/*
 * Copyright (C) 2017-2019  Christopher J. Howard
 *
 * This file is part of Antkeeper Source Code.
 *
 * Antkeeper Source Code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper Source Code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper Source Code.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "resource-loader.hpp"
#include "resource-manager.hpp"
#include <algorithm>
#include <stdexcept>
#include <sstream>
#include <vector>

#include <emergent/emergent.hpp>
using namespace Emergent;

static bool loadShaderInt(ShaderInt* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		int value;
		std::stringstream stream;
		stream << elements[i][0];
		stream >> value;
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderFloat(ShaderFloat* variable, const std::vector<std::vector<std::string>>& elements)
{	
	for (int i = 0; i < elements.size(); ++i)
	{
		float value;
		std::stringstream stream;
		stream << elements[i][0];
		stream >> value;
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderVector2(ShaderVector2* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		Vector2 value;
		
		for (int j = 0; j < 2; ++j)
		{
			std::stringstream stream;
			stream << elements[i][j];
			stream >> value[j];
		}
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderVector3(ShaderVector3* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		Vector3 value;
		
		for (int j = 0; j < 3; ++j)
		{
			std::stringstream stream;
			stream << elements[i][j];
			stream >> value[j];
		}
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderVector4(ShaderVector4* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		Vector4 value;
		
		for (int j = 0; j < 4; ++j)
		{
			std::stringstream stream;
			stream << elements[i][j];
			stream >> value[j];
		}
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderMatrix3(ShaderMatrix3* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		Matrix3 value;
		
		for (int j = 0; j < 3; ++j)
		{
			for (int k = 0; k < 3; ++k)
			{
				std::stringstream stream;
				stream << elements[i][k * 3 + j];
				stream >> value[j][k];
			}
		}
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderMatrix4(ShaderMatrix4* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		Matrix4 value;
		
		for (int j = 0; j < 4; ++j)
		{
			for (int k = 0; k < 4; ++k)
			{
				std::stringstream stream;
				stream << elements[i][k * 4 + j];
				stream >> value[j][k];
			}
		}
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderTexture2D(ResourceManager* resourceManager, ShaderTexture2D* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		std::string filename;
		std::stringstream stream;
		stream << elements[i][0];
		stream >> filename;

		Texture2D* value = resourceManager->load<Texture2D>(filename);
		
		variable->setValue(i, value);
	}
	
	return true;
}

static bool loadShaderTextureCube(ResourceManager* resourceManager, ShaderTextureCube* variable, const std::vector<std::vector<std::string>>& elements)
{
	for (int i = 0; i < elements.size(); ++i)
	{
		std::string filename;
		std::stringstream stream;
		stream << elements[i][0];
		stream >> filename;
		
		TextureCube* value = resourceManager->load<TextureCube>(filename);
		
		variable->setValue(i, value);
	}
	
	return true;
}

template <>
Material* ResourceLoader<Material>::load(ResourceManager* resourceManager, std::istream* is)
{
	// Allocate new material
	Material* material = new Material();
	
	std::string line;
	std::size_t lineNumber = 0;
	const std::string whitespace = " \t\r\n";
	
	// Parse lines
	while (is->good() && std::getline(*is, line))
	{
		if (is->bad() || is->fail())
		{
			break;
		}

		// Increment current line number
		++lineNumber;
		
		// Skip empty lines
		if (line.empty())
		{
			continue;
		}
		
		// Find position of first character in the command
		std::size_t commandPosition = line.find_first_not_of(whitespace, 0);
		if (commandPosition == std::string::npos)
		{
			// Skip whitespace-only lines
			continue;
		}
		
		// Determine command type
		std::string command = line.substr(commandPosition, line.find_first_of(" \t=", commandPosition) - commandPosition);
		
		// Parse command
		if (command == "shader" || command == "flags")
		{
			// Find position of equals sign
			std::size_t equalsSignPosition = line.find_first_of("=", commandPosition);
			if (equalsSignPosition == std::string::npos)
			{
				// Line has no equals sign
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			// Find position of first character in the value string
			std::size_t valueStartPosition = line.find_first_not_of(whitespace, equalsSignPosition + 1);
			if (valueStartPosition == std::string::npos)
			{
				// Line has no value
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			// Find position the end of the value string
			std::size_t valueEndPosition = line.find_first_of(" \t;\r\n", valueStartPosition);
			
			// Determine value string
			std::string valueString;
			if (valueEndPosition == std::string::npos)
			{
				valueString = line.substr(valueStartPosition);
			}
			else
			{
				valueString = line.substr(valueStartPosition, valueEndPosition - valueStartPosition);
			}
			
			// Execute command
			if (command == "shader")
			{
				// Load shader
				Shader* shader = nullptr;
				try
				{
					shader = resourceManager->load<Shader>(valueString);
				}
				catch (const std::exception& e)
				{
					std::string error = std::string("ResourceLoader<Material>::load(): Failed to load shader \"") + valueString + std::string("\": \"") + e.what() + std::string("\"");
					throw std::runtime_error(error.c_str());
				}

				material->setShader(shader);
			}
			else
			{
				// Parse flags
				std::uint64_t flags;
				std::stringstream stream;
				stream << valueString;
				stream >> flags;

				material->setFlags(flags);
			}
		}
		else if (command == "var")
		{
			// Find position of first character in variable name
			std::size_t variableNamePosition = line.find_first_not_of(whitespace, commandPosition + command.length());
			if (variableNamePosition == std::string::npos)
			{
				// Skip lines with no variable name
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid variable on line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			// Find position of equals sign
			std::size_t equalsSignPosition = line.find_first_of("=", variableNamePosition);
			if (equalsSignPosition == std::string::npos)
			{
				// Skip lines with no equals sign
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid variable on line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			// Find position of first character in variable type
			std::size_t variableTypePosition = line.find_first_not_of(whitespace, equalsSignPosition + 1);
			if (variableTypePosition == std::string::npos)
			{
				// Skip lines with no variable type definition
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid variable on line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			// Count parentheses
			std::size_t leftParenthesisCount = std::count(line.begin() + variableNamePosition, line.end(), '(');
			std::size_t rightParenthesisCount = std::count(line.begin() + variableNamePosition, line.end(), ')');
			if (leftParenthesisCount != rightParenthesisCount || leftParenthesisCount == 0)
			{
				// Skip lines with invalid number of parentheses
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Invalid variable on line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			std::string variableName = line.substr(variableNamePosition, line.find_first_of(" \t=", variableNamePosition) - variableNamePosition);
			std::string variableType = line.substr(variableTypePosition, line.find_first_of(" \t[(", variableTypePosition) - variableTypePosition);
			std::size_t elementCount = leftParenthesisCount;
			
			std::size_t currentPosition = variableTypePosition;
			std::vector<std::vector<std::string>> elements;
			bool invalid = false;
			for (std::size_t i = 0; i < elementCount; ++i)
			{
				std::size_t leftParenthesisPosition = line.find_first_of("(", currentPosition);
				std::size_t rightParenthesisPosition = line.find_first_of(")", leftParenthesisPosition + 1);
				
				if (leftParenthesisPosition == std::string::npos || rightParenthesisPosition == std::string::npos)
				{
					invalid = true;
					break;
				}
				
				currentPosition = leftParenthesisPosition + 1;
				std::size_t argumentCount = std::count(line.begin() + leftParenthesisPosition + 1, line.begin() + rightParenthesisPosition, ',') + 1;
				std::vector<std::string> arguments;
				for (std::size_t j = 0; j < argumentCount; ++j)
				{
					std::size_t argumentStart = line.find_first_not_of(whitespace, currentPosition);
					std::size_t argumentEnd = line.find_first_of(" \t,)", argumentStart + 1);
					
					if (argumentStart == std::string::npos || argumentEnd == std::string::npos)
					{
						// Unable to parse argument
						invalid = true;
						break;
					}
					
					std::string argument = line.substr(argumentStart, argumentEnd - argumentStart);
					arguments.push_back(argument);
					
					currentPosition = argumentEnd + 1;
				}
				
				if (invalid)
				{
					std::stringstream stream;
					stream << "ResourceLoader<Material>::load(): Unable to parse element on line " << lineNumber << ".";
					throw std::runtime_error(stream.str().c_str());
				}
				
				elements.push_back(arguments);
				
				currentPosition = rightParenthesisPosition + 1;
			}
			
			if (invalid)
			{
				// Unable to parse line
				std::stringstream stream;
				stream << "ResourceLoader<Material>::load(): Unable to parse line " << lineNumber << ".";
				throw std::runtime_error(stream.str().c_str());
			}
			
			if (variableType == "int")
			{
				ShaderInt* variable = material->addVariable<int>(variableName, elements.size());
				loadShaderInt(variable, elements);
			}
			else if (variableType == "float")
			{
				ShaderFloat* variable = material->addVariable<float>(variableName, elements.size());
				loadShaderFloat(variable, elements);
			}
			else if (variableType == "vec2")
			{
				ShaderVector2* variable = material->addVariable<Vector2>(variableName, elements.size());
				loadShaderVector2(variable, elements);
			}
			else if (variableType == "vec3")
			{

				ShaderVector3* variable = material->addVariable<Vector3>(variableName, elements.size());
				loadShaderVector3(variable, elements);
			}
			else if (variableType == "vec4")
			{
				ShaderVector4* variable = material->addVariable<Vector4>(variableName, elements.size());
				loadShaderVector4(variable, elements);
			}
			else if (variableType == "mat3")
			{
				ShaderMatrix3* variable = material->addVariable<Matrix3>(variableName, elements.size());
				loadShaderMatrix3(variable, elements);
			}
			else if (variableType == "mat4")
			{
				ShaderMatrix4* variable = material->addVariable<Matrix4>(variableName, elements.size());
				loadShaderMatrix4(variable, elements);
			}
			else if (variableType == "texture")
			{
				ShaderTexture2D* variable = material->addVariable<const Texture2D*>(variableName, elements.size());
				loadShaderTexture2D(resourceManager, variable, elements);
			}
			else if (variableType == "textureCube")
			{
				ShaderTextureCube* variable = material->addVariable<const TextureCube*>(variableName, elements.size());
				loadShaderTextureCube(resourceManager, variable, elements);
			}
		}
		else
		{
			if (command[0] == '#')
			{
				// Skip comments
				continue;
			}
			
			// Invalid command
			std::stringstream stream;
			stream << "ResourceLoader<Material>::load(): Invalid command \"" << command << "\" on line " << lineNumber << ".";
			throw std::runtime_error(stream.str().c_str());
		}
	}
	
	return material;
}