// Filename: glShaderContext_src.cxx
// Created by: jyelon (01Sep05)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001 - 2004, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://etc.cmu.edu/panda3d/docs/license/ .
//
// To contact the maintainers of this program write to
// panda3d-general@lists.sourceforge.net .
//
////////////////////////////////////////////////////////////////////

#ifdef HAVE_CG
#include "Cg/cgGL.h"
#endif

#define DEBUG_GL_SHADER 0

TypeHandle CLP(ShaderContext)::_type_handle;


////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::Constructor
//       Access: Public
//  Description: xyz
////////////////////////////////////////////////////////////////////
CLP(ShaderContext)::
CLP(ShaderContext)(ShaderExpansion *s, GSG *gsg) : ShaderContext(s) {
#ifdef HAVE_CG
  if (s->get_header() == "//Cg") {
    
    // Ask the shader expansion to compile itself for us and 
    // to give us the resulting Cg program objects.

    if (!s->cg_compile_for(gsg->_shader_caps,
                           _cg_context,
                           _cg_vprogram,
                           _cg_fprogram, 
                           _cg_parameter_map)) {
      return;
    }
        
    // Load the program.
    
    cgGLLoadProgram(_cg_vprogram);
    CGerror verror = cgGetError();
    cgGLLoadProgram(_cg_fprogram);
    CGerror ferror = cgGetError();
    if ((verror != CG_NO_ERROR)||(ferror != CG_NO_ERROR)) {
      GLCAT.error() << "Could not load Cg shader:" << s->get_name() << "\n";
      release_resources();
    }
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::Destructor
//       Access: Public
//  Description: xyz
////////////////////////////////////////////////////////////////////
CLP(ShaderContext)::
~CLP(ShaderContext)() {
  release_resources();
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::release_resources
//       Access: Public
//  Description: Should deallocate all system resources (such as
//               vertex program handles or Cg contexts).
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
release_resources() {
#ifdef HAVE_CG
  if (_cg_context) {
    cgDestroyContext(_cg_context);
    _cg_context = 0;
    _cg_vprogram = 0;
    _cg_fprogram = 0;
    _cg_parameter_map.clear();
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::bind
//       Access: Public
//  Description: This function is to be called to enable a new
//               shader.  It also initializes all of the shader's
//               input parameters.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
bind(GSG *gsg) {
#ifdef HAVE_CG
  if (_cg_context != 0) {

    // Pass in k-parameters and transform-parameters
    issue_parameters(gsg, true);

    // Bind the shaders.
    cgGLEnableProfile(cgGetProgramProfile(_cg_vprogram));
    cgGLBindProgram(_cg_vprogram);
    cgGLEnableProfile(cgGetProgramProfile(_cg_fprogram));
    cgGLBindProgram(_cg_fprogram);
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::unbind
//       Access: Public
//  Description: This function disables a currently-bound shader.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
unbind() {
#ifdef HAVE_CG
  if (_cg_context != 0) {
    cgGLDisableProfile(cgGetProgramProfile(_cg_vprogram));
    cgGLDisableProfile(cgGetProgramProfile(_cg_fprogram));
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::issue_parameters
//       Access: Public
//  Description: This function gets called whenever the RenderState
//               or TransformState has changed, but the ShaderExpansion
//               itself has not changed.  It loads new values into the
//               shader's parameters.
//
//               If "altered" is false, that means you promise that
//               the parameters for this shader context have already
//               been issued once, and that since the last time the
//               parameters were issued, no part of the render
//               state has changed except the external and internal
//               transforms.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
issue_parameters(GSG *gsg, bool altered) {
#ifdef HAVE_CG
  if (_cg_context == 0) {
    return;
  }

  for (int i=0; i<(int)_expansion->_mat_spec.size(); i++) {
    if (altered || _expansion->_mat_spec[i]._trans_dependent) {
      CGparameter p = _cg_parameter_map[_expansion->_mat_spec[i]._id._seqno];
      const LMatrix4f *val = gsg->fetch_specified_value(_expansion->_mat_spec[i], altered);
      if (val) {
        const float *data = val->get_data();
        switch (_expansion->_mat_spec[i]._piece) {
        case ShaderExpansion::SMP_whole: cgGLSetMatrixParameterfc(p, data); break;
        case ShaderExpansion::SMP_transpose: cgGLSetMatrixParameterfr(p, data); break;
        case ShaderExpansion::SMP_row0: cgGLSetParameter4fv(p, data+ 0); break;
        case ShaderExpansion::SMP_row1: cgGLSetParameter4fv(p, data+ 4); break;
        case ShaderExpansion::SMP_row2: cgGLSetParameter4fv(p, data+ 8); break;
        case ShaderExpansion::SMP_row3: cgGLSetParameter4fv(p, data+12); break;
        case ShaderExpansion::SMP_col0: cgGLSetParameter4f(p, data[0], data[4], data[ 8], data[12]); break;
        case ShaderExpansion::SMP_col1: cgGLSetParameter4f(p, data[1], data[5], data[ 9], data[13]); break;
        case ShaderExpansion::SMP_col2: cgGLSetParameter4f(p, data[2], data[6], data[10], data[14]); break;
        case ShaderExpansion::SMP_col3: cgGLSetParameter4f(p, data[3], data[7], data[11], data[15]); break;
        }
      }
    }
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::disable_shader_vertex_arrays
//       Access: Public
//  Description: Disable all the vertex arrays used by this shader.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
disable_shader_vertex_arrays(GSG *gsg) {
#ifdef HAVE_CG
  if (_cg_context == 0) {
    return;
  }

  for (int i=0; i<(int)_expansion->_var_spec.size(); i++) {
    CGparameter p = _cg_parameter_map[_expansion->_var_spec[i]._id._seqno];
    cgGLDisableClientState(p);
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::update_shader_vertex_arrays
//       Access: Public
//  Description: Disables all vertex arrays used by the previous
//               shader, then enables all the vertex arrays needed
//               by this shader.  Extracts the relevant vertex array
//               data from the gsg.
//               The current implementation is inefficient, because
//               it may unnecessarily disable arrays then immediately
//               reenable them.  We may optimize this someday.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
update_shader_vertex_arrays(CLP(ShaderContext) *prev, GSG *gsg) {
  if (prev) prev->disable_shader_vertex_arrays(gsg);
#ifdef HAVE_CG
  if (_cg_context == 0) {
    return;
  }

#ifdef SUPPORT_IMMEDIATE_MODE
  if (gsg->_use_sender) {
    GLCAT.error() << "immediate mode shaders not implemented yet\n";
  } else
#endif // SUPPORT_IMMEDIATE_MODE
  {
    const GeomVertexArrayDataPipelineReader *array_reader;
    Geom::NumericType numeric_type;
    int start, stride, num_values;
    int nvarying = _expansion->_var_spec.size();
    for (int i=0; i<nvarying; i++) {
      CGparameter p = _cg_parameter_map[_expansion->_var_spec[i]._id._seqno];
      InternalName *name = _expansion->_var_spec[i]._name;
      int texslot = _expansion->_var_spec[i]._append_uv;
      if (texslot >= 0) {
        const Geom::ActiveTextureStages &active_stages =
          gsg->_state._texture->get_on_stages();
        if (texslot < (int)active_stages.size()) {
          TextureStage *stage = active_stages[texslot];
          InternalName *texname = stage->get_texcoord_name();
          if (name == InternalName::get_texcoord()) {
            name = texname;
          } else if (texname != InternalName::get_texcoord()) {
            name = name->append(texname->get_basename());
          }
        }
      }
      if (gsg->_data_reader->get_array_info(name,
                                            array_reader, num_values, numeric_type,
                                            start, stride)) {
        const unsigned char *client_pointer = gsg->setup_array_data(array_reader);
        cgGLSetParameterPointer(p,
                                num_values, gsg->get_numeric_type(numeric_type),
                                stride, client_pointer + start);
        cgGLEnableClientState(p);
      } else {
        cgGLDisableClientState(p);
      }
    }
  }
#endif // HAVE_CG
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::disable_shader_texture_bindings
//       Access: Public
//  Description: Disable all the texture bindings used by this shader.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
disable_shader_texture_bindings(GSG *gsg) {
#ifdef HAVE_CG
  if (_cg_context == 0) {
    return;
  }

  for (int i=0; i<(int)_expansion->_tex_spec.size(); i++) {
    CGparameter p = _cg_parameter_map[_expansion->_tex_spec[i]._id._seqno];
    int texunit = cgGetParameterResourceIndex(p);
    gsg->_glActiveTexture(GL_TEXTURE0 + texunit);
    GLP(Disable)(GL_TEXTURE_1D);
    GLP(Disable)(GL_TEXTURE_2D);
    if (gsg->_supports_3d_texture) {
      GLP(Disable)(GL_TEXTURE_3D);
    }
    if (gsg->_supports_cube_map) {
      GLP(Disable)(GL_TEXTURE_CUBE_MAP);
    }
    // This is probably faster - but maybe not as safe?
    // cgGLDisableTextureParameter(p);
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: GLShaderContext::update_shader_texture_bindings
//       Access: Public
//  Description: Disables all texture bindings used by the previous
//               shader, then enables all the texture bindings needed
//               by this shader.  Extracts the relevant vertex array
//               data from the gsg.
//               The current implementation is inefficient, because
//               it may unnecessarily disable textures then immediately
//               reenable them.  We may optimize this someday.
////////////////////////////////////////////////////////////////////
void CLP(ShaderContext)::
update_shader_texture_bindings(CLP(ShaderContext) *prev, GSG *gsg) {
  if (prev) prev->disable_shader_texture_bindings(gsg);
#ifdef HAVE_CG
  if (_cg_context == 0) {
    return;
  }

  for (int i=0; i<(int)_expansion->_tex_spec.size(); i++) {
    CGparameter p = _cg_parameter_map[_expansion->_tex_spec[i]._id._seqno];
    Texture *tex = 0;
    InternalName *id = _expansion->_tex_spec[i]._name;
    if (id != 0) {
      const ShaderInput *input = gsg->_target._shader->get_shader_input(id);
      tex = input->get_texture();
    } else {
      if (_expansion->_tex_spec[i]._stage >= gsg->_target._texture->get_num_on_stages()) {
        continue;
      }
      TextureStage *stage = gsg->_target._texture->get_on_stage(_expansion->_tex_spec[i]._stage);
      tex = gsg->_target._texture->get_on_texture(stage);
    }
    if (_expansion->_tex_spec[i]._suffix != 0) {
      // The suffix feature is inefficient. It is a temporary hack.
      if (tex == 0) {
        continue;
      }
      tex = tex->load_related(_expansion->_tex_spec[i]._suffix);
    }
    if ((tex == 0) || (tex->get_texture_type() != _expansion->_tex_spec[i]._desired_type)) {
      continue;
    }
    TextureContext *tc = tex->prepare_now(gsg->_prepared_objects, gsg);
    if (tc == (TextureContext*)NULL) {
      continue;
    }

    int texunit = cgGetParameterResourceIndex(p);
    gsg->_glActiveTexture(GL_TEXTURE0 + texunit);

    GLenum target = gsg->get_texture_target(tex->get_texture_type());
    if (target == GL_NONE) {
      // Unsupported texture mode.
      continue;
    }
    GLP(Enable)(target);

    gsg->apply_texture(tc);
  }
#endif
}