//! Server tick cycle — named system set phases (#843).
//!
//! Replaces ad-hoc `.after()`/`.before()` constraints with a linear pipeline.
//! Each system belongs to exactly one phase. Phases execute sequentially.
//! Within a phase, systems with no intra-phase ordering run in parallel
//! (when the multi-threaded executor is enabled).
//!
//! ```text
//! PreInput → Input → Movement → Simulation → Economy
//!     → Storyteller → Snapshot → PostSnapshot → Knowledge → TickAdvance
//! ```
//!
//! ## Rules
//!
//! 1. Every system in the Update schedule MUST have `.in_set(TickPhase::X)`.
//! 2. Cross-phase `.after()`/`.before()` is FORBIDDEN — if you need it,
//!    the system is in the wrong phase.
//! 3. Intra-phase `.after()`/`.before()` is allowed for systems within
//!    the same phase that have a real data dependency.

use bevy_app::prelude::*;
use bevy_ecs::prelude::*;
use bevy_ecs::schedule::IntoScheduleConfigs;

/// The 10 phases of the server tick cycle.
///
/// Ordered linearly: each phase completes before the next begins.
/// Configure once in the App with `configure_sets(Update, ...)`.
#[derive(SystemSet, Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum TickPhase {
    /// Setup before player input: chunk streaming, bridge input, NPC routine transitions.
    PreInput,
    /// Process player actions: input dispatch, door/terminal/examine interactions, dialogue.
    Input,
    /// Position resolution: pathfinding, path following, movement validation, spatial indexing.
    Movement,
    /// Game logic: NPC behavior, vision, conversations, monologue, sound, visibility geometry.
    Simulation,
    /// Economics: tick the economy simulation, serve economy state queries.
    Economy,
    /// Storyteller: contamination, activation, tell escalation, tell state derivation.
    Storyteller,
    /// Assemble tick output: observer snapshot, ticker, settings, debug commands, save/load.
    Snapshot,
    /// React to snapshot: observation events, send to client, anomaly detection.
    PostSnapshot,
    /// Update persistent state: knowledge events, cognitive delay, relationships.
    Knowledge,
    /// Increment the clock. Must be last.
    TickAdvance,
}

impl TickPhase {
    /// Configure the linear phase ordering on the app.
    ///
    /// Call once during plugin setup:
    /// ```ignore
    /// TickPhase::configure(&mut app);
    /// ```
    pub fn configure(app: &mut bevy_app::App) {
        use TickPhase::*;
        app.configure_sets(
            Update,
            (
                PreInput,
                Input,
                Movement,
                Simulation,
                Economy,
                Storyteller,
                Snapshot,
                PostSnapshot,
                Knowledge,
                TickAdvance,
            )
                .chain(),
        );
    }
}