/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2005 Blender Foundation. All rights reserved. */

/** \file
 * \ingroup modifiers
 *
 * Weld modifier: Remove doubles.
 */

/* TODOs:
 * - Review weight and vertex color interpolation.;
 */

#include "MEM_guardedalloc.h"

#include "BLI_utildefines.h"

#include "BLI_array.hh"
#include "BLI_index_range.hh"
#include "BLI_span.hh"
#include "BLI_vector.hh"

#include "BLT_translation.h"

#include "DNA_defaults.h"
#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_modifier_types.h"
#include "DNA_screen_types.h"

#ifdef USE_BVHTREEKDOP
#  include "BKE_bvhutils.h"
#endif

#include "BKE_context.h"
#include "BKE_deform.h"
#include "BKE_modifier.h"
#include "BKE_screen.h"

#include "UI_interface.h"
#include "UI_resources.h"

#include "RNA_access.h"
#include "RNA_prototypes.h"

#include "DEG_depsgraph.h"

#include "MOD_modifiertypes.h"
#include "MOD_ui_common.h"

#include "GEO_mesh_merge_by_distance.hh"

using blender::Array;
using blender::IndexMask;
using blender::Span;
using blender::Vector;

static Span<MDeformVert> get_vertex_group(const Mesh &mesh, const int defgrp_index)
{
  if (defgrp_index == -1) {
    return {};
  }
  const MDeformVert *vertex_group = static_cast<const MDeformVert *>(
      CustomData_get_layer(&mesh.vdata, CD_MDEFORMVERT));
  if (!vertex_group) {
    return {};
  }
  return {vertex_group, mesh.totvert};
}

static Vector<int64_t> selected_indices_from_vertex_group(Span<MDeformVert> vertex_group,
                                                          const int index,
                                                          const bool invert)
{
  Vector<int64_t> selected_indices;
  for (const int i : vertex_group.index_range()) {
    const bool found = BKE_defvert_find_weight(&vertex_group[i], index) > 0.0f;
    if (found != invert) {
      selected_indices.append(i);
    }
  }
  return selected_indices;
}

static Array<bool> selection_array_from_vertex_group(Span<MDeformVert> vertex_group,
                                                     const int index,
                                                     const bool invert)
{
  Array<bool> selection(vertex_group.size());
  for (const int i : vertex_group.index_range()) {
    const bool found = BKE_defvert_find_weight(&vertex_group[i], index) > 0.0f;
    selection[i] = (found != invert);
  }
  return selection;
}

static std::optional<Mesh *> calculate_weld(const Mesh &mesh, const WeldModifierData &wmd)
{
  const int defgrp_index = BKE_id_defgroup_name_index(&mesh.id, wmd.defgrp_name);
  Span<MDeformVert> vertex_group = get_vertex_group(mesh, defgrp_index);
  const bool invert = (wmd.flag & MOD_WELD_INVERT_VGROUP) != 0;

  if (wmd.mode == MOD_WELD_MODE_ALL) {
    if (!vertex_group.is_empty()) {
      Vector<int64_t> selected_indices = selected_indices_from_vertex_group(
          vertex_group, defgrp_index, invert);
      return blender::geometry::mesh_merge_by_distance_all(
          mesh, IndexMask(selected_indices), wmd.merge_dist);
    }
    return blender::geometry::mesh_merge_by_distance_all(
        mesh, IndexMask(mesh.totvert), wmd.merge_dist);
  }
  if (wmd.mode == MOD_WELD_MODE_CONNECTED) {
    const bool only_loose_edges = (wmd.flag & MOD_WELD_LOOSE_EDGES) != 0;
    if (!vertex_group.is_empty()) {
      Array<bool> selection = selection_array_from_vertex_group(
          vertex_group, defgrp_index, invert);
      return blender::geometry::mesh_merge_by_distance_connected(
          mesh, selection, wmd.merge_dist, only_loose_edges);
    }
    Array<bool> selection(mesh.totvert, true);
    return blender::geometry::mesh_merge_by_distance_connected(
        mesh, selection, wmd.merge_dist, only_loose_edges);
  }

  BLI_assert_unreachable();
  return nullptr;
}

static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *UNUSED(ctx), Mesh *mesh)
{
  const WeldModifierData &wmd = reinterpret_cast<WeldModifierData &>(*md);

  std::optional<Mesh *> result = calculate_weld(*mesh, wmd);
  if (!result) {
    return mesh;
  }
  return *result;
}

static void initData(ModifierData *md)
{
  WeldModifierData *wmd = (WeldModifierData *)md;

  BLI_assert(MEMCMP_STRUCT_AFTER_IS_ZERO(wmd, modifier));

  MEMCPY_STRUCT_AFTER(wmd, DNA_struct_default_get(WeldModifierData), modifier);
}

static void requiredDataMask(Object *UNUSED(ob),
                             ModifierData *md,
                             CustomData_MeshMasks *r_cddata_masks)
{
  WeldModifierData *wmd = (WeldModifierData *)md;

  /* Ask for vertexgroups if we need them. */
  if (wmd->defgrp_name[0] != '\0') {
    r_cddata_masks->vmask |= CD_MASK_MDEFORMVERT;
  }
}

static void panel_draw(const bContext *UNUSED(C), Panel *panel)
{
  uiLayout *layout = panel->layout;

  PointerRNA ob_ptr;
  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
  int weld_mode = RNA_enum_get(ptr, "mode");

  uiLayoutSetPropSep(layout, true);

  uiItemR(layout, ptr, "mode", 0, nullptr, ICON_NONE);
  uiItemR(layout, ptr, "merge_threshold", 0, IFACE_("Distance"), ICON_NONE);
  if (weld_mode == MOD_WELD_MODE_CONNECTED) {
    uiItemR(layout, ptr, "loose_edges", 0, nullptr, ICON_NONE);
  }
  modifier_vgroup_ui(layout, ptr, &ob_ptr, "vertex_group", "invert_vertex_group", nullptr);

  modifier_panel_end(layout, ptr);
}

static void panelRegister(ARegionType *region_type)
{
  modifier_panel_register(region_type, eModifierType_Weld, panel_draw);
}

ModifierTypeInfo modifierType_Weld = {
    /* name */ "Weld",
    /* structName */ "WeldModifierData",
    /* structSize */ sizeof(WeldModifierData),
    /* srna */ &RNA_WeldModifier,
    /* type */ eModifierTypeType_Constructive,
    /* flags */
    (ModifierTypeFlag)(eModifierTypeFlag_AcceptsMesh | eModifierTypeFlag_SupportsMapping |
                       eModifierTypeFlag_SupportsEditmode | eModifierTypeFlag_EnableInEditmode |
                       eModifierTypeFlag_AcceptsCVs),
    /* icon */ ICON_AUTOMERGE_OFF, /* TODO: Use correct icon. */

    /* copyData */ BKE_modifier_copydata_generic,

    /* deformVerts */ nullptr,
    /* deformMatrices */ nullptr,
    /* deformVertsEM */ nullptr,
    /* deformMatricesEM */ nullptr,
    /* modifyMesh */ modifyMesh,
    /* modifyGeometrySet */ nullptr,

    /* initData */ initData,
    /* requiredDataMask */ requiredDataMask,
    /* freeData */ nullptr,
    /* isDisabled */ nullptr,
    /* updateDepsgraph */ nullptr,
    /* dependsOnTime */ nullptr,
    /* dependsOnNormals */ nullptr,
    /* foreachIDLink */ nullptr,
    /* foreachTexLink */ nullptr,
    /* freeRuntimeData */ nullptr,
    /* panelRegister */ panelRegister,
    /* blendWrite */ nullptr,
    /* blendRead */ nullptr,
};