/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/

#pragma once

#include "interfaces/IMaterial.h"
#include "utilities/Classes.h"
#include "model/Texture.h"
#include "gl/shader.h"
#include "gl/ubo.h"

// a collection of parameters for the rendering setup.
// for modern opengl this translates to set of attributes for shaders
struct opengl_material : public IMaterial {
    using texture_set = std::array<texture_handle, gl::MAX_TEXTURES>;

    texture_set textures = { null_handle };
    // alternative texture sets, defined with "textureN_variants:" key.
    // one of them is picked per rendered model instance, empty when the material declares no variants.
    // NOTE: all variants share the remaining material properties, opacity and translucency included
    std::vector<texture_set> texture_variants;
    std::array<glm::vec4, gl::MAX_PARAMS> params;
    std::vector<gl::shader::param_entry> params_state;

    std::shared_ptr<gl::program> shader;
    std::optional<float> opacity;
    std::optional<float> selfillum;
    float glossiness { 10.f };
    int shadow_rank { 0 }; // priority as shadow caster; higher = more likely to be skipped

    std::string name;
    glm::vec2 size { -1.f, -1.f }; // 'physical' size of bound texture, in meters

// constructors
    opengl_material();

// methods
    bool deserialize(cParser &Input, bool const Loadnow);
	  virtual void finalize(bool Loadnow) override;
	  virtual bool update() override;
	  virtual float get_or_guess_opacity() const override;
	  virtual bool is_translucent() const override;
	  virtual glm::vec2 GetSize() const override
	  {
		  return size;
	  }
	  virtual std::string GetName() const override
	  {
		  return name;
	  }
	  virtual std::optional<float> GetSelfillum() const override
	  {
		  return selfillum;
	  }
	  virtual int GetShadowRank() const override
	  {
		  return shadow_rank;
	  }
	  virtual texture_handle GetTexture(int slot) const override
	  {
		  return textures[slot];
	  }
	  // returns texture set to use for model instance identified by provided variant id
	  texture_set const &GetTextures(std::uint32_t const Variant) const
	  {
		  return (
			  texture_variants.empty() ?
				  textures :
				  texture_variants[Variant % texture_variants.size()]);
	  }
	// members
    static struct path_data {
        std::unordered_map<std::string, int> index_map;
        std::vector<std::string> data;
    } paths;
    bool is_good { false }; // indicates material was compiled without failure
    int path{ -1 }; // index to material path
    bool update_on_weather_change{ false };
    bool update_on_season_change{ false };

private:
// types
    // texture binding which comes with a pool of alternatives: slot the binding fills, and the pool itself
    using variant_binding = std::pair<std::size_t, std::vector<std::string> const *>;

// methods
    // imports member data pair from the config file
    bool
        deserialize_mapping( cParser &Input, int const Priority, bool const Loadnow );
    // imports texture binding, potentially carrying a pool of alternatives, from the config file
    void
        deserialize_texture_mapping( cParser &Input, std::string const &Key, int const Priority );
    // returns texture slot provided binding key resolves to, or -1 if it doesn't resolve to any
    int
        texture_slot( std::string const &Key );
    // fills the alternative texture sets from provided pools, one set per entry of the longest pool
    void
        build_texture_variants( std::vector<variant_binding> const &Bindings, bool const Loadnow );
        void log_error(const std::string &str);

// members
    // priorities for textures, shader, opacity
    int m_shader_priority = -1;
    int m_opacity_priority = -1;
    int m_selfillum_priority = -1;
    int m_glossiness_priority = -1;

    struct parse_info_s
    {
        struct tex_def
        {
            std::string name;
            int priority;
            // optional pool of alternative textures for the same binding, one picked per model instance.
            // empty for regular, single texture bindings
            std::vector<std::string> variants;
        };
        struct param_def
        {
            glm::vec4 data;
            int priority;
        };
        std::unordered_map<std::string, tex_def> tex_mapping;
        std::unordered_map<std::string, param_def> param_mapping;
    };
    std::unique_ptr<parse_info_s> parse_info;
};

class material_manager {

public:
    material_manager() { m_materials.emplace_back( opengl_material() ); } // empty bindings for null material

    material_handle
        create( std::string const &Filename, bool const Loadnow );
    opengl_material const &
        material( material_handle const Material ) const { return m_materials[ Material ]; }
    opengl_material &
        material( material_handle const Material ) { return m_materials[ Material ]; }
    // material updates executed when environment changes
    // TODO: registerable callbacks in environment manager
    void
        on_weather_change();
    void
        on_season_change();

private:
// types
    using material_sequence = std::vector<opengl_material>;
    using index_map = std::unordered_map<std::string, std::size_t>;
// methods:
    // checks whether specified texture is in the texture bank. returns texture id, or npos.
    material_handle
        find_in_databank( std::string const &Materialname ) const;
    public:
    // checks whether specified file exists. returns name of the located file, or empty string.
    static std::pair<std::string, std::string>
        find_on_disk( std::string const &Materialname );

	private:
	  // members:
    material_sequence m_materials;
    index_map m_materialmappings;
};

//---------------------------------------------------------------------------