// Copyright © SixtyFPS GmbH <info@slint-ui.com>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial

#![doc = include_str!("README.md")]
#![doc(html_logo_url = "https://slint-ui.com/logo/slint-logo-square-light.svg")]
#![cfg_attr(not(any(feature = "i-slint-backend-qt", feature = "i-slint-backend-winit")), no_std)]

use core::pin::Pin;

cfg_if::cfg_if! {
    if #[cfg(all(feature = "i-slint-backend-qt", not(no_qt)))] {
        use i_slint_backend_qt as default_backend;

        fn create_default_backend() -> Box<dyn i_slint_core::backend::Backend + 'static> {
            Box::new(default_backend::Backend)
        }
    } else if #[cfg(feature = "i-slint-backend-winit")] {
        use i_slint_backend_winit as default_backend;
        fn create_default_backend() -> Box<dyn i_slint_core::backend::Backend + 'static> {
            Box::new(i_slint_backend_winit::Backend::new(None))
        }
    }
}

cfg_if::cfg_if! {
    if #[cfg(any(
            all(feature = "i-slint-backend-qt", not(no_qt)),
            feature = "i-slint-backend-winit"
        ))] {
        pub fn backend() -> &'static dyn i_slint_core::backend::Backend {
            i_slint_core::backend::instance_or_init(|| {
                let backend_config = std::env::var("SLINT_BACKEND").or_else(|_| {
                    let legacy_fallback = std::env::var("SIXTYFPS_BACKEND");
                    if legacy_fallback.is_ok() {
                        eprintln!("Using `SIXTYFPS_BACKEND` environment variable for dynamic backend selection. This is deprecated, use `SLINT_BACKEND` instead.")
                    }
                    legacy_fallback
                }).unwrap_or_default();

                let backend_config = backend_config.to_lowercase();
                if let Some((event_loop, _renderer)) = backend_config.split_once('-').or_else(|| match backend_config.as_str() {
                    "qt" => Some(("qt", "qpainter")),
                    "gl" => Some(("winit", "femtovg")),
                    "skia" => Some(("winit", "skia")),
                    _ => None,
                }) {
                    match event_loop {
                        #[cfg(all(feature = "i-slint-backend-qt", not(no_qt)))]
                        "qt" => return Box::new(i_slint_backend_qt::Backend),
                        #[cfg(feature = "i-slint-backend-winit")]
                        "winit" => return Box::new(i_slint_backend_winit::Backend::new(Some(_renderer))),
                        _ => {},
                    }
                };

                #[cfg(any(
                    feature = "i-slint-backend-qt",
                    feature = "i-slint-backend-winit"
                ))]
                if !backend_config.is_empty() {
                    eprintln!("Could not load rendering backend {}, fallback to default", backend_config)
                }

                create_default_backend()
            })
        }
        pub use default_backend::{
            native_widgets, Backend, NativeGlobals, NativeWidgets, HAS_NATIVE_STYLE,
        };
    } else {
        pub fn backend() -> &'static dyn i_slint_core::backend::Backend {
            i_slint_core::backend::instance().expect("no default backend configured, the backend must be initialized manually")
        }

        pub type NativeWidgets = ();
        pub type NativeGlobals = ();
        pub mod native_widgets {
            pub struct NativeStyleMetrics{}
        }
        pub const HAS_NATIVE_STYLE: bool = false;
    }
}

#[doc(hidden)]
#[cold]
#[cfg(not(target_arch = "wasm32"))]
pub fn use_modules() {
    i_slint_core::use_modules();
    #[cfg(feature = "i-slint-backend-qt")]
    i_slint_backend_qt::use_modules();
    #[cfg(feature = "i-slint-backend-winit")]
    i_slint_backend_winit::use_modules();
}

#[no_mangle]
pub extern "C" fn slint_native_style_metrics_init(_self: Pin<&native_widgets::NativeStyleMetrics>) {
    #[cfg(any(
        all(feature = "i-slint-backend-qt", not(no_qt)),
        feature = "i-slint-backend-winit"
    ))]
    default_backend::native_style_metrics_init(_self);
}

#[no_mangle]
pub extern "C" fn slint_native_style_metrics_deinit(
    _self: Pin<&mut native_widgets::NativeStyleMetrics>,
) {
    #[cfg(any(
        all(feature = "i-slint-backend-qt", not(no_qt)),
        feature = "i-slint-backend-winit"
    ))]
    default_backend::native_style_metrics_deinit(_self);
}