezt->h2 = HD_AUTO;

        bezt->f1 |= SELECT;
        bezt->f2 |= SELECT;
        bezt->f3 |= SELECT;

        bezt++;
      }
    }
#endif

    BKE_nurb_handles_calc(nu);
  }
  else { /* CU_POLY */
    BLI_mempool_iter iter;
    const struct StrokeElem *selem;

    nu->pntsu = stroke_len;
    nu->pntsv = 1;
    nu->type = CU_POLY;
    nu->bp = MEM_callocN(nu->pntsu * sizeof(BPoint), __func__);

    /* Misc settings. */
    nu->resolu = cu->resolu;
    nu->resolv = 1;
    nu->orderu = 4;
    nu->orderv = 1;

    BPoint *bp = nu->bp;

    BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
    for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
      copy_v3_v3(bp->vec, selem->location_local);
      if (!is_3d) {
        bp->vec[2] = 0.0f;
      }

      if (use_pressure_radius) {
        bp->radius = (selem->pressure * radius_range) + radius_min;
      }
      else {
        bp->radius = cps->radius_max;
      }
      bp->f1 = SELECT;
      bp->vec[3] = 1.0f;

      bp++;
    }

    BKE_nurb_knot_calc_u(nu);
  }

  BLI_addtail(nurblist, nu);

  BKE_curve_nurb_active_set(cu, nu);
  cu->actvert = nu->pntsu - 1;

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

  curve_draw_exit(op);

  return OPERATOR_FINISHED;
}

static int curve_draw_invoke(bContext *C, wmOperator *op, const wmEvent *event)
{
  if (RNA_struct_property_is_set(op->ptr, "stroke")) {
    return curve_draw_exec(C, op);
  }

  if (!curve_draw_init(C, op, true)) {
    return OPERATOR_CANCELLED;
  }

  struct CurveDrawData *cdd = op->customdata;

  const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

  const bool is_modal = RNA_boolean_get(op->ptr, "wait_for_input");

  /* Fallback (in case we can't find the depth on first test). */
  {
    const float mval_fl[2] = {UNPACK2(event->mval)};
    float center[3];
    negate_v3_v3(center, cdd->vc.rv3d->ofs);
    ED_view3d_win_to_3d(cdd->vc.v3d, cdd->vc.region, center, mval_fl, cdd->prev.location_world);
    copy_v3_v3(cdd->prev.location_world_valid, cdd->prev.location_world);
  }

  cdd->draw_handle_view = ED_region_draw_cb_activate(
      cdd->vc.region->type, curve_draw_stroke_3d, op, REGION_DRAW_POST_VIEW);
  WM_cursor_modal_set(cdd->vc.win, WM_CURSOR_PAINT_BRUSH);

  {
    View3D *v3d = cdd->vc.v3d;
    RegionView3D *rv3d = cdd->vc.rv3d;
    Object *obedit = cdd->vc.obedit;
    Curve *cu = obedit->data;

    const float *plane_no = NULL;
    const float *plane_co = NULL;

    if (CU_IS_2D(cu)) {
      /* 2D overrides other options */
      plane_co = obedit->obmat[3];
      plane_no = obedit->obmat[2];
      cdd->project.use_plane = true;
    }
    else {
      if ((cps->depth_mode == CURVE_PAINT_PROJECT_SURFACE) && (v3d->shading.type > OB_WIRE)) {
        /* needed or else the draw matrix can be incorrect */
        view3d_operator_needs_opengl(C);

        ED_view3d_depth_override(cdd->vc.depsgraph,
                                 cdd->vc.region,
                                 cdd->vc.v3d,
                                 NULL,
                                 V3D_DEPTH_NO_GPENCIL,
                                 &cdd->depths);

        if (cdd->depths != NULL) {
          cdd->project.use_depth = true;
        }
        else {
          BKE_report(op->reports, RPT_WARNING, "Unable to access depth buffer, using view plane");
          cdd->project.use_depth = false;
        }
      }

      /* use view plane (when set or as fallback when surface can't be found) */
      if (cdd->project.use_depth == false) {
        plane_co = cdd->vc.scene->cursor.location;
        plane_no = rv3d->viewinv[2];
        cdd->project.use_plane = true;
      }

      if (cdd->project.use_depth && (cdd->curve_type != CU_POLY)) {
        cdd->sample.use_substeps = true;
      }
    }

    if (cdd->project.use_plane) {
      normalize_v3_v3(cdd->project.plane, plane_no);
      cdd->project.plane[3] = -dot_v3v3(cdd->project.plane, plane_co);
    }
  }

  if (is_modal == false) {
    curve_draw_event_add_first(op, event);
  }

  /* add temp handler */
  WM_event_add_modal_handler(C, op);

  return OPERATOR_RUNNING_MODAL;
}

static void curve_draw_cancel(bContext *UNUSED(C), wmOperator *op)
{
  curve_draw_exit(op);
}

/* Modal event handling of frame changing */
static int curve_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
{
  int ret = OPERATOR_RUNNING_MODAL;
  struct CurveDrawData *cdd = op->customdata;

  UNUSED_VARS(C, op);

  if (event->type == cdd->init_event_type) {
    if (event->val == KM_RELEASE) {
      ED_region_tag_redraw(cdd->vc.region);

      curve_draw_exec_precalc(op);

      curve_draw_stroke_to_operator(op);

      curve_draw_exec(C, op);

      return OPERATOR_FINISHED;
    }
  }
  else if (ELEM(event->type, EVT_ESCKEY, RIGHTMOUSE)) {
    ED_region_tag_redraw(cdd->vc.region);
    curve_draw_cancel(C, op);
    return OPERATOR_CANCELLED;
  }
  else if (ELEM(event->type, LEFTMOUSE)) {
    if (event->val == KM_PRESS) {
      curve_draw_event_add_first(op, event);
    }
  }
  else if (ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE)) {
    if (cdd->state == CURVE_DRAW_PAINTING) {
      const float mval_fl[2] = {UNPACK2(event->mval)};
      if (len_squared_v2v2(mval_fl, cdd->prev.mouse) > square_f(STROKE_SAMPLE_DIST_MIN_PX)) {
        curve_draw_event_add(op, event);
      }
    }
  }

  return ret;
}

void CURVE_OT_draw(wmOperatorType *ot)
{
  /* identifiers */
  ot->name = "Draw Curve";
  ot->idname = "CURVE_OT_draw";
  ot->description = "Draw a freehand spline";

  /* api callbacks */
  ot->exec = curve_draw_exec;
  ot->invoke = curve_draw_invoke;
  ot->cancel = curve_draw_cancel;
  ot->modal = curve_draw_modal;
  ot->poll = ED_operator_editcurve;

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

  /* properties */
  PropertyRNA *prop;

  prop = RNA_def_float_distance(ot->srna,
                                "error_threshold",
                                0.0f,
                                0.0f,
                                10.0f,
                                "Error",
                                "Error distance threshold (in object units)",
                                0.0001f,
                                10.0f);
  RNA_def_property_ui_range(prop, 0.0, 10, 1, 4);

  RNA_def_enum(ot->srna,
               "fit_method",
               rna_enum_curve_fit_method_items,
               CURVE_PAINT_FIT_METHOD_REFIT,
               "Fit Method",
               "");

  prop = RNA_def_float_distance(
      ot->srna, "corner_angle", DEG2RADF(70.0f), 0.0f, M_PI, "Corner Angle", "", 0.0f, M_PI);
  RNA_def_property_subtype(prop, PROP_ANGLE);

  prop = RNA_def_boolean(ot->srna, "use_cyclic", true, "Cyclic", "");
  RNA_def_property_flag(prop, PROP_SKIP_SAVE);

  prop = RNA_def_collection_runtime(ot->srna, "stroke", &RNA_OperatorStrokeElement, "Stroke", "");
  RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);

  prop = RNA_def_boolean(ot->srna, "wait_for_input", true, "Wait for Input", "");
  RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);
}

/** \} */