//! Backfill `image_exif.content_hash` + `size_bytes` for rows that were
//! ingested before hash computation was wired into the watcher.
//!
//! The watcher computes hashes for new files as they're ingested, so this
//! binary is a one-shot tool for the historical backlog. Safe to re-run;
//! only rows with NULL content_hash are processed.

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

use clap::Parser;
use log::{error, warn};
use rayon::prelude::*;

use image_api::bin_progress;
use image_api::content_hash;
use image_api::database::{ExifDao, SqliteExifDao, connect};
use image_api::libraries::{self, Library};

#[derive(Parser, Debug)]
#[command(name = "backfill_hashes")]
#[command(about = "Compute content_hash for image_exif rows missing one")]
struct Args {
    /// Max rows to hash per batch. The process loops until no rows remain.
    #[arg(long, default_value_t = 500)]
    batch_size: i64,

    /// Rayon parallelism override. 0 uses the default thread pool size.
    #[arg(long, default_value_t = 0)]
    parallelism: usize,

    /// Dry-run: log what would be hashed without writing to the DB.
    #[arg(long)]
    dry_run: bool,
}

fn main() -> anyhow::Result<()> {
    env_logger::init();
    dotenv::dotenv().ok();

    let args = Args::parse();
    if args.parallelism > 0 {
        rayon::ThreadPoolBuilder::new()
            .num_threads(args.parallelism)
            .build_global()
            .expect("Unable to configure rayon thread pool");
    }

    // Resolve libraries (patch placeholder if still unset) so we can map
    // library_id back to a root_path on disk.
    let base_path = dotenv::var("BASE_PATH").ok();
    let mut seed_conn = connect();
    if let Some(base) = base_path.as_deref() {
        libraries::seed_or_patch_from_env(&mut seed_conn, base);
    }
    let libs = libraries::load_all(&mut seed_conn);
    drop(seed_conn);
    if libs.is_empty() {
        anyhow::bail!("No libraries configured; cannot backfill hashes");
    }
    let libs_by_id: std::collections::HashMap<i32, Library> =
        libs.into_iter().map(|lib| (lib.id, lib)).collect();
    println!(
        "Configured libraries: {}",
        libs_by_id
            .values()
            .map(|l| format!("{} -> {}", l.name, l.root_path))
            .collect::<Vec<_>>()
            .join(", ")
    );

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

    let mut total_hashed = 0u64;
    let mut total_missing = 0u64;
    let mut total_errors = 0u64;
    let start = Instant::now();

    let pb = bin_progress::spinner("hashing");

    loop {
        let rows = {
            let mut guard = dao.lock().expect("Unable to lock ExifDao");
            guard
                .get_rows_missing_hash(&ctx, args.batch_size)
                .map_err(|e| anyhow::anyhow!("DB error: {:?}", e))?
        };
        if rows.is_empty() {
            break;
        }
        let batch_size = rows.len();
        pb.set_message(format!(
            "batch of {} (hashed={} missing={} errors={})",
            batch_size, total_hashed, total_missing, total_errors
        ));

        // Compute hashes in parallel (I/O-bound; rayon helps on local disks,
        // throttled by network on SMB mounts — use --parallelism to tune).
        let results: Vec<(i32, String, Option<content_hash::FileIdentity>)> = rows
            .into_par_iter()
            .map(|(library_id, rel_path)| {
                let abs = libs_by_id
                    .get(&library_id)
                    .map(|lib| Path::new(&lib.root_path).join(&rel_path));
                match abs {
                    Some(abs_path) if abs_path.exists() => match content_hash::compute(&abs_path) {
                        Ok(id) => (library_id, rel_path, Some(id)),
                        Err(e) => {
                            error!("hash error for {}: {:?}", abs_path.display(), e);
                            (library_id, rel_path, None)
                        }
                    },
                    Some(_) => (library_id, rel_path, None), // file missing on disk
                    None => {
                        warn!("Row refers to unknown library_id {}", library_id);
                        (library_id, rel_path, None)
                    }
                }
            })
            .collect();

        // Persist sequentially — SQLite writes serialize anyway.
        if !args.dry_run {
            let mut guard = dao.lock().expect("Unable to lock ExifDao");
            for (library_id, rel_path, ident) in &results {
                match ident {
                    Some(id) => {
                        match guard.backfill_content_hash(
                            &ctx,
                            *library_id,
                            rel_path,
                            &id.content_hash,
                            id.size_bytes,
                        ) {
                            Ok(_) => {
                                total_hashed += 1;
                                pb.inc(1);
                            }
                            Err(e) => {
                                pb.println(format!("persist error for {}: {:?}", rel_path, e));
                                total_errors += 1;
                            }
                        }
                    }
                    None => {
                        total_missing += 1;
                    }
                }
            }
        } else {
            for (_, rel_path, ident) in &results {
                match ident {
                    Some(id) => {
                        pb.println(format!(
                            "[dry-run] {} -> {} ({} bytes)",
                            rel_path, id.content_hash, id.size_bytes
                        ));
                        total_hashed += 1;
                        pb.inc(1);
                    }
                    None => {
                        total_missing += 1;
                    }
                }
            }
            pb.println(format!(
                "[dry-run] processed one batch of {}. Stopping — a real run would continue \
                 until no NULL content_hash rows remain.",
                results.len()
            ));
            break;
        }
    }

    pb.finish_and_clear();
    println!(
        "Done. hashed={}, skipped (missing on disk)={}, errors={}, elapsed={:.1}s",
        total_hashed,
        total_missing,
        total_errors,
        start.elapsed().as_secs_f64()
    );
    Ok(())
}