use bevy_ecs::system::Resource;
use bevy_utils::Duration;

/// Settings for the [`WinitPlugin`](super::WinitPlugin).
#[derive(Debug, Resource)]
pub struct WinitSettings {
    /// Controls how the [`EventLoop`](winit::event_loop::EventLoop) is deployed.
    ///
    /// - If this value is set to `false` (default), [`run`] is called, and exiting the loop will
    /// terminate the program.
    /// - If this value is set to `true`, [`run_return`] is called, and exiting the loop will
    /// return control to the caller.
    ///
    /// **Note:** This cannot be changed while the loop is running. `winit` also discourages use of
    /// `run_return`.
    ///
    /// # Supported platforms
    ///
    /// `run_return` is only available on the following `target_os` environments:
    /// - `windows`
    /// - `macos`
    /// - `linux`
    /// - `freebsd`
    /// - `openbsd`
    /// - `netbsd`
    /// - `dragonfly`
    ///
    /// The runner will panic if this is set to `true` on other platforms.
    ///
    /// [`run`]: https://docs.rs/winit/latest/winit/event_loop/struct.EventLoop.html#method.run
    /// [`run_return`]: https://docs.rs/winit/latest/winit/platform/run_return/trait.EventLoopExtRunReturn.html#tymethod.run_return
    pub return_from_run: bool,
    /// Determines how frequently the application can update when it has focus.
    pub focused_mode: UpdateMode,
    /// Determines how frequently the application can update when it's out of focus.
    pub unfocused_mode: UpdateMode,
}

impl WinitSettings {
    /// Default settings for games.
    pub fn game() -> Self {
        WinitSettings::default()
    }

    /// Default settings for desktop applications.
    ///
    /// [`Reactive`](UpdateMode::Reactive) if windows have focus,
    /// [`ReactiveLowPower`](UpdateMode::ReactiveLowPower) otherwise.
    pub fn desktop_app() -> Self {
        WinitSettings {
            focused_mode: UpdateMode::Reactive {
                wait: Duration::from_secs(5),
            },
            unfocused_mode: UpdateMode::ReactiveLowPower {
                wait: Duration::from_secs(60),
            },
            ..Default::default()
        }
    }

    /// Returns the current [`UpdateMode`].
    ///
    /// **Note:** The output depends on whether the window has focus or not.
    pub fn update_mode(&self, focused: bool) -> &UpdateMode {
        match focused {
            true => &self.focused_mode,
            false => &self.unfocused_mode,
        }
    }
}

impl Default for WinitSettings {
    fn default() -> Self {
        WinitSettings {
            return_from_run: false,
            focused_mode: UpdateMode::Continuous,
            unfocused_mode: UpdateMode::Continuous,
        }
    }
}

#[allow(clippy::doc_markdown)]
/// Determines how frequently an [`App`](bevy_app::App) should update.
///
/// **Note:** This setting is independent of VSync. VSync is controlled by a window's
/// [`PresentMode`](bevy_window::PresentMode) setting. If an app can update faster than the refresh
/// rate, but VSync is enabled, the update rate will be indirectly limited by the renderer.
#[derive(Debug, Clone, Copy)]
pub enum UpdateMode {
    /// The [`App`](bevy_app::App) will update over and over, as fast as it possibly can, until an
    /// [`AppExit`](bevy_app::AppExit) event appears.
    Continuous,
    /// The [`App`](bevy_app::App) will update in response to the following, until an
    /// [`AppExit`](bevy_app::AppExit) event appears:
    /// - `wait` time has elapsed since the previous update
    /// - a redraw has been requested by [`RequestRedraw`](bevy_window::RequestRedraw)
    /// - new [window](`winit::event::WindowEvent`) or [raw input](`winit::event::DeviceEvent`)
    /// events have appeared
    Reactive {
        /// The minimum time from the start of one update to the next.
        ///
        /// **Note:** This has no upper limit.
        /// The [`App`](bevy_app::App) will wait indefinitely if you set this to [`Duration::MAX`].
        wait: Duration,
    },
    /// The [`App`](bevy_app::App) will update in response to the following, until an
    /// [`AppExit`](bevy_app::AppExit) event appears:
    /// - `wait` time has elapsed since the previous update
    /// - a redraw has been requested by [`RequestRedraw`](bevy_window::RequestRedraw)
    /// - new [window events](`winit::event::WindowEvent`) have appeared
    ///
    /// **Note:** Unlike [`Reactive`](`UpdateMode::Reactive`), this mode will ignore events that
    /// don't come from interacting with a window, like [`MouseMotion`](winit::event::DeviceEvent::MouseMotion).
    /// Use this mode if, for example, you only want your app to update when the mouse cursor is
    /// moving over a window, not just moving in general. This can greatly reduce power consumption.
    ReactiveLowPower {
        /// The minimum time from the start of one update to the next.
        ///
        /// **Note:** This has no upper limit.
        /// The [`App`](bevy_app::App) will wait indefinitely if you set this to [`Duration::MAX`].
        wait: Duration,
    },
}