//! Probe binary for CLIP semantic search.
//!
//! No DB writes. Walks a library's `image_exif` rows, encodes a sample
//! via Apollo's `/encode_image`, encodes the user's --query via
//! `/encode_text`, and prints the top-K most similar photos by cosine
//! similarity so the operator can eyeball quality before committing to
//! the persistence phase (column populated by backlog drain, search
//! endpoint, UI).
//!
//! Usage:
//!     cargo run --release --bin probe_clip_search -- \
//!         --library 1 --limit 200 --query "a beach at sunset" --top 10
//!
//! Env: standard ImageApi `.env`. Requires either
//! `APOLLO_CLIP_API_BASE_URL` or `APOLLO_API_BASE_URL` to be set.

use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};
use std::time::Instant;

use clap::Parser;
use log::{info, warn};

use image_api::ai::clip_client::{ClipClient, ClipError, EncodeImageMeta};
use image_api::database::{ExifDao, SqliteExifDao, connect};
use image_api::exif;
use image_api::file_types;
use image_api::libraries::{self, Library};

#[derive(Parser, Debug)]
#[command(name = "probe_clip_search")]
#[command(about = "Top-K CLIP semantic search over a sample of image_exif rows")]
struct Args {
    /// Library id to sample from.
    #[arg(long)]
    library: i32,

    /// Max files to encode. CPU inference is slow (~1-3 s per photo at
    /// ViT-L/14); start small and grow once GPU is sorted.
    #[arg(long, default_value_t = 50)]
    limit: usize,

    /// Natural-language query. Empty triggers an error from Apollo.
    #[arg(long)]
    query: String,

    /// How many top results to print.
    #[arg(long, default_value_t = 10)]
    top: usize,

    /// Offset into the library's rel_path listing.
    #[arg(long, default_value_t = 0)]
    offset: i64,

    /// How many DB rows to scan before giving up on hitting the limit.
    #[arg(long, default_value_t = 5000)]
    max_scan: i64,
}

/// Same as `face_watch::read_image_bytes_for_detect` (which is pub(crate)).
/// Inlined for the throwaway probe.
fn read_image_bytes(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)
}

/// Decode a base64'd LE float32 vector to a `Vec<f32>`.
fn decode_f32_vec(b64: &str) -> anyhow::Result<Vec<f32>> {
    use base64::Engine;
    let bytes = base64::engine::general_purpose::STANDARD.decode(b64.as_bytes())?;
    if bytes.len() % 4 != 0 {
        anyhow::bail!("embedding byte length {} not divisible by 4", bytes.len());
    }
    let mut out = Vec::with_capacity(bytes.len() / 4);
    for chunk in bytes.chunks_exact(4) {
        out.push(f32::from_le_bytes([chunk[0], chunk[1], chunk[2], chunk[3]]));
    }
    Ok(out)
}

/// Plain dot product. Apollo L2-normalizes both sides, so this is cosine sim.
fn dot(a: &[f32], b: &[f32]) -> f32 {
    a.iter().zip(b.iter()).map(|(x, y)| x * y).sum()
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    env_logger::init();
    dotenv::dotenv().ok();

    let args = Args::parse();
    if args.query.trim().is_empty() {
        anyhow::bail!("--query must not be empty");
    }

    let client = ClipClient::from_env();
    if !client.is_enabled() {
        anyhow::bail!(
            "ClipClient disabled: set APOLLO_CLIP_API_BASE_URL or APOLLO_API_BASE_URL in .env"
        );
    }

    match client.health().await {
        Ok(h) => info!(
            "clip engine: loaded={} device={} model={} dim={}",
            h.loaded, h.device, h.model_version, h.embedding_dim
        ),
        Err(e) => warn!("health probe failed (continuing): {e}"),
    }

    let mut seed_conn = connect();
    if let Some(base) = dotenv::var("BASE_PATH").ok().as_deref() {
        libraries::seed_or_patch_from_env(&mut seed_conn, base);
    }
    let libs = libraries::load_all(&mut seed_conn);
    drop(seed_conn);
    let lib: Library = libs
        .into_iter()
        .find(|l| l.id == args.library)
        .ok_or_else(|| anyhow::anyhow!("library id {} not found", args.library))?;
    info!(
        "probing library #{} ({}) at {}",
        lib.id, lib.name, lib.root_path
    );

    let dao: Arc<Mutex<Box<dyn ExifDao>>> = Arc::new(Mutex::new(Box::new(SqliteExifDao::new())));
    let ctx = opentelemetry::Context::new();

    // Encode the query up-front so the long image-encode loop doesn't
    // race a slow query encode. Fails fast on a misspelled query.
    let query_resp = client
        .encode_text(&args.query)
        .await
        .map_err(|e| anyhow::anyhow!("encode_text: {e}"))?;
    let query_vec = decode_f32_vec(&query_resp.embedding)?;
    info!(
        "query encoded ({}d, {}ms): {:?}",
        query_resp.embedding_dim, query_resp.duration_ms, args.query
    );

    // Page through (id, rel_path), filter to images on disk, encode up
    // to `limit`. Each encoded photo gets scored against the query and
    // kept in a top-K heap.
    const PAGE: i64 = 500;
    let mut offset = args.offset;
    let mut scanned: i64 = 0;
    let mut encoded = 0usize;
    let mut perm_fail = 0usize;
    let mut transient_fail = 0usize;
    let root = PathBuf::from(&lib.root_path);
    let started = Instant::now();
    // (similarity, rel_path) — we keep all scored results and sort at
    // the end. With limit≤few-hundred this is trivial.
    let mut scores: Vec<(f32, String)> = Vec::with_capacity(args.limit);

    'outer: loop {
        if scanned >= args.max_scan {
            warn!(
                "scan cap ({}) reached before hitting limit ({}); bump --max-scan to scan deeper",
                args.max_scan, args.limit
            );
            break;
        }
        let rows = {
            let mut guard = dao.lock().expect("dao lock");
            guard
                .list_rel_paths_for_library_page(&ctx, lib.id, PAGE, offset)
                .map_err(|e| anyhow::anyhow!("list rel_paths: {:?}", e))?
        };
        if rows.is_empty() {
            info!("no more rows after offset {}", offset);
            break;
        }
        offset += rows.len() as i64;
        scanned += rows.len() as i64;

        for (_id, rel_path) in rows {
            if encoded >= args.limit {
                break 'outer;
            }
            let abs = root.join(&rel_path);
            if !file_types::is_image_file(&abs) || !abs.exists() {
                continue;
            }
            let bytes = match read_image_bytes(&abs) {
                Ok(b) => b,
                Err(e) => {
                    warn!("read {rel_path}: {e}");
                    continue;
                }
            };
            let meta = EncodeImageMeta {
                content_hash: String::new(),
                library_id: lib.id,
                rel_path: rel_path.clone(),
            };
            let call_start = Instant::now();
            match client.encode_image(bytes, meta).await {
                Ok(resp) => {
                    encoded += 1;
                    let vec = match decode_f32_vec(&resp.embedding) {
                        Ok(v) => v,
                        Err(e) => {
                            warn!("decode {rel_path}: {e}");
                            continue;
                        }
                    };
                    if vec.len() != query_vec.len() {
                        warn!(
                            "dim mismatch for {rel_path}: image={} query={}",
                            vec.len(),
                            query_vec.len()
                        );
                        continue;
                    }
                    let sim = dot(&vec, &query_vec);
                    scores.push((sim, rel_path.clone()));
                    if encoded % 10 == 0 {
                        info!(
                            "progress: {} encoded, {:.1}s elapsed",
                            encoded,
                            started.elapsed().as_secs_f32()
                        );
                    }
                    let _ = call_start;
                }
                Err(ClipError::Permanent(e)) => {
                    perm_fail += 1;
                    warn!("permanent encode failure for {rel_path}: {e}");
                }
                Err(ClipError::Transient(e)) => {
                    transient_fail += 1;
                    warn!("transient encode failure for {rel_path}: {e}");
                }
                Err(ClipError::Disabled) => {
                    anyhow::bail!("clip client became disabled mid-run; impossible");
                }
            }
        }
    }

    scores.sort_by(|a, b| b.0.partial_cmp(&a.0).unwrap_or(std::cmp::Ordering::Equal));
    let elapsed = started.elapsed();
    println!();
    println!(
        "── top {} for query: {:?} ──",
        args.top.min(scores.len()),
        args.query
    );
    for (i, (sim, path)) in scores.iter().take(args.top).enumerate() {
        println!("[{:>2}] sim={:.3}  {}", i + 1, sim, path);
    }
    println!();
    println!("── summary ─────────────────────────────────────");
    println!("query                : {:?}", args.query);
    println!("scanned rows         : {scanned}");
    println!("encoded photos       : {encoded}");
    println!("permanent failures   : {perm_fail}");
    println!("transient failures   : {transient_fail}");
    println!("elapsed              : {:.1}s", elapsed.as_secs_f32());
    if encoded > 0 {
        println!(
            "throughput           : {:.2} photos/s ({:.0}ms/photo avg)",
            encoded as f32 / elapsed.as_secs_f32().max(0.001),
            elapsed.as_millis() as f32 / encoded as f32
        );
    }
    Ok(())
}