//! Examine interaction system (#242).
//!
//! Handles the Examine verb: player examines an NPC or object at close range,
//! generating character-filtered observation text and a DirectObservation
//! KnowledgeGraph entry.
//!
//! Pipeline:
//!   Interact { verb: "Examine NPC" | "ExamineNpc" | "ExamineObject" }
//!   → process_player_input inserts ExamineRequest on player
//!   → process_examine_interaction reads request, generates text, pushes KG event
//!   → ExamineResultBuffer consumed by compute_observer_snapshot
//!   → ObserverSnapshot.examine_result delivered to client

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

use crate::bridge::types::CharacterArchetype;
use crate::knowledge::events::{KnowledgeEvent, KnowledgeEventQueue, KnowledgeEventType};
use crate::knowledge::EntityRegistry;
use crate::npc::mood::{MoodState, NpcMood};
use crate::npc::{PersonalityTrait, PersonalityTraits, ToleranceThreshold};
use crate::simulation::interaction::{ObjectType, CLOSE_RANGE};
use crate::simulation::movement::{PlayerCharacter, TilePosition};
use crate::simulation::time::SimulationTime;

// ---------------------------------------------------------------------------
// Components
// ---------------------------------------------------------------------------

/// Marker: player requested Examine interaction with a target entity this tick.
///
/// Inserted by process_player_input when verb == "Examine NPC", "ExamineNpc",
/// "Examine Object", or "ExamineObject". Consumed and removed by
/// process_examine_interaction each tick.
#[derive(Component, Debug)]
pub struct ExamineRequest {
    pub target: Entity,
}

/// Character-filtered examination result for snapshot delivery.
///
/// Content differs per CharacterArchetype:
///   Smuggler — physical threat read, cargo-handling posture, opportunity windows.
///   Detective — procedural tells, behavioral inconsistencies, stress indicators.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ExamineResultEvent {
    /// Character-filtered observation text for client display.
    pub text: String,
    /// Wire-format entity identifier of the examined entity.
    pub target_entity_id: u64,
}

/// Authored examine text for a non-NPC entity (#246).
///
/// Attach to any examinable object (Readable, Terminal, etc.) to provide
/// a fixed description returned when the player examines it.
/// If absent, examining a non-NPC entity returns a generic fallback.
#[derive(Component, Debug, Clone)]
pub struct ExamineText(pub String);

/// Buffer holding the examine result for snapshot inclusion.
///
/// Consumed once per snapshot via `take()`. Cleared at snapshot build time.
/// Attach to the player entity alongside other buffer components.
#[derive(Component, Debug, Default)]
pub struct ExamineResultBuffer {
    pub(crate) result: Option<ExamineResultEvent>,
}

impl ExamineResultBuffer {
    /// Drain and return the examine result, leaving the buffer empty.
    pub fn take(&mut self) -> Option<ExamineResultEvent> {
        self.result.take()
    }
}

// ---------------------------------------------------------------------------
// Text generation (deterministic, integer-only — D-010)
// ---------------------------------------------------------------------------

/// Stress ratio 0..=100 derived from ToleranceThreshold components.
/// Uses integer multiplication to avoid division by zero.
fn stress_ratio(threshold: &ToleranceThreshold) -> u8 {
    if threshold.threshold <= 0 {
        return 0;
    }
    ((threshold.current_stress.max(0) as i32 * 100) / threshold.threshold as i32).clamp(0, 100)
        as u8
}

/// Map NpcMood to a terse descriptor shared by both archetypes.
fn mood_word(mood: NpcMood) -> &'static str {
    match mood {
        NpcMood::Neutral => "neutral",
        NpcMood::Anxious => "anxious",
        NpcMood::Frustrated => "frustrated",
        NpcMood::Content => "at ease",
        NpcMood::Suspicious => "watchful",
        NpcMood::Warm => "open",
        NpcMood::Hostile => "hostile",
        NpcMood::Focused => "focused",
    }
}

fn has_trait(traits_opt: Option<&PersonalityTraits>, t: PersonalityTrait) -> bool {
    traits_opt.map(|p| p.traits.contains(&t)).unwrap_or(false)
}

/// Generate character-filtered examination text from NPC component state.
/// All logic is pure, deterministic, and integer-based (D-010).
pub fn generate_examine_text(
    mood: NpcMood,
    ratio: u8,
    archetype: CharacterArchetype,
    traits_opt: Option<&PersonalityTraits>,
) -> String {
    let stress_label = match ratio {
        0..=30 => "relaxed",
        31..=60 => "tense",
        61..=85 => "stressed",
        _ => "near breaking point",
    };

    let mood_label = mood_word(mood);

    match archetype {
        CharacterArchetype::Smuggler => {
            // Physical threat read + cargo opportunity window
            let threat = if matches!(mood, NpcMood::Hostile | NpcMood::Suspicious) {
                "Threat posture. Don't push it."
            } else if has_trait(traits_opt, PersonalityTrait::Bold) {
                "Confident bearing. Will push back if cornered."
            } else if has_trait(traits_opt, PersonalityTrait::Cautious) {
                "Nervous type. Predictable under pressure."
            } else {
                "No obvious threat read."
            };

            let window = if ratio > 60 {
                "Too distracted to track cargo movement."
            } else if matches!(mood, NpcMood::Focused) {
                "Paying close attention to this section."
            } else {
                "Standard patrol pattern. Window is there."
            };

            format!("Appears {mood_label}, {stress_label}. {threat} {window}")
        }

        CharacterArchetype::Detective => {
            // Procedural tells + behavioral read
            let tell = if has_trait(traits_opt, PersonalityTrait::Deceptive) {
                "Controlled affect — practiced concealment."
            } else if matches!(mood, NpcMood::Anxious | NpcMood::Frustrated) {
                "Involuntary stress markers present."
            } else if matches!(mood, NpcMood::Suspicious) {
                "Scanning. Aware of being observed."
            } else {
                "Baseline presentation."
            };

            let read = if ratio > 60 {
                "Under pressure — potential liability or asset."
            } else if matches!(mood, NpcMood::Content | NpcMood::Warm) {
                "Comfortable. Less guarded than usual."
            } else {
                "Routine behavior pattern."
            };

            format!("Subject: {mood_label}, {stress_label}. {tell} {read}")
        }
    }
}

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

/// Process examine interaction: generate character-filtered observation text,
/// push DirectObservation to KnowledgeGraph, write result to ExamineResultBuffer.
///
/// Handles two target types:
/// - NPC entities: generate character-filtered text from NPC component state.
/// - Non-NPC entities with `ExamineText`: use the authored text directly.
/// - Non-NPC entities without `ExamineText`: generic fallback text.
///
/// System ordering: after process_player_input, before compute_observer_snapshot.
#[allow(clippy::type_complexity)]
pub fn process_examine_interaction(
    mut commands: Commands,
    time: Res<SimulationTime>,
    registry: Res<EntityRegistry>,
    mut kg_events: ResMut<KnowledgeEventQueue>,
    mut player_query: Query<
        (
            Entity,
            &TilePosition,
            &ExamineRequest,
            Option<&CharacterArchetype>,
            &mut ExamineResultBuffer,
        ),
        With<PlayerCharacter>,
    >,
    npc_query: Query<
        (
            &TilePosition,
            Option<&MoodState>,
            Option<&ToleranceThreshold>,
            Option<&PersonalityTraits>,
        ),
        Without<ObjectType>,
    >,
    examine_text_query: Query<(&TilePosition, Option<&ExamineText>)>,
) {
    let Ok((player_entity, player_pos, examine_req, archetype_opt, mut result_buffer)) =
        player_query.single_mut()
    else {
        return;
    };

    let target = examine_req.target;
    let archetype = archetype_opt.copied().unwrap_or_default();

    // Try NPC examine path first
    if let Ok((target_pos, mood_opt, tolerance_opt, traits_opt)) = npc_query.get(target) {
        let distance = player_pos
            .manhattan_distance(target_pos)
            .unwrap_or(u32::MAX);
        if distance > CLOSE_RANGE {
            tracing::info!(
                distance,
                "Examine: NPC target out of range (max {})",
                CLOSE_RANGE
            );
            commands.entity(player_entity).remove::<ExamineRequest>();
            return;
        }

        let mood = mood_opt.map(|m| m.mood).unwrap_or(NpcMood::Neutral);
        let ratio = tolerance_opt.map(stress_ratio).unwrap_or(0);
        let text = generate_examine_text(mood, ratio, archetype, traits_opt);

        kg_events.push(KnowledgeEvent {
            observer: player_entity,
            tick: time.tick,
            event_type: KnowledgeEventType::DirectObservation {
                target,
                position: *target_pos,
            },
        });

        let target_entity_id = registry
            .to_stable(target)
            .map(|sid| sid.0)
            .unwrap_or_else(|| {
                tracing::warn!(?target, "Examine: NPC not in EntityRegistry, using bits");
                target.to_bits()
            });

        result_buffer.result = Some(ExamineResultEvent {
            text,
            target_entity_id,
        });
        tracing::debug!(target_entity_id, "Examine: NPC result written to buffer");
        commands.entity(player_entity).remove::<ExamineRequest>();
        return;
    }

    // Object examine path: entity has a TilePosition but no NPC mood components.
    if let Ok((target_pos, examine_text_opt)) = examine_text_query.get(target) {
        let distance = player_pos
            .manhattan_distance(target_pos)
            .unwrap_or(u32::MAX);
        if distance > CLOSE_RANGE {
            tracing::info!(
                distance,
                "Examine: object target out of range (max {})",
                CLOSE_RANGE
            );
            commands.entity(player_entity).remove::<ExamineRequest>();
            return;
        }

        let text = examine_text_opt
            .map(|et| et.0.clone())
            .unwrap_or_else(|| "No further details are apparent.".to_string());

        let target_entity_id = registry
            .to_stable(target)
            .map(|sid| sid.0)
            .unwrap_or_else(|| {
                tracing::warn!(?target, "Examine: object not in EntityRegistry, using bits");
                target.to_bits()
            });

        result_buffer.result = Some(ExamineResultEvent {
            text,
            target_entity_id,
        });
        tracing::debug!(target_entity_id, "Examine: object result written to buffer");
        commands.entity(player_entity).remove::<ExamineRequest>();
        return;
    }

    tracing::warn!(
        ?target,
        "process_examine_interaction: target has no position component"
    );
    commands.entity(player_entity).remove::<ExamineRequest>();
}

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

#[cfg(test)]
mod tests {
    use super::*;
    use crate::npc::PersonalityTrait;

    fn traits(t: &[PersonalityTrait]) -> PersonalityTraits {
        PersonalityTraits { traits: t.to_vec() }
    }

    #[test]
    fn smuggler_hostile_npc_gives_threat_read() {
        let text = generate_examine_text(NpcMood::Hostile, 20, CharacterArchetype::Smuggler, None);
        assert!(
            text.contains("Threat posture"),
            "expected threat read, got: {text}"
        );
    }

    #[test]
    fn smuggler_focused_npc_notes_attention() {
        let text = generate_examine_text(NpcMood::Focused, 30, CharacterArchetype::Smuggler, None);
        assert!(
            text.contains("close attention"),
            "expected attention note, got: {text}"
        );
    }

    #[test]
    fn smuggler_high_stress_identifies_distraction() {
        let text = generate_examine_text(NpcMood::Anxious, 80, CharacterArchetype::Smuggler, None);
        assert!(
            text.contains("Too distracted"),
            "expected distraction read, got: {text}"
        );
    }

    #[test]
    fn detective_deceptive_npc_notes_concealment() {
        let t = traits(&[PersonalityTrait::Deceptive]);
        let text = generate_examine_text(
            NpcMood::Neutral,
            20,
            CharacterArchetype::Detective,
            Some(&t),
        );
        assert!(
            text.contains("Controlled affect"),
            "expected concealment note, got: {text}"
        );
    }

    #[test]
    fn detective_anxious_npc_notes_stress_markers() {
        let text = generate_examine_text(NpcMood::Anxious, 50, CharacterArchetype::Detective, None);
        assert!(
            text.contains("stress markers"),
            "expected stress markers, got: {text}"
        );
    }

    #[test]
    fn detective_content_npc_notes_low_guard() {
        let text = generate_examine_text(NpcMood::Content, 10, CharacterArchetype::Detective, None);
        assert!(
            text.contains("Less guarded"),
            "expected low guard note, got: {text}"
        );
    }

    #[test]
    fn stress_ratio_zero_when_threshold_zero() {
        let t = ToleranceThreshold {
            current_stress: 50,
            threshold: 0,
        };
        assert_eq!(stress_ratio(&t), 0);
    }

    #[test]
    fn stress_ratio_clamped_at_100() {
        let t = ToleranceThreshold {
            current_stress: 200,
            threshold: 100,
        };
        assert_eq!(stress_ratio(&t), 100);
    }

    #[test]
    fn stress_ratio_negative_stress_is_zero() {
        let t = ToleranceThreshold {
            current_stress: -10,
            threshold: 70,
        };
        assert_eq!(stress_ratio(&t), 0);
    }

    #[test]
    fn examine_result_buffer_take_drains() {
        let mut buf = ExamineResultBuffer::default();
        assert!(buf.take().is_none());
        buf.result = Some(ExamineResultEvent {
            text: "Test".into(),
            target_entity_id: 42,
        });
        assert!(buf.take().is_some());
        assert!(buf.take().is_none()); // idempotent drain
    }
}