linux-wallpaperengine/src/WallpaperEngine/Render/Shaders/Compiler.h

#pragma once

#include <iostream>
#include <vector>
#include <map>

#include "WallpaperEngine/Core/Core.h"
#include "WallpaperEngine/Assets/CContainer.h"
#include "WallpaperEngine/FileSystem/FileSystem.h"
#include "WallpaperEngine/Core/Objects/Effects/Constants/CShaderConstant.h"
#include "WallpaperEngine/Render/Shaders/Variables/CShaderVariable.h"

namespace WallpaperEngine::Render::Shaders
{
    using json = nlohmann::json;
    using namespace WallpaperEngine::Assets;
    using namespace WallpaperEngine::Core::Objects::Effects::Constants;

    /**
     * A basic shader loader that adds basic function definitions to every loaded shader
     */
    class Compiler
    {
    public:
        /**
         * Types of shaders
         */
        enum Type
        {
            Type_Vertex = 0,
            Type_Pixel = 1,
            Type_Include = 2
        };

        /**
         * Types of variables the pre-processor understands
         */
        static std::vector<std::string> sTypes;

        /**
         * Compiler constructor, loads the given shader file and prepares
         * the pre-processing and compilation of the shader, adding
         * required definitions if needed
         *
         * @param context The irrlicht context
         * @param file The file to load
         * @param type The type of shader
         * @param combos Settings for the shader
         * @param constants Default values for shader variables
         * @param recursive Whether the compiler should add base definitions or not
         */
        Compiler (
            CContainer* container,
            std::string filename,
            Type type,
            std::map<std::string, int> combos,
            const std::map<std::string, CShaderConstant*>& constants,
            bool recursive = false
        );
        /**
         * Performs the actual pre-compilation/pre-processing over the shader files
         * This step is kinda big, replaces variables names on sVariableReplacement,
         * ensures #include directives are correctly handled
         * and takes care of attribute comments for the wallpaper engine specifics
         */
        void precompile ();
        /**
         * @return The compiled shader's text (if available)
         */
        std::string& getCompiled ();

        /**
         * Searches the list of parameters available for the parameter with the given value
         *
         * @param identifier The identifier to search for
         * @return The shader information
         */
        Variables::CShaderVariable* findParameter (const std::string& identifier);

        /**
         * @return The list of parameters available for this shader with their default values
         */
        const std::vector <Variables::CShaderVariable*>& getParameters () const;
        /**
         * @return The list of combos available for this shader after compilation
         */
        const std::map <std::string, int>& getCombos () const;

    private:
        /**
         * Checks if there is "str" in the current position without advancing the
         * iterator in use
         *
         * @param str The string to check for
         * @param it  The position to start checking at
         *
         * @return
         */
        bool peekString (std::string str, std::string::const_iterator& it);
        /**
         * Checks for a semicolon as current character, advancing the iterator
         * after finding it, otherwise returns an error
         *
         * @param it The position where to expect the semicolon
         *
         * @return
         */
        bool expectSemicolon (std::string::const_iterator& it);
        /**
         * Ignores contiguous space characters in the string advancing the iterator
         * until the first non-space character
         *
         * @param it The iterator to increase
         */
        void ignoreSpaces (std::string::const_iterator& it);
        /**
         * Ignores all characters until next line-fee (\n) advancing the interator
         *
         * @param it The iterator to increase
         */
        void ignoreUpToNextLineFeed (std::string::const_iterator& it);
        /**
         * Ignores all characters until a block comment end is found, advancing the iterator
         *
         * @param it The iterator to increase
         */
        void ignoreUpToBlockCommentEnd (std::string::const_iterator& it);
        /**
         * Parses the current position as a variable type, extracts it and compares it
         * to the registered types in the pre-processor, returning it's name if valid
         * increasing the iterator at the same time
         *
         * @param it The position to extract it from
         *
         * @return The type name
         */
        std::string extractType (std::string::const_iterator& it);
        /**
         * Parses the current position as a variable name, extractig it's name and
         * increasing the iterator as the name is extracted
         *
         * @param it The position to start extracting the variable name from
         *
         * @return The variable name
         */
        std::string extractName (std::string::const_iterator& it);
        /**
         * Parses the current position as an array indicator
         *
         * @param it            The position to start extracting the array from
         * @param mustExists    Whether the array indicator must exists or not
         * @return
         */
        std::string extractArray(std::string::const_iterator &it, bool mustExists = false);
        /**
         * Parses the current position as a quoted value, extracting it's value
         * and increasing the iterator at the same time
         *
         * @param it The position to start extracting the value from
         *
         * @return The value
         */
        std::string extractQuotedValue (std::string::const_iterator& it);
        /**
         * Tries to find the given shader file and compile it
         *
         * @param filename The shader's filename
         *
         * @return The compiled contents
         */
        std::string lookupShaderFile (std::string filename);

        /**
         * @return Whether the character in the current position is a character or not
         */
        bool isChar (std::string::const_iterator& it);
        /**
         * @return Whether the character in the current position is a number or not
         */
        bool isNumeric (std::string::const_iterator& it);
        /**
         * Parses a COMBO value to add the proper define to the code
         *
         * @param content The parameter configuration
         */
        void parseComboConfiguration (const std::string& content);
        /**
         * Parses a parameter extra metadata created by wallpaper engine
         *
         * @param type The type of variable to parse
         * @param name The name of the variable in the shader (for actual variable declaration)
         * @param content The parameter configuration
         */
        void parseParameterConfiguration (const std::string& type, const std::string& name, const std::string& content);
        /**
         * The shader file this instance is loading
         */
        std::string m_file;
        /**
         * The original file content
         */
        std::string m_content;
        /**
         * The final, compiled content ready to be used by OpenGL
         */
        std::string m_compiledContent;
        /**
         * Whether there was any kind of error in the compilation or not
         */
        bool m_error;
        /**
         * Extra information about the error (if any)
         */
        std::string m_errorInfo;
        /**
         * The type of shader
         */
        Type m_type;
        /**
         * The parameters the shader needs
         */
        std::vector <Variables::CShaderVariable*> m_parameters;
        /**
         * The combos the shader should be generated with
         */
         std::map <std::string, int> m_combos;
         /**
          * The shader constants with values for variables inside the shader
          */
         const std::map<std::string, CShaderConstant*>& m_constants;
         /**
          * Whether this compilation is a recursive one or not
          */
         bool m_recursive;
         /**
          * The container to load files from
          */
         CContainer* m_container;
    };
}