#include <cstdint>
#include <cmath>
#include <cassert>
#include "utils/logger.h"
#include "render/ui.h"
#include "render/vertexbuffer.h"
#include "render/indexbuffer.h"
#include "render/renderdevice.h"
#include "render/shadersystem.h"
#include "render/texturesmanager.h"
#include "render/texture2d.h"

struct DrawInfo
{
	uint16_t vxcount;
	uint16_t idxcount;
};

struct UIGlobals {
	VertexBuffer* vb;
	IndexBuffer* ib;
	Shader* shader;
	Texture2D* activetexture = nullptr;
	Texture2D* defaultTexture = nullptr;

	UIVertex* vertices = nullptr;
	uint16_t* indices = nullptr;
	DrawInfo drawInfo[MAX_UI_VERTICES];
	uint16_t count = 0;
	uint16_t position = 0;
	uint16_t Indexposition = 0;
	uint16_t currentIdx = 0;
} g_ui;


void uiInit()
{
	//////////////////////////////////////////////////////////////////////////
	// Buffer and context state

	// Buffer creation
	g_ui.vb = g_renderDevice->CreateVertexBuffer(nullptr, MAX_UI_VERTICES, true);
	g_ui.ib = g_renderDevice->CreateIndexBuffer(nullptr, MAX_UI_INDICES, true);

	// Create shader

	InputLayoutDesc_t inputLayout[] =
	{
		{ VERTEXATTR_VEC2, SHADERSEMANTIC_POSITION },
		{ VERTEXATTR_VEC2, SHADERSEMANTIC_TEXCOORD },
		{ VERTEXATTR_VEC4, SHADERSEMANTIC_COLOR },
	};

	g_ui.shader = g_shaderSystem->CreateShader("ui", "content/shaders/ui_base.vs", "content/shaders/ui_tex.ps", inputLayout, sizeof(inputLayout) / sizeof(inputLayout[0]));
	g_ui.shader->m_stride = sizeof( UIVertex );

	g_ui.defaultTexture = g_texturesManager->LoadTexture2D("$white$");
}

void uiShutdown()
{
	delete g_ui.ib;
	delete g_ui.vb;
}

void uiDumpBuffers()
{
	LogMsg( "--- UI Vertex Buffer ---" );

	g_ui.vertices = (UIVertex*)g_ui.vb->MapBuffer(BA_WRITE_ONLY);
	assert(g_ui.vertices);

	for ( int i = 0; i < g_ui.position; i++ )
	{
		LogMsg( "%i: POSITION = %.2f %.2f", i, g_ui.vertices[ i ].position.x, g_ui.vertices[ i ].position.y );
		LogMsg( "%i: TEXCOORD = %.2f %.2f", i, g_ui.vertices[ i ].uv.x, g_ui.vertices[ i ].uv.y );
		LogMsg( "%i: COLOR = %.2f %.2f %.2f %.2f", i,
			g_ui.vertices[ i ].color.x,
			g_ui.vertices[ i ].color.y,
			g_ui.vertices[ i ].color.z,
			g_ui.vertices[ i ].color.w);
	}

	LogMsg( "------------------------" );

	g_ui.vb->UnmapBuffer();
}

void uiBeginRender()
{
	g_ui.vertices = (UIVertex*)g_ui.vb->MapBuffer(BA_WRITE_ONLY);
	assert(g_ui.vertices);

	g_ui.indices = (uint16_t*)g_ui.ib->MapBuffer(BA_WRITE_ONLY);
	assert(g_ui.indices);
}

void uiDrawQuad(const Vec2& a, const Vec2& b, const Vec2& c, const Vec2& d, const Vec4& color)
{
	DrawInfo& drawInfo = g_ui.drawInfo[g_ui.count];
	drawInfo.vxcount = 4;
	drawInfo.idxcount = 6;

	g_ui.indices[g_ui.Indexposition + 0] = g_ui.currentIdx;
	g_ui.indices[g_ui.Indexposition + 1] = g_ui.currentIdx + 1;
	g_ui.indices[g_ui.Indexposition + 2] = g_ui.currentIdx + 2;
	g_ui.indices[g_ui.Indexposition + 3] = g_ui.currentIdx;
	g_ui.indices[g_ui.Indexposition + 4] = g_ui.currentIdx + 2;
	g_ui.indices[g_ui.Indexposition + 5] = g_ui.currentIdx + 3;
	g_ui.vertices[g_ui.position + 0].position = a; g_ui.vertices[g_ui.position + 0].color = color;
	g_ui.vertices[g_ui.position + 1].position = b; g_ui.vertices[g_ui.position + 1].color = color;
	g_ui.vertices[g_ui.position + 2].position = c; g_ui.vertices[g_ui.position + 2].color = color;
	g_ui.vertices[g_ui.position + 3].position = d; g_ui.vertices[g_ui.position + 3].color = color;

	// texcoord
	g_ui.vertices[g_ui.position + 0].uv = Vec2{ 0.0f, 1.0f };
	g_ui.vertices[g_ui.position + 1].uv = Vec2{ 1.0f, 1.0f };
	g_ui.vertices[g_ui.position + 2].uv = Vec2{ 1.0f, 0.0f };
	g_ui.vertices[g_ui.position + 3].uv = Vec2{ 0.0f, 0.0f };
	
	g_ui.currentIdx += 4;
	g_ui.Indexposition += 6;
	g_ui.position += 4;
	g_ui.count++;
}

static inline float  Rsqrt(float x) { return 1.0f / sqrtf(x); }
#define NORMALIZE2F_OVER_ZERO(VX,VY)     { float d2 = VX*VX + VY*VY; if (d2 > 0.0f) { float inv_len = Rsqrt(d2); VX *= inv_len; VY *= inv_len; } } (void)0

void uiDrawLines(const Vec2* drawPoints, const size_t pointsCount, bool closed, const Vec4& color)
{
	float thickness = 2.1f;

	const int count = closed ? pointsCount : pointsCount - 1;
	const int vtxCount = (count) * 4;
	const int idxCount = (count) * 6;

	for (int i1 = 0; i1 < count; i1++)
	{
		const int i2 = (i1 + 1) == pointsCount ? 0 : i1 + 1;
		const Vec2& p1 = drawPoints[i1];
		const Vec2& p2 = drawPoints[i2];

		float dx = p2.x - p1.x;
		float dy = p2.y - p1.y;
		NORMALIZE2F_OVER_ZERO(dx, dy);
		dx *= (thickness * 0.5f);
		dy *= (thickness * 0.5f);

		g_ui.vertices[g_ui.position + 0].position.x = p1.x + dy; g_ui.vertices[g_ui.position + 0].position.y = p1.y - dx; g_ui.vertices[g_ui.position + 0].color = color;
		g_ui.vertices[g_ui.position + 1].position.x = p2.x + dy; g_ui.vertices[g_ui.position + 1].position.y = p2.y - dx; g_ui.vertices[g_ui.position + 1].color = color;
		g_ui.vertices[g_ui.position + 2].position.x = p2.x - dy; g_ui.vertices[g_ui.position + 2].position.y = p2.y + dx; g_ui.vertices[g_ui.position + 2].color = color;
		g_ui.vertices[g_ui.position + 3].position.x = p1.x - dy; g_ui.vertices[g_ui.position + 3].position.y = p1.y + dx; g_ui.vertices[g_ui.position + 3].color = color;

		g_ui.indices[g_ui.Indexposition + 0] = g_ui.currentIdx;
		g_ui.indices[g_ui.Indexposition + 1] = g_ui.currentIdx + 1;
		g_ui.indices[g_ui.Indexposition + 2] = g_ui.currentIdx + 2;
		g_ui.indices[g_ui.Indexposition + 3] = g_ui.currentIdx;
		g_ui.indices[g_ui.Indexposition + 4] = g_ui.currentIdx + 2;
		g_ui.indices[g_ui.Indexposition + 5] = g_ui.currentIdx + 3;
		g_ui.currentIdx += 4;
		g_ui.Indexposition += 6;
		g_ui.position += 4;

		DrawInfo& drawInfo = g_ui.drawInfo[g_ui.count];
		drawInfo.vxcount = 4;
		drawInfo.idxcount = 6;
		g_ui.count++;
	}
}

void uiDrawRect(const Vec2& position, const Vec2& size, const Vec4& color)
{
	Vec2 quad[4];
	quad[0] = { position.x, position.y };
	quad[1] = { position.x + size.x, position.y };
	quad[2] = { position.x + size.x, position.y + size.y };
	quad[3] = { position.x, position.y + size.y };
	uiDrawQuad(quad[0], quad[1], quad[2], quad[3], color);
}

void uiSetTexture(Texture2D* texture)
{
	g_ui.activetexture = texture ? texture : g_ui.defaultTexture;
}

void uiSetTextureByName(const char* filename)
{
	uiSetTexture( g_texturesManager->LoadTexture2D( filename ) );
}

void uiEndRender()
{
	g_ui.indices = nullptr;
	g_ui.vertices = nullptr;

	g_ui.ib->UnmapBuffer();
	g_ui.vb->UnmapBuffer();

	int x = 0, y = 0, w = g_renderView.width, h = g_renderView.height;
	g_renderDevice->SetViewport(x, y, w, h);

	float L = x;
	float R = x + w;
	float T = y;
	float B = y + h;
#if defined(GL_CLIP_ORIGIN)
	if (!clip_origin_lower_left) { float tmp = T; T = B; B = tmp; } // Swap top and bottom if origin is upper left
#endif
	const float orthoProjection[4][4] =
	{
		{ 2.0f / (R - L),   0.0f,         0.0f,   0.0f },
		{ 0.0f,         2.0f / (T - B),   0.0f,   0.0f },
		{ 0.0f,         0.0f,        -1.0f,   0.0f },
		{ (R + L) / (L - R),  (T + B) / (B - T),  0.0f,   1.0f },
	};

	if ( g_ui.activetexture == nullptr  )
		 g_ui.activetexture = g_ui.defaultTexture;

	g_texturesManager->SetTexture( 0, g_ui.activetexture );
	g_ui.activetexture->SetMin(TF_LINEAR);
	g_ui.activetexture->SetMag(TF_LINEAR);
	g_ui.activetexture->SetWrapS(TW_CLAMP_TO_EDGE);
	g_ui.activetexture->SetWrapT(TW_CLAMP_TO_EDGE);

	g_shaderSystem->SetShader( g_ui.shader );
	g_shaderSystem->SetUniformMatrix( g_ui.shader, UNIFORM_PROJ_MATRIX, orthoProjection );

	g_renderDevice->SetVerticesBuffer( g_ui.vb );
	g_renderDevice->SetIndicesBuffer( g_ui.ib );

	// Enable blending
	g_renderDevice->SetBlending( true );
	g_renderDevice->SetBlendingFunction( BF_SRC_ALPHA, BF_ONE_MINUS_SRC_ALPHA );

	// Disable depth
	g_renderDevice->SetDepthTest( false );
	g_renderDevice->SetBackfaceCull( false );

	g_renderDevice->DrawElements( PT_TRIANGLES, g_ui.Indexposition, true );

	// Uncomment for UI VB debugging
	//uiDumpBuffers();

	g_ui.currentIdx = 0;
	g_ui.Indexposition = 0;
	g_ui.position = 0;
	g_ui.count = 0;
}

typedef struct Character {
	int codePoint, x, y, width, height, originX, originY;
} Character;

typedef struct Font {
	const char* name;
	int size, bold, italic, width, height, characterCount;
	Character* characters;
} Font;