//! NPC player-awareness system (#244).
//!
//! Tracks how aware an NPC is of the player's attention. When the player
//! lingers in an NPC's field of view, the NPC's suspicion accumulates and
//! feeds stress into `ToleranceThreshold` (D-024 axis 4).
//!
//! Reads `NpcVisionState.player_visible` from the NPC vision system (#115).
//! Separate from the follow mechanic (#241): follow tracks player-initiated
//! proximity, awareness tracks NPC-perceived attention.
//!
//! ## System ordering
//!
//! `detect_player_awareness` runs:
//! - after `vision::compute_npc_vision` (needs player_visible)
//! - before `tolerance::check_tolerance_threshold` (feeds stress)
//!
//! ## Suspicion lifecycle
//!
//! 1. Player enters NPC's LOS → `consecutive_los_ticks` starts counting
//! 2. After `AWARENESS_NOTICE_TICKS` consecutive ticks → suspicion starts building
//! 3. Each tick past threshold: `suspicion_level` increases, stress added to tolerance
//! 4. Player leaves LOS → `consecutive_los_ticks` resets, suspicion decays slowly
//!
//! All arithmetic is integer-only (D-010 determinism).

use bevy_ecs::prelude::*;
use serde::{Deserialize, Serialize};

use crate::npc::vision::NpcVisionState;
use crate::npc::{Npc, ToleranceThreshold};
use crate::simulation::time::SimulationTime;
use crate::simulation::tier::ActiveSim;

// ---------------------------------------------------------------------------
// Constants
// ---------------------------------------------------------------------------

/// Consecutive ticks the player must remain in an NPC's LOS before suspicion
/// starts building. 30 ticks = 3 game-minutes (D-031: 10 ticks = 1 game-minute).
pub const AWARENESS_NOTICE_TICKS: u64 = 30;

/// Stress increment per tick applied to `ToleranceThreshold` once the NPC
/// notices sustained player attention. Lighter than follow stress (2/tick)
/// because watching is less intrusive than tailing.
pub const AWARENESS_STRESS_PER_TICK: i16 = 1;

/// Ticks between suspicion decay checks when player is NOT in LOS.
/// 10 ticks = 1 game-minute (D-031).
pub const AWARENESS_DECAY_INTERVAL: u64 = 10;

/// Suspicion decay amount per interval when player is not in LOS.
pub const AWARENESS_DECAY_AMOUNT: i16 = 1;

// ---------------------------------------------------------------------------
// Component
// ---------------------------------------------------------------------------

/// Tracks an NPC's awareness of sustained player attention (#244).
///
/// Updated each tick by `detect_player_awareness` for Active-tier NPCs.
/// Feeds stress into `ToleranceThreshold` when `suspicion_level` rises.
///
/// ## Fields
/// - `player_in_los` — mirrors `NpcVisionState.player_visible` for downstream queries
/// - `consecutive_los_ticks` — resets when player leaves LOS
/// - `suspicion_level` — 0–100, accumulates while player watches, decays when they leave
#[derive(Component, Debug, Clone, Default, Serialize, Deserialize)]
pub struct PlayerAwareness {
    /// Whether the player is currently in this NPC's line of sight.
    pub player_in_los: bool,
    /// Consecutive ticks the player has been in this NPC's LOS.
    pub consecutive_los_ticks: u64,
    /// Accumulated suspicion level (0–100, integer for D-010).
    pub suspicion_level: i16,
}

// ---------------------------------------------------------------------------
// System
// ---------------------------------------------------------------------------

/// Detect sustained player attention and build NPC suspicion.
///
/// For each Active-tier NPC with `PlayerAwareness`:
/// - Sync `player_in_los` from `NpcVisionState.player_visible`
/// - If player visible: increment `consecutive_los_ticks`; once past
///   `AWARENESS_NOTICE_TICKS`, increase `suspicion_level` and apply
///   stress to `ToleranceThreshold`
/// - If player NOT visible: reset `consecutive_los_ticks`, decay
///   `suspicion_level` periodically
pub fn detect_player_awareness(
    time: Res<SimulationTime>,
    mut npc_query: Query<
        (
            &NpcVisionState,
            &mut PlayerAwareness,
            &mut ToleranceThreshold,
        ),
        (With<Npc>, With<ActiveSim>),
    >,
) {
    for (vision, mut awareness, mut tolerance) in npc_query.iter_mut() {
        awareness.player_in_los = vision.player_visible;

        if vision.player_visible {
            awareness.consecutive_los_ticks += 1;

            // Once the NPC has noticed sustained player attention, build suspicion
            if awareness.consecutive_los_ticks >= AWARENESS_NOTICE_TICKS {
                awareness.suspicion_level =
                    (awareness.suspicion_level + AWARENESS_STRESS_PER_TICK).min(100);
                tolerance.current_stress = tolerance
                    .current_stress
                    .saturating_add(AWARENESS_STRESS_PER_TICK);
            }
        } else {
            // Player left LOS — reset consecutive counter
            awareness.consecutive_los_ticks = 0;

            // Decay suspicion slowly when player is not visible
            if time.tick % AWARENESS_DECAY_INTERVAL == 0 && awareness.suspicion_level > 0 {
                awareness.suspicion_level =
                    (awareness.suspicion_level - AWARENESS_DECAY_AMOUNT).max(0);
            }
        }
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use super::*;
    use crate::npc::vision::NpcVisionState;
    use crate::npc::{Npc, ToleranceThreshold};
    use crate::simulation::time::SimulationTime;
    use crate::simulation::tier::ActiveSim;
    use bevy_ecs::world::World;

    fn setup_world() -> World {
        let mut world = World::new();
        world.init_resource::<SimulationTime>();
        world
    }

    fn run_system(world: &mut World) {
        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(detect_player_awareness);
        schedule.run(world);
    }

    fn default_tolerance() -> ToleranceThreshold {
        ToleranceThreshold {
            current_stress: 0,
            threshold: 80,
        }
    }

    fn vision_with_player(visible: bool) -> NpcVisionState {
        NpcVisionState {
            player_visible: visible,
            ..Default::default()
        }
    }

    // -----------------------------------------------------------------------
    // Basic LOS tracking
    // -----------------------------------------------------------------------

    #[test]
    fn player_in_los_increments_consecutive_ticks() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness::default(),
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert!(awareness.player_in_los);
        assert_eq!(awareness.consecutive_los_ticks, 1);
    }

    #[test]
    fn player_leaving_los_resets_consecutive_ticks() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(false),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: 20,
                    suspicion_level: 5,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert!(!awareness.player_in_los);
        assert_eq!(awareness.consecutive_los_ticks, 0);
    }

    #[test]
    fn player_in_los_syncs_from_vision_state() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: false, // was false
                    consecutive_los_ticks: 0,
                    suspicion_level: 0,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert!(awareness.player_in_los, "should sync from NpcVisionState");
    }

    // -----------------------------------------------------------------------
    // Suspicion threshold — no stress before notice ticks
    // -----------------------------------------------------------------------

    #[test]
    fn no_stress_before_notice_threshold() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS - 2, // not yet at threshold
                    suspicion_level: 0,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.suspicion_level, 0,
            "suspicion should not build before notice threshold"
        );
        let tolerance = world.get::<ToleranceThreshold>(npc).unwrap();
        assert_eq!(
            tolerance.current_stress, 0,
            "stress should not increase before notice threshold"
        );
    }

    #[test]
    fn stress_starts_at_notice_threshold() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS - 1, // will reach threshold
                    suspicion_level: 0,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.consecutive_los_ticks, AWARENESS_NOTICE_TICKS,
            "consecutive ticks should reach threshold"
        );
        assert_eq!(
            awareness.suspicion_level, AWARENESS_STRESS_PER_TICK,
            "suspicion should increase at threshold"
        );
        let tolerance = world.get::<ToleranceThreshold>(npc).unwrap();
        assert_eq!(
            tolerance.current_stress, AWARENESS_STRESS_PER_TICK,
            "stress should increase at threshold"
        );
    }

    // -----------------------------------------------------------------------
    // Suspicion accumulation
    // -----------------------------------------------------------------------

    #[test]
    fn suspicion_accumulates_past_threshold() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS + 5,
                    suspicion_level: 10,
                },
                ToleranceThreshold {
                    current_stress: 20,
                    threshold: 80,
                },
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.suspicion_level,
            10 + AWARENESS_STRESS_PER_TICK,
            "suspicion should accumulate"
        );
        let tolerance = world.get::<ToleranceThreshold>(npc).unwrap();
        assert_eq!(
            tolerance.current_stress,
            20 + AWARENESS_STRESS_PER_TICK,
            "stress should accumulate"
        );
    }

    #[test]
    fn suspicion_caps_at_100() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS + 100,
                    suspicion_level: 100,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(awareness.suspicion_level, 100, "suspicion should cap at 100");
    }

    #[test]
    fn tolerance_stress_saturates() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS,
                    suspicion_level: 50,
                },
                ToleranceThreshold {
                    current_stress: i16::MAX - 1,
                    threshold: i16::MAX,
                },
            ))
            .id();

        run_system(&mut world);

        let tolerance = world.get::<ToleranceThreshold>(npc).unwrap();
        assert_eq!(
            tolerance.current_stress,
            i16::MAX,
            "stress should saturate, not overflow"
        );
    }

    // -----------------------------------------------------------------------
    // Suspicion decay
    // -----------------------------------------------------------------------

    #[test]
    fn suspicion_decays_when_player_not_in_los_on_interval() {
        let mut world = setup_world();
        // Set tick to a decay interval boundary
        world.resource_mut::<SimulationTime>().tick = 20; // divisible by AWARENESS_DECAY_INTERVAL

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(false),
                PlayerAwareness {
                    player_in_los: false,
                    consecutive_los_ticks: 0,
                    suspicion_level: 10,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.suspicion_level,
            10 - AWARENESS_DECAY_AMOUNT,
            "suspicion should decay on interval tick"
        );
    }

    #[test]
    fn suspicion_does_not_decay_off_interval() {
        let mut world = setup_world();
        // Set tick to a non-interval boundary
        world.resource_mut::<SimulationTime>().tick = 13; // not divisible by AWARENESS_DECAY_INTERVAL

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(false),
                PlayerAwareness {
                    player_in_los: false,
                    consecutive_los_ticks: 0,
                    suspicion_level: 10,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.suspicion_level, 10,
            "suspicion should not decay on non-interval tick"
        );
    }

    #[test]
    fn suspicion_does_not_go_below_zero() {
        let mut world = setup_world();
        world.resource_mut::<SimulationTime>().tick = 10;

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(false),
                PlayerAwareness {
                    player_in_los: false,
                    consecutive_los_ticks: 0,
                    suspicion_level: 0,
                },
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.suspicion_level, 0,
            "suspicion should not go below zero"
        );
    }

    // -----------------------------------------------------------------------
    // Background NPC not processed
    // -----------------------------------------------------------------------

    #[test]
    fn background_npc_not_processed() {
        let mut world = setup_world();

        let npc = world
            .spawn((
                Npc,
                crate::simulation::tier::BackgroundSim,
                vision_with_player(true),
                PlayerAwareness::default(),
                default_tolerance(),
            ))
            .id();

        run_system(&mut world);

        let awareness = world.get::<PlayerAwareness>(npc).unwrap();
        assert_eq!(
            awareness.consecutive_los_ticks, 0,
            "background NPC should not have awareness processed"
        );
    }

    // -----------------------------------------------------------------------
    // No panic with missing components
    // -----------------------------------------------------------------------

    #[test]
    fn npc_without_awareness_no_panic() {
        let mut world = setup_world();

        // NPC with vision but no PlayerAwareness — system should skip
        world.spawn((
            Npc,
            ActiveSim,
            vision_with_player(true),
            default_tolerance(),
        ));

        run_system(&mut world); // should not panic
    }

    // -----------------------------------------------------------------------
    // Integration: follow + awareness stress stacking
    // -----------------------------------------------------------------------

    #[test]
    fn awareness_stress_stacks_with_existing_stress() {
        let mut world = setup_world();

        // NPC already has stress from other sources (e.g., follow mechanic)
        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                vision_with_player(true),
                PlayerAwareness {
                    player_in_los: true,
                    consecutive_los_ticks: AWARENESS_NOTICE_TICKS, // past threshold
                    suspicion_level: 5,
                },
                ToleranceThreshold {
                    current_stress: 30, // pre-existing stress
                    threshold: 80,
                },
            ))
            .id();

        run_system(&mut world);

        let tolerance = world.get::<ToleranceThreshold>(npc).unwrap();
        assert_eq!(
            tolerance.current_stress,
            30 + AWARENESS_STRESS_PER_TICK,
            "awareness stress should stack with existing stress"
        );
    }

    // -----------------------------------------------------------------------
    // Constant value assertions (#244 spec compliance)
    // -----------------------------------------------------------------------

    #[test]
    fn awareness_constants_have_expected_values() {
        assert_eq!(
            AWARENESS_NOTICE_TICKS, 30,
            "#244: NPC notices sustained attention after 30 ticks (3 game-minutes)"
        );
        assert_eq!(
            AWARENESS_STRESS_PER_TICK, 1,
            "#244: stress per tick lighter than follow stress (D-010 integer)"
        );
        assert_eq!(
            AWARENESS_DECAY_INTERVAL, 10,
            "#244: suspicion decays every 10 ticks (1 game-minute, D-031)"
        );
        assert_eq!(
            AWARENESS_DECAY_AMOUNT, 1,
            "#244: suspicion decays by 1 per interval"
        );
    }
}