/* r3d_screen_shader.odin -- R3D Screen Shader 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",
    }
}

ScreenShader :: struct {}

@(default_calling_convention="c", link_prefix="R3D_")
foreign lib {
    /**
     * @brief Loads a screen shader from a file.
     *
     * The shader must define a single entry point:
     * `void fragment()`. Any other entry point, such as `vertex()`,
     * or any varyings will be ignored.
     *
     * @param filePath Path to the shader source file.
     * @return Pointer to the loaded screen shader, or NULL on failure.
     */
    LoadScreenShader :: proc(filePath: cstring) -> ^ScreenShader ---

    /**
     * @brief Loads a screen shader from a source code string in memory.
     *
     * The shader must define a single entry point:
     * `void fragment()`. Any other entry point, such as `vertex()`,
     * or any varyings will be ignored.
     *
     * @param code Null-terminated shader source code.
     * @return Pointer to the loaded screen shader, or NULL on failure.
     */
    LoadScreenShaderFromMemory :: proc(code: cstring) -> ^ScreenShader ---

    /**
     * @brief Unloads and destroys a screen shader.
     *
     * @param shader Screen shader to unload.
     */
    UnloadScreenShader :: proc(shader: ^ScreenShader) ---

    /**
     * @brief Sets a uniform value for the current frame.
     *
     * Once a uniform is set, it remains valid for the all frames.
     * If an uniform is set multiple times during the same frame,
     * the last value defined before R3D_End() is used.
     *
     * Supported types:
     * bool, int, float,
     * ivec2, ivec3, ivec4,
     * vec2, vec3, vec4,
     * mat2, mat3, mat4
     *
     * @warning Boolean values are read as 4 bytes.
     *
     * @param shader Target screen shader.
     *               May be NULL. In that case, the call is ignored
     *               and a warning is logged.
     * @param name   Name of the uniform. Must not be NULL.
     * @param value  Pointer to the uniform value. Must not be NULL.
     */
    SetScreenShaderUniform :: proc(shader: ^ScreenShader, name: cstring, value: rawptr) ---

    /**
     * @brief Sets a texture sampler for the current frame.
     *
     * Once a sampler is set, it remains valid for all frames.
     * If a sampler is set multiple times during the same frame,
     * the last value defined before R3D_End() is used.
     *
     * Supported samplers:
     * sampler1D, sampler2D, sampler3D, samplerCube
     *
     * @param shader  Target screen shader.
     *                May be NULL. In that case, the call is ignored
     *                and a warning is logged.
     * @param name    Name of the sampler uniform. Must not be NULL.
     * @param texture rl.Texture to bind to the sampler.
     */
    SetScreenShaderSampler :: proc(shader: ^ScreenShader, name: cstring, texture: rl.Texture) ---

    /**
     * @brief Sets the list of screen shaders to execute at the end of the frame.
     *
     * The maximum number of shaders is defined by `R3D_MAX_SCREEN_SHADERS`.
     * If the provided count exceeds this limit, a warning is emitted and only
     * the first `R3D_MAX_SCREEN_SHADERS` shaders are used.
     *
     * Shader pointers are copied internally, so the original array can be modified or freed after the call.
     * NULL entries are allowed safely within the list.
     *
     * Calling this function resets all internal screen shaders before copying the new list.
     * To disable all screen shaders, call this function with `shaders = NULL` and/or `count = 0`.
     *
     * @param shaders Array of pointers to R3D_ScreenShader objects.
     * @param count Number of shaders in the array.
     */
    SetScreenShaderChain :: proc(shaders: ^^ScreenShader, count: i32) ---
}