#include "Graphics.h"
#include <ft2build.h>
#include FT_FREETYPE_H

#include <bx/math.h>

#include <iostream>
#include <optional>
#include <algorithm>

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

namespace {
	using namespace ADVect::Graphics;

	bgfx::ShaderHandle loadShader(const std::string& FILENAME)
	{
		std::string shaderPath{};

		switch (bgfx::getRendererType()) {
		case bgfx::RendererType::Noop:
		case bgfx::RendererType::Direct3D9:  shaderPath = "shaders/dx9/";   break;
		case bgfx::RendererType::Direct3D11:
		case bgfx::RendererType::Direct3D12: shaderPath = "shaders/dx11/";  break;
		case bgfx::RendererType::Gnm:        shaderPath = "shaders/pssl/";  break;
		case bgfx::RendererType::Metal:      shaderPath = "shaders/metal/"; break;
		case bgfx::RendererType::OpenGL:     shaderPath = "shaders/glsl/";  break;
		case bgfx::RendererType::OpenGLES:   shaderPath = "shaders/essl/";  break;
		case bgfx::RendererType::Vulkan:     shaderPath = "shaders/spirv/"; break;
		}


		std::string filePath = shaderPath + FILENAME;

		FILE* file = fopen(filePath.c_str(), "rb");
		fseek(file, 0, SEEK_END);
		long fileSize = ftell(file);
		fseek(file, 0, SEEK_SET);

		const bgfx::Memory* mem = bgfx::alloc(fileSize + 1);
		fread(mem->data, 1, fileSize, file);
		mem->data[mem->size - 1] = '\0';
		fclose(file);

		return bgfx::createShader(mem);
	}

	struct PosUVVertex {
		f32 x;
		f32 y;
		f32 z;
		f32 u;
		f32 v;
	};

	static PosUVVertex quad_vert[] =
	{
		{ 0.f, 0.f, 0.0f, 0.0f, 0.0f },
		{ 0.f, 1.f, 0.0f, 0.0f, 1.0f },
		{ 1.f, 0.f, 0.0f, 1.0f, 0.0f },
		{ 1.f, 1.f, 0.0f, 1.0f, 1.0f }
	};

	static const u16 quad_indices[] =
	{
		0, 2, 1,
		1, 2, 3
	};

	FT_Library library;
	FT_Error error;

	struct Font {
		FT_Face face = nullptr;
		std::unordered_map<NVL::Char, std::tuple<std::optional<bgfx::TextureHandle>, u32, u32, i32, i32, i32, i32>> cache{};

		std::tuple<std::optional<bgfx::TextureHandle>, u32, u32, i32, i32, i32, i32>& get_char(NVL::Char c) {
			if (cache.find(c) == cache.end()) {
				FT_GlyphSlot slot = face->glyph;

				error = FT_Load_Char(face, c, FT_LOAD_RENDER);
				if (error) {
					std::cerr << "ADV: Failed to load character" << std::endl;
				}

				if (slot->bitmap.width != 0) {
					const bgfx::Memory* buf = bgfx::copy(slot->bitmap.buffer, slot->bitmap.pitch * slot->bitmap.rows);

					cache.emplace(c, std::make_tuple(
						bgfx::createTexture2D(
							slot->bitmap.width,
							slot->bitmap.rows,
							false,
							1,
							bgfx::TextureFormat::A8,
							BGFX_TEXTURE_NONE | BGFX_SAMPLER_UVW_CLAMP,
							buf
						),
						slot->bitmap.width,
						slot->bitmap.rows,
						slot->bitmap_left,
						slot->bitmap_top,
						slot->advance.x,
						slot->advance.y
					));
				}
				else cache.emplace(c, std::make_tuple(
					std::nullopt,
					0,
					0,
					0,
					0,
					slot->advance.x,
					slot->advance.y));
			}
			return cache[c];
		}
	};

	std::optional<Font> get_font(const char* path) {
		Font f;

		error = FT_New_Face(library, path, 0, &f.face);
		if (error == FT_Err_Unknown_File_Format) {
			std::cerr << "ADV: FreeType Unknown_File_Format: " << error << std::endl;
			return std::nullopt;
		}
		else if (error) {
			std::cerr << "ADV: FreeType font loading error: " << error << std::endl;
			return std::nullopt;
		}

		error = FT_Set_Char_Size(f.face, 0, 20 * 64, 72, 72);
		if (error) {
			std::cerr << "ADV: FreeType Set_Char_Size error: " << error << std::endl;
			return std::nullopt;
		}

		return f;
	}

	void destroy_font(Font& f) {
		FT_Done_Face(f.face);
		for (auto it = f.cache.begin(); it != f.cache.end(); it++) {
			if(auto& tx = std::get<0>(it->second))
				bgfx::destroy(*tx);
		}
	}

	inline bgfx::ProgramHandle load_shader_program(const std::string& shader) {
		return bgfx::createProgram(loadShader(shader + ".vert.bin"), loadShader(shader + ".frag.bin"), false);
	}

	std::optional<ImageTexture> get_image_texture(const std::string& file) {
		ImageTexture i;
		i.buffer = stbi_load(file.c_str(), &i.w, &i.h, &i.channels, 0);
		if (i.buffer == NULL) {
			std::cerr << "ADV: STB IMAGE loading failed for " << file << std::endl;
			return std::nullopt;
		}
		const bgfx::Memory* buf = bgfx::makeRef(i.buffer, i.w * i.h * i.channels * sizeof(u8));
		i.tx = bgfx::createTexture2D(
			i.w,
			i.h,
			false,
			1,
			i.channels == 4 ? bgfx::TextureFormat::RGBA8 : bgfx::TextureFormat::RGB8,
			BGFX_TEXTURE_NONE | BGFX_SAMPLER_UVW_CLAMP,
			buf
		);
		return i;
	}

	void destroy_image_texture(ImageTexture& i) {
		stbi_image_free(i.buffer);
		bgfx::destroy(i.tx);
	}

	Font regular, bold;
	bgfx::ProgramHandle a_program, img_program, imga_program;

	bgfx::UniformHandle s_texColor;
	bgfx::UniformHandle imga_opacity;

	bgfx::IndexBufferHandle ibh;
	bgfx::VertexBufferHandle vbh;
	bgfx::VertexLayout pcvDecl;

	std::unordered_map<std::string, ImageTexture> imgs;

	inline Font* ResolveStyleFlags(u32 style_flags) {
		Font* f = &regular;
		switch (style_flags) {
		case TEXT_NONE: break;
		case TEXT_BOLD: f = &bold; break;
		case TEXT_ITALIC: break;
		case TEXT_ITALIC | TEXT_BOLD: break;
		}
		return f;
	}
	
	inline void HandleMarkupFlags(const NVL::Environment::MarkupSegment& s, u32& style_flags, const NVL::String*& ruby) {
		for (const auto& e : s.efs) {
			if (e.first == u"b") { style_flags |= TEXT_BOLD; }
			else if (e.first == u"i") { style_flags |= TEXT_ITALIC; }
			else if (e.first == u"u") { style_flags |= TEXT_UNDERLINE; }
			else if (e.first == u"s") { style_flags |= TEXT_STRIKETHROUGH; }
			else if (e.first == u"o") { style_flags |= TEXT_OVERLINE; }
			else if (e.first == u"rb") { ruby = &e.second[0]; }
			else {
				std::cerr << "ADV: Unrecognized text markup: " << NVL::to_std_string(e.first) << std::endl;
			}
		}
	}
}

namespace ADVect::Graphics {
	bool Init(u16 width, u16 height) {
		error = FT_Init_FreeType(&library);
		if (error) {
			std::cerr << "ADV: FreeType init error: " << error << std::endl;
			return false;
		}

		if (auto f = get_font("SourceHanSerif-Regular.ttc")) regular = *f; else return false;
		if (auto f = get_font("SourceHanSerif-Heavy.ttc")) bold = *f; else return false;

		pcvDecl.begin()
			.add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float)
			.add(bgfx::Attrib::TexCoord0, 2, bgfx::AttribType::Float)
			.end();
		ibh = bgfx::createIndexBuffer(bgfx::makeRef(quad_indices, sizeof(quad_indices)));
		vbh = bgfx::createVertexBuffer(bgfx::makeRef(quad_vert, sizeof(quad_vert)), pcvDecl);

//		img_program = load_shader_program("test"); // RGBA
		imga_program = load_shader_program("ImageAlpha"); // RGBA + Opacity
		a_program = load_shader_program("AlphaStencil"); // A -> FFFA

		imga_opacity = bgfx::createUniform("f_opacity", bgfx::UniformType::Vec4); // x -> alpha, yzw are dummies
		s_texColor = bgfx::createUniform("s_texColor", bgfx::UniformType::Sampler);

		return true;
	}

	void Shutdown() {
		destroy_font(regular);
		destroy_font(bold);
		FT_Done_FreeType(library);

		for (auto it = imgs.begin(); it != imgs.end(); it++) {
			destroy_image_texture(it->second);
		}

		bgfx::destroy(a_program);
		//bgfx::destroy(img_program);
		bgfx::destroy(imga_program);

		bgfx::destroy(ibh);
		bgfx::destroy(vbh);

		bgfx::destroy(s_texColor);
		bgfx::destroy(imga_opacity);
	}

	// Draws quad with texture on Z = 0
	void DrawTexture(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h, u64 state, const bgfx::ProgramHandle& pg) {
		f32 mtx1[16], mtx2[16], mtx3[16];
		bx::mtxTranslate(mtx1, pos_x, pos_y, 0.0f);
		bx::mtxScale(mtx2, w, h, 1.0f);
		bx::mtxMul(mtx3, mtx2, mtx1);

		bgfx::setTransform(mtx3);

		bgfx::setVertexBuffer(0, vbh);
		bgfx::setIndexBuffer(ibh);

		bgfx::setTexture(0, s_texColor, tex);

		bgfx::setState(state);
		bgfx::submit(0, pg);
	}

	void DrawTextureImage(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h) {
		DrawTexture(tex, pos_x, pos_y, w, h, (BGFX_STATE_DEFAULT | BGFX_STATE_BLEND_ALPHA) & ~(BGFX_STATE_WRITE_Z | BGFX_STATE_DEPTH_TEST_LESS), img_program);
	}

	void DrawTextureImage(const ImageTexture& img, i32 pos_x, i32 pos_y) {
		DrawTextureImage(img.tx, pos_x, pos_y, img.w, img.h);
	}

	void DrawTextureImageAlpha(const ImageTexture& img, i32 pos_x, i32 pos_y, f32 alpha) {
		f32 pack[4]{};
		pack[0] = alpha;
		bgfx::setUniform(imga_opacity, pack);
		DrawTexture(img.tx, pos_x, pos_y, img.w, img.h, (BGFX_STATE_DEFAULT | BGFX_STATE_BLEND_ALPHA) & ~(BGFX_STATE_WRITE_Z | BGFX_STATE_DEPTH_TEST_LESS), imga_program);
	}

	ImageTexture* GetImageTextureFromFile(const std::string& file) {
		if (imgs.find(file) == imgs.end()) {
			if (auto i = get_image_texture(file)) {
				imgs[file] = std::move(*i);
				return &imgs[file];
			}
			else return nullptr;
		}
		else
			return &imgs[file];
	}

	void DrawTextureStencilAlpha(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h) {
		DrawTexture(tex, pos_x, pos_y, w, h, (BGFX_STATE_DEFAULT | BGFX_STATE_BLEND_ALPHA) & ~(BGFX_STATE_WRITE_Z | BGFX_STATE_DEPTH_TEST_LESS), a_program);
	}

	template <bool DoRender, bool Walk>
	void RenderGlyph(NVL::Char c, std::conditional_t<Walk, i32&, i32> pos_x, std::conditional_t<Walk, i32&, i32> pos_y, u32 col, u32 style_flags) {
		Font* f = ResolveStyleFlags(style_flags);

		auto& [tx, w, h, l, t, x, y] = f->get_char(c);

		pos_x += l;

		if (auto& buf = tx; DoRender && tx && w != 0) {
			DrawTextureStencilAlpha(*buf, pos_x, pos_y - (h - t), w, h);
		}

		pos_x += x >> 6;
		pos_y += y >> 6;
	}

	template <bool DoRender, bool Walk>
	void RenderString(const NVL::String& s, std::conditional_t<Walk, i32&, i32> pos_x, std::conditional_t<Walk, i32&, i32> pos_y, u32 col, u32 style_flags) {
		for (const auto& c : s) {
			RenderGlyph<DoRender>(c, pos_x, pos_y, col, style_flags);
		}
	}

	template <bool DoRender, bool Walk>
	void RenderString(NVL::String::const_iterator cbegin, NVL::String::const_iterator cend, std::conditional_t<Walk, i32&, i32> pos_x, std::conditional_t<Walk, i32&, i32> pos_y, u32 col, u32 style_flags) {
		while (cbegin < cend) {
			RenderGlyph<DoRender>(*cbegin++, pos_x, pos_y, col, style_flags);
		}
	}

	void RenderStringCentered(const NVL::String& s, i32 pos_x, i32 pos_y, u32 col, u32 style_flags = TEXT_NONE) {
		i32 copy_x = 0, copy_y = 0;
		RenderString<false, true>(s, copy_x, copy_y, col, style_flags);
		RenderString<true, false>(s, pos_x - copy_x / 2, pos_y, col, style_flags);
	}

	// I cannot reason this function, returns where the string would end if it was not halted
	i32 RenderSubstringBox(const NVL::String& s, i32& pos_x, i32& pos_y, i32 reset_x, u32 w, u32 col, u32 style_flags, size_t s_end) {
		Font* f = ResolveStyleFlags(style_flags);

		NVL::String::const_iterator last = s.cbegin(), end = s.cend(), pos = std::find(last, end, u' '),
			halt = s_end > s.length() ? end : last + s_end;
		if (pos == end) { // Render the entire thing with hard break if we don't split at all
			NVL::String::const_iterator last_copy = last;
			i32 copy_x = pos_x, copy_y = pos_y;
			while (last != std::min(pos, halt)) {
				RenderGlyph(*last++, pos_x, pos_y, col, style_flags);
				if (pos_x - reset_x > w) {
					pos_x = reset_x;
					pos_y -= f->face->size->metrics.height / 64;
				}
				if (last >= halt) { 
					RenderString<false>(last_copy, pos, copy_x, copy_y, col, style_flags);
					return copy_x;
				};
			}
		}
		else while (last != end) { // Loop through all segments
			i32 copy_x = pos_x, old_x = pos_x, copy_y = pos_y;
			RenderString<false>(last, pos, copy_x, copy_y, col, style_flags);
			if (copy_x - reset_x > w) { // if walk exceeded max w
				copy_x = reset_x, copy_y = pos_y; // try walk again from leftmost of box, see if a soft break works; reset y from last walk
				RenderString<false>(last, pos, copy_x, copy_y, col, style_flags);
				if (copy_x - reset_x > w) { // soft break won't work, go back to old x and hard break
					pos_x = old_x;
					while (last != pos) {
						RenderGlyph(*last++, pos_x, pos_y, col, style_flags);
						if (pos_x - reset_x > w) {
							pos_x = reset_x;
							pos_y -= f->face->size->metrics.height / 64;
						}
						if (last >= halt) return copy_x;
					}
				}
				else { // soft break and kill beginning space
					pos_x = reset_x;
					pos_y -= f->face->size->metrics.height / 64;
					last++;
					RenderString(last, std::min(pos, halt), pos_x, pos_y, col, style_flags);
					if (last >= halt) return copy_x;
				}
			}
			else {
				RenderString(last, std::min(pos, halt), pos_x, pos_y, col, style_flags);
				if (last >= halt) return copy_x;
			}

			last = pos;
			if (pos != end)
				pos = std::find(std::next(pos), end, u' ');
		}
		return pos_x;
	}
	
	void RenderSubstringMarkupBox(const NVL::Environment::MarkupString& ms, i32 pos_x, i32 pos_y, u32 w, u32 col, size_t end) {
		i32 init_x = pos_x;
		size_t acc_length = 0;
		// We assume markups are already sorted
		for (const NVL::Environment::MarkupSegment& s : ms.segments) {
			u32 style_flags = TEXT_NONE;
			const NVL::String* ruby = nullptr;
			HandleMarkupFlags(s, style_flags, ruby);

			i32 last_x = pos_x,

			segment_end = RenderSubstringBox(s.str, pos_x, pos_y, init_x, w, col, style_flags, end - acc_length);

			if (ruby != nullptr && segment_end != last_x) {
				RenderStringCentered(*ruby, segment_end / 2 + last_x / 2, i32(pos_y + 20), col);
			}

			acc_length += s.str.length();
			if (acc_length > end) return;
		}
	}

}