bevy_gauge 0.1.0

use bevy::{ecs::component::Mutable, prelude::*};
use super::prelude::*;

/// An extension trait for `bevy::prelude::App` to simplify the setup of components
/// that derive their values from the stat system or write their values back to it.
///
/// This provides convenient methods to register the necessary systems for components
/// that implement `StatDerived` and/or `WriteBack`.
pub trait StatsAppExtension {
    /// Registers systems to manage a component `T` that implements `StatDerived`.
    ///
    /// This includes a system to update the fields of `T` based on values from the `Stats` component
    /// when the `StatsProxy` changes. The component must already exist on the entity.
    ///
    /// # Type Parameters
    ///
    /// * `T`: The component type that implements `StatDerived`.
    fn add_stat_component<T: StatDerived + Component<Mutability = Mutable>>(&mut self) -> &mut Self;

    /// Registers systems to manage a component `T` that implements `WriteBack`.
    ///
    /// This typically includes a system to update stat values in the `Stats` component
    /// based on changes detected in the fields of `T`.
    ///
    /// # Type Parameters
    ///
    /// * `T`: The component type that implements `WriteBack`.
    fn add_writeback_component<T: WriteBack + Component>(&mut self) -> &mut Self;

    /// A convenience method that combines `add_stat_component` and `add_writeback_component`.
    /// Use this for components that both derive from stats and write back to them.
    ///
    /// # Type Parameters
    ///
    /// * `T`: The component type that implements both `StatDerived` and `WriteBack`.
    fn add_complex_component<T: StatDerived + WriteBack + Component<Mutability = Mutable>>(&mut self) -> &mut Self;
}

impl StatsAppExtension for App {
    fn add_stat_component<T: StatDerived + Component<Mutability = Mutable>>(&mut self) -> &mut Self {
        self.add_systems(StatsMutation, update_stat_component_system::<T>
            .before(update_stats_proxy_system)
        );
        self
    }

    fn add_writeback_component<T: WriteBack + Component>(&mut self) -> &mut Self {
        self.add_systems(UpdateWriteBack, update_writeback_value_system::<T>);
        self
    }

    fn add_complex_component<T: StatDerived + WriteBack + Component<Mutability = Mutable>>(&mut self) -> &mut Self {
        self.add_stat_component::<T>();
        self.add_writeback_component::<T>();
        self
    }
}

use bevy::{app::MainScheduleOrder, ecs::schedule::ScheduleLabel};

/// Plugin function for the app extension module.
/// Sets up custom schedules used by the stat system for managing derived components and write-back mechanisms.
///
/// This ensures that stat calculations, updates to `StatDerived` components, and `WriteBack` operations
/// occur in a controlled order relative to Bevy's main update cycle.
/// Specifically, it inserts:
/// - `StatsMutation`: After `PreUpdate`.
/// - `UpdateStatDerived`: After `StatsMutation`.
/// - `UpdateWriteBack`: After `UpdateStatDerived`.
pub fn plugin(app: &mut App) {
    
    app.init_schedule(StatsMutation)
        .world_mut()
        .resource_mut::<MainScheduleOrder>()
        .insert_after(First, StatsMutation);

    app.init_schedule(UpdateStatDerived)
        .world_mut()
        .resource_mut::<MainScheduleOrder>()
        .insert_after(StatsMutation, UpdateStatDerived);

    app.init_schedule(UpdateWriteBack)
        .world_mut()
        .resource_mut::<MainScheduleOrder>()
        .insert_after(UpdateStatDerived, UpdateWriteBack);
}

/// Custom Bevy schedule label for systems that perform mutations on `Stats` components.
///
/// This schedule runs after `PreUpdate` and before `UpdateStatDerived`.
/// It's intended for systems that directly add/remove modifiers or change stat values.
#[derive(ScheduleLabel, Debug, Clone, PartialEq, Eq, Hash)]
pub struct StatsMutation;

/// Custom Bevy schedule label for systems that update components implementing `StatDerived`.
///
/// This schedule runs after `StatsMutation` and before `UpdateWriteBack` (and `Update`).
/// Systems in this schedule read from `Stats` components and update the fields of `StatDerived` components.
#[derive(ScheduleLabel, Debug, Clone, PartialEq, Eq, Hash)]
pub struct UpdateStatDerived;

/// Custom Bevy schedule label for systems that write values from `WriteBack` components back to `Stats` components.
///
/// This schedule runs after `UpdateStatDerived` and before `Update` (if `UpdateWriteBack` itself is placed before `Update`).
/// Systems here detect changes in `WriteBack` components and update the underlying stats.
#[derive(ScheduleLabel, Debug, Clone, PartialEq, Eq, Hash)]
pub struct UpdateWriteBack;