//! NPC mood state machine (#323).
//!
//! Implements the 8-state NPC mood FSM (D-024 MoodState axis, D-035 taxonomy).
//! Mood is derived each tick from simulation inputs (stress, time of day,
//! recent interactions) and drives Layer 4 dialogue selection and monologue tone.
//!
//! All state transitions are deterministic — integer arithmetic only (D-010).
//! No floats. No HashMap.
//!
//! ## Integration points
//! - `ToleranceThreshold.current_stress` → primary mood driver
//! - `SimulationTime.day_phase()` → Evening phase adds Frustrated pressure
//! - `InteractionMemory` (Sprint 14, #325) → will set warm_active flag
//! - `CurrentMood` (dialogue.rs) → synced each tick for Layer 4 selection
//! - Monologue trigger system → reads NpcMood for tone selection (D-016, future)
//! - Tell system (#337, deferred to Sprint 15) → reads MoodState

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

use crate::npc::interaction::InteractionMemory;
use crate::npc::{Npc, ToleranceThreshold};
use crate::simulation::dialogue::CurrentMood;
use crate::simulation::line_pool::Mood as ContentMood;
use crate::simulation::tier::ActiveSim;
use crate::simulation::time::{DayPhase, SimulationTime};

// ---------------------------------------------------------------------------
// NpcMood enum
// ---------------------------------------------------------------------------

/// NPC simulation mood — 8-state FSM (D-024, D-035 converged taxonomy).
///
/// Driven by `ToleranceThreshold` stress, time of day, and interaction events.
/// Maps to `content::line_pool::Mood` for Layer 4 dialogue tag matching.
///
/// Copy team references this enum when scripting mood conditions.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
pub enum NpcMood {
    /// Default state: no notable stressors, no recent positive events.
    #[default]
    Neutral,
    /// Elevated stress approaching threshold — heightened wariness.
    Anxious,
    /// Late-shift fatigue or repeated minor irritations.
    Frustrated,
    /// Low stress, positive recent context — settled and cooperative.
    Content,
    /// Observing unusual or off-script behavior — targeted wariness.
    /// Not reachable from `derive_mood()` — set externally by observation pipeline.
    Suspicious,
    /// Recent positive player interaction within memory window.
    Warm,
    /// Stress at or above threshold — confrontational or withdrawn.
    Hostile,
    /// Actively engaged in a scheduled activity — task-focused.
    /// Not reachable from `derive_mood()` — set externally by activity scheduler (#101).
    Focused,
}

// ---------------------------------------------------------------------------
// MoodState component
// ---------------------------------------------------------------------------

/// Per-NPC mood component — wraps NpcMood for ECS queries.
///
/// Updated each tick by `update_mood` for Active-tier NPCs.
/// Read by: dialogue Layer 4 (via CurrentMood sync), tell system (#337),
/// monologue tone selection (D-016, future scope).
#[derive(Component, Debug, Clone, Default, Serialize, Deserialize)]
pub struct MoodState {
    pub mood: NpcMood,
    /// Tick when mood last changed — guards against thrashing in tests.
    pub changed_tick: u64,
}

// ---------------------------------------------------------------------------
// Mood mapping: NpcMood → content::line_pool::Mood
// ---------------------------------------------------------------------------

/// Map NPC simulation mood to the content dialogue tag.
///
/// Bridges the simulation FSM (NpcMood) with the dialogue line pool system
/// (content::line_pool::Mood). The mapping is intentionally lossy in some
/// directions — multiple simulation moods map to the same content tag when
/// the distinction matters for behavior but not for line selection.
pub fn mood_to_content_mood(mood: NpcMood) -> ContentMood {
    match mood {
        NpcMood::Neutral => ContentMood::Content,
        NpcMood::Anxious => ContentMood::Anxious,
        NpcMood::Frustrated => ContentMood::Frustrated,
        NpcMood::Content => ContentMood::Relieved,
        NpcMood::Suspicious => ContentMood::Suspicious,
        NpcMood::Warm => ContentMood::Warm,
        NpcMood::Hostile => ContentMood::Hostile,
        NpcMood::Focused => ContentMood::Focused,
    }
}

// ---------------------------------------------------------------------------
// Mood derivation (pure, testable)
// ---------------------------------------------------------------------------

/// Stress fraction threshold for Anxious: 60% of tolerance threshold.
///
/// Uses integer multiplication to avoid division:
///   Anxious when `current_stress * 100 >= threshold * ANXIOUS_STRESS_NUMERATOR`
/// Equivalent to: `current_stress >= threshold * 0.60`
const ANXIOUS_STRESS_NUMERATOR: i16 = 60;

/// Stress level below which an NPC is considered Content (no notable pressure).
const CONTENT_STRESS_CEILING: i16 = 20;

/// Minimum stress for Evening → Frustrated (avoids Frustrated at zero stress).
const FRUSTRATED_STRESS_FLOOR: i16 = 10;

/// Ticks within which a completed Talk interaction keeps the Warm mood active.
/// 300 ticks = 30 game-minutes (D-031: 10 ticks/minute).
pub const WARM_INTERACTION_WINDOW_TICKS: u64 = 300;

/// Derive NPC mood from simulation inputs.
///
/// Priority ordering (high to low):
///   1. Hostile  — stress at or above threshold
///   2. Anxious  — stress at 60% of threshold or above
///   3. Warm     — recent positive player interaction
///   4. Frustrated — Evening phase with non-trivial stress
///   5. Content  — very low stress (< CONTENT_STRESS_CEILING)
///   6. Neutral  — everything else
///
/// Inputs are all integer or enum — no floats (D-010 determinism).
///
/// `warm_active`: set by InteractionMemory (#325, Sprint 14) when a positive
/// interaction occurred within the memory window. Placeholder `false` until
/// #325 is wired.
pub fn derive_mood(
    current_stress: i16,
    threshold: i16,
    phase: DayPhase,
    warm_active: bool,
) -> NpcMood {
    // 1. Hostile: at or above threshold
    if current_stress >= threshold {
        return NpcMood::Hostile;
    }

    // 2. Anxious: above 60% of threshold.
    // Guard: skip if threshold == 0 (divide-by-zero equivalent — entity
    // has no tolerance and is already Hostile from rule 1).
    if threshold > 0
        && (current_stress as i32) * 100 >= (threshold as i32) * (ANXIOUS_STRESS_NUMERATOR as i32)
    {
        return NpcMood::Anxious;
    }

    // 3. Warm: recent positive interaction (priority over Frustrated/Content)
    if warm_active {
        return NpcMood::Warm;
    }

    // 4. Frustrated: Evening phase with non-trivial stress
    if phase == DayPhase::Evening && current_stress >= FRUSTRATED_STRESS_FLOOR {
        return NpcMood::Frustrated;
    }

    // 5. Content: very low stress
    if current_stress < CONTENT_STRESS_CEILING {
        return NpcMood::Content;
    }

    // 6. Neutral: moderate stress, no special conditions
    NpcMood::Neutral
}

// ---------------------------------------------------------------------------
// System: update_mood
// ---------------------------------------------------------------------------

/// System: update NpcMood and sync CurrentMood for Active-tier NPCs.
///
/// Reads `ToleranceThreshold` stress and `SimulationTime` day phase to derive
/// the new mood. Updates `MoodState` when mood changes (records changed_tick).
/// Syncs `CurrentMood` (used by dialogue Layer 4) every tick regardless of
/// whether MoodState changed.
///
/// Scoped to `ActiveSim` — Background-tier NPCs retain their last mood state
/// (D-026). This is intentional: background NPCs simulate passage of time via
/// last-known state, not per-tick derivation.
///
pub fn update_mood(
    time: Res<SimulationTime>,
    mut query: Query<
        (
            &mut MoodState,
            Option<&mut CurrentMood>,
            Option<&ToleranceThreshold>,
            Option<&InteractionMemory>,
        ),
        (With<Npc>, With<ActiveSim>),
    >,
) {
    let phase = time.day_phase();
    let tick = time.tick;

    for (mut mood_state, current_mood_opt, tolerance_opt, interaction_mem_opt) in query.iter_mut() {
        let (stress, threshold) = tolerance_opt
            .map(|t| (t.current_stress, t.threshold))
            .unwrap_or((0, 50)); // Default: no stress, moderate threshold

        // Warm: recent positive player interaction within memory window (#325)
        let warm_active = interaction_mem_opt
            .map(|mem| {
                mem.interaction_count > 0
                    && tick.saturating_sub(mem.last_interaction_tick)
                        < WARM_INTERACTION_WINDOW_TICKS
            })
            .unwrap_or(false);

        let new_mood = derive_mood(stress, threshold, phase, warm_active);

        if mood_state.mood != new_mood {
            mood_state.mood = new_mood;
            mood_state.changed_tick = tick;
        }

        // Sync CurrentMood for dialogue pipeline — always, not just on change.
        // CurrentMood drives Layer 4 scoring; it must reflect current simulation
        // state even if MoodState itself didn't change this tick.
        if let Some(mut current_mood) = current_mood_opt {
            current_mood.0 = mood_to_content_mood(new_mood);
        }
    }
}

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

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

    // --- derive_mood unit tests ---

    #[test]
    fn mood_hostile_when_stress_equals_threshold() {
        assert_eq!(
            derive_mood(50, 50, DayPhase::Morning, false),
            NpcMood::Hostile
        );
    }

    #[test]
    fn mood_hostile_when_stress_above_threshold() {
        assert_eq!(
            derive_mood(80, 50, DayPhase::Morning, false),
            NpcMood::Hostile
        );
    }

    #[test]
    fn mood_anxious_at_60_percent_threshold() {
        // 60% of threshold=100 is 60. stress=60 → Anxious.
        assert_eq!(
            derive_mood(60, 100, DayPhase::Morning, false),
            NpcMood::Anxious
        );
    }

    #[test]
    fn mood_anxious_boundary_above() {
        // threshold=50: 60% = 30. stress=30 → Anxious (30*100=3000 >= 50*60=3000).
        assert_eq!(
            derive_mood(30, 50, DayPhase::Morning, false),
            NpcMood::Anxious
        );
    }

    #[test]
    fn mood_not_anxious_just_below_boundary() {
        // threshold=50: 60% = 30. stress=29 → not Anxious (29*100=2900 < 3000).
        // stress=29 < 20 is false, so → Neutral.
        assert_eq!(
            derive_mood(29, 50, DayPhase::Morning, false),
            NpcMood::Neutral
        );
    }

    #[test]
    fn mood_warm_when_positive_interaction() {
        assert_eq!(derive_mood(0, 50, DayPhase::Morning, true), NpcMood::Warm);
    }

    #[test]
    fn mood_frustrated_when_evening_with_stress() {
        // stress=25 (not hostile/anxious), Evening phase → Frustrated
        assert_eq!(
            derive_mood(25, 50, DayPhase::Evening, false),
            NpcMood::Frustrated
        );
    }

    #[test]
    fn mood_not_frustrated_in_morning() {
        assert_eq!(
            derive_mood(25, 50, DayPhase::Morning, false),
            NpcMood::Neutral
        );
    }

    #[test]
    fn mood_not_frustrated_when_stress_below_floor() {
        // stress=5 < FRUSTRATED_STRESS_FLOOR=10 → Content (stress < 20)
        assert_eq!(
            derive_mood(5, 50, DayPhase::Evening, false),
            NpcMood::Content
        );
    }

    #[test]
    fn mood_content_when_low_stress() {
        assert_eq!(
            derive_mood(15, 50, DayPhase::Morning, false),
            NpcMood::Content
        );
    }

    #[test]
    fn mood_content_boundary_at_19() {
        // stress=19 < CONTENT_STRESS_CEILING=20 → Content
        assert_eq!(
            derive_mood(19, 50, DayPhase::Morning, false),
            NpcMood::Content
        );
    }

    #[test]
    fn mood_neutral_otherwise() {
        // stress=25, not anxious (25*100=2500 < 50*60=3000), not Warm, morning, not Content
        // Wait: 25*100=2500, 50*60=3000 → not Anxious. 25 >= 20 → not Content. Morning → not Frustrated. → Neutral
        assert_eq!(
            derive_mood(25, 50, DayPhase::Morning, false),
            NpcMood::Neutral
        );
    }

    #[test]
    fn mood_priority_hostile_over_anxious_at_threshold() {
        // At exactly threshold → Hostile, not Anxious
        assert_eq!(
            derive_mood(50, 50, DayPhase::Morning, false),
            NpcMood::Hostile
        );
    }

    #[test]
    fn mood_priority_hostile_over_frustrated_evening() {
        assert_eq!(
            derive_mood(50, 50, DayPhase::Evening, false),
            NpcMood::Hostile
        );
    }

    #[test]
    fn mood_priority_anxious_over_warm() {
        // Anxious takes priority over Warm interaction
        assert_eq!(
            derive_mood(60, 100, DayPhase::Morning, true),
            NpcMood::Anxious
        );
    }

    #[test]
    fn mood_priority_warm_over_frustrated() {
        // Warm takes priority over Frustrated (checked before Evening test)
        assert_eq!(derive_mood(25, 50, DayPhase::Evening, true), NpcMood::Warm);
    }

    #[test]
    fn mood_zero_threshold_is_hostile() {
        // stress=0, threshold=0: 0 >= 0 → Hostile
        assert_eq!(
            derive_mood(0, 0, DayPhase::Morning, false),
            NpcMood::Hostile
        );
    }

    #[test]
    fn mood_content_zero_stress_moderate_threshold() {
        // stress=0, threshold=50: not hostile, not anxious (threshold > 0, 0*100=0 < 50*60=3000),
        // not warm, not evening, stress < 20 → Content
        assert_eq!(
            derive_mood(0, 50, DayPhase::Morning, false),
            NpcMood::Content
        );
    }

    // --- mood_to_content_mood mapping coverage ---

    #[test]
    fn mood_mapping_covers_all_variants() {
        for mood in [
            NpcMood::Neutral,
            NpcMood::Anxious,
            NpcMood::Frustrated,
            NpcMood::Content,
            NpcMood::Suspicious,
            NpcMood::Warm,
            NpcMood::Hostile,
            NpcMood::Focused,
        ] {
            let _ = mood_to_content_mood(mood); // must not panic
        }
    }

    #[test]
    fn mood_mapping_anxious_is_anxious() {
        assert_eq!(mood_to_content_mood(NpcMood::Anxious), ContentMood::Anxious);
    }

    #[test]
    fn mood_mapping_warm_is_warm() {
        assert_eq!(mood_to_content_mood(NpcMood::Warm), ContentMood::Warm);
    }

    #[test]
    fn mood_mapping_suspicious_is_suspicious() {
        assert_eq!(
            mood_to_content_mood(NpcMood::Suspicious),
            ContentMood::Suspicious
        );
    }

    #[test]
    fn mood_mapping_focused_is_focused() {
        assert_eq!(mood_to_content_mood(NpcMood::Focused), ContentMood::Focused);
    }

    // --- update_mood system integration tests ---

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

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

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                MoodState::default(),
                CurrentMood::default(),
                ToleranceThreshold {
                    current_stress: 50,
                    threshold: 50,
                },
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let mood_state = world.get::<MoodState>(npc).unwrap();
        assert_eq!(mood_state.mood, NpcMood::Hostile);

        let current_mood = world.get::<CurrentMood>(npc).unwrap();
        assert_eq!(current_mood.0, ContentMood::Hostile);
    }

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

        // No ToleranceThreshold → defaults (stress=0, threshold=50) → Content
        let npc = world
            .spawn((Npc, ActiveSim, MoodState::default(), CurrentMood::default()))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let mood_state = world.get::<MoodState>(npc).unwrap();
        assert_eq!(mood_state.mood, NpcMood::Content);
    }

    #[test]
    fn update_mood_records_changed_tick_on_transition() {
        let mut world = setup_world();
        world.resource_mut::<SimulationTime>().tick = 42;

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                // Start Warm, will transition to Hostile
                MoodState {
                    mood: NpcMood::Warm,
                    changed_tick: 0,
                },
                CurrentMood::default(),
                ToleranceThreshold {
                    current_stress: 50,
                    threshold: 50,
                },
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let mood_state = world.get::<MoodState>(npc).unwrap();
        assert_eq!(mood_state.mood, NpcMood::Hostile);
        assert_eq!(mood_state.changed_tick, 42);
    }

    #[test]
    fn update_mood_does_not_update_changed_tick_when_unchanged() {
        let mut world = setup_world();
        world.resource_mut::<SimulationTime>().tick = 42;

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                // Already Content; no tolerance → will derive Content again
                MoodState {
                    mood: NpcMood::Content,
                    changed_tick: 5,
                },
                CurrentMood::default(),
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let mood_state = world.get::<MoodState>(npc).unwrap();
        assert_eq!(mood_state.mood, NpcMood::Content);
        assert_eq!(mood_state.changed_tick, 5); // unchanged
    }

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

        // BackgroundSim NPC — must not be updated
        let npc = world
            .spawn((
                Npc,
                BackgroundSim,
                MoodState {
                    mood: NpcMood::Warm,
                    changed_tick: 0,
                },
                CurrentMood::default(),
                ToleranceThreshold {
                    current_stress: 50,
                    threshold: 50, // Would → Hostile if processed
                },
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let mood_state = world.get::<MoodState>(npc).unwrap();
        // Must remain Warm — not processed because BackgroundSim, not ActiveSim
        assert_eq!(mood_state.mood, NpcMood::Warm);
    }

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

        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                MoodState::default(),
                CurrentMood::default(), // Starts at Content
                ToleranceThreshold {
                    current_stress: 70,
                    threshold: 100, // → Anxious (70% of 100)
                },
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        let current_mood = world.get::<CurrentMood>(npc).unwrap();
        // Anxious maps to Anxious
        assert_eq!(current_mood.0, ContentMood::Anxious);
    }

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

        // NPC without CurrentMood — system must not panic
        let npc = world
            .spawn((
                Npc,
                ActiveSim,
                MoodState::default(),
                // No CurrentMood
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world); // must not panic

        let mood_state = world.get::<MoodState>(npc).unwrap();
        assert_eq!(mood_state.mood, NpcMood::Content);
    }

    // -- Additional QA coverage (Hoshe, Sprint 14) --------------------------

    #[test]
    fn derive_mood_negative_stress_is_content() {
        // i16 stress can be negative (e.g. buffs reducing stress below zero).
        // Negative stress is well below CONTENT_STRESS_CEILING (20) → Content.
        // Note: `current_stress * 100` in the Anxious check can overflow i16 for extreme
        // values (stress < -327 or > 327 at threshold=50). Realistic game values stay small.
        assert_eq!(
            derive_mood(-10, 50, DayPhase::Morning, false),
            NpcMood::Content,
            "Negative stress not hostile/anxious, morning, stress<20 → Content"
        );
        assert_eq!(
            derive_mood(-50, 50, DayPhase::Evening, false),
            NpcMood::Content,
            "Negative stress in Evening: stress < FRUSTRATED_STRESS_FLOOR (10) → Content not Frustrated"
        );
    }

    #[test]
    fn derive_mood_cannot_return_suspicious_or_focused() {
        // Suspicious and Focused are valid NpcMood states but are NOT reachable
        // from derive_mood(). They must be set externally by other systems
        // (e.g., observation pipeline for Suspicious, activity scheduler for Focused).
        // This test documents the invariant: derive_mood never emits these states.
        use std::collections::HashSet;

        let phases = [
            DayPhase::Morning,
            DayPhase::Afternoon,
            DayPhase::Evening,
            DayPhase::Night,
        ];
        let stresses: &[i16] = &[-50, -1, 0, 1, 19, 20, 29, 30, 49, 50, 51, 100];
        let thresholds: &[i16] = &[0, 1, 50, 100];
        let warm_flags = [false, true];

        let mut observed = HashSet::new();
        for &phase in &phases {
            for &stress in stresses {
                for &threshold in thresholds {
                    for warm in warm_flags {
                        let m = derive_mood(stress, threshold, phase, warm);
                        observed.insert(format!("{:?}", m));
                    }
                }
            }
        }

        assert!(
            !observed.contains("Suspicious"),
            "derive_mood should never return Suspicious — set by observation pipeline"
        );
        assert!(
            !observed.contains("Focused"),
            "derive_mood should never return Focused — set by activity scheduler (#101)"
        );
    }

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

        let calm = world
            .spawn((
                Npc,
                ActiveSim,
                MoodState::default(),
                CurrentMood::default(),
                ToleranceThreshold {
                    current_stress: 5,
                    threshold: 50,
                },
            ))
            .id();

        let stressed = world
            .spawn((
                Npc,
                ActiveSim,
                MoodState::default(),
                CurrentMood::default(),
                ToleranceThreshold {
                    current_stress: 50,
                    threshold: 50,
                },
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(update_mood);
        schedule.run(&mut world);

        assert_eq!(world.get::<MoodState>(calm).unwrap().mood, NpcMood::Content);
        assert_eq!(
            world.get::<MoodState>(stressed).unwrap().mood,
            NpcMood::Hostile
        );
    }
}