//! Observer integration for the voice pipeline (D-138, Phase 3).
//!
//! Two enrichment systems run before `compute_observer_snapshot` and rewrite
//! NPC text in the dialogue and conversation buffers with voiced variants
//! looked up from the cache. Cache miss → base text (never blocks).
//!
//! ## System ordering
//!
//! ```text
//! process_talk_interaction  ─┐
//! run_npc_conversations     ─┤─► voice_enrich_dialogue_response ─┐
//!                             └─► voice_enrich_conversation_events ─► compute_observer_snapshot
//! ```
//!
//! ## Content index derivation
//!
//! The voice cache key uses a `content_index: u16` to distinguish individual
//! lines for the same NPC. For dialogue lines the index is derived via
//! FNV-1a hash of `line_id`, matching the derivation used when requests
//! are submitted to the worker queue for pre-voicing.

use bevy_ecs::prelude::*;

use crate::knowledge::{EntityRegistry, StableId};
use crate::npc::tell_state::DerivedTellState;
use crate::npc::{Npc, NpcVoiceProfile};
use crate::simulation::conversation::ConversationEventBuffer;
use crate::simulation::dialogue::DialogueResponseBuffer;
use crate::simulation::movement::{PlayerCharacter, TilePosition};
use crate::simulation::zone::ZoneMap;
use crate::voice::lookup::{voiced_behavior, VoiceCacheResource};
use crate::voice::prompt_builder::ContentType;

// ---------------------------------------------------------------------------
// Content index derivation
// ---------------------------------------------------------------------------

/// Derive a deterministic content_index (u16) from a string line identifier.
///
/// Uses FNV-1a (64-bit) truncated to u16 — same algorithm used by the worker
/// queue when submitting pre-voicing requests, ensuring cache key consistency.
pub fn content_index_from_line_id(line_id: &str) -> u16 {
    let mut hash: u64 = 0xcbf29ce484222325;
    for b in line_id.bytes() {
        hash ^= b as u64;
        hash = hash.wrapping_mul(0x100000001b3);
    }
    hash as u16
}

// ---------------------------------------------------------------------------
// Player zone resolution
// ---------------------------------------------------------------------------

fn player_zone_id(
    player_query: &Query<&TilePosition, With<PlayerCharacter>>,
    zone_map: Option<&ZoneMap>,
) -> u32 {
    let Ok(pos) = player_query.single() else {
        return 0;
    };
    zone_map
        .and_then(|zm| zm.zone_at(pos.x, pos.y, pos.z))
        .map(|id| id as u32)
        .unwrap_or(0)
}

// ---------------------------------------------------------------------------
// Systems
// ---------------------------------------------------------------------------

/// Enrich the dialogue response buffer with a voiced line from the cache.
///
/// Must run after `process_talk_interaction` and before
/// `compute_observer_snapshot`. No-op when the voice cache resource is absent.
///
/// The system looks up the NPC's voice culture and current tell state, then
/// calls `voiced_behavior()` to retrieve a cached voiced line. On cache miss
/// the buffer text is unchanged (base text serves as fallback).
#[allow(clippy::type_complexity)]
pub fn voice_enrich_dialogue_response(
    voice_cache: Option<Res<VoiceCacheResource>>,
    registry: Res<EntityRegistry>,
    zone_map: Option<Res<ZoneMap>>,
    player_query: Query<&TilePosition, With<PlayerCharacter>>,
    npc_voice_query: Query<(&NpcVoiceProfile, Option<&DerivedTellState>), With<Npc>>,
    mut dialogue_buffer: Query<&mut DialogueResponseBuffer, With<PlayerCharacter>>,
) {
    let Some(voice_cache) = voice_cache else {
        return;
    };

    let Ok(mut buffer) = dialogue_buffer.single_mut() else {
        return;
    };

    let Some(ref mut response) = buffer.response else {
        return;
    };

    let zone_id = player_zone_id(&player_query, zone_map.as_deref());

    let speaker_entity = registry.to_entity(&StableId(response.speaker_entity_id));
    let Some(entity) = speaker_entity else {
        return;
    };

    let Ok((voice_profile, tell_state_opt)) = npc_voice_query.get(entity) else {
        return;
    };

    let tell_state = tell_state_opt.and_then(|t| t.category);
    let content_index = content_index_from_line_id(&response.line_id);

    let voiced = voiced_behavior(
        &voice_cache.cache,
        zone_id,
        &voice_profile.culture_id,
        response.speaker_entity_id,
        ContentType::Dialogue,
        content_index,
        tell_state,
        &response.text,
        false,
    );

    response.text = voiced;
}

/// Enrich the conversation event buffer with voiced lines from the cache.
///
/// Must run after `run_npc_conversations` and before
/// `compute_observer_snapshot`. No-op when the voice cache resource is absent.
///
/// Each event in the buffer is processed: the pre-occlusion base text is
/// not available at this point (occlusion has already been applied), so the
/// `occluded_line` is treated as the base text for the voice lookup.
/// This means the voice register wraps the already-occluded line.
///
/// ## Accepted risk: re-voicing of heavily occluded text
///
/// When many words are dropped by D-078 occlusion, the remaining text may
/// be fragmentary ("... the ... came in ..."). Re-voicing such fragments can
/// produce incoherent output. This is acceptable for two reasons:
/// 1. Cache misses are common for conversation text (no pre-baking pipeline),
///    so the base text fallback in `voiced_behavior()` fires most of the time.
/// 2. Even incoherent voiced output is no worse than the already-degraded
///    overheard line — the occlusion itself has already broken coherence.
///    The player's inability to fully parse overheard speech is the mechanic.
#[allow(clippy::type_complexity)]
pub fn voice_enrich_conversation_events(
    voice_cache: Option<Res<VoiceCacheResource>>,
    registry: Res<EntityRegistry>,
    zone_map: Option<Res<ZoneMap>>,
    player_query: Query<&TilePosition, With<PlayerCharacter>>,
    npc_voice_query: Query<(&NpcVoiceProfile, Option<&DerivedTellState>), With<Npc>>,
    mut conversation_buffer: Query<&mut ConversationEventBuffer, With<PlayerCharacter>>,
) {
    let Some(voice_cache) = voice_cache else {
        return;
    };

    let Ok(mut buffer) = conversation_buffer.single_mut() else {
        return;
    };

    if buffer.events.is_empty() {
        return;
    }

    let zone_id = player_zone_id(&player_query, zone_map.as_deref());

    for event in &mut buffer.events {
        let speaker_entity = registry.to_entity(&StableId(event.speaker_id));
        let Some(entity) = speaker_entity else {
            continue;
        };

        let Ok((voice_profile, tell_state_opt)) = npc_voice_query.get(entity) else {
            continue;
        };

        let tell_state = tell_state_opt.and_then(|t| t.category);
        // Conversation lines don't have a stable line_id; derive content_index
        // from the occluded line text. The full cache key is
        // (culture_id, npc_stable_id, content_type, content_index, tell_state),
        // so a u16 hash collision requires two different lines from the same
        // speaker with the same tell state to hash identically — at ~65K
        // possible values this is extremely rare, and the worst outcome is
        // a stale voiced line being served instead of base text. Acceptable.
        let content_index = content_index_from_line_id(&event.occluded_line);

        let voiced = voiced_behavior(
            &voice_cache.cache,
            zone_id,
            &voice_profile.culture_id,
            event.speaker_id,
            ContentType::Dialogue,
            content_index,
            tell_state,
            &event.occluded_line,
            false,
        );

        event.occluded_line = voiced;
    }
}

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

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

    #[test]
    fn content_index_is_deterministic() {
        let a = content_index_from_line_id("dock_d_001");
        let b = content_index_from_line_id("dock_d_001");
        assert_eq!(a, b);
    }

    #[test]
    fn content_index_differs_for_different_ids() {
        let a = content_index_from_line_id("dock_d_001");
        let b = content_index_from_line_id("dock_d_002");
        assert_ne!(a, b);
    }

    #[test]
    fn content_index_empty_string() {
        // Should not panic
        let _ = content_index_from_line_id("");
    }
}