/* r3d_ambient_map.odin -- R3D Ambient Map Module.
 *
 * Copyright (c) 2025-2026 Le Juez Victor
 *
 * This software is provided 'as-is', without any express or implied warranty.
 * For conditions of distribution and use, see accompanying LICENSE file.
 */
package r3d

import rl "vendor:raylib"

when ODIN_OS == .Windows {
    foreign import lib {
        "windows/libr3d.a",
        "system:raylib",
        "system:assimp",
    }
} else when ODIN_OS == .Linux {
    foreign import lib {
        "linux/libr3d.a",
        "system:raylib",
        "system:assimp",
    }
} else when ODIN_OS == .Darwin {
    foreign import lib {
        "darwin/libr3d.a",
        "system:raylib",
        "system:assimp",
    }
}

/**
 * @brief Global environment lighting data.
 *
 * An ambient map is built from a cubemap (like a skybox)
 * and preprocessed into two specialized textures:
 *
 *  - irradiance:
 *      Low-frequency lighting used for diffuse IBL.
 *      Captures soft ambient light from all directions.
 *
 *  - prefilter:
 *      Mipmapped environment used for specular reflections.
 *      Higher mip levels simulate rougher surfaces.
 *
 * Both textures are derived from the same source cubemap,
 * but serve different shading purposes.
 */
AmbientMap :: struct {
    flags:      AmbientFlags, ///< Components generated for this map
    irradiance: u32,          ///< Diffuse IBL cubemap (may be 0 if not generated)
    prefilter:  u32,          ///< Specular prefiltered cubemap (may be 0 if not generated)
}

@(default_calling_convention="c", link_prefix="R3D_")
foreign lib {
    /**
     * @brief Loads a ambient map from an image file.
     *
     * The layout parameter tells how faces are arranged inside the source image.
     */
    LoadAmbientMap :: proc(fileName: cstring, layout: CubemapLayout, flags: AmbientFlags) -> AmbientMap ---

    /**
     * @brief Builds a ambient map from an existing rl.Image.
     *
     * Same behavior as R3D_LoadAmbientMap(), but without loading from disk.
     */
    LoadAmbientMapFromImage :: proc(image: rl.Image, layout: CubemapLayout, flags: AmbientFlags) -> AmbientMap ---

    /**
     * @brief Generates an ambient map from a cubemap.
     *
     * The source cubemap should usually be an HDR sky/environment.
     *
     * Depending on the provided flags, this function:
     *  - convolves the cubemap into diffuse irradiance
     *  - builds a mipmapped prefiltered cubemap for reflections
     *
     * @param cubemap Source cubemap (environment / sky).
     * @param flags   Which components to generate (irradiance, reflection, or both).
     * @return A fully initialized ambient map.
     */
    GenAmbientMap :: proc(cubemap: Cubemap, flags: AmbientFlags) -> AmbientMap ---

    /**
     * @brief Frees the textures used by an ambient map.
     *
     * After this call, the ambient map is no longer valid.
     */
    UnloadAmbientMap :: proc(ambientMap: AmbientMap) ---

    /**
     * @brief Rebuilds an existing ambient map from a new cubemap.
     *
     * Use this when the environment changes dynamically (time of day,
     * weather, interior/exterior transitions, etc).
     *
     * Only the components enabled in `ambientMap.flags` are regenerated.
     *
     * @param ambientMap Existing ambient map to update.
     * @param cubemap    New cubemap source.
     */
    UpdateAmbientMap :: proc(ambientMap: AmbientMap, cubemap: Cubemap) ---
}

/**
 * @brief Bit-flags controlling what components are generated.
 *
 * - R3D_AMBIENT_ILLUMINATION -> generate diffuse irradiance
 * - R3D_AMBIENT_REFLECTION   -> generate specular prefiltered map
 */
AmbientFlag :: enum u32 {
    ILLUMINATION = 0,
    REFLECTION   = 1,
}

AmbientFlags :: bit_set[AmbientFlag; u32]