/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2016 by Mike Erwin.
 * All rights reserved.
 */

/** \file
 * \ingroup gpu
 *
 * GPU shader interface (C --> GLSL)
 *
 * Structure detailing needed vertex inputs and resources for a specific shader.
 * A shader interface can be shared between two similar shaders.
 */

#pragma once

#include <cstring> /* required for STREQ later on. */

#include "BLI_hash.h"
#include "BLI_utildefines.h"

#include "GPU_shader.h"

namespace blender::gpu {

typedef struct ShaderInput {
  uint32_t name_offset;
  uint32_t name_hash;
  int32_t location;
  /** Defined at interface creation or in shader. Only for Samplers, UBOs and Vertex Attribs. */
  int32_t binding;
} ShaderInput;

/**
 * Implementation of Shader interface.
 * Base class which is then specialized for each implementation (GL, VK, ...).
 **/
class ShaderInterface {
  /* TODO(fclem): should be protected. */
 public:
  /** Flat array. In this order: Attributes, Ubos, Uniforms. */
  ShaderInput *inputs_ = NULL;
  /** Buffer containing all inputs names separated by '\0'. */
  char *name_buffer_ = NULL;
  /** Input counts inside input array. */
  uint attr_len_ = 0;
  uint ubo_len_ = 0;
  uint uniform_len_ = 0;
  /** Enabled bindpoints that needs to be fed with data. */
  uint16_t enabled_attr_mask_ = 0;
  uint16_t enabled_ubo_mask_ = 0;
  uint8_t enabled_ima_mask_ = 0;
  uint64_t enabled_tex_mask_ = 0;
  /** Location of builtin uniforms. Fast access, no lookup needed. */
  int32_t builtins_[GPU_NUM_UNIFORMS];
  int32_t builtin_blocks_[GPU_NUM_UNIFORM_BLOCKS];

 public:
  ShaderInterface();
  virtual ~ShaderInterface();

  void debug_print(void);

  inline const ShaderInput *attr_get(const char *name) const
  {
    return input_lookup(inputs_, attr_len_, name);
  }

  inline const ShaderInput *ubo_get(const char *name) const
  {
    return input_lookup(inputs_ + attr_len_, ubo_len_, name);
  }
  inline const ShaderInput *ubo_get(const int binding) const
  {
    return input_lookup(inputs_ + attr_len_, ubo_len_, binding);
  }

  inline const ShaderInput *uniform_get(const char *name) const
  {
    return input_lookup(inputs_ + attr_len_ + ubo_len_, uniform_len_, name);
  }

  inline const ShaderInput *texture_get(const int binding) const
  {
    return input_lookup(inputs_ + attr_len_ + ubo_len_, uniform_len_, binding);
  }

  inline const char *input_name_get(const ShaderInput *input) const
  {
    return name_buffer_ + input->name_offset;
  }

  /* Returns uniform location. */
  inline int32_t uniform_builtin(const GPUUniformBuiltin builtin) const
  {
    BLI_assert(builtin >= 0 && builtin < GPU_NUM_UNIFORMS);
    return builtins_[builtin];
  }

  /* Returns binding position. */
  inline int32_t ubo_builtin(const GPUUniformBlockBuiltin builtin) const
  {
    BLI_assert(builtin >= 0 && builtin < GPU_NUM_UNIFORM_BLOCKS);
    return builtin_blocks_[builtin];
  }

 protected:
  static inline const char *builtin_uniform_name(GPUUniformBuiltin u);
  static inline const char *builtin_uniform_block_name(GPUUniformBlockBuiltin u);

  inline uint32_t set_input_name(ShaderInput *input, char *name, uint32_t name_len) const;

  /* Finalize interface construction by sorting the ShaderInputs for faster lookups. */
  void sort_inputs(void);

 private:
  inline const ShaderInput *input_lookup(const ShaderInput *const inputs,
                                         const uint inputs_len,
                                         const char *name) const;

  inline const ShaderInput *input_lookup(const ShaderInput *const inputs,
                                         const uint inputs_len,
                                         const int binding) const;
};

inline const char *ShaderInterface::builtin_uniform_name(GPUUniformBuiltin u)
{
  switch (u) {
    case GPU_UNIFORM_MODEL:
      return "ModelMatrix";
    case GPU_UNIFORM_VIEW:
      return "ViewMatrix";
    case GPU_UNIFORM_MODELVIEW:
      return "ModelViewMatrix";
    case GPU_UNIFORM_PROJECTION:
      return "ProjectionMatrix";
    case GPU_UNIFORM_VIEWPROJECTION:
      return "ViewProjectionMatrix";
    case GPU_UNIFORM_MVP:
      return "ModelViewProjectionMatrix";

    case GPU_UNIFORM_MODEL_INV:
      return "ModelMatrixInverse";
    case GPU_UNIFORM_VIEW_INV:
      return "ViewMatrixInverse";
    case GPU_UNIFORM_MODELVIEW_INV:
      return "ModelViewMatrixInverse";
    case GPU_UNIFORM_PROJECTION_INV:
      return "ProjectionMatrixInverse";
    case GPU_UNIFORM_VIEWPROJECTION_INV:
      return "ViewProjectionMatrixInverse";

    case GPU_UNIFORM_NORMAL:
      return "NormalMatrix";
    case GPU_UNIFORM_ORCO:
      return "OrcoTexCoFactors";
    case GPU_UNIFORM_CLIPPLANES:
      return "WorldClipPlanes";

    case GPU_UNIFORM_COLOR:
      return "color";
    case GPU_UNIFORM_BASE_INSTANCE:
      return "baseInstance";
    case GPU_UNIFORM_RESOURCE_CHUNK:
      return "resourceChunk";
    case GPU_UNIFORM_RESOURCE_ID:
      return "resourceId";
    case GPU_UNIFORM_SRGB_TRANSFORM:
      return "srgbTarget";

    default:
      return NULL;
  }
}

inline const char *ShaderInterface::builtin_uniform_block_name(GPUUniformBlockBuiltin u)
{
  switch (u) {
    case GPU_UNIFORM_BLOCK_VIEW:
      return "viewBlock";
    case GPU_UNIFORM_BLOCK_MODEL:
      return "modelBlock";
    case GPU_UNIFORM_BLOCK_INFO:
      return "infoBlock";
    default:
      return NULL;
  }
}

/* Returns string length including '\0' terminator. */
inline uint32_t ShaderInterface::set_input_name(ShaderInput *input,
                                                char *name,
                                                uint32_t name_len) const
{
  /* remove "[0]" from array name */
  if (name[name_len - 1] == ']') {
    name[name_len - 3] = '\0';
    name_len -= 3;
  }

  input->name_offset = (uint32_t)(name - name_buffer_);
  input->name_hash = BLI_hash_string(name);
  return name_len + 1; /* include NULL terminator */
}

inline const ShaderInput *ShaderInterface::input_lookup(const ShaderInput *const inputs,
                                                        const uint inputs_len,
                                                        const char *name) const
{
  const uint name_hash = BLI_hash_string(name);
  /* Simple linear search for now. */
  for (int i = inputs_len - 1; i >= 0; i--) {
    if (inputs[i].name_hash == name_hash) {
      if ((i > 0) && UNLIKELY(inputs[i - 1].name_hash == name_hash)) {
        /* Hash colision resolve. */
        for (; i >= 0 && inputs[i].name_hash == name_hash; i--) {
          if (STREQ(name, name_buffer_ + inputs[i].name_offset)) {
            return inputs + i; /* not found */
          }
        }
        return NULL; /* not found */
      }

      /* This is a bit dangerous since we could have a hash collision.
       * where the asked uniform that does not exist has the same hash
       * as a real uniform. */
      BLI_assert(STREQ(name, name_buffer_ + inputs[i].name_offset));
      return inputs + i;
    }
  }
  return NULL; /* not found */
}

inline const ShaderInput *ShaderInterface::input_lookup(const ShaderInput *const inputs,
                                                        const uint inputs_len,
                                                        const int binding) const
{
  /* Simple linear search for now. */
  for (int i = inputs_len - 1; i >= 0; i--) {
    if (inputs[i].binding == binding) {
      return inputs + i;
    }
  }
  return NULL; /* not found */
}

}  // namespace blender::gpu