############################################################
#
# Stripped down from the Perl OpenGL::Shader package by Vojtech Bubnik
# to only support the GLSL shaders. The original source was not maintained
# and did not install properly through the CPAN archive, and it was unnecessary
# complex.
#
# Original copyright:
#
# Copyright 2007 Graphcomp - ALL RIGHTS RESERVED
# Author: Bob "grafman" Free - grafman@graphcomp.com
#
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
############################################################

package Slic3r::GUI::GLShader;
use OpenGL(':all');

# Avoid cloning this class by the worker threads.
sub CLONE_SKIP { 1 }

# Shader constructor
sub new
{
  # Check for required OpenGL extensions
  return undef if (OpenGL::glpCheckExtension('GL_ARB_shader_objects'));
  return undef if (OpenGL::glpCheckExtension('GL_ARB_fragment_shader'));
  return undef if (OpenGL::glpCheckExtension('GL_ARB_vertex_shader'));
  return undef if (OpenGL::glpCheckExtension('GL_ARB_shading_language_100'));
#  my $glsl_version = glGetString(GL_SHADING_LANGUAGE_VERSION);
#  my $glsl_version_ARB = glGetString(GL_SHADING_LANGUAGE_VERSION_ARB );
#  print "GLSL version: $glsl_version, ARB: $glsl_version_ARB\n";

  my $this = shift;
  my $class = ref($this) || $this;
  my($type) = @_;
  my $self = {type => uc($type)};
  bless($self,$class);

  # Get GL_SHADING_LANGUAGE_VERSION_ARB
  my $shader_ver = glGetString(0x8B8C);
  $shader_ver =~ m|([\d\.]+)|;
  $self->{version} = $1 || '0';
  print 
  return $self;
}

# Shader destructor
# Must be disabled first
sub DESTROY
{
  my($self) = @_;

  if ($self->{program})
  {
    glDetachObjectARB($self->{program},$self->{fragment_id}) if ($self->{fragment_id});
    glDetachObjectARB($self->{program},$self->{vertex_id}) if ($self->{vertex_id});
    glDeleteProgramsARB_p($self->{program});
  }

  glDeleteProgramsARB_p($self->{fragment_id}) if ($self->{fragment_id});
  glDeleteProgramsARB_p($self->{vertex_id}) if ($self->{vertex_id});
}


# Load shader strings
sub Load
{
  my($self,$fragment,$vertex) = @_;

  # Load fragment code
  if ($fragment)
  {
    $self->{fragment_id} = glCreateShaderObjectARB(GL_FRAGMENT_SHADER);
    return undef if (!$self->{fragment_id});

    glShaderSourceARB_p($self->{fragment_id}, $fragment);
    #my $frag = glGetShaderSourceARB_p($self->{fragment_id});
    #print STDERR "Loaded fragment:\n$frag\n";

    glCompileShaderARB($self->{fragment_id});
    my $stat = glGetInfoLogARB_p($self->{fragment_id});
    return "Fragment shader: $stat" if ($stat);
  }

  # Load vertex code
  if ($vertex)
  {
    $self->{vertex_id} = glCreateShaderObjectARB(GL_VERTEX_SHADER);
    return undef if (!$self->{vertex_id});

    glShaderSourceARB_p($self->{vertex_id}, $vertex);
    #my $vert = glGetShaderSourceARB_p($self->{vertex_id});
    #print STDERR "Loaded vertex:\n$vert\n";

    glCompileShaderARB($self->{vertex_id});
    $stat = glGetInfoLogARB_p($self->{vertex_id});
    return "Vertex shader: $stat" if ($stat);
  }


  # Link shaders
  my $sp = glCreateProgramObjectARB();
  glAttachObjectARB($sp, $self->{fragment_id}) if ($fragment);
  glAttachObjectARB($sp, $self->{vertex_id}) if ($vertex);
  glLinkProgramARB($sp);
  my $linked = glGetObjectParameterivARB_p($sp, GL_OBJECT_LINK_STATUS_ARB);
  if (!$linked)
  {
    $stat = glGetInfoLogARB_p($sp);
    #print STDERR "Load shader: $stat\n";
    return "Link shader: $stat" if ($stat);
    return 'Unable to link shader';
  }

  $self->{program} = $sp;

  return '';
}

# Enable shader
sub Enable
{
  my($self) = @_;
  glUseProgramObjectARB($self->{program}) if ($self->{program});
}

# Disable shader
sub Disable
{
  my($self) = @_;
  glUseProgramObjectARB(0) if ($self->{program});
}

# Return shader vertex attribute ID
sub MapAttr
{
  my($self,$attr) = @_;
  return undef if (!$self->{program});
  my $id = glGetAttribLocationARB_p($self->{program},$attr);
  return undef if ($id < 0);
  return $id;
}

# Return shader uniform variable ID
sub Map
{
  my($self,$var) = @_;
  return undef if (!$self->{program});
  my $id = glGetUniformLocationARB_p($self->{program},$var);
  return undef if ($id < 0);
  return $id;
}

# Set shader vector
sub SetVector
{
  my($self,$var,@values) = @_;

  my $id = $self->Map($var);
  return 'Unable to map $var' if (!defined($id));

  my $count = scalar(@values);
  eval('glUniform'.$count.'fARB($id,@values)');

  return '';
}

# Set shader 4x4 matrix
sub SetMatrix
{
  my($self,$var,$oga) = @_;

  my $id = $self->Map($var);
  return 'Unable to map $var' if (!defined($id));

  glUniformMatrix4fvARB_c($id,1,0,$oga->ptr());
  return '';
}

1;
__END__