//! CLIP-encoding pass for the file watcher.
//!
//! `process_clip_backlog` in `backfill.rs` calls [`run_clip_encoding_pass`]
//! with the page of candidates returned by
//! `ExifDao::list_clip_unencoded_candidates`. We walk those, fan out K
//! parallel encode calls to Apollo, and persist the resulting embeddings
//! into `image_exif.clip_embedding` / `clip_model_version`.
//!
//! Unlike the face pipeline, CLIP has no marker rows — a permanent
//! failure (un-decodable bytes) leaves the row's `clip_embedding` NULL
//! and the drain will retry on the next tick. For personal-library
//! scale this is fine; the per-tick cap bounds the wasted work, and
//! `file_types::is_image_file` filters out videos / non-media client-
//! side so most permanent failures are decoded-but-corrupt files (rare).
//!
//! The watcher thread isn't in any pre-existing async context, so we
//! build a short-lived tokio runtime per pass and `block_on` the join
//! of K encode futures. Concurrency knob: `CLIP_ENCODE_CONCURRENCY`
//! (default 4 — lower than faces because Apollo's CLIP path doesn't
//! release the GIL between preprocess and forward as cleanly).

use crate::ai::clip_client::{ClipClient, ClipError, EncodeImageMeta};
use crate::database::ExifDao;
use crate::exif;
use crate::file_types;
use crate::libraries::Library;
use crate::memories::PathExcluder;
use log::{debug, info, warn};
use std::path::Path;
use std::sync::{Arc, Mutex};
use tokio::sync::Semaphore;

/// One file the watcher would like to CLIP-encode. Built from the DAO
/// `list_clip_unencoded_candidates` result — needs the `content_hash`
/// for traceability in Apollo's log lines, even though the embedding
/// itself is keyed on `(library_id, rel_path)` for the back-write.
#[derive(Debug, Clone)]
pub struct ClipCandidate {
    pub rel_path: String,
    pub content_hash: String,
}

/// Synchronous entry point. Returns once every candidate has been
/// processed (or definitively skipped). No-op when the client is
/// disabled so the caller can call unconditionally.
pub fn run_clip_encoding_pass(
    library: &Library,
    excluded_dirs: &[String],
    clip_client: &ClipClient,
    exif_dao: Arc<Mutex<Box<dyn ExifDao>>>,
    candidates: Vec<ClipCandidate>,
) {
    if !clip_client.is_enabled() {
        return;
    }
    if candidates.is_empty() {
        return;
    }

    let base = Path::new(&library.root_path);
    let filtered = filter_excluded(base, excluded_dirs, candidates, Some(&library.name));
    if filtered.is_empty() {
        return;
    }

    let concurrency: usize = std::env::var("CLIP_ENCODE_CONCURRENCY")
        .ok()
        .and_then(|s| s.parse().ok())
        .filter(|n: &usize| *n > 0)
        .unwrap_or(4);

    info!(
        "clip_watch: encoding {} candidate(s) for library '{}' (concurrency {})",
        filtered.len(),
        library.name,
        concurrency
    );

    let rt = match tokio::runtime::Builder::new_multi_thread()
        .worker_threads(2)
        .enable_all()
        .build()
    {
        Ok(rt) => rt,
        Err(e) => {
            warn!("clip_watch: failed to build tokio runtime: {e}");
            return;
        }
    };

    let library_id = library.id;
    let library_root = library.root_path.clone();
    rt.block_on(async move {
        let sem = Arc::new(Semaphore::new(concurrency));
        let mut handles = Vec::with_capacity(filtered.len());
        for cand in filtered {
            let permit_sem = sem.clone();
            let clip_client = clip_client.clone();
            let exif_dao = exif_dao.clone();
            let library_root = library_root.clone();
            handles.push(tokio::spawn(async move {
                let _permit = permit_sem.acquire().await.expect("clip semaphore");
                process_one(library_id, &library_root, cand, &clip_client, exif_dao).await;
            }));
        }
        for h in handles {
            let _ = h.await;
        }
    });
}

async fn process_one(
    library_id: i32,
    library_root: &str,
    cand: ClipCandidate,
    clip_client: &ClipClient,
    exif_dao: Arc<Mutex<Box<dyn ExifDao>>>,
) {
    let abs = Path::new(library_root).join(&cand.rel_path);
    let bytes = match read_image_bytes_for_encode(&abs) {
        Ok(b) => b,
        Err(e) => {
            // Same rationale as face_watch: don't mark — the file may
            // have been moved/renamed mid-scan; let the next pass retry.
            warn!(
                "clip_watch: read failed for {} (lib {}): {}",
                cand.rel_path, library_id, e
            );
            return;
        }
    };

    let meta = EncodeImageMeta {
        content_hash: cand.content_hash.clone(),
        library_id,
        rel_path: cand.rel_path.clone(),
    };
    let ctx = opentelemetry::Context::current();

    match clip_client.encode_image(bytes, meta).await {
        Ok(resp) => {
            let emb_bytes = match resp.decode_embedding() {
                Ok(b) => b,
                Err(e) => {
                    warn!("clip_watch: bad embedding for {}: {:?}", cand.rel_path, e);
                    return;
                }
            };
            let mut dao = exif_dao.lock().expect("exif dao");
            if let Err(e) = dao.backfill_clip_embedding(
                &ctx,
                library_id,
                &cand.rel_path,
                &emb_bytes,
                &resp.model_version,
            ) {
                warn!(
                    "clip_watch: backfill_clip_embedding failed for {}: {:?}",
                    cand.rel_path, e
                );
                return;
            }
            debug!(
                "clip_watch: {} → dim={} ({}ms, {})",
                cand.rel_path, resp.embedding_dim, resp.duration_ms, resp.model_version
            );
        }
        Err(ClipError::Permanent(e)) => {
            // No marker — the row sits with NULL embedding and the drain
            // retries next pass. For personal-library scale the cost of
            // re-attempting permanently-broken files is bounded by the
            // per-tick cap. If this becomes a recurring noise source,
            // add a `clip_status` column with `failed` semantics like
            // face_detections has.
            warn!(
                "clip_watch: permanent failure on {} (will retry next pass): {}",
                cand.rel_path, e
            );
        }
        Err(ClipError::Transient(e)) => {
            debug!(
                "clip_watch: transient on {}: {} (will retry next pass)",
                cand.rel_path, e
            );
        }
        Err(ClipError::Disabled) => {
            // Defensive — the entry-point already checked is_enabled().
        }
    }
}

/// Drop candidates whose paths land in an excluded dir or whose
/// extension isn't an image. Mirrors `face_watch::filter_excluded` so
/// the two backlogs stay shape-consistent. Library name is passed
/// purely for the log line that surfaces an exclusion hit.
pub fn filter_excluded(
    base: &Path,
    excluded_dirs: &[String],
    candidates: Vec<ClipCandidate>,
    library_name: Option<&str>,
) -> Vec<ClipCandidate> {
    let excluder = if excluded_dirs.is_empty() {
        None
    } else {
        Some(PathExcluder::new(base, excluded_dirs))
    };
    candidates
        .into_iter()
        .filter(|c| {
            let abs = base.join(&c.rel_path);
            if !file_types::is_image_file(&abs) {
                debug!(
                    "clip_watch: skipping non-image '{}' (lib {})",
                    c.rel_path,
                    library_name.unwrap_or("<unknown>")
                );
                return false;
            }
            if let Some(ex) = excluder.as_ref()
                && ex.is_excluded(&abs)
            {
                debug!(
                    "clip_watch: skipping excluded '{}' (lib {})",
                    c.rel_path,
                    library_name.unwrap_or("<unknown>")
                );
                return false;
            }
            true
        })
        .collect()
}

/// Read image bytes for CLIP encoding. Same logic as
/// `face_watch::read_image_bytes_for_detect` — RAW / HEIC files don't
/// decode in Apollo's PIL pipeline, so we pull the embedded JPEG
/// preview the thumbnail pipeline already extracts. Plain JPEG / PNG /
/// WebP go through a direct read.
pub fn read_image_bytes_for_encode(path: &Path) -> std::io::Result<Vec<u8>> {
    if file_types::needs_ffmpeg_thumbnail(path)
        && let Some(preview) = exif::extract_embedded_jpeg_preview(path)
    {
        return Ok(preview);
    }
    std::fs::read(path)
}