//! `/photos/search/unified?q=<natural language>` — unified NL photo search.
//!
//! One free-text box that composes the two existing engines instead of making
//! the user pick between them:
//!  1. A grounded local-LLM call ([`crate::ai::nl_query`]) translates the
//!     query into a structured filter + a semantic term.
//!  2. Structured filters (tags / EXIF / geo / date / media-type) define the
//!     candidate set; the semantic term ranks within it via CLIP.
//!
//! Path A (orchestration): we reuse `clip_search`'s scoring core and the
//! existing `ExifDao` / `TagDao` queries, joining on `content_hash`. EXIF rows
//! are the universal candidate carrier — each has `(library_id, file_path,
//! content_hash, date_taken)` — so the structured filter is just a predicate
//! over them, and the CLIP hits (which key on `content_hash`) intersect by
//! hash. No new schema, no surgery on `list_photos`.
//!
//! Degenerate cases collapse to the existing behavior: semantic-only → plain
//! CLIP search; filters-only → a date-sorted filtered listing.
//!
//! Person filtering is intentionally deferred (no person→photos resolver yet).

use crate::AppState;
use crate::ai::backend::{BackendKind, SamplingOverrides};
use crate::ai::nl_query::{StructuredQuery, translate_nl_query};
use crate::clip_search::{
    SearchHit, parse_library_scope, resolve_hits, score_error_response, score_photos,
};
use crate::data::Claims;
use crate::database::ExifDao;
use crate::file_types::{is_image_file, is_video_file};
use crate::geo::{forward_geocode, gps_bounding_box, haversine_distance};
use crate::tags::TagDao;
use actix_web::HttpResponse;
use actix_web::web::{Data, Query};
use serde::{Deserialize, Serialize};
use std::collections::HashSet;
use std::path::Path;
use std::sync::Mutex;

#[derive(Debug, Deserialize)]
pub struct UnifiedQuery {
    /// Natural-language query. Required; empty triggers 400.
    pub q: String,
    #[serde(default = "default_limit")]
    pub limit: usize,
    #[serde(default)]
    pub offset: usize,
    /// CLIP cosine floor for the semantic ranking stage. Same default as the
    /// plain search endpoint.
    #[serde(default = "default_threshold")]
    pub threshold: f32,
    /// Legacy single-library scope (see clip_search).
    pub library: Option<i32>,
    /// Multi-library scope, comma-separated ids.
    pub library_ids: Option<String>,
    /// Optional model override. The client passes the user's currently-selected
    /// local model so the translation step reuses a model that's already loaded
    /// (avoids a llama-swap eviction / cold start). Falls back to the configured
    /// default local model when absent. Local only — no hybrid here.
    pub model: Option<String>,
}

fn default_limit() -> usize {
    20
}
fn default_threshold() -> f32 {
    0.20
}

/// A geocoded place echoed back so the client can show / edit the location
/// filter it actually searched.
#[derive(Debug, Serialize)]
struct ResolvedPlace {
    display_name: String,
    lat: f64,
    lon: f64,
    radius_km: f64,
}

/// How the server interpreted the NL query — echoed to the client to render
/// editable filter chips. tag ids map to the client's existing tag list.
#[derive(Debug, Serialize)]
struct Interpreted {
    semantic: Option<String>,
    tag_ids: Vec<i32>,
    exclude_tag_ids: Vec<i32>,
    /// Words the model treated as tags that don't exist in the vocab; folded
    /// into the semantic term and surfaced here so the UI can explain it.
    unmatched_tags: Vec<String>,
    camera_make: Option<String>,
    camera_model: Option<String>,
    lens_model: Option<String>,
    date_from: Option<i64>,
    date_to: Option<i64>,
    media_type: Option<String>,
    place: Option<ResolvedPlace>,
}

#[derive(Debug, Serialize)]
struct UnifiedResponse {
    query: String,
    interpreted: Interpreted,
    /// CLIP model version used for ranking; `None` when the query had no
    /// semantic term (filters-only).
    model_version: Option<String>,
    /// Embeddings scored by CLIP (0 when filters-only).
    considered: usize,
    /// Matches before pagination.
    total_matching: usize,
    offset: usize,
    results: Vec<SearchHit>,
}

#[derive(Debug, Serialize)]
struct ErrorBody {
    error: String,
}

fn bad_request(msg: impl Into<String>) -> HttpResponse {
    HttpResponse::BadRequest().json(ErrorBody { error: msg.into() })
}

/// Combine the model's semantic term with any tag words that didn't match the
/// vocab, so a hallucinated/non-vocab tag becomes a soft semantic signal
/// rather than being dropped.
fn effective_semantic(sq: &StructuredQuery) -> Option<String> {
    let mut parts: Vec<String> = Vec::new();
    if let Some(s) = sq.semantic.as_deref() {
        parts.push(s.to_string());
    }
    parts.extend(sq.unmatched_tags.iter().cloned());
    if parts.is_empty() {
        None
    } else {
        Some(parts.join(" "))
    }
}

pub async fn unified_search<TagD: TagDao>(
    _: Claims,
    state: Data<AppState>,
    exif_dao: Data<Mutex<Box<dyn ExifDao>>>,
    tag_dao: Data<Mutex<TagD>>,
    query: Query<UnifiedQuery>,
) -> HttpResponse {
    let nl = query.q.trim().to_string();
    if nl.is_empty() {
        return bad_request("query parameter `q` is required");
    }

    let limit = query.limit.clamp(1, 200);
    let offset = query.offset;
    let threshold = query.threshold.clamp(-1.0, 1.0);

    let library_ids = match parse_library_scope(query.library_ids.as_deref(), query.library) {
        Ok(ids) => ids,
        Err(msg) => return bad_request(msg),
    };

    let ctx = opentelemetry::Context::current();

    // ── 1. Translate the NL query, grounded on the real tag vocabulary ──
    let tag_vocab: Vec<(i32, String)> = {
        let mut dao = tag_dao.lock().expect("tag dao");
        match dao.get_all_tags(&ctx, None) {
            Ok(tags) => tags.into_iter().map(|(_, t)| (t.id, t.name)).collect(),
            Err(e) => {
                log::warn!("unified_search: get_all_tags failed: {e:?}");
                Vec::new()
            }
        }
    };

    // Respect env/config for the LLM backend (LLM_BACKEND → ollama or
    // llama-swap); local only, no hybrid, per the feature's design. The
    // client-supplied model (the user's current selection) routes translation
    // to an already-loaded model when possible; otherwise resolve_backend
    // falls back to the configured default.
    let overrides = SamplingOverrides {
        model: query.model.clone().filter(|m| !m.is_empty()),
        num_ctx: None,
        temperature: None,
        top_p: None,
        top_k: None,
        min_p: None,
    };
    let backend = match state
        .insight_generator
        .resolve_backend(BackendKind::Local, &overrides)
        .await
    {
        Ok(b) => b,
        Err(e) => {
            log::warn!("unified_search: resolve_backend failed: {e:?}");
            return HttpResponse::ServiceUnavailable().json(ErrorBody {
                error: "LLM backend unavailable".into(),
            });
        }
    };

    let today = chrono::Utc::now().date_naive();
    let sq = match translate_nl_query(backend.chat(), &nl, &tag_vocab, today).await {
        Ok(sq) => sq,
        Err(e) => {
            log::warn!("unified_search: translate_nl_query failed: {e:?}");
            return HttpResponse::BadGateway().json(ErrorBody {
                error: "could not interpret the query".into(),
            });
        }
    };

    // ── 2. Forward-geocode the place name into a gps circle ──
    let resolved_place = match sq.place.as_deref() {
        Some(p) => forward_geocode(p).await.map(|g| ResolvedPlace {
            display_name: g.display_name,
            lat: g.lat,
            lon: g.lon,
            radius_km: g.radius_km,
        }),
        None => None,
    };
    let gps = resolved_place.as_ref().map(|p| (p.lat, p.lon, p.radius_km));

    let semantic = effective_semantic(&sq);

    let has_exif_filter = sq.camera_make.is_some()
        || sq.camera_model.is_some()
        || sq.lens_model.is_some()
        || sq.date_from.is_some()
        || sq.date_to.is_some();
    let has_struct =
        has_exif_filter || gps.is_some() || !sq.tag_ids.is_empty() || sq.media_type.is_some();

    // Stage trace: what the model extracted + whether a structured filter is
    // active. The chips show this to the user too, but logging it makes the
    // "why no results" path debuggable from the server side.
    log::info!(
        "unified_search: q={nl:?} semantic={:?} tag_ids={:?} exclude={:?} place={:?} gps={:?} date=({:?},{:?}) media={:?} unmatched={:?} has_struct={has_struct}",
        sq.semantic,
        sq.tag_ids,
        sq.exclude_tag_ids,
        resolved_place.as_ref().map(|p| p.display_name.as_str()),
        gps,
        sq.date_from,
        sq.date_to,
        sq.media_type,
        sq.unmatched_tags,
    );

    // ── 3. Build the structured candidate set (EXIF rows passing every
    // filter). Skipped entirely for a pure-semantic query. ──
    let mut candidate: Vec<crate::database::models::ImageExif> = Vec::new();
    let mut allowed_hashes: HashSet<String> = HashSet::new();
    if has_struct {
        // Tag membership set (rel_path only — same cross-library imprecision
        // as the existing /photos tag listing). ALL-mode: the photo must
        // carry every named tag.
        let tag_set: Option<HashSet<String>> = if sq.tag_ids.is_empty() {
            None
        } else {
            let mut dao = tag_dao.lock().expect("tag dao");
            match dao.get_files_with_all_tag_ids(
                sq.tag_ids.clone(),
                sq.exclude_tag_ids.clone(),
                &ctx,
            ) {
                Ok(files) => Some(files.into_iter().map(|f| f.file_name).collect()),
                Err(e) => {
                    log::warn!("unified_search: tag filter failed: {e:?}");
                    Some(HashSet::new())
                }
            }
        };
        log::info!(
            "unified_search: tag_ids={:?} -> tag_set_files={:?}",
            sq.tag_ids,
            tag_set.as_ref().map(|s| s.len())
        );

        // EXIF query handles camera/lens/gps-box/date. With no EXIF filters
        // it returns the whole table, which we then narrow by the predicates
        // below (tags / media / scope). Fine at personal-library scale.
        let gps_bounds = gps.map(|(lat, lon, r)| gps_bounding_box(lat, lon, r));
        let rows = {
            let mut dao = exif_dao.lock().expect("exif dao");
            dao.query_by_exif(
                &ctx,
                None, // scope filtered in-Rust to support multi-library
                sq.camera_make.as_deref(),
                sq.camera_model.as_deref(),
                sq.lens_model.as_deref(),
                gps_bounds,
                sq.date_from,
                sq.date_to,
            )
            .unwrap_or_else(|e| {
                log::warn!("unified_search: query_by_exif failed: {e:?}");
                Vec::new()
            })
        };

        candidate = rows
            .into_iter()
            .filter(|row| {
                // Library scope.
                if !library_ids.is_empty() && !library_ids.contains(&row.library_id) {
                    return false;
                }
                // Precise GPS distance (the EXIF query only did a coarse box).
                if let Some((lat, lon, radius_km)) = gps {
                    match (row.gps_latitude, row.gps_longitude) {
                        (Some(plat), Some(plon)) => {
                            if haversine_distance(lat, lon, plat as f64, plon as f64) > radius_km {
                                return false;
                            }
                        }
                        _ => return false,
                    }
                }
                // Media type.
                if let Some(mt) = sq.media_type.as_deref() {
                    let p = Path::new(&row.file_path);
                    let ok = if mt == "video" {
                        is_video_file(p)
                    } else {
                        is_image_file(p)
                    };
                    if !ok {
                        return false;
                    }
                }
                // Tag membership.
                if let Some(ts) = &tag_set
                    && !ts.contains(&row.file_path)
                {
                    return false;
                }
                true
            })
            .collect();

        allowed_hashes = candidate
            .iter()
            .filter_map(|r| r.content_hash.clone())
            .collect();
        log::info!(
            "unified_search: candidate_rows={} allowed_hashes={}",
            candidate.len(),
            allowed_hashes.len()
        );
    }

    // ── 4. Rank ──
    match semantic {
        Some(ref sem) => {
            // Semantic term present: CLIP-rank, then keep only hits that pass
            // the structured filters (by content_hash).
            let scored =
                match score_photos(&state, &exif_dao, sem, &library_ids, threshold, None).await {
                    Ok(s) => s,
                    Err(e) => return score_error_response(e),
                };
            let considered = scored.considered;
            let clip_hits = scored.hits.len();
            let hits: Vec<(f32, String)> = if has_struct {
                scored
                    .hits
                    .into_iter()
                    .filter(|(_, h)| allowed_hashes.contains(h))
                    .collect()
            } else {
                scored.hits
            };
            log::info!(
                "unified_search: clip considered={considered} hits={clip_hits} after_struct_filter={}",
                hits.len()
            );
            let total_matching = hits.len();
            let page = paginate(&hits, offset, limit);
            let results = resolve_hits(&exif_dao, &page);
            HttpResponse::Ok().json(UnifiedResponse {
                query: nl,
                interpreted: interpreted(&sq, resolved_place),
                model_version: Some(scored.model_version),
                considered: scored.considered,
                total_matching,
                offset,
                results,
            })
        }
        None => {
            // Filters-only: no semantic term. Require at least one filter,
            // then return the candidate set newest-first.
            if !has_struct {
                return bad_request("query had no searchable terms");
            }
            candidate.sort_by(|a, b| b.date_taken.cmp(&a.date_taken));
            let total_matching = candidate.len();
            log::info!("unified_search: filters-only matches={total_matching}");
            let end = (offset + limit).min(total_matching);
            let results: Vec<SearchHit> = if offset >= total_matching {
                Vec::new()
            } else {
                candidate[offset..end]
                    .iter()
                    .map(|r| SearchHit {
                        library_id: r.library_id,
                        rel_path: r.file_path.clone(),
                        content_hash: r.content_hash.clone().unwrap_or_default(),
                        score: 0.0,
                    })
                    .collect()
            };
            HttpResponse::Ok().json(UnifiedResponse {
                query: nl,
                interpreted: interpreted(&sq, resolved_place),
                model_version: None,
                considered: 0,
                total_matching,
                offset,
                results,
            })
        }
    }
}

/// Slice a sorted hit list at `[offset, offset+limit)`, tolerating
/// out-of-range offsets (empty page).
fn paginate(hits: &[(f32, String)], offset: usize, limit: usize) -> Vec<(f32, String)> {
    if offset >= hits.len() {
        return Vec::new();
    }
    let end = (offset + limit).min(hits.len());
    hits[offset..end].to_vec()
}

fn interpreted(sq: &StructuredQuery, place: Option<ResolvedPlace>) -> Interpreted {
    Interpreted {
        semantic: sq.semantic.clone(),
        tag_ids: sq.tag_ids.clone(),
        exclude_tag_ids: sq.exclude_tag_ids.clone(),
        unmatched_tags: sq.unmatched_tags.clone(),
        camera_make: sq.camera_make.clone(),
        camera_model: sq.camera_model.clone(),
        lens_model: sq.lens_model.clone(),
        date_from: sq.date_from,
        date_to: sq.date_to,
        media_type: sq.media_type.clone(),
        place,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ai::nl_query::StructuredQuery;

    #[test]
    fn effective_semantic_combines_semantic_and_unmatched() {
        let sq = StructuredQuery {
            semantic: Some("sunset".into()),
            unmatched_tags: vec!["golden hour".into()],
            ..Default::default()
        };
        assert_eq!(
            effective_semantic(&sq).as_deref(),
            Some("sunset golden hour")
        );
    }

    #[test]
    fn effective_semantic_none_when_empty() {
        let sq = StructuredQuery::default();
        assert_eq!(effective_semantic(&sq), None);
    }

    #[test]
    fn effective_semantic_unmatched_only() {
        let sq = StructuredQuery {
            unmatched_tags: vec!["disco".into()],
            ..Default::default()
        };
        assert_eq!(effective_semantic(&sq).as_deref(), Some("disco"));
    }

    #[test]
    fn paginate_handles_out_of_range_offset() {
        let hits = vec![(0.9, "a".to_string()), (0.8, "b".to_string())];
        assert_eq!(paginate(&hits, 5, 10).len(), 0);
        assert_eq!(paginate(&hits, 0, 1).len(), 1);
        assert_eq!(paginate(&hits, 1, 10).len(), 1);
    }
}