// Copyright (C) 2012-2013 Kornel Kisielewicz
// This file is part of NV Libraries.
// For conditions of distribution and use, see copyright notice in nv.hh

#include "nv/gl/gl_context.hh"

#include "nv/gl/gl_enum.hh"
#include "nv/lib/gl.hh"

using namespace nv;

void gl_context::clear( const clear_state& cs )
{
	// apply_framebuffer
	
	apply_scissor_test( cs.scissor_test );
	apply_color_mask( cs.color_mask );
	apply_depth_mask( cs.depth_mask );
	// stencil_mask_separate

	if ( m_clear_color != cs.color )
	{
		glClearColor( cs.color.r, cs.color.g, cs.color.b, cs.color.a );
		m_clear_color = cs.color;
	}

	if ( m_clear_depth != cs.depth )
	{
		glClearDepth( cs.depth );
		m_clear_depth = cs.depth;
	}

	if ( m_clear_stencil != cs.stencil )
	{
		glClearStencil( cs.stencil );
		m_clear_stencil = cs.stencil;
	}
	
	glClear( clear_state_buffers_to_mask( cs.buffers ) );
}

const ivec4& gl_context::get_viewport()
{
	return m_viewport;
}

void gl_context::set_viewport( const ivec4& viewport )
{
	if ( viewport.z < 0 || viewport.w < 0 )
	{
		NV_THROW( logic_error, "viewport width and height must be greater than zero!");
	}

	m_viewport = viewport;
	glViewport( viewport.x, viewport.y, viewport.z, viewport.w );
}

void gl_context::enable( unsigned int what, bool value )
{
	if ( value )
	{
		glEnable( what );
	}
	else
	{
		glDisable( what );
	}
}

void gl_context::apply_stencil_test( const stencil_test& stencil )
{
	if ( m_render_state.stencil_test.enabled != stencil.enabled )
	{
		enable( GL_STENCIL_TEST, stencil.enabled );
		m_render_state.stencil_test.enabled = stencil.enabled;
	}

	if ( stencil.enabled )
	{
		apply_stencil_face( GL_FRONT, m_render_state.stencil_test.front_face, stencil.front_face );
		apply_stencil_face( GL_BACK,  m_render_state.stencil_test.back_face,  stencil.back_face );
	}
}

void gl_context::apply_stencil_face( unsigned face, stencil_test_face& stencil, const stencil_test_face& new_stencil )
{
	if (( stencil.op_fail       != new_stencil.op_fail       ) ||
		( stencil.op_depth_fail != new_stencil.op_depth_fail ) ||
		( stencil.op_depth_pass != new_stencil.op_depth_pass ) )
	{
		glStencilOpSeparate( face,
			stencil_operation_to_enum( new_stencil.op_fail ),
			stencil_operation_to_enum( new_stencil.op_depth_fail ),
			stencil_operation_to_enum( new_stencil.op_depth_pass )
		);

		stencil.op_fail       = new_stencil.op_fail;
		stencil.op_depth_fail = new_stencil.op_depth_fail;
		stencil.op_depth_pass = new_stencil.op_depth_pass;
	}

	if (( stencil.function  != new_stencil.function ) ||
		( stencil.ref_value != new_stencil.ref_value ) ||
		( stencil.mask      != new_stencil.mask ))
	{
		glStencilFuncSeparate( face,
			stencil_function_to_enum( new_stencil.function ),
			new_stencil.ref_value,
			new_stencil.mask
		);

		stencil.function  = new_stencil.function;
		stencil.ref_value = new_stencil.ref_value;
		stencil.mask      = new_stencil.mask;
	}
}

void gl_context::apply_scissor_test( const scissor_test& scissor )
{
	if ( m_render_state.scissor_test.enabled != scissor.enabled )
	{
		enable( GL_SCISSOR_TEST, scissor.enabled );
		m_render_state.scissor_test.enabled = scissor.enabled;
	}

	if ( scissor.dim.x < 0 || scissor.dim.y < 0 )
	{
		NV_THROW( logic_error, "scissor_test.rect width and height must be greater than zero!" );
	}

	if ( scissor.enabled )
	{
		if ( m_render_state.scissor_test.dim != scissor.dim || m_render_state.scissor_test.pos != scissor.pos )
		{
			glScissor( 
				scissor.pos.x, scissor.pos.y, 
				scissor.dim.x, scissor.dim.y
			);
			m_render_state.scissor_test.dim = scissor.dim;
			m_render_state.scissor_test.pos = scissor.pos;
		}
	}
}

void gl_context::apply_depth_test( const depth_test& depth )
{
	if ( m_render_state.depth_test.enabled != depth.enabled )
	{
		enable( GL_DEPTH_TEST, depth.enabled );
		m_render_state.depth_test.enabled = depth.enabled;
	}

	if ( depth.enabled )
	{
		if ( m_render_state.depth_test.function != depth.function )
		{
			glDepthFunc( depth_state_function_to_enum( depth.function ) );
			m_render_state.depth_test.function = depth.function;
		}
	}
}

void gl_context::apply_depth_mask( bool mask )
{
	if ( m_render_state.depth_mask != mask )
	{
		glDepthMask( mask );
		m_render_state.depth_mask = mask;
	}
}

void gl_context::apply_depth_range( const depth_range& range )
{
	if ( range.near < 0.0 || range.near > 1.0 )
	{
		NV_THROW( logic_error, "render_state.depth_range.near must be between zero and one!");
	}
	if ( range.far < 0.0 || range.far > 1.0 )
	{
		NV_THROW( logic_error, "render_state.depth_range.far must be between zero and one!");
	}

	if ((m_render_state.depth_range.far  != range.far) ||
		(m_render_state.depth_range.near != range.near))
	{
		glDepthRange( range.near, range.far );

		m_render_state.depth_range.far  = range.far;
		m_render_state.depth_range.near = range.near;
	}
}

void gl_context::apply_color_mask( const color_mask& mask )
{
	if ( m_render_state.color_mask != mask )
	{
		glColorMask( mask.red, mask.green, mask.blue, mask.alpha );
		m_render_state.color_mask = mask;
	}
}

void gl_context::apply_blending( const blending& blend )
{
	if ( m_render_state.blending.enabled != blend.enabled )
	{
		enable( GL_BLEND, blend.enabled );
		m_render_state.blending.enabled = blend.enabled;
	}

	if ( blend.enabled )
	{
		if ((m_render_state.blending.src_rgb_factor   != blend.src_rgb_factor ) ||
			(m_render_state.blending.dst_rgb_factor   != blend.dst_rgb_factor ) ||
			(m_render_state.blending.src_alpha_factor != blend.src_alpha_factor ) ||
			(m_render_state.blending.dst_alpha_factor != blend.dst_alpha_factor ))
		{
			glBlendFuncSeparate(
				blending_factor_to_enum( blend.src_rgb_factor ),
				blending_factor_to_enum( blend.dst_rgb_factor ),
				blending_factor_to_enum( blend.src_alpha_factor ),
				blending_factor_to_enum( blend.dst_alpha_factor )
			);

			m_render_state.blending.src_rgb_factor   = blend.src_rgb_factor;
			m_render_state.blending.dst_rgb_factor   = blend.dst_rgb_factor;
			m_render_state.blending.src_alpha_factor = blend.src_alpha_factor;
			m_render_state.blending.dst_alpha_factor = blend.dst_alpha_factor; 
		}

		if ((m_render_state.blending.rgb_equation   != blend.rgb_equation ) ||
			(m_render_state.blending.alpha_equation != blend.alpha_equation ))
		{
			glBlendEquationSeparate(
				blending_equation_to_enum( blend.rgb_equation ),
				blending_equation_to_enum( blend.alpha_equation )
			);

			m_render_state.blending.rgb_equation   = blend.rgb_equation;
			m_render_state.blending.alpha_equation = blend.alpha_equation;
		}

		if (( m_render_state.blending.color != blend.color ))
		{
			glBlendColor( blend.color.r, blend.color.g, blend.color.b, blend.color.a );
			m_render_state.blending.color = blend.color;
		}
	}
}


void gl_context::apply_culling( const culling& cull )
{
	if ( m_render_state.culling.enabled != cull.enabled )
	{
		enable( GL_CULL_FACE, cull.enabled );
		m_render_state.culling.enabled = cull.enabled;
	}

	if ( cull.enabled )
	{
		if ( m_render_state.culling.face != cull.face )
		{
			glCullFace( culling_face_type_to_enum(cull.face) );
			m_render_state.culling.face = cull.face;
		}

		if ( m_render_state.culling.order != cull.order )
		{
			glFrontFace( culling_order_type_to_enum( cull.order ) );
			m_render_state.culling.order = cull.order;
		}
	}
}


void gl_context::force_apply_render_state( const render_state& state )
{
	enable( GL_CULL_FACE, state.culling.enabled );
	glCullFace( culling_face_type_to_enum( state.culling.face ) );
	glFrontFace( culling_order_type_to_enum( state.culling.order ) );

	enable( GL_SCISSOR_TEST, state.scissor_test.enabled );
	glScissor( 
		state.scissor_test.pos.x, state.scissor_test.pos.y, 
		state.scissor_test.dim.x, state.scissor_test.dim.y 
	);

	enable( GL_STENCIL_TEST, state.stencil_test.enabled );
	force_apply_stencil_face( GL_FRONT, state.stencil_test.front_face );
	force_apply_stencil_face( GL_BACK,  state.stencil_test.back_face  );

	enable( GL_DEPTH_TEST, state.depth_test.enabled );
	glDepthFunc( depth_state_function_to_enum( state.depth_test.function ) );
	glDepthRange( state.depth_range.near, state.depth_range.far );

	enable( GL_BLEND, state.blending.enabled );
	glBlendFuncSeparate(
		blending_factor_to_enum( state.blending.src_rgb_factor ),
		blending_factor_to_enum( state.blending.dst_rgb_factor ),
		blending_factor_to_enum( state.blending.src_alpha_factor ),
		blending_factor_to_enum( state.blending.dst_alpha_factor )
	);
	glBlendEquationSeparate(
		blending_equation_to_enum( state.blending.rgb_equation ),
		blending_equation_to_enum( state.blending.alpha_equation )
	);
	glBlendColor( 
		state.blending.color.r, state.blending.color.g, 
		state.blending.color.b, state.blending.color.a 
	);

	glDepthMask( state.depth_mask );
	glColorMask( 
		state.color_mask.red, state.color_mask.green, 
		state.color_mask.blue, state.color_mask.alpha 
	);
}

void gl_context::force_apply_stencil_face( unsigned face, const stencil_test_face& stencil )
{
	glStencilOpSeparate( face,
		stencil_operation_to_enum( stencil.op_fail ),
		stencil_operation_to_enum( stencil.op_depth_fail ),
		stencil_operation_to_enum( stencil.op_depth_pass )
	);

	glStencilFuncSeparate( face,
		stencil_function_to_enum( stencil.function ),
		stencil.ref_value,
		stencil.mask
	);
}


void gl_context::apply_render_state( const render_state& state )
{
	// apply_primitive_restart
	apply_culling( state.culling );
	// apply_program_point_size
	// apply_rasterization_mode
	apply_scissor_test( state.scissor_test );
	apply_stencil_test( state.stencil_test );
	apply_depth_test( state.depth_test );
	apply_depth_range( state.depth_range );
	apply_blending( state.blending );
	apply_color_mask( state.color_mask );
	apply_depth_mask( state.depth_mask );
}


gl_context::gl_context( device* a_device )
	: context( a_device )
{
	// TODO: do we really need this?
	glPixelStorei( GL_UNPACK_ALIGNMENT, 1 );
	force_apply_render_state( m_render_state );
}

void gl_context::draw( primitive prim, const render_state& rs, program* p, vertex_array* va, size_t count )
{
	apply_render_state( rs );
	if ( count > 0 )
	{
		p->bind();
		va->bind();
		if ( va->has_index_buffer() )
		{
			glDrawElements( primitive_to_enum(prim), static_cast<GLsizei>( count ), datatype_to_gl_enum( va->get_index_buffer_type() ), 0 );
		}
		else
		{
			glDrawArrays( primitive_to_enum(prim), 0, static_cast<GLsizei>( count ) );
		}
		va->unbind();
		p->unbind();
	}
}