/**
 * @file font_system.h
 * @author Travis Vroman (travis@kohiengine.com)
 * @brief A system responsible for the management of bitmap
 * and system fonts.
 * @version 2.0
 * @date 2026-01-06
 *
 * @copyright Kohi Game Engine is Copyright (c) Travis Vroman 2021-2026
 *
 * A "bitmap" font uses an image containing pre-rendered glyphs which are then referenced
 * in an internal lookup table by character codepoint. The display of characters for this
 * font type is thus limited to characters contained within the image and configuration asset.
 *
 * A "system" font uses a .ttf or .ttc font file and generates glyphs to an internal atlas
 * on the fly, as needed (although standard ascii characters are rendered to it by default).
 * Display of characters is limited only by those contained in the font. System fonts have
 * "variants", one per font-size (i.e. a font size of 19 and a size of 20 would be unique variants).
 * Each variant keeps its own internal atlas and list of codepoints contained, based on
 * the needs of the string being rendered. These can be updated on the fly.
 * See font_system_system_font_verify_atlas().
 *
 */
#pragma once

#include <containers/array.h>
#include <core_render_types.h>
#include <identifiers/khandle.h>
#include <math/math_types.h>
#include <strings/kname.h>

struct font_system_state;

typedef enum font_type {
	FONT_TYPE_BITMAP,
	FONT_TYPE_SYSTEM
} font_type;

typedef struct font_glyph {
	i32 codepoint;
	u16 x;
	u16 y;
	u16 width;
	u16 height;
	i16 x_offset;
	i16 y_offset;
	i16 x_advance;
	u8 page_id;
} font_glyph;

typedef struct font_kerning {
	i32 codepoint_0;
	i32 codepoint_1;
	i16 amount;
} font_kerning;

typedef struct font_page {
	kname image_asset_name;
} font_page;

ARRAY_TYPE(font_glyph);
ARRAY_TYPE(font_kerning);
ARRAY_TYPE(font_page);

/**
 * Represents a system font size variant and its "base" font.
 * This is used to acquire a system font and its size variant,
 * and contains handles to both.
 */
typedef struct system_font_variant {
	// Handle to the base font.
	khandle base_font;
	// Handle to the font size variant.
	khandle variant;
} system_font_variant;

/**
 * @brief The configuration for a bitmap font in the font system config.
 */
typedef struct font_system_bitmap_font_config {
	// The resource name.
	kname resource_name;
	// The resource name.
	kname package_name;
} font_system_bitmap_font_config;

/**
 * @brief The configuration for a system font in the font system config.
 */
typedef struct font_system_system_font_config {
	// The resource name.
	kname resource_name;
	// The resource name.
	kname package_name;
	// The default font size to be used with the system font.
	u16 default_size;
} font_system_system_font_config;

/**
 * @brief The configuration of the font system.
 * Should be setup by the application during the boot
 * process.
 */
typedef struct font_system_config {
	/** @brief The max number of bitmap fonts that can be loaded. */
	u8 max_bitmap_font_count;
	/** @brief The max number of system fonts that can be loaded. */
	u8 max_system_font_count;

	/** @brief The number of bitmap fonts configured in the system. */
	u8 bitmap_font_count;
	/** @brief A collection of bitmap fonts configured in the system. */
	font_system_bitmap_font_config *bitmap_fonts;

	/** @brief The number of system fonts configured in the system. */
	u8 system_font_count;
	/** @brief A collection of system fonts configured in the system. */
	font_system_system_font_config *system_fonts;
} font_system_config;

/**
 * Geometry generated from either a bitmap or system font.
 */
typedef struct font_geometry {
	/** @brief The number of quads created in total. */
	u32 quad_count;
	/** @brief The number of quads to be drawn. */
	u32 render_quad_count;
	/** @brief The size of the vertex buffer data in bytes. */
	u64 vertex_buffer_size;
	/** @brief The size of the index buffer data in bytes. */
	u64 index_buffer_size;
	/** @brief The vertex buffer data. */
	vertex_2d *vertex_buffer_data;
	/** @brief The index buffer data. */
	u32 *index_buffer_data;
} font_geometry;

/**
 * @brief Deserializes font system configuration from the provided string.
 *
 * @param config_str The configuration in string format to be deserialized. Required.
 * @param out_config A pointer to hold the deserialized configuration. Required.
 * @return True if successful; otherwise false.
 */
b8 font_system_deserialize_config (const char *config_str, font_system_config *out_config);

/**
 * @brief Initializes the font system. As with other systems, this should
 * be called twice; once to get the memory requirement (where memory = 0),
 * and a second time passing allocated memory.
 *
 * @param memory_requirement A pointer to hold the memory requirement.
 * @param memory The allocated memory for the system state.
 * @param config The font system config.
 * @return True on success; otherwise false.
 */
b8 font_system_initialize (u64 *memory_requirement, void *memory, font_system_config *config);

/**
 * @brief Shuts down the font system.
 *
 * @param state The system state memory.
 */
void font_system_shutdown (struct font_system_state *state);

/**
 * @brief Attempts to acquire a bitmap font of the given name. Must be a registered/loaded font.
 *
 * @param state A pointer to the font system state.
 * @param name The name of the font to acquire.
 * @param out_font A pointer to hold a handle to bitmap font if successful. Required.
 * @return True on load success; otherwise false.
 */
KAPI b8 font_system_bitmap_font_acquire (struct font_system_state *state, kname name, khandle *out_font);

/**
 * @brief Attempts to load a bitmap font from the given named resource.
 *
 * @param state A pointer to the font system state.
 * @param asset_name The name of the font asset to load.
 * @param package_name The name of the package containing the resource.
 * @return True on load success; otherwise false.
 */
KAPI b8 font_system_bitmap_font_load (struct font_system_state *state, kname asset_name, kname package_name);

/**
 * @brief Measures the given string to find out how large it is at the widest/tallest point
 * using the given bitmap font.
 *
 * @param state A pointer to the font system state.
 * @param font A handle to the bitmap font to use for measuring.
 * @param text The text to be measured.
 * @param max_width The width to wrap text at, if wrapping. Pass 0 for no wrapping.
 * @param out_size A pointer to hold the measured size, if successful. Required.
 * @return True on success; otherwise false.
 */
KAPI b8 font_system_bitmap_font_measure_string (struct font_system_state *state, khandle font, const char *text, f32 max_width, vec2 *out_size);

/**
 * @brief Gets a pointer to the font's atlas.
 *
 * @param state A pointer to the font system state.
 * @param font A handle to the bitmap font to use for measuring.
 * @return A pointer to the font's atlas if successful; otherwise 0.
 */
KAPI ktexture font_system_bitmap_font_atlas_get (struct font_system_state *state, khandle font);

/**
 * @brief Gets the line height of the given font.
 *
 * @param state A pointer to the font system state.
 * @param font A handle to the bitmap font to use.
 * @return The line height. Can return 0 if font is not found.
 */
KAPI f32 font_system_bitmap_font_line_height_get (struct font_system_state *state, khandle font);

/**
 * @brief Generates geometry data for a bitmap font.
 *
 * @param state A pointer to the font system state.
 * @param font A handle to the bitmap font to use for generation.
 * @param text The text to use for generation.
 * @param out_size A pointer to hold the generated font geometry, if successful. Required.
 * @return True on success; otherwise false.
 */
KAPI b8 font_system_bitmap_font_generate_geometry (struct font_system_state *state, khandle font, const char *text, f32 max_width, b8 truncate, b8 use_ellipsis, font_geometry *out_geometry);

/**
 * @brief Attempts to acquire a system font variant of the given name and size. Must be a registered/loaded font.
 *
 * @param state A pointer to the font system state.
 * @param name The name of the font to acquire.
 * @param font_size The font size. Ignored for bitmap fonts.
 * @param out_variant A pointer to hold a system font variant, with handles to both the "base" font and the size variant. if successful. Required.
 * @return True if successful; otherwise false.
 */
KAPI b8 font_system_system_font_acquire (struct font_system_state *state, kname name, u16 font_size, system_font_variant *out_variant);

/**
 * @brief Attempts to load a system font from the given named resource.
 *
 * @param state A pointer to the font system state.
 * @param resource_name The name of the font resource to load.
 * @param package_name The name of the package containing the resource.
 * @param default_size The default font size. Clamped to an acceptable range.
 * @return True on load success; otherwise false.
 */
KAPI b8 font_system_system_font_load (struct font_system_state *state, kname resource_name, kname package_name, u16 default_size);

/**
 * @brief Verifies the atlas of the provided system font contains
 * the characters in text.
 *
 * @param state A pointer to the font system state.
 * @param variant The system font variant to verify.
 * @param text The text containing the characters required.
 * @return True on success; otherwise false.
 */
KAPI b8 font_system_system_font_verify_atlas (struct font_system_state *state, system_font_variant variant, const char *text);

/**
 * @brief Measures the given string to find out how large it is at the widest/tallest point
 * using the given system font.
 *
 * @param state A pointer to the font system state.
 * @param variant The system font variant to use for measuring.
 * @param text The text to be measured.
 * @param max_width The width to wrap text at, if wrapping. Pass 0 for no wrapping.
 * @param out_size A pointer to hold the measured size, if successful. Required.
 * @return True on success; otherwise false.
 */
KAPI b8 font_system_system_font_measure_string (struct font_system_state *state, system_font_variant variant, const char *text, f32 max_width, vec2 *out_size);

/**
 * @brief Gets the line height of the given font.
 *
 * @param state A pointer to the font system state.
 * @param variant The system font variant to use.
 * @return The line height. Can return 0 if font is not found.
 */
KAPI f32 font_system_system_font_line_height_get (struct font_system_state *state, system_font_variant variant);

/**
 * @brief Generates geometry data for a system font variant.
 *
 * @param state A pointer to the font system state.
 * @param variant The system font variant to use for generation.
 * @param text The text to use for generation.
 * @param out_size A pointer to hold the generated font geometry, if successful. Required.
 * @return True on success; otherwise false.
 */
KAPI b8 font_system_system_font_generate_geometry (struct font_system_state *state, system_font_variant variant, const char *text, f32 max_width, b8 truncate, b8 use_ellipsis, font_geometry *out_geometry);

/**
 * @brief Gets a pointer to the font's atlas.
 *
 * @param state A pointer to the font system state.
 * @param variant The system font variant to use for retrieval.
 * @return A pointer to the font's atlas if successful; otherwise 0.
 */
KAPI ktexture font_system_system_font_atlas_get (struct font_system_state *state, system_font_variant variant);