import logging
import threading
import time
from pathlib import Path

import config
import db
import extractor
import sftp as sftp_module
from uploader import CalibreClient

log = logging.getLogger(__name__)

_lock = threading.Lock()
_running = False


def is_running() -> bool:
    return _running


def run_sync(limit: int | None = None) -> None:
    """
    Process all unprocessed remote zips in chunks.

    limit: if set, process at most this many zips (used by test mode).
           If None, processes all unprocessed zips in batches of sync_batch_size.
    """
    global _running
    if not _lock.acquire(blocking=False):
        log.warning("Sync already running, skipping")
        return

    _running = True
    run_id = db.start_sync_run()
    counters = dict(zips_found=0, zips_new=0, books_uploaded=0, books_skipped=0, books_errored=0)

    try:
        log.info("Sync started (limit=%s)", limit)
        cfg = config.load()
        _validate_config(cfg)
        log.info("Config OK — work dir: %s", cfg.local_work_dir)

        work_dir = Path(cfg.local_work_dir)
        work_dir.mkdir(parents=True, exist_ok=True)
        log.info("Work dir ready: %s", work_dir)

        log.info("Connecting to SFTP %s@%s:%s ...", cfg.sftp.user, cfg.sftp.host, cfg.sftp.port)
        new_zips = sftp_module.list_new_zips(cfg.sftp, max_results=limit)
        counters["zips_found"] = len(new_zips)

        counters["zips_new"] = len(new_zips)

        if not new_zips:
            log.info("No new zips to process")
            db.finish_sync_run(run_id, status="success", **counters)
            return

        # Determine chunk size; 0 means process everything in one chunk
        batch_size = int(db.get_setting("sync_batch_size", "0") or "0")
        if batch_size <= 0:
            batch_size = len(new_zips)

        total_batches = -(-len(new_zips) // batch_size)  # ceiling division
        client = CalibreClient(cfg.calibre)

        for batch_num, i in enumerate(range(0, len(new_zips), batch_size), start=1):
            chunk = new_zips[i : i + batch_size]
            log.info("Batch %d/%d — processing %d zip(s)", batch_num, total_batches, len(chunk))

            for remote_zip in chunk:
                zip_status = "success"
                zip_error = None
                local_zip = None
                try:
                    t0 = time.monotonic()
                    local_zip = sftp_module.download(cfg.sftp, remote_zip, str(work_dir / "downloads"))
                    log.info("Download done in %.1fs (%.1f MB)", time.monotonic() - t0, local_zip.stat().st_size / 1_048_576)

                    t1 = time.monotonic()
                    books = extractor.extract(local_zip, work_dir / "extracted")
                    log.info("Extract done in %.1fs — %d book(s)", time.monotonic() - t1, len(books))

                    books_errored_this_zip = 0
                    for book in books:
                        t2 = time.monotonic()
                        status = client.upload(book, zip_source=remote_zip.remote_path)
                        log.info("Upload '%s' → %s (%.1fs)", book.name, status, time.monotonic() - t2)
                        if status == "uploaded":
                            counters["books_uploaded"] += 1
                        elif status == "skipped_duplicate":
                            counters["books_skipped"] += 1
                        else:
                            counters["books_errored"] += 1
                            books_errored_this_zip += 1

                    if books_errored_this_zip:
                        zip_status = "error"
                        zip_error = f"{books_errored_this_zip} book upload(s) failed — will retry next sync"

                    extractor.cleanup(work_dir / "extracted" / local_zip.stem)
                except Exception as e:
                    log.error("Error processing %s: %s", remote_zip.remote_path, e)
                    zip_status = "error"
                    zip_error = str(e)
                finally:
                    if local_zip and local_zip.exists():
                        extractor.cleanup(local_zip)
                    db.mark_zip_processed(remote_zip.remote_path, remote_zip.file_size, zip_status, zip_error)

            log.info("Batch %d/%d done", batch_num, total_batches)

        db.finish_sync_run(run_id, status="success", **counters)
        log.info(
            "Sync complete. Total zips: %d, Uploaded: %d, Skipped: %d, Errors: %d",
            counters["zips_new"], counters["books_uploaded"],
            counters["books_skipped"], counters["books_errored"],
        )
    except Exception as e:
        log.exception("Sync run failed: %s", e)
        db.finish_sync_run(run_id, status="error", error_msg=str(e), **counters)
    finally:
        _running = False
        _lock.release()


def _validate_config(cfg) -> None:
    missing = []
    if not cfg.sftp.host:
        missing.append("SFTP host")
    if not cfg.sftp.user:
        missing.append("SFTP user")
    if not cfg.sftp.remote_path:
        missing.append("SFTP remote path")
    if cfg.sftp.auth_method == "key" and not cfg.sftp.key:
        missing.append("SSH private key")
    if cfg.sftp.auth_method == "password" and not cfg.sftp.password:
        missing.append("SSH password")
    if not cfg.calibre.url:
        missing.append("Calibre-Web URL")
    if not cfg.calibre.user:
        missing.append("Calibre-Web username")
    if missing:
        raise ValueError(f"Missing configuration: {', '.join(missing)}")