#include <psemek/app/app.hpp>
#include <psemek/app/main.hpp>
#include <psemek/gfx/mesh.hpp>
#include <psemek/gfx/program.hpp>
#include <psemek/gfx/texture.hpp>
#include <psemek/gfx/painter.hpp>
#include <psemek/gfx/framebuffer.hpp>
#include <psemek/gfx/renderbuffer.hpp>
#include <psemek/geom/camera.hpp>
#include <psemek/geom/math.hpp>
#include <psemek/geom/rotation.hpp>
#include <psemek/geom/scale.hpp>
#include <psemek/geom/translation.hpp>
#include <psemek/geom/easing.hpp>
#include <psemek/geom/gradient.hpp>
#include <psemek/geom/permutation.hpp>
#include <psemek/random/device.hpp>
#include <psemek/random/generator.hpp>
#include <psemek/random/uniform_sphere.hpp>
#include <psemek/random/uniform_ball.hpp>
#include <psemek/random/uniform_box.hpp>
#include <psemek/pcg/perlin.hpp>
#include <psemek/pcg/sample.hpp>
#include <psemek/util/clock.hpp>
#include <psemek/util/assert.hpp>
#include <psemek/util/moving_average.hpp>
#include <psemek/util/to_string.hpp>
#include <psemek/util/pretty_print.hpp>

using namespace psemek;

static char const ground_vs[] =
R"(#version 330

uniform mat4 u_transform;

layout (location = 0) in vec4 in_position;
layout (location = 1) in vec4 in_color;

out vec4 color;

void main()
{
	gl_Position = u_transform * in_position;
	color = in_color;
}
)";

static char const ground_fs[] =
R"(#version 330

in vec4 color;

out vec4 out_color;

void main()
{
	out_color = color;
}
)";

static char const grass_vs[] =
R"(#version 330

uniform mat4 u_transform;
uniform mat4 u_tile_transform;
uniform float u_height00;
uniform float u_height01;
uniform float u_height10;
uniform float u_height11;
uniform sampler1D u_texture;

layout (location = 0) in vec4 in_position;
layout (location = 1) in float in_t;

out vec4 color;

void main()
{
	vec2 p = (u_tile_transform * vec4(in_position.xy * 2.0 - vec2(0.5), 0.0, 1.0)).xy;

	vec2 o = (u_tile_transform * vec4(0.5, 0.5, 0.0, 1.0)).xy;

	o = vec2(floor(o.x), floor(o.y));

	vec2 d = p - o;

	float h = mix(mix(u_height00, u_height01, d.x), mix(u_height10, u_height11, d.x), d.y);

	gl_Position = u_transform * vec4(p, in_position.z * h, 1.0);
//	color = mix(vec4(0.0, 0.0, 0.0, 1.0), texture(u_texture, in_t), in_position.z);
	color = texture(u_texture, in_t);
}
)";

static char const grass_fs[] =
R"(#version 330

in vec4 color;

out vec4 out_color;

void main()
{
	out_color = color;
}
)";

static char const grass_slice_vs[] =
R"(#version 330

uniform mat4 u_transform;
uniform mat4 u_tile_transform;

uniform float u_density00;
uniform float u_density01;
uniform float u_density10;
uniform float u_density11;

layout (location = 0) in vec4 in_position;
layout (location = 1) in vec2 in_texcoord;

out vec3 texcoord;

void main()
{
	vec2 p = (u_tile_transform * vec4(in_position.xy, 0.0, 1.0)).xy;

	vec2 o = (u_tile_transform * vec4(0.5, 0.5, 0.0, 1.0)).xy;

	o = vec2(floor(o.x), floor(o.y));

	vec2 d = p - o;

	float level = mix(mix(u_density00, u_density01, d.x), mix(u_density10, u_density11, d.x), d.y);

	gl_Position = u_transform * vec4(p, in_position.z, 1.0);
	texcoord = vec3(in_texcoord, level);
}
)";

static char const grass_slice_fs[] =
R"(#version 330

uniform sampler2DArray u_texture;

in vec3 texcoord;

out vec4 out_color;

void main()
{
	float l0 = floor(texcoord.z);
	float l1 = l0 + 1;
	float t = texcoord.z - l0;
	vec4 c0 = texture(u_texture, vec3(texcoord.xy, l0));
	vec4 c1 = texture(u_texture, vec3(texcoord.xy, l1));
	vec4 c = mix(c0, c1, t);
//	vec4 c = c0;
	out_color = vec4(c.rgb / c.a, c.a);
}
)";

struct grass_app
	: app::app
{
	geom::free_camera camera;

	int size = 64;

	int const density_level_count = 8;

	pcg::perlin<float, 2> density;

	gfx::program ground_program{ground_vs, ground_fs};
	gfx::mesh ground_mesh;

	gfx::program grass_program{grass_vs, grass_fs};
	gfx::mesh grass_mesh;
	gfx::texture_1d grass_texture;

	gfx::program grass_slice_program{grass_slice_vs, grass_slice_fs};
	gfx::texture_2d_array grass_slice_z_texture;
	gfx::mesh grass_slice_z_mesh;

	gfx::framebuffer grass_slice_framebuffer;
	gfx::renderbuffer grass_slice_renderbuffer;

	geom::matrix<float, 4, 4> random_transform[8];
	util::array<int, 2> random_transform_index;

	util::clock<> frame_clock;
	util::moving_average<double> frame_time{64};

	util::clock<std::chrono::duration<float>> update_clock;

	gfx::painter painter;

	grass_app()
		: app("Grass", 4)
	{
		vsync(false);

		camera.fov_y = geom::rad(45.f);
		camera.near_clip = 0.1f;
		camera.far_clip = 1000.f;
		camera.pos = {0.5f, 0.5f, 1.5f};
		camera.rotateYZ(geom::rad(-90.f));

		init_ground();
		init_grass();
		init_grass_slices();

		random::generator rng;
		random::uniform_sphere_vector_distribution<float, 2> d;

		util::array<geom::vector<float, 2>, 2> grad({size / 8 + 1, size / 8 + 1});
		for (auto & v : grad) v = d(rng);
		density = pcg::perlin<float, 2>(std::move(grad));

		for (int i = 0; i < 8; ++i)
		{
			if (i < 4)
				random_transform[i] = geom::matrix<float, 4, 4>::identity();
			else
				random_transform[i] = geom::swap<float, 3>(0, 1).homogeneous_matrix();

			random_transform[i] = random_transform[i]
				* geom::translation<float, 3>(geom::vector{0.5f, 0.5f, 0.f}).homogeneous_matrix()
				* geom::plane_rotation<float, 3>(0, 1, i * geom::pi / 2.f).homogeneous_matrix()
				* geom::translation<float, 3>(geom::vector{-0.5f, -0.5f, 0.f}).homogeneous_matrix();
		}

		random_transform_index.resize({size, size});
		for (auto & i : random_transform_index)
			i = random::uniform_int_distribution<int>{0, 7}(rng);
	}

	void init_ground()
	{
		ground_mesh.setup<geom::point<float, 3>, gfx::normalized<gfx::color_rgba>>();

		struct vertex
		{
			geom::point<float, 3> pos;
			gfx::color_rgba color;
		};

		std::vector<vertex> vertices;
		std::vector<geom::triangle<std::uint32_t>> triangles;

		gfx::color_rgba ground_color{47, 23, 11, 255};

		for (int x = 0; x < size; ++x)
		{
			for (int y = 0; y < size; ++y)
			{
				std::uint32_t base = vertices.size();

				float d = 0.0f;

				vertices.push_back({{x + d, y + d, 0.f}, ground_color});
				vertices.push_back({{x + 1 - d, y + d, 0.f}, ground_color});
				vertices.push_back({{x + d, y + 1 - d, 0.f}, ground_color});
				vertices.push_back({{x + 1 - d, y + 1 - d, 0.f}, ground_color});

				triangles.push_back({base + 0, base + 1, base + 2});
				triangles.push_back({base + 2, base + 1, base + 3});
			}
		}

		ground_mesh.load(vertices, triangles, gl::STATIC_DRAW);
	}

	void init_grass()
	{
		frame_clock.restart();
		struct vertex
		{
			geom::point<std::uint16_t, 3> pos;
			std::uint8_t t;
			std::uint8_t density;

			vertex(geom::point<float, 3> const & p, float t, float d)
			{
				for (std::size_t i = 0; i < 2; ++i)
					pos[i] = geom::clamp(std::round((p[i] + 0.5f) / 2.f * 65535.f), {0.f, 65535.f});

				pos[2] = geom::clamp(std::round(p[2] * 65535.f), {0.f, 65535.f});

				this->t = geom::clamp(std::round(t * 255.f), {0.f, 255.f});
				this->density = geom::clamp(std::round(d * 255.f), {0.f, 255.f});
			}
		};

		{
			geom::gradient<float, gfx::color_4f> g
			{
				std::make_pair(-1.f, gfx::color_4f{0.f, 0.2f, 0.f, 1.f}),
				geom::easing_type::linear,
				std::pair{0.f, gfx::color_4f{0.4f, 0.65f, 0.35f, 1.f}},
				geom::easing_type::linear,
				std::pair{1.f, gfx::color_4f{0.7f, 0.75f, 0.2f, 1.f}}
			};

			util::array<gfx::color_rgba, 1> pm({256});
			for (std::size_t i = 0; i < pm.width(); ++i)
			{
				pm(i) = gfx::to_coloru8(g((i + 0.5f) / pm.width()));
			}

			grass_texture.load(pm);
			grass_texture.linear_filter();
			grass_texture.generate_mipmap();
		}

		random::generator rng;

		std::size_t memory = 0;

		grass_mesh.setup<gfx::normalized<geom::point<std::uint16_t, 3>>, gfx::normalized<std::uint8_t>, gfx::normalized<std::uint8_t>>();

		std::vector<vertex> vertices;
		std::vector<geom::triangle<std::uint32_t>> triangles;
		random::uniform_box_point_distribution<float, 2> d_origin({{{0.f, 1.f}, {0.f, 1.f}}});
		random::uniform_sphere_vector_distribution<float, 2> d_orientation;
		random::uniform_real_distribution<float> d_width{1.f / 64.f, 1.f / 128.f};
		random::uniform_real_distribution<float> d_height{0.25f, 1.f};
		random::uniform_real_distribution<float> d_density{0.f, 1.f};

		for (int blade = 0; blade < 4096; ++blade)
		{
			int const segments = 8;
			float const max_lean = 0.2f;

			int tx = (blade % 64) % 8;
			int ty = (blade % 64) / 8;

			auto o = d_origin(rng);
			o[0] = o[0] / 8.f + tx / 8.f;
			o[1] = o[1] / 8.f + ty / 8.f;

			auto r = d_orientation(rng);
			auto s = d_width(rng) * 0.5f;
			auto h = d_height(rng);

			auto n = geom::ort(r);

			auto color = random::uniform_real_distribution<float>{0.f, 1.f}(rng);

			float den = d_density(rng);

			auto get = [&](float x, float z) -> vertex
			{
				assert(z >= 0.f);
				assert(z <= 1.f);
				float y = (1.f - std::sqrt(1.f - z * z)) * max_lean;

				float w = 1.f - z / h;

				return {geom::point{o[0] + r[0] * s * x * w + n[0] * y, o[1] + r[1] * s * x * w + n[1] * y, z}, color, den};
			};


			for (int s = 0; s <= segments; ++s)
			{
				float t = (s * 1.f) / segments;
				t = geom::easing(geom::easing_type::quadratic_out, t);
				float z = h * t;
					std::uint32_t base = vertices.size();

				if (s < segments)
				{
					vertices.push_back(get(-1.f, z));
					vertices.push_back(get( 1.f, z));

					if (s > 0)
					{
						triangles.push_back({base - 2, base - 1, base});
						triangles.push_back({base, base - 1, base + 1});
					}
				}
				else
				{
					vertices.push_back(get(0.f, z));
					triangles.push_back({base - 2, base - 1, base});
				}
			}
		}

		grass_mesh.load(vertices, triangles, gl::STATIC_DRAW);

		memory += (vertices.size() * sizeof(vertices[0]) + triangles.size() * sizeof(triangles[0]));

		log::info() << memory << " bytes";
		log::info() << vertices.size() << " vertices";
		log::info() << frame_clock.count();
	}

	void init_grass_slices()
	{
		struct vertex
		{
			geom::point<float, 3> position;
			geom::vector<float, 2> texcoord;
		};

		int const slice_count = 4;
		float slice_width = 1.f / slice_count;

		std::vector<vertex> vertices;
		vertices.push_back({{0.f, 0.f, slice_width}, {0.f, 0.f}});
		vertices.push_back({{1.f, 0.f, slice_width}, {1.f, 0.f}});
		vertices.push_back({{0.f, 1.f, slice_width}, {0.f, 1.f}});
		vertices.push_back({{0.f, 1.f, slice_width}, {0.f, 1.f}});
		vertices.push_back({{1.f, 0.f, slice_width}, {1.f, 0.f}});
		vertices.push_back({{1.f, 1.f, slice_width}, {1.f, 1.f}});

		grass_slice_z_mesh.setup<geom::point<float, 3>, geom::vector<float, 2>>();
		grass_slice_z_mesh.load(vertices, gl::TRIANGLES, gl::STATIC_DRAW);

		std::size_t slice_resolution = 256;

		grass_slice_z_texture.load<gfx::color_rgba>({slice_resolution, slice_resolution, density_level_count});
		grass_slice_renderbuffer.storage(gl::DEPTH24_STENCIL8, {slice_resolution, slice_resolution});
		for (int d = 0; d < density_level_count; ++d)
		{
			grass_slice_framebuffer.color(grass_slice_z_texture, d);
			grass_slice_framebuffer.depth(grass_slice_renderbuffer);
			grass_slice_framebuffer.assert_complete();
			gl::Viewport(0, 0, slice_resolution, slice_resolution);
			gl::ClearColor(0.f, 0.f, 0.f, 0.f);
			gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT);
			gl::Enable(gl::DEPTH_TEST);
			gl::DepthFunc(gl::LEQUAL);
			grass_program.bind();
			grass_program["u_tile_transform"] = geom::matrix<float, 4, 4>::identity();
			grass_program["u_height00"] = 1.f;
			grass_program["u_height01"] = 1.f;
			grass_program["u_height10"] = 1.f;
			grass_program["u_height11"] = 1.f;
			grass_program["u_texture"] = 0;
			grass_texture.bind();
			for (int x = -1; x <= 1; ++x)
			{
				for (int y = -1; y <= 1; ++y)
				{
					grass_program["u_transform"] = geom::translation<float, 3>({-1.f + 2.f * x, -1.f + 2.f * y, 0.f}).homogeneous_matrix() * geom::scale<float, 3>({2.f, 2.f, 1.f}).homogeneous_matrix();
					grass_mesh.draw(0, (grass_mesh.index_count() * (d + 1)) / density_level_count);
				}
			}
		}
		gfx::framebuffer::null().bind();

		grass_slice_z_texture.linear_filter();
		grass_slice_z_texture.anisotropy();
		grass_slice_z_texture.generate_mipmap();
		grass_slice_z_texture.clamp();
//		grass_slice_z_texture.bind();
//		gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::NEAREST);
//		gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::LINEAR);
	}

	void on_resize(int width, int height) override
	{
		app::on_resize(width, height);
		camera.set_fov(camera.fov_y, (1.f * width) / height);
	}

	void on_mouse_move(int x, int y, int dx, int dy) override
	{
		app::on_mouse_move(x, y, dx, dy);

		if (is_middle_button_down())
		{
			camera.rotateZX(0.01f * dx);
			camera.rotateYZ(0.01f * dy);
		}
	}

	void on_mouse_wheel(int delta) override
	{
		app::on_mouse_wheel(delta);
	}

	void update() override
	{
		float dt = update_clock.restart().count();

		auto d = camera.direction();
		float s = 20.f;

		if (is_key_down(SDLK_LSHIFT))
			s = 2.5f;

		if (is_key_down(SDLK_SPACE))
		{
			d[2] = 0.f;
			d = geom::normalized(d);
		}

		auto n = geom::normalized(geom::cross(d, geom::vector{0.f, 0.f, 1.f}));

		if (is_key_down(SDLK_w))
		{
			camera.pos += d * dt * s;
		}

		if (is_key_down(SDLK_s))
		{
			camera.pos -= d * dt * s;
		}

		if (is_key_down(SDLK_a))
		{
			camera.pos -= n * dt * s;
		}

		if (is_key_down(SDLK_d))
		{
			camera.pos += n * dt * s;
		}
	}

	void present() override
	{
		gl::ClearColor(0.8f, 0.8f, 1.f, 1.f);
		gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT);

		gl::Enable(gl::DEPTH_TEST);
		gl::DepthFunc(gl::LEQUAL);
		gl::Enable(gl::BLEND);
		gl::BlendFunc(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA);

		auto camera_transform = camera.transform();

		ground_program.bind();
		ground_program["u_transform"] = camera_transform;
		ground_mesh.draw();

		grass_program.bind();
		grass_program["u_texture"] = 0;
		grass_texture.bind();
		grass_program["u_transform"] = camera_transform;

		std::size_t triangles = 0;

		for (int x = 0; x < size; ++x)
		{
			for (int y = 0; y < size; ++y)
			{
				if (x < size / 2) continue;

				grass_program["u_tile_transform"] = geom::translation<float, 3>(geom::vector{x, y, 0.f}).homogeneous_matrix()
					* random_transform[random_transform_index(x, y)];

				float d = density({(x + 0.5f) / size, (y + 0.5f) / size});

				int i = std::floor(d * density_level_count);
				if (i > density_level_count - 1) i = density_level_count - 1;

				{
					float h00 = density({(x + 0.f) / size, (y + 0.f) / size});
					float h01 = density({(x + 1.f) / size, (y + 0.f) / size});
					float h10 = density({(x + 0.f) / size, (y + 1.f) / size});
					float h11 = density({(x + 1.f) / size, (y + 1.f) / size});

					grass_program["u_height00"] = h00;
					grass_program["u_height01"] = h01;
					grass_program["u_height10"] = h10;
					grass_program["u_height11"] = h11;
					grass_mesh.draw(0, ((i + 1) * grass_mesh.index_count()) / density_level_count);

					triangles += (((i + 1) * grass_mesh.index_count()) / density_level_count) / 3;
				}
			}
		}

		grass_slice_program.bind();;
		grass_slice_program["u_transform"] = camera_transform;
		grass_slice_program["u_texture"] = 0;
		grass_slice_z_texture.bind();

		for (int x = 0; x < size; ++x)
		{
			for (int y = 0; y < size; ++y)
			{
				if (x >= size / 2) continue;

				grass_slice_program["u_tile_transform"] = geom::translation<float, 3>(geom::vector{x, y, 0.f}).homogeneous_matrix()
					* random_transform[random_transform_index(x, y)];

				float d00 = density({(x + 0.f) / size, (y + 0.f) / size}) * density_level_count;
				float d01 = density({(x + 1.f) / size, (y + 0.f) / size}) * density_level_count;
				float d10 = density({(x + 0.f) / size, (y + 1.f) / size}) * density_level_count;
				float d11 = density({(x + 1.f) / size, (y + 1.f) / size}) * density_level_count;

				grass_slice_program["u_density00"] = d00;
				grass_slice_program["u_density01"] = d01;
				grass_slice_program["u_density10"] = d10;
				grass_slice_program["u_density11"] = d11;

				grass_slice_z_mesh.draw();
			}
		}

		frame_time.push(frame_clock.restart().count());

		{
			gfx::painter::text_options opts;
			opts.x = gfx::painter::x_align::left;
			opts.y = gfx::painter::y_align::top;
			opts.f = gfx::painter::font::font_9x12;
			opts.scale = 2.f;
			opts.c = {0, 0, 0, 255};

			painter.text({0.f, 0.f}, util::to_string("FPS: ", std::round(1.0 / frame_time.average())), opts);
			painter.text({0.f, 24.f}, util::to_string("Camera: ", camera.position()), opts);
			painter.text({0.f, 48.f}, util::to_string("Triangles: ", triangles), opts);
		}

		gl::Disable(gl::DEPTH_TEST);
		gl::Enable(gl::BLEND);
		gl::BlendFunc(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA);
		geom::window_camera camera;
		camera.width = width();
		camera.height = height();
		painter.render(camera.transform());
	}

};

int main()
{
	return app::main<grass_app>();
}