//! Observer visibility query system (#112)
//!
//! Two-stage pipeline:
//! 1. compute_visibility_geometry — FOV + vision cone → VisibilityGeometry resource
//! 2. compute_observer_snapshot — entity filtering + knowledge overlay → ObserverSnapshot
//!
//! D-017 perception modes swap the geometry producer via PerceptionQuery trait.

use bevy_ecs::prelude::*;
use std::collections::BTreeSet;

use crate::bridge::types::*;
use crate::knowledge::graph::filter_by_access;
use crate::knowledge::types::{AccessRule, KnowledgeState};
use crate::knowledge::{EntityRegistry, KnowledgeGraph, StableId};
use crate::perception::cognitive_delay::CognitiveDelay;
use crate::perception::query::{ActivePerceptionMode, VisibilityGeometry};
use crate::perception::vision_cone::Facing;
use crate::simulation::contraband::ScanEventBuffer;
use crate::simulation::dialogue::DialogueResponseBuffer;
use crate::simulation::interaction::NearbyInteractionBuffer;
use crate::simulation::inventory::{CarriedBy, InventorySlot, ItemName};
use crate::simulation::monologue::{MonologueBuffer, SprintAnomalyQueue};
use crate::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
use crate::simulation::rng::SimRng;
use crate::simulation::sound::SoundEventQueue;
use crate::simulation::stance::Stance;
use crate::simulation::time::SimulationTime;

/// Compute visibility geometry using the active perception mode.
/// Stage 1 of the observer pipeline: FOV + vision cone → VisibilityGeometry.
///
/// System ordering: after validate_movement, before compute_observer_snapshot.
#[tracing::instrument(level = "debug", skip_all)]
pub fn compute_visibility_geometry(
    walkability: Res<WalkabilityMap>,
    mode: Res<ActivePerceptionMode>,
    observer_query: Query<(&TilePosition, Option<&Facing>), With<PlayerCharacter>>,
    mut geometry: ResMut<VisibilityGeometry>,
) {
    let Ok((observer_pos, facing_opt)) = observer_query.single() else {
        tracing::error!("compute_visibility_geometry: PlayerCharacter query failed");
        return;
    };

    let facing = facing_opt
        .map(|f| f.0)
        .unwrap_or(FacingDirection::default());

    *geometry = mode.0.compute_geometry(observer_pos, facing, &walkability);
}

/// Assemble observer snapshot from precomputed geometry and entity state.
/// Stage 2 of the observer pipeline: entity filtering + knowledge overlay → snapshot.
///
/// System ordering: after compute_visibility_geometry + compute_nearby_interactions,
/// before advance_tick.
#[tracing::instrument(level = "debug", skip_all)]
#[allow(clippy::type_complexity, clippy::too_many_arguments)]
pub fn compute_observer_snapshot(
    time: Res<SimulationTime>,
    geometry: Res<VisibilityGeometry>,
    registry: Res<EntityRegistry>,
    sound_queue: Option<Res<SoundEventQueue>>,
    mut observer_query: Query<
        (
            Entity,
            &TilePosition,
            Option<&Facing>,
            &KnowledgeGraph,
            &mut NearbyInteractionBuffer,
            &mut MonologueBuffer,
            Option<&Stance>,
            Option<&CharacterArchetype>,
            Option<&mut SprintAnomalyQueue>,
            Option<&CognitiveDelay>,
            Option<&mut DialogueResponseBuffer>,
            Option<&mut ScanEventBuffer>,
        ),
        With<PlayerCharacter>,
    >,
    all_entities: Query<(
        Entity,
        &TilePosition,
        Option<&PlayerCharacter>,
        Option<&crate::npc::Npc>,
        Option<&AccessRule>,
    )>,
    inventory_items: Query<(Entity, &CarriedBy, &ItemName, &InventorySlot)>,
    mut buffer: ResMut<SnapshotBuffer>,
    sim_rng: Option<Res<SimRng>>,
) {
    let Ok((
        observer_entity,
        observer_pos,
        facing_opt,
        observer_kg,
        mut interaction_buffer,
        mut monologue_buffer,
        stance_opt,
        archetype_opt,
        mut anomaly_queue_opt,
        cognitive_delay_opt,
        mut dialogue_response_opt,
        mut scan_event_buffer_opt,
    )) = observer_query.single_mut()
    else {
        tracing::error!("compute_observer_snapshot: PlayerCharacter query failed");
        return;
    };

    let facing = facing_opt
        .map(|f| f.0)
        .unwrap_or(FacingDirection::default());

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

    // Collect player inventory (D-065 info boundary: only own items)
    let player_inventory = registry
        .to_stable(observer_entity)
        .map(|player_sid| {
            crate::simulation::inventory::collect_inventory_for(
                player_sid,
                &inventory_items,
                &registry,
            )
        })
        .unwrap_or_default();

    // Resolve observer's StableId for component-level access control (#139, D-010)
    let observer_stable_id = registry
        .to_stable(observer_entity)
        .unwrap_or(StableId(0));

    let (mut entities, visible_ids, blocked_entities) =
        filter_visible_entities(&geometry, &registry, observer_kg, observer_stable_id, &all_entities);

    collect_remembered_entities(
        observer_kg,
        &visible_ids,
        &geometry.visible_positions,
        geometry.observer_z,
        time.tick,
        &mut entities,
    );

    // Sprint anomaly detection (#428, D-055)
    // When sprinting, scan visible entities for Contradicted KG state.
    // Queue the first match for delayed "double-take" monologue.
    if stance_opt.map(|s| s.0) == Some(MovementStance::Sprint) {
        if let Some(anomaly_queue) = anomaly_queue_opt.as_mut() {
            if !anomaly_queue.has_pending() {
                for &wire_id in &visible_ids {
                    let stable_id = StableId(wire_id);
                    if let Some(knowledge) = observer_kg.entity_knowledge(&stable_id) {
                        if knowledge.state == KnowledgeState::Contradicted {
                            anomaly_queue.push_anomaly(wire_id, time.tick);
                            break; // First-in wins
                        }
                    }
                }
            }
        }
    }

    let game_time = GameTime {
        day: time.day(),
        time_of_day: time.time_of_day_minutes(),
        day_phase: time.day_phase(),
        tick_rate: time.tick_rate,
    };

    // Take interactions and apply Phase 2 verb filter (D-057, #422)
    let mut nearby_interactions = interaction_buffer.take();
    apply_phase2_verb_filter(&mut nearby_interactions, observer_kg, archetype);

    tracing::trace!(
        "compute_observer_snapshot: tick={}, visible={}, remembered={}, tiles={}",
        time.tick,
        visible_ids.len(),
        entities.len() - visible_ids.len(),
        geometry.visible_tiles.len(),
    );

    let current_monologue = monologue_buffer.take();
    let dialogue_response = dialogue_response_opt.as_mut().and_then(|buf| buf.take());
    let scan_events = scan_event_buffer_opt
        .as_mut()
        .map(|buf| buf.take())
        .unwrap_or_default();

    // Collect sound events audible to the observer (D-038, #124).
    // Filter by D-018 range: only events the player can hear based on distance.
    let sound_events = if let Some(ref queue) = sound_queue {
        queue.audible_at(observer_pos).cloned().collect()
    } else {
        Vec::new()
    };

    // Build pending recognitions from CognitiveDelay (#423, D-060)
    let pending_recognitions = cognitive_delay_opt
        .map(|delay| {
            delay
                .pending()
                .iter()
                .map(|p| {
                    let (rx, ry, rz) = p.position.to_render_coords();
                    PendingRecognitionWire {
                        entity_id: p.stable_id.0,
                        x: rx,
                        y: ry,
                        z: rz,
                        remaining_ticks: p.delay_until_tick.saturating_sub(time.tick),
                        total_delay_ticks: p.trigger.delay_ticks(),
                    }
                })
                .collect()
        })
        .unwrap_or_default();

    // Sort entities by entity_id for deterministic snapshot ordering (#457)
    entities.sort_by_key(|e| e.entity_id);

    buffer.snapshot = Some(ObserverSnapshot {
        version: crate::bridge::types::PROTOCOL_VERSION,
        tick: time.tick,
        game_time,
        player_facing: facing,
        player_stance: stance_opt.map(|s| s.0).unwrap_or_default(),
        player_inventory,
        entities,
        visible_tiles: geometry.visible_tiles.clone(),
        nearby_interactions,
        current_monologue,
        pending_recognitions,
        dialogue_response,
        blocked_entities,
        scan_events,
        sound_events,
        rng_seed: sim_rng.as_deref().map(|r| r.seed()),
    });
}

/// Filter entities by visibility using precomputed geometry.
/// Returns (visible entities, set of visible wire IDs, blocked entity IDs).
/// Blocked entities are on the same z-level but not in visible_positions (#514).
#[allow(clippy::type_complexity)]
fn filter_visible_entities(
    geometry: &VisibilityGeometry,
    registry: &EntityRegistry,
    observer_kg: &KnowledgeGraph,
    observer_stable_id: StableId,
    all_entities: &Query<(
        Entity,
        &TilePosition,
        Option<&PlayerCharacter>,
        Option<&crate::npc::Npc>,
        Option<&AccessRule>,
    )>,
) -> (Vec<VisibleEntity>, BTreeSet<u64>, Vec<u64>) {
    let mut entities = Vec::new();
    let mut visible_ids: BTreeSet<u64> = BTreeSet::new();
    let mut blocked_ids: BTreeSet<u64> = BTreeSet::new();

    for (entity, pos, is_player, is_npc, access_rule) in all_entities.iter() {
        if pos.z != geometry.observer_z {
            continue;
        }

        // Resolve wire ID early — needed for both visible and blocked paths
        let wire_id = registry
            .to_stable(entity)
            .map(|sid| sid.0)
            .unwrap_or_else(|| {
                tracing::error!(?entity, "entity not in EntityRegistry");
                entity.to_bits()
            });

        if !geometry.visible_positions.contains(&(pos.x, pos.y)) {
            // Same z-level but not visible — blocked by LOS or outside vision cone.
            // Exclude the player entity (always at origin, always visible).
            if is_player.is_none() {
                blocked_ids.insert(wire_id);
            }
            continue;
        }

        let (rx, ry, rz) = pos.to_render_coords();
        let kind = if is_player.is_some() {
            EntityKind::Player
        } else if is_npc.is_some() {
            EntityKind::Npc
        } else {
            EntityKind::Object
        };

        let sector = geometry
            .sector_lookup
            .get(&(pos.x, pos.y))
            .copied()
            .unwrap_or(VisibilitySector::Peripheral);

        let relationship = if is_player.is_some() {
            RelationshipState::Known // Self
        } else if let Some(stable_id) = registry.to_stable(entity) {
            // D-010 principle 2: check access control before exposing relationship (#139)
            let access_granted = match access_rule {
                Some(rule) => filter_by_access(observer_stable_id, stable_id, &rule.0, observer_kg),
                None => true, // No AccessRule → Public (default)
            };
            if access_granted {
                observer_kg.relationship_with(&stable_id)
            } else {
                RelationshipState::Unknown // Access denied — redact relationship data
            }
        } else {
            RelationshipState::Unknown
        };

        visible_ids.insert(wire_id);
        entities.push(VisibleEntity {
            entity_id: wire_id,
            x: rx,
            y: ry,
            z: rz,
            kind,
            visibility: sector,
            relationship,
            observation: EntityVisibility::Visible,
        });
    }

    // BTreeSet iteration is sorted — deterministic output guaranteed
    let blocked_vec: Vec<u64> = blocked_ids.into_iter().collect();
    (entities, visible_ids, blocked_vec)
}

/// Collect remembered entities from the knowledge graph — entities the observer
/// knows about but can't currently see. Filters out: already-visible entities,
/// entities without known positions, wrong z-level, visible-tile ghosts, and
/// transient Direct-confidence inconsistencies.
fn collect_remembered_entities(
    observer_kg: &KnowledgeGraph,
    visible_ids: &BTreeSet<u64>,
    visible_positions: &BTreeSet<(i32, i32)>,
    observer_z: i32,
    current_tick: u64,
    entities: &mut Vec<VisibleEntity>,
) {
    for (stable_id, knowledge) in observer_kg.known_entities_iter() {
        if visible_ids.contains(&stable_id.0) {
            continue;
        }

        let Some(position) = knowledge.last_known_position else {
            continue;
        };

        if position.z != observer_z {
            continue;
        }

        // Tile is visible but entity isn't there — player knows it moved
        if visible_positions.contains(&(position.x, position.y)) {
            continue;
        }

        // Direct confidence = should be in LOS; skip transient inconsistency
        if knowledge.confidence == KnowledgeConfidence::Direct {
            continue;
        }

        let (rx, ry, rz) = position.to_render_coords();
        debug_assert!(
            knowledge.last_observed_tick <= current_tick,
            "last_observed_tick {} > current tick {}",
            knowledge.last_observed_tick,
            current_tick,
        );
        let age_ticks = current_tick.saturating_sub(knowledge.last_observed_tick);

        entities.push(VisibleEntity {
            entity_id: stable_id.0,
            x: rx,
            y: ry,
            z: rz,
            kind: EntityKind::Npc,
            visibility: VisibilitySector::Forward,
            relationship: knowledge.relationship,
            observation: EntityVisibility::Remembered {
                confidence: knowledge.confidence,
                age_ticks,
            },
        });
    }
}

/// Phase 2 verb filter: KG-gated observer-side verb processing (#422, D-057).
///
/// Runs after Phase 1 (simulation-level verb computation) and applies:
/// 1. POI priority flips (D-060) — ExamineNpc above Talk for POI entities
/// 2. Confront injection — adds Confront verb for NPCs when KnowsDetails+
/// 3. Contradiction marking — sets contradicted flag when entity knowledge is Contradicted
/// 4. Archetype label relabeling — smuggler/detective see different labels for same verb
///
/// Phase boundary: Phase 1 (interaction.rs) determines verb availability from
/// ObjectType + proximity. Phase 2 (here) reads the observer's KnowledgeGraph
/// to filter, augment, and relabel. This separation keeps D-010 principle 1
/// (info boundary) clean — simulation doesn't know what the observer knows.
fn apply_phase2_verb_filter(
    interactions: &mut [NearbyInteraction],
    observer_kg: &KnowledgeGraph,
    archetype: CharacterArchetype,
) {
    for interaction in interactions.iter_mut() {
        let stable_id = StableId(interaction.entity_id);
        let knowledge = observer_kg.entity_knowledge(&stable_id);

        // --- Contradiction marking ---
        // If observer's knowledge of this entity is Contradicted, mark the
        // interaction. Client renders a visual indicator (D-041).
        if let Some(k) = knowledge {
            if k.state == KnowledgeState::Contradicted {
                interaction.contradicted = true;
            }
        }

        // --- NPC-specific Phase 2 ---
        if interaction.entity_type == EntityKind::Npc {
            let relationship = observer_kg.relationship_with(&stable_id);

            // POI priority flip (D-060): Observe first, Talk second
            if relationship == RelationshipState::PersonOfInterest {
                for verb in &mut interaction.verbs {
                    match verb.kind {
                        VerbKind::ExamineNpc => verb.priority = 1,
                        VerbKind::Talk => verb.priority = 2,
                        _ => {}
                    }
                }
            }

            // Confront injection: available when observer has KnowsDetails+
            // on this NPC and is at close range (distance ≤ 2).
            if interaction.distance <= 2 {
                let has_details = knowledge
                    .map(|k| k.confidence >= KnowledgeConfidence::KnowsDetails)
                    .unwrap_or(false);

                if has_details {
                    // Priority 3 = after Talk/ExamineNpc in normal case,
                    // after ExamineNpc/Talk in POI case. Always the escalation option.
                    interaction.verbs.push(VerbOption {
                        kind: VerbKind::Confront,
                        label: "Confront".into(),
                        priority: 3,
                        available: true,
                    });
                }
            }
        }

        // --- Archetype label relabeling ---
        // Phase 2 swaps verb labels based on character archetype.
        // The VerbKind stays the same (same handler), only the display label changes.
        // This implements D-057: "Character differentiation via Phase 2 observer
        // filter, not separate verb systems."
        for verb in &mut interaction.verbs {
            if let Some(label) = archetype_verb_label(archetype, interaction.object_type, verb.kind)
            {
                verb.label = label.into();
            }
        }

        // Re-sort after priority changes and verb additions
        interaction
            .verbs
            .sort_by_key(|v| (v.priority, v.kind as u8));
    }
}

/// Archetype-specific verb label overrides (#422, D-057).
///
/// Returns a replacement label for the given (archetype, object_type, verb_kind)
/// combination, or None to keep the Phase 1 default label.
///
/// v0.1: Container verbs differ by archetype. Other object types keep defaults.
/// Add match arms here for future archetype-specific labels.
fn archetype_verb_label(
    archetype: CharacterArchetype,
    object_type: Option<ObjectType>,
    kind: VerbKind,
) -> Option<&'static str> {
    match (archetype, object_type, kind) {
        // Smuggler: Container verbs — physical manipulation vocabulary
        (CharacterArchetype::Smuggler, Some(ObjectType::Container), VerbKind::Open) => Some("Move"),
        (CharacterArchetype::Smuggler, Some(ObjectType::Container), VerbKind::Search) => {
            Some("Stash")
        }

        // Detective: Container verbs — investigation vocabulary
        (CharacterArchetype::Detective, Some(ObjectType::Container), VerbKind::Open) => {
            Some("Scan")
        }
        (CharacterArchetype::Detective, Some(ObjectType::Container), VerbKind::Search) => {
            Some("Flag")
        }

        // All other combinations: keep Phase 1 default label
        _ => None,
    }
}

#[cfg(test)]
mod tests;