ShaderLibrary.hpp

#pragma once
#ifndef SHADERLIBRARY_H_
#define SHADERLIBRARY_H_

#include <unordered_map>
#include <vector>
#include <string>
#include "common.h"
#include "Program.h"

using namespace std;

class ShaderLibrary{

public:
    static ShaderLibrary& getInstance(){
        static ShaderLibrary instance;
        return(instance);
    }

    // Add a shader to the library by name and pointer
    void add(const string &name, Program* program);
    void add(const char* name, Program* program){add(string(name), program);}

    bool loadFromJSONCollection(string path, bool silent = false);

    bool buildAndAdd(string name, const json& program_obj);
    bool buildAndAdd(const char* const name, const json& program_obj) {return(buildAndAdd(string(name), program_obj));}

    bool buildAndAdd(string name, istream &vertex, istream &fragment);
    bool buildAndAdd(const char* const name, istream &vertex, istream &fragment) {return(buildAndAdd(string(name), vertex, fragment));}
    bool buildAndAdd(string name, const string &vpath, const string &fpath);
    bool buildAndAdd(const char* const name, const string &vpath, const string &fpath) {return(buildAndAdd(string(name), vpath, fpath));}

    void printLibary() const;

    // Bind the program stored under the given name and mark it as active
    void makeActive(const string &name);
    void makeActive(const char* name){makeActive(string(name));}

    // Automatically swaps to and binds on the given program pointer. This enables calls to be made to the
    // library during rendering that skip the overhead of the hash-table whilst avoiding redundant bind calls.
    void fastActivate(Program* prog);

    Program& getActive();

    // Should only be used in combination with fastActivate()! Do not use to bind manually!
    Program* getActivePtr();

    Program* operator[](const string& name) {return(getPtr(name));}
    Program* operator[](const char* name) {return(getPtr(string(name)));}

    // Same as getActivePtr but for any program in the library. If the given name is not found returns NULL
    Program* getPtr(const string &name);
    Program* getPtr(const char* name){return(getPtr(string(name)));}

    void dumpBinary(const string& name);
    void dumpBinary(const char* name){dumpBinary(string(name));}

    ShaderLibrary(ShaderLibrary const&) = delete;
    void operator=(ShaderLibrary const&) = delete;
private:
    ShaderLibrary();
    
    // Hash-table associative array linking GLSL programs to a simple name such as "blinn-phong" 
    // Most pointers should point to an element of 'localPrograms', but don't need to. 
    unordered_map<string, Program*> programs;
    
    // Collection of Program objects scoped within the class for the sake of unambiguous memory management.
    vector<Program> localPrograms; 

    // Always initialized "error shader" that can be fallen back on if another shader is missing or fails
    Program fallback;

    // Pointer to active shader which is currently bound in OpenGL
    Program* active;

    // Hardcoded fallback shadercode
    constexpr const static char* errorvs = "#version  330 core\n"
        "layout(location = 0) in vec4 vertPos;\n"
        "\n"
        "uniform mat4 P;\n"
        "uniform mat4 V;\n"
        "uniform mat4 M;\n"
        "\n"
        "void main()\n"
        "{\n"
        "  gl_Position = P * V * M * vertPos;\n"
        "}\n"
        ;

    constexpr const static char* errorfs = "#version 330 core\n"
        "\n"
        "out vec4 color;\n"
        "\n"
        "void main()\n"
        "{\n"
        "  vec3 col = vec3(1.0,0.0,1.0);\n"
        "  color = vec4(col, 1.0);\n"
        "}\n"
    ;

};

#endif