/**************************************************************************/
/*  shader_gles3.h                                                        */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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/* Permission is hereby granted, free of charge, to any person obtaining  */
/* a copy of this software and associated documentation files (the        */
/* "Software"), to deal in the Software without restriction, including    */
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/* distribute, sublicense, and/or sell copies of the Software, and to     */
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#pragma once

#include "core/math/projection.h"
#include "core/os/mutex.h"
#include "core/string/string_builder.h"
#include "core/templates/hash_map.h"
#include "core/templates/local_vector.h"
#include "core/templates/rid_owner.h"
#include "servers/rendering/rendering_server.h"

#ifdef GLES3_ENABLED

#include "platform_gl.h"

class ShaderGLES3 {
public:
	struct TextureUniformData {
		StringName name;
		int array_size;
	};

protected:
	struct TexUnitPair {
		const char *name;
		int index;
	};

	struct UBOPair {
		const char *name;
		int index;
	};

	struct Specialization {
		const char *name;
		bool default_value = false;
	};

	struct Feedback {
		const char *name;
		uint64_t specialization;
	};

private:
	//versions
	CharString general_defines;

	// A version is a high-level construct which is a combination of built-in and user-defined shader code, Each user-created Shader makes one version
	// Variants use #ifdefs to toggle behavior on and off to change behavior of the shader
	// All variants are compiled each time a new version is created
	// Specializations use #ifdefs to toggle behavior on and off for performance, on supporting hardware, they will compile a version with everything enabled, and then compile more copies to improve performance
	// Use specializations to enable and disabled advanced features, use variants to toggle behavior when different data may be used (e.g. using a samplerArray vs a sampler, or doing a depth prepass vs a color pass)
	struct Version {
		LocalVector<TextureUniformData> texture_uniforms;
		CharString uniforms;
		CharString vertex_globals;
		CharString fragment_globals;
		HashMap<StringName, CharString> code_sections;
		Vector<CharString> custom_defines;

		struct Specialization {
			GLuint id;
			GLuint vert_id;
			GLuint frag_id;
			LocalVector<GLint> uniform_location;
			LocalVector<GLint> texture_uniform_locations;
			bool build_queued = false;
			bool ok = false;
			Specialization() {
				id = 0;
				vert_id = 0;
				frag_id = 0;
			}
		};

		LocalVector<AHashMap<uint64_t, Specialization>> variants;
	};

	Mutex variant_set_mutex;

	void _get_uniform_locations(Version::Specialization &spec, Version *p_version);
	void _compile_specialization(Version::Specialization &spec, uint32_t p_variant, Version *p_version, uint64_t p_specialization);

	void _clear_version(Version *p_version);
	void _initialize_version(Version *p_version);

	RID_Owner<Version, true> version_owner;

	struct StageTemplate {
		struct Chunk {
			enum Type {
				TYPE_MATERIAL_UNIFORMS,
				TYPE_VERTEX_GLOBALS,
				TYPE_FRAGMENT_GLOBALS,
				TYPE_CODE,
				TYPE_TEXT
			};

			Type type;
			StringName code;
			CharString text;
		};
		LocalVector<Chunk> chunks;
	};

	String name;

	String base_sha256;

	static String shader_cache_dir;
	static bool shader_cache_cleanup_on_start;
	static bool shader_cache_save_compressed;
	static bool shader_cache_save_compressed_zstd;
	static bool shader_cache_save_debug;
	bool shader_cache_dir_valid = false;

	GLint max_image_units = 0;

	enum StageType {
		STAGE_TYPE_VERTEX,
		STAGE_TYPE_FRAGMENT,
		STAGE_TYPE_MAX,
	};

	StageTemplate stage_templates[STAGE_TYPE_MAX];

	void _build_variant_code(StringBuilder &p_builder, uint32_t p_variant, const Version *p_version, StageType p_stage_type, uint64_t p_specialization);

	void _add_stage(const char *p_code, StageType p_stage_type);

	String _version_get_sha1(Version *p_version) const;
	bool _load_from_cache(Version *p_version);
	void _save_to_cache(Version *p_version);

	const char **uniform_names = nullptr;
	int uniform_count = 0;
	const UBOPair *ubo_pairs = nullptr;
	int ubo_count = 0;
	const Feedback *feedbacks;
	int feedback_count = 0;
	const TexUnitPair *texunit_pairs = nullptr;
	int texunit_pair_count = 0;
	int specialization_count = 0;
	const Specialization *specializations = nullptr;
	uint64_t specialization_default_mask = 0;
	const char **variant_defines = nullptr;
	int variant_count = 0;

	int base_texture_index = 0;
	Version::Specialization *current_shader = nullptr;

protected:
	ShaderGLES3();
	void _setup(const char *p_vertex_code, const char *p_fragment_code, const char *p_name, int p_uniform_count, const char **p_uniform_names, int p_ubo_count, const UBOPair *p_ubos, int p_feedback_count, const Feedback *p_feedback, int p_texture_count, const TexUnitPair *p_tex_units, int p_specialization_count, const Specialization *p_specializations, int p_variant_count, const char **p_variants);

	_FORCE_INLINE_ bool _version_bind_shader(RID p_version, int p_variant, uint64_t p_specialization) {
		ERR_FAIL_INDEX_V(p_variant, variant_count, false);

		Version *version = version_owner.get_or_null(p_version);
		ERR_FAIL_NULL_V(version, false);

		if (version->variants.is_empty()) {
			_initialize_version(version); //may lack initialization
		}

		Version::Specialization *spec = version->variants[p_variant].getptr(p_specialization);
		if (!spec) {
			if (false) {
				// Queue load this specialization and use defaults in the meantime (TODO)

				spec = version->variants[p_variant].getptr(specialization_default_mask);
			} else {
				// Compile on the spot
				Version::Specialization s;
				_compile_specialization(s, p_variant, version, p_specialization);
				version->variants[p_variant].insert(p_specialization, s);
				spec = version->variants[p_variant].getptr(p_specialization);
				if (shader_cache_dir_valid) {
					_save_to_cache(version);
				}
			}
		} else if (spec->build_queued) {
			// Still queued, wait
			spec = version->variants[p_variant].getptr(specialization_default_mask);
		}

		if (!spec || !spec->ok) {
			WARN_PRINT_ONCE("shader failed to compile, unable to bind shader.");
			return false;
		}

		glUseProgram(spec->id);
		current_shader = spec;
		return true;
	}

	_FORCE_INLINE_ int _version_get_uniform(int p_which, RID p_version, int p_variant, uint64_t p_specialization) {
		ERR_FAIL_INDEX_V(p_which, uniform_count, -1);
		Version *version = version_owner.get_or_null(p_version);
		ERR_FAIL_NULL_V(version, -1);
		ERR_FAIL_INDEX_V(p_variant, int(version->variants.size()), -1);
		Version::Specialization *spec = version->variants[p_variant].getptr(p_specialization);
		ERR_FAIL_NULL_V(spec, -1);
		ERR_FAIL_INDEX_V(p_which, int(spec->uniform_location.size()), -1);
		return spec->uniform_location[p_which];
	}

	virtual void _init() = 0;

public:
	RID version_create();

	void version_set_code(RID p_version, const HashMap<String, String> &p_code, const String &p_uniforms, const String &p_vertex_globals, const String &p_fragment_globals, const Vector<String> &p_custom_defines, const LocalVector<ShaderGLES3::TextureUniformData> &p_texture_uniforms, bool p_initialize = false);

	bool version_is_valid(RID p_version);

	bool version_free(RID p_version);

	static void set_shader_cache_dir(const String &p_dir);
	static void set_shader_cache_save_compressed(bool p_enable);
	static void set_shader_cache_save_compressed_zstd(bool p_enable);
	static void set_shader_cache_save_debug(bool p_enable);

	RS::ShaderNativeSourceCode version_get_native_source_code(RID p_version);

	void initialize(const String &p_general_defines = "", int p_base_texture_index = 0);
	virtual ~ShaderGLES3();
};

#endif // GLES3_ENABLED
