/*
 * Copyright 2011-2019 Branimir Karadzic. All rights reserved.
 * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause
 */

#include "common.h"
#include "bgfx_utils.h"
#include "imgui/imgui.h"

namespace
{

struct PosColorTexCoord0Vertex
{
	float m_x;
	float m_y;
	float m_z;
	uint32_t m_abgr;
	float m_u;
	float m_v;

	static void init()
	{
		ms_decl
			.begin()
			.add(bgfx::Attrib::Position,  3, bgfx::AttribType::Float)
			.add(bgfx::Attrib::Color0,    4, bgfx::AttribType::Uint8, true)
			.add(bgfx::Attrib::TexCoord0, 2, bgfx::AttribType::Float)
			.end();
	}

	static bgfx::VertexLayout ms_decl;
};

bgfx::VertexLayout PosColorTexCoord0Vertex::ms_decl;

void renderScreenSpaceQuad(uint8_t _view, bgfx::ProgramHandle _program, float _x, float _y, float _width, float _height)
{
	bgfx::TransientVertexBuffer tvb;
	bgfx::TransientIndexBuffer tib;

	if (bgfx::allocTransientBuffers(&tvb, PosColorTexCoord0Vertex::ms_decl, 4, &tib, 6) )
	{
		PosColorTexCoord0Vertex* vertex = (PosColorTexCoord0Vertex*)tvb.data;

		float zz = 0.0f;

		const float minx = _x;
		const float maxx = _x + _width;
		const float miny = _y;
		const float maxy = _y + _height;

		float minu = -1.0f;
		float minv = -1.0f;
		float maxu =  1.0f;
		float maxv =  1.0f;

		vertex[0].m_x = minx;
		vertex[0].m_y = miny;
		vertex[0].m_z = zz;
		vertex[0].m_abgr = 0xff0000ff;
		vertex[0].m_u = minu;
		vertex[0].m_v = minv;

		vertex[1].m_x = maxx;
		vertex[1].m_y = miny;
		vertex[1].m_z = zz;
		vertex[1].m_abgr = 0xff00ff00;
		vertex[1].m_u = maxu;
		vertex[1].m_v = minv;

		vertex[2].m_x = maxx;
		vertex[2].m_y = maxy;
		vertex[2].m_z = zz;
		vertex[2].m_abgr = 0xffff0000;
		vertex[2].m_u = maxu;
		vertex[2].m_v = maxv;

		vertex[3].m_x = minx;
		vertex[3].m_y = maxy;
		vertex[3].m_z = zz;
		vertex[3].m_abgr = 0xffffffff;
		vertex[3].m_u = minu;
		vertex[3].m_v = maxv;

		uint16_t* indices = (uint16_t*)tib.data;

		indices[0] = 0;
		indices[1] = 2;
		indices[2] = 1;
		indices[3] = 0;
		indices[4] = 3;
		indices[5] = 2;

		bgfx::setState(BGFX_STATE_DEFAULT);
		bgfx::setIndexBuffer(&tib);
		bgfx::setVertexBuffer(0, &tvb);
		bgfx::submit(_view, _program);
	}
}

class ExampleRaymarch : public entry::AppI
{
public:
	ExampleRaymarch(const char* _name, const char* _description)
		: entry::AppI(_name, _description)
	{
	}

	void init(int32_t _argc, const char* const* _argv, uint32_t _width, uint32_t _height) override
	{
		Args args(_argc, _argv);

		m_width  = _width;
		m_height = _height;
		m_debug  = BGFX_DEBUG_NONE;
		m_reset  = BGFX_RESET_VSYNC;

		bgfx::Init init;
		init.type     = args.m_type;
		init.vendorId = args.m_pciId;
		init.resolution.width  = m_width;
		init.resolution.height = m_height;
		init.resolution.reset  = m_reset;
		bgfx::init(init);

		// Enable debug text.
		bgfx::setDebug(m_debug);

		// Set view 0 clear state.
		bgfx::setViewClear(0
				, BGFX_CLEAR_COLOR|BGFX_CLEAR_DEPTH
				, 0x303030ff
				, 1.0f
				, 0
				);

		// Create vertex stream declaration.
		PosColorTexCoord0Vertex::init();

		u_mtx          = bgfx::createUniform("u_mtx",      bgfx::UniformType::Mat4);
		u_lightDirTime = bgfx::createUniform("u_lightDirTime", bgfx::UniformType::Vec4);

		// Create program from shaders.
		m_program = loadProgram("vs_raymarching", "fs_raymarching");

		m_timeOffset = bx::getHPCounter();

		imguiCreate();
	}

	int shutdown() override
	{
		imguiDestroy();

		// Cleanup.
		bgfx::destroy(m_program);

		bgfx::destroy(u_mtx);
		bgfx::destroy(u_lightDirTime);

		// Shutdown bgfx.
		bgfx::shutdown();

		return 0;
	}

	bool update() override
	{
		if (!entry::processEvents(m_width, m_height, m_debug, m_reset, &m_mouseState) )
		{
			imguiBeginFrame(m_mouseState.m_mx
				,  m_mouseState.m_my
				, (m_mouseState.m_buttons[entry::MouseButton::Left  ] ? IMGUI_MBUT_LEFT   : 0)
				| (m_mouseState.m_buttons[entry::MouseButton::Right ] ? IMGUI_MBUT_RIGHT  : 0)
				| (m_mouseState.m_buttons[entry::MouseButton::Middle] ? IMGUI_MBUT_MIDDLE : 0)
				,  m_mouseState.m_mz
				, uint16_t(m_width)
				, uint16_t(m_height)
				);

			showExampleDialog(this);

			imguiEndFrame();
			// Set view 0 default viewport.
			bgfx::setViewRect(0, 0, 0, uint16_t(m_width), uint16_t(m_height) );

			// Set view 1 default viewport.
			bgfx::setViewRect(1, 0, 0, uint16_t(m_width), uint16_t(m_height) );

			// This dummy draw call is here to make sure that view 0 is cleared
			// if no other draw calls are submitted to viewZ 0.
			bgfx::touch(0);

			const bx::Vec3 at  = { 0.0f, 0.0f,   0.0f };
			const bx::Vec3 eye = { 0.0f, 0.0f, -15.0f };

			float view[16];
			float proj[16];
			bx::mtxLookAt(view, eye, at);

			const bgfx::Caps* caps = bgfx::getCaps();
			bx::mtxProj(proj, 60.0f, float(m_width)/float(m_height), 0.1f, 100.0f, caps->homogeneousDepth);

			// Set view and projection matrix for view 1.
			bgfx::setViewTransform(0, view, proj);

			float ortho[16];
			bx::mtxOrtho(ortho, 0.0f, 1280.0f, 720.0f, 0.0f, 0.0f, 100.0f, 0.0, caps->homogeneousDepth);

			// Set view and projection matrix for view 0.
			bgfx::setViewTransform(1, NULL, ortho);

			float time = (float)( (bx::getHPCounter()-m_timeOffset)/double(bx::getHPFrequency() ) );

			float vp[16];
			bx::mtxMul(vp, view, proj);

			float mtx[16];
			bx::mtxRotateXY(mtx
				, time
				, time*0.37f
				);

			float mtxInv[16];
			bx::mtxInverse(mtxInv, mtx);
			float lightDirTime[4];
			const bx::Vec3 lightDirModelN = bx::normalize(bx::Vec3{-0.4f, -0.5f, -1.0f});
			bx::store(lightDirTime, bx::mul(lightDirModelN, mtxInv) );
			lightDirTime[3] = time;
			bgfx::setUniform(u_lightDirTime, lightDirTime);

			float mvp[16];
			bx::mtxMul(mvp, mtx, vp);

			float invMvp[16];
			bx::mtxInverse(invMvp, mvp);
			bgfx::setUniform(u_mtx, invMvp);

			renderScreenSpaceQuad(1, m_program, 0.0f, 0.0f, 1280.0f, 720.0f);

			// Advance to next frame. Rendering thread will be kicked to
			// process submitted rendering primitives.
			bgfx::frame();

			return true;
		}

		return false;
	}

	entry::MouseState m_mouseState;

	uint32_t m_width;
	uint32_t m_height;
	uint32_t m_debug;
	uint32_t m_reset;

	int64_t m_timeOffset;
	bgfx::UniformHandle u_mtx;
	bgfx::UniformHandle u_lightDirTime;
	bgfx::ProgramHandle m_program;
};

} // namespace

ENTRY_IMPLEMENT_MAIN(ExampleRaymarch, "03-raymarch", "Updating shader uniforms.");