/*
 * Copyright 2016 - 2023 Gary Talent (gary@drinkingtea.net). All rights reserved.
 */

#include <ox/std/array.hpp>
#include <ox/std/fmt.hpp>
#include <ox/std/vec.hpp>

#include <keel/media.hpp>

#include <glutils/glutils.hpp>

#include <nostalgia/core/context.hpp>
#include <nostalgia/core/gfx.hpp>

#include "context.hpp"

namespace nostalgia::core {

namespace gl {

void drawMainView(core::Context *ctx, ox::Size const&renderSz) noexcept;

}

namespace renderer {

void Drawer::draw(turbine::Context &tctx) noexcept {
	core::gl::drawMainView(m_ctx, turbine::getScreenSize(tctx));
}

constexpr ox::StringView bgvshadTmpl = R"(
	{}
	in vec2 vTexCoord;
	in vec2 vPosition;
	out vec2 fTexCoord;
	uniform float vXScale;
	uniform float vTileHeight;
	void main() {
		float xScaleInvert = 1.0 - vXScale;
		gl_Position = vec4(
				vPosition.x * vXScale - xScaleInvert, vPosition.y,
				0.0, 1.0);
		fTexCoord = vTexCoord * vec2(1, vTileHeight);
	})";

constexpr ox::StringView bgfshadTmpl = R"(
	{}
	out vec4 outColor;
	in vec2 fTexCoord;
	uniform sampler2D image;
	uniform vec4 fPalette[256];
	void main() {
		int idx = int(texture(image, fTexCoord).rgb.r * 256);
		outColor = fPalette[idx];
		//outColor = vec4(0.0, 0.7, 1.0, 1.0);
	})";

constexpr ox::StringView spritevshadTmpl = R"(
	{}
	in float vEnabled;
	in vec2 vTexCoord;
	in vec2 vPosition;
	out vec2 fTexCoord;
	uniform float vXScale;
	uniform float vTileHeight;
	void main() {
		float xScaleInvert = 1.0 - vXScale;
		gl_Position = vec4(
				vPosition.x * vXScale - xScaleInvert, vPosition.y,
				0.0, 1.0);
		fTexCoord = vTexCoord * vec2(1, vTileHeight) * vec2(vEnabled, vEnabled);
	})";

constexpr ox::StringView spritefshadTmpl = bgfshadTmpl;

[[nodiscard]]
static constexpr auto bgVertexRow(unsigned x, unsigned y) noexcept {
	return y * TileRows + x;
}

static void setSpriteBufferObject(Context*,
                                  unsigned vi,
                                  float enabled,
                                  float x, float y,
                                  unsigned textureRow,
                                  unsigned flipX,
                                  float *vbo,
                                  GLuint *ebo) noexcept {
	// don't worry, this memcpy gets optimized to something much more ideal
	constexpr float xmod = 0.1f;
	constexpr float ymod = 0.1f;
	x *= xmod;
	y *= -ymod;
	x -= 1.f;
	y += 1.f - ymod;
	const auto textureRowf = static_cast<float>(textureRow);
	const float L = flipX ? 1 : 0;
	const float R = flipX ? 0 : 1;
	const ox::Array<float, SpriteVertexVboLength> vertices {
			enabled,        x,        y, L, textureRowf + 1, // bottom left
			enabled, x + xmod,        y, R, textureRowf + 1, // bottom right
			enabled, x + xmod, y + ymod, R, textureRowf + 0, // top right
			enabled,        x, y + ymod, L, textureRowf + 0, // top left
	};
	memcpy(vbo, vertices.data(), sizeof(vertices));
	const ox::Array<GLuint, SpriteVertexEboLength> elms {
			vi + 0, vi + 1, vi + 2,
			vi + 2, vi + 3, vi + 0,
	};
	memcpy(ebo, elms.data(), sizeof(elms));
}

static void setTileBufferObject(Context*,
                                unsigned vi,
                                float x,
                                float y,
                                unsigned textureRow,
                                float *vbo,
                                GLuint *ebo) noexcept {
	// don't worry, this memcpy gets optimized to something much more ideal
	constexpr float ymod = 0.1f;
	constexpr float xmod = 0.1f;
	x *= xmod;
	y *= -ymod;
	x -= 1.0f;
	y += 1.0f - ymod;
	const auto textureRowf = static_cast<float>(textureRow);
	const ox::Array<float, BgVertexVboLength> vertices {
			x,        y, 0, textureRowf + 1, // bottom left
			x + xmod,        y, 1, textureRowf + 1, // bottom right
			x + xmod, y + ymod, 1, textureRowf + 0, // top right
			x, y + ymod, 0, textureRowf + 0, // top left
	};
	memcpy(vbo, vertices.data(), sizeof(vertices));
	const ox::Array<GLuint, BgVertexEboLength> elms {
			vi + 0, vi + 1, vi + 2,
			vi + 2, vi + 3, vi + 0,
	};
	memcpy(ebo, elms.data(), sizeof(elms));
}

static void initSpriteBufferObjects(Context *ctx, glutils::BufferSet *bs) noexcept {
	for (auto i = 0u; i < SpriteCount; ++i) {
		auto vbo = &bs->vertices[i * static_cast<std::size_t>(SpriteVertexVboLength)];
		auto ebo = &bs->elements[i * static_cast<std::size_t>(SpriteVertexEboLength)];
		setSpriteBufferObject(ctx, i * SpriteVertexVboRows, 0, 0, 0, 0, false, vbo, ebo);
	}
}

static void initBackgroundBufferObjects(Context *ctx, glutils::BufferSet *bg) noexcept {
	for (auto x = 0u; x < TileColumns; ++x) {
		for (auto y = 0u; y < TileRows; ++y) {
			const auto i = bgVertexRow(x, y);
			auto vbo = &bg->vertices[i * static_cast<std::size_t>(BgVertexVboLength)];
			auto ebo = &bg->elements[i * static_cast<std::size_t>(BgVertexEboLength)];
			setTileBufferObject(
				ctx,
				static_cast<unsigned>(i * BgVertexVboRows),
				static_cast<float>(x),
				static_cast<float>(y),
				0,
				vbo,
				ebo);
		}
	}
}

static void initSpritesBufferset(Context *ctx, GLuint shader, glutils::BufferSet *bs) noexcept {
	// vao
	bs->vao = glutils::generateVertexArrayObject();
	glBindVertexArray(bs->vao);
	// vbo & ebo
	bs->vbo = glutils::generateBuffer();
	bs->ebo = glutils::generateBuffer();
	initSpriteBufferObjects(ctx, bs);
	glutils::sendVbo(*bs);
	glutils::sendEbo(*bs);
	// vbo layout
	auto enabledAttr = static_cast<GLuint>(glGetAttribLocation(shader, "vEnabled"));
	glEnableVertexAttribArray(enabledAttr);
	glVertexAttribPointer(enabledAttr, 1, GL_FLOAT, GL_FALSE, SpriteVertexVboRowLength * sizeof(float), nullptr);
	auto posAttr = static_cast<GLuint>(glGetAttribLocation(shader, "vPosition"));
	glEnableVertexAttribArray(posAttr);
	glVertexAttribPointer(posAttr, 2, GL_FLOAT, GL_FALSE, SpriteVertexVboRowLength * sizeof(float),
	                      reinterpret_cast<void*>(1 * sizeof(float)));
	auto texCoordAttr = static_cast<GLuint>(glGetAttribLocation(shader, "vTexCoord"));
	glEnableVertexAttribArray(texCoordAttr);
	glVertexAttribPointer(texCoordAttr, 2, GL_FLOAT, GL_FALSE, SpriteVertexVboRowLength * sizeof(float),
	                      reinterpret_cast<void*>(3 * sizeof(float)));
}

static void initBackgroundBufferset(Context *ctx, GLuint shader, glutils::BufferSet *bg) noexcept {
	// vao
	bg->vao = glutils::generateVertexArrayObject();
	glBindVertexArray(bg->vao);
	// vbo & ebo
	bg->vbo = glutils::generateBuffer();
	bg->ebo = glutils::generateBuffer();
	initBackgroundBufferObjects(ctx, bg);
	glutils::sendVbo(*bg);
	glutils::sendEbo(*bg);
	// vbo layout
	auto posAttr = static_cast<GLuint>(glGetAttribLocation(shader, "vPosition"));
	glEnableVertexAttribArray(posAttr);
	glVertexAttribPointer(posAttr, 2, GL_FLOAT, GL_FALSE, BgVertexVboRowLength * sizeof(float), nullptr);
	auto texCoordAttr = static_cast<GLuint>(glGetAttribLocation(shader, "vTexCoord"));
	glEnableVertexAttribArray(texCoordAttr);
	glVertexAttribPointer(texCoordAttr, 2, GL_FLOAT, GL_FALSE, BgVertexVboRowLength * sizeof(float),
	                      reinterpret_cast<void*>(2 * sizeof(float)));
}

static glutils::GLTexture loadTexture(GLsizei w, GLsizei h, const void *pixels) noexcept {
	GLuint texId = 0;
	glGenTextures(1, &texId);
	glutils::GLTexture tex(texId);
	tex.width = w;
	tex.height = h;
	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, tex.id);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex.width, tex.height, 0,  GL_RGBA, GL_UNSIGNED_BYTE, pixels);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	return tex;
}

static void drawBackground(CBB *cbb) noexcept {
	glBindVertexArray(cbb->vao);
	if (cbb->updated) {
		cbb->updated = false;
		glutils::sendVbo(*cbb);
	}
	glBindTexture(GL_TEXTURE_2D, cbb->tex);
	glDrawElements(GL_TRIANGLES, static_cast<GLsizei>(cbb->elements.size()), GL_UNSIGNED_INT, nullptr);
}

static void drawBackgrounds(GlContext *gctx, ox::Size const&renderSz) noexcept {
	// load background shader and its uniforms
	glUseProgram(gctx->bgShader);
	const auto uniformXScale = static_cast<GLint>(glGetUniformLocation(gctx->bgShader, "vXScale"));
	const auto uniformTileHeight = static_cast<GLint>(glGetUniformLocation(gctx->bgShader, "vTileHeight"));
	const auto [wi, hi] = renderSz;
	const auto wf = static_cast<float>(wi);
	const auto hf = static_cast<float>(hi);
	glUniform1f(uniformXScale, hf / wf);
	for (const auto &bg : gctx->backgrounds) {
		if (bg.enabled) {
			auto &cbb = gctx->cbbs[bg.cbbIdx];
			const auto tileRows = cbb.tex.height / TileHeight;
			glUniform1f(uniformTileHeight, 1.0f / static_cast<float>(tileRows));
			drawBackground(&cbb);
		}
	}
}

static void drawSprites(GlContext *gctx, ox::Size const&renderSz) noexcept {
	glUseProgram(gctx->spriteShader);
	auto &sb = gctx->spriteBlocks;
	const auto uniformXScale = static_cast<GLint>(glGetUniformLocation(gctx->bgShader, "vXScale"));
	const auto uniformTileHeight = static_cast<GLint>(glGetUniformLocation(gctx->spriteShader, "vTileHeight"));
	const auto [wi, hi] = renderSz;
	const auto wf = static_cast<float>(wi);
	const auto hf = static_cast<float>(hi);
	glUniform1f(uniformXScale, hf / wf);
	// update vbo
	glBindVertexArray(sb.vao);
	if (sb.updated) {
		sb.updated = false;
		glutils::sendVbo(sb);
	}
	// set vTileHeight uniform
	const auto tileRows = sb.tex.height / TileHeight;
	glUniform1f(uniformTileHeight, 1.0f / static_cast<float>(tileRows));
	// draw
	glBindTexture(GL_TEXTURE_2D, sb.tex);
	glDrawElements(GL_TRIANGLES, static_cast<GLsizei>(sb.elements.size()), GL_UNSIGNED_INT, nullptr);
}

static void loadPalette(GLuint shaderPgrm, const Palette &pal, bool firstIsTransparent = false) noexcept {
	static constexpr std::size_t ColorCnt = 256;
	ox::Array<GLfloat, ColorCnt * 4> palette{};
	for (auto i = 0u; const auto c : pal.colors) {
		palette[i++] = redf(c);
		palette[i++] = greenf(c);
		palette[i++] = bluef(c);
		palette[i++] = 255;
	}
	if (firstIsTransparent) {
		palette[3] = 0;
	}
	glUseProgram(shaderPgrm);
	const auto uniformPalette = static_cast<GLint>(glGetUniformLocation(shaderPgrm, "fPalette"));
	glUniform4fv(uniformPalette, ColorCnt, palette.data());
}

static void loadBgPalette(GlContext *gctx, const Palette &pal) noexcept {
	loadPalette(gctx->bgShader, pal);
}

static void loadSpritePalette(GlContext *gctx, const Palette &pal) noexcept {
	loadPalette(gctx->spriteShader, pal, true);
}

static void loadBgTexture(GlContext *gctx, unsigned cbbIdx, const void *pixels, int w, int h) noexcept {
	oxTracef("nostalgia::core::gfx::gl", "loadBgTexture: { cbbIdx: {}, w: {}, h: {} }", cbbIdx, w, h);
	gctx->cbbs[cbbIdx].tex = loadTexture(w, h, pixels);
}

static void loadSpriteTexture(GlContext *gctx, const void *pixels, int w, int h) noexcept {
	oxTracef("nostalgia::core::gfx::gl", "loadSpriteTexture: { w: {}, h: {} }", w, h);
	gctx->spriteBlocks.tex = loadTexture(w, h, pixels);
}

}

ox::Error initGfx(Context *ctx, const InitParams &initParams) noexcept {
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	const auto bgVshad = ox::sfmt(renderer::bgvshadTmpl, glutils::GlslVersion);
	const auto bgFshad = ox::sfmt(renderer::bgfshadTmpl, glutils::GlslVersion);
	const auto spriteVshad = ox::sfmt(renderer::spritevshadTmpl, glutils::GlslVersion);
	const auto spriteFshad = ox::sfmt(renderer::spritefshadTmpl, glutils::GlslVersion);
	auto &gctx = static_cast<GlContext&>(*ctx);
	oxReturnError(glutils::buildShaderProgram(bgVshad.c_str(), bgFshad.c_str()).moveTo(&gctx.bgShader));
	oxReturnError(glutils::buildShaderProgram(spriteVshad.c_str(), spriteFshad.c_str()).moveTo(&gctx.spriteShader));
	for (auto &bg : gctx.cbbs) {
		initBackgroundBufferset(ctx, gctx.bgShader, &bg);
	}
	gctx.drawer.m_ctx = ctx;
	if (initParams.glInstallDrawer) {
		turbine::gl::addDrawer(*gctx.turbineCtx, &gctx.drawer);
		initSpritesBufferset(ctx, gctx.spriteShader, &gctx.spriteBlocks);
	}
	return {};
}

void shutdownGfx(Context *ctx) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	turbine::gl::removeDrawer(*gctx.turbineCtx, &gctx.drawer);
}

ox::Error initConsole(Context *ctx) noexcept {
	constexpr ox::FileAddress TilesheetAddr("/TileSheets/Charset.ng");
	constexpr ox::FileAddress PaletteAddr("/Palettes/Charset.npal");
	setBgStatus(ctx, 0b0001);
	setBgCbb(ctx, 0, 0);
	return loadBgTileSheet(ctx, 0, TilesheetAddr, PaletteAddr);
}

struct TileSheetData {
	ox::Vector<uint32_t> pixels;
	int width = 0;
	int height = 0;
};

ox::Result<TileSheetData> loadTileSheet(Context *ctx, const CompactTileSheet &tilesheet) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	const unsigned bytesPerTile = tilesheet.bpp == 8 ? PixelsPerTile : PixelsPerTile / 2;
	const auto tiles = tilesheet.pixels.size() / bytesPerTile;
	constexpr int width = 8;
	const int height = 8 * static_cast<int>(tiles);
	ox::Vector<uint32_t> pixels;
	if (bytesPerTile == 64) { // 8 BPP
		pixels.resize(tilesheet.pixels.size());
		for (std::size_t i = 0; i < tilesheet.pixels.size(); ++i) {
			pixels[i] = tilesheet.pixels[i];
		}
	} else { // 4 BPP
		pixels.resize(tilesheet.pixels.size() * 2);
		for (std::size_t i = 0; i < tilesheet.pixels.size(); ++i) {
			pixels[i * 2 + 0] = tilesheet.pixels[i] & 0xF;
			pixels[i * 2 + 1] = tilesheet.pixels[i] >> 4;
		}
	}
	renderer::loadSpriteTexture(&gctx, pixels.data(), width, height);
	return TileSheetData{std::move(pixels), width, height};
}

ox::Error loadBgTileSheet(Context *ctx,
                          unsigned cbb,
                          const ox::FileAddress &tilesheetAddr,
                          const ox::FileAddress &paletteAddr) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto &kctx = *gctx.turbineCtx;
	oxRequire(tilesheet, readObj<CompactTileSheet>(&kctx, tilesheetAddr));
	oxRequire(palette, readObj<Palette>(&kctx, paletteAddr ? paletteAddr : tilesheet->defaultPalette));
	oxRequire(tsd, loadTileSheet(ctx, *tilesheet));
	renderer::loadBgTexture(&gctx, cbb, tsd.pixels.data(), tsd.width, tsd.height);
	renderer::loadBgPalette(&gctx, *palette);
	return {};
}

ox::Error loadSpriteTileSheet(Context *ctx,
                              const ox::FileAddress &tilesheetAddr,
                              const ox::FileAddress &paletteAddr) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto &kctx = *gctx.turbineCtx;
	oxRequire(tilesheet, readObj<CompactTileSheet>(&kctx, tilesheetAddr));
	oxRequire(palette, readObj<Palette>(&kctx, paletteAddr ? paletteAddr : tilesheet->defaultPalette));
	oxRequire(tsd, loadTileSheet(ctx, *tilesheet));
	renderer::loadSpriteTexture(&gctx, tsd.pixels.data(), tsd.width, tsd.height);
	renderer::loadSpritePalette(&gctx, *palette);
	return {};
}

void puts(Context *ctx, int column, int row, ox::CRStringView str) noexcept {
	const auto col = static_cast<unsigned>(column);
	for (auto i = 0u; i < str.bytes(); ++i) {
		setTile(ctx, 0, static_cast<int>(col + i), row, static_cast<uint8_t>(charMap[static_cast<uint8_t>(str[i])]));
	}
}
void setBgCbb(Context *ctx, unsigned bgIdx, unsigned cbbIdx) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto &bg = gctx.backgrounds[bgIdx];
	bg.cbbIdx = cbbIdx;
}

uint8_t bgStatus(Context *ctx) noexcept {
	const auto &gctx = static_cast<GlContext&>(*ctx);
	uint8_t out = 0;
	for (unsigned i = 0; i < gctx.cbbs.size(); ++i) {
		out |= static_cast<uint8_t>(static_cast<unsigned>(gctx.backgrounds[i].enabled) << i);
	}
	return out;
}

void setBgStatus(Context *ctx, uint32_t status) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	for (unsigned i = 0; i < gctx.cbbs.size(); ++i) {
		gctx.backgrounds[i].enabled = (status >> i) & 1;
	}
}

bool bgStatus(Context *ctx, unsigned bg) noexcept {
	const auto &gctx = static_cast<GlContext&>(*ctx);
	return gctx.backgrounds[bg].enabled;
}

void setBgStatus(Context *ctx, unsigned bg, bool status) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	gctx.backgrounds[bg].enabled = status;
}


void glearTileLayer(Context *ctx, unsigned bgIdx) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto &bg = gctx.cbbs[static_cast<std::size_t>(bgIdx)];
	initBackgroundBufferObjects(&gctx, &bg);
	bg.updated = true;
}

void hideSprite(Context *ctx, unsigned idx) noexcept {
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto vbo = &gctx.spriteBlocks.vertices[idx * renderer::SpriteVertexVboLength];
	auto ebo = &gctx.spriteBlocks.elements[idx * renderer::SpriteVertexEboLength];
	renderer::setSpriteBufferObject(ctx, idx * renderer::SpriteVertexVboRows, 0,
	                                0, 0, 0, false, vbo, ebo);
	gctx.spriteBlocks.updated = true;
}

void setSprite(Context *ctx,
               unsigned idx,
               int x,
               int y,
               unsigned tileIdx,
               [[maybe_unused]] unsigned spriteShape,
               [[maybe_unused]] unsigned spriteSize,
               unsigned flipX) noexcept {
	//oxTracef("nostalgia::core::gfx::gl", "setSprite(ctx, {}, {}, {}, {}, {}, {}, {})",
	//         idx, x, y, tileIdx, spriteShape, spriteSize, flipX);
	// Tonc Table 8.4
	static constexpr ox::Array<ox::Vec<unsigned>, 12> dimensions{
			// col 0
			{1, 1}, // 0, 0
			{2, 2}, // 0, 1
			{4, 4}, // 0, 2
			{8, 8}, // 0, 3
			// col 1
			{2, 1}, // 1, 0
			{4, 1}, // 1, 1
			{4, 2}, // 1, 2
			{8, 4}, // 1, 3
			// col 2
			{1, 1}, // 2, 0
			{1, 4}, // 2, 1
			{2, 4}, // 2, 2
			{4, 8}, // 2, 3
	};
	const auto dim = dimensions[(spriteShape << 2) | spriteSize];
	const auto uX = static_cast<int>(x) % 255;
	const auto uY = static_cast<int>(y + 8) % 255 - 8;
	auto &gctx = static_cast<GlContext&>(*ctx);
	auto i = 0u;
	const auto set = [&](int xIt, int yIt) {
		const auto fX = static_cast<float>(uX + xIt * 8) / 8;
		const auto fY = static_cast<float>(uY + yIt * 8) / 8;
		const auto cidx = idx + i;
		auto vbo = &gctx.spriteBlocks.vertices[cidx * renderer::SpriteVertexVboLength];
		auto ebo = &gctx.spriteBlocks.elements[cidx * renderer::SpriteVertexEboLength];
		renderer::setSpriteBufferObject(ctx, cidx * renderer::SpriteVertexVboRows, 1,
		                                fX, fY, tileIdx + i, flipX, vbo, ebo);
		++i;
	};
	if (!flipX) {
		for (auto yIt = 0; yIt < static_cast<int>(dim.y); ++yIt) {
			for (auto xIt = 0u; xIt < dim.x; ++xIt) {
				set(static_cast<int>(xIt), static_cast<int>(yIt));
			}
		}
	} else {
		for (auto yIt = 0u; yIt < dim.y; ++yIt) {
			for (auto xIt = dim.x - 1; xIt < ~0u; --xIt) {
				set(static_cast<int>(xIt), static_cast<int>(yIt));
			}
		}
	}
	gctx.spriteBlocks.updated = true;
}

void setTile(Context *ctx, unsigned bgIdx, int column, int row, uint8_t tile) noexcept {
	oxTracef(
			"nostalgia::core::gfx::setTile",
			"bgIdx: {}, column: {}, row: {}, tile: {}",
			bgIdx, column, row, tile);
	auto &gctx = static_cast<GlContext&>(*ctx);
	const auto z = static_cast<unsigned>(bgIdx);
	const auto y = static_cast<unsigned>(row);
	const auto x = static_cast<unsigned>(column);
	const auto i = renderer::bgVertexRow(x, y);
	auto &bg = gctx.cbbs[z];
	auto vbo = &bg.vertices[i * renderer::BgVertexVboLength];
	auto ebo = &bg.elements[i * renderer::BgVertexEboLength];
	renderer::setTileBufferObject(
			ctx,
			static_cast<unsigned>(i * renderer::BgVertexVboRows),
			static_cast<float>(x),
			static_cast<float>(y),
			tile,
			vbo,
			ebo);
	bg.updated = true;
}

namespace gl {

void drawMainView(core::Context *ctx, ox::Size const&renderSz) noexcept {
	// clear screen
	glClearColor(0, 0, 0, 1);
	glClear(GL_COLOR_BUFFER_BIT);
	auto &gctx = static_cast<GlContext&>(*ctx);
	renderer::drawBackgrounds(&gctx, renderSz);
	if (gctx.spriteBlocks.tex) {
		renderer::drawSprites(&gctx, renderSz);
	}
}

}

}