"""
SerieScanner - Scans directories for anime series and missing episodes.

This module provides functionality to scan anime directories, identify
missing episodes, and report progress through callback interfaces.

Note:
    This module is pure domain logic. Database operations are handled
    by the service layer (AnimeService).
"""
from __future__ import annotations

import asyncio
import logging
import os
import re
import traceback
import uuid
from typing import Callable, Iterable, Iterator, Optional

from events import Events

from src.config.settings import settings
from src.server.database.models import AnimeSeries
from src.server.exceptions.exceptions.Exceptions import MatchNotFoundError
from src.server.providers.base_provider import Loader
from src.server.database.connection import get_sync_session
from src.server.database.service import AnimeSeriesService, EpisodeService

logger = logging.getLogger(__name__)
error_logger = logging.getLogger("error")
no_key_found_logger = logging.getLogger("series.nokey")


class SerieScanner:
    """
    Scans directories for anime series and identifies missing episodes.

    Supports progress callbacks for real-time scanning updates.
    
    Note:
        This class is pure domain logic. Database operations are handled
        by the service layer (AnimeService). Scan results are stored
        in keyDict and can be retrieved after scanning.
    
    Example:
        # Synchronous context (CLI):
        scanner = SerieScanner("/path/to/anime", loader)
        scanner.scan()  # asyncio.run() used internally when no event loop

        # Asynchronous context (server/scheduler):
        # scan() detects running event loop and uses create_task()
        # internally, so no special handling needed by caller.
        # Results are in scanner.keyDict
    """

    def __init__(
        self,
        basePath: str,
        loader: Loader,
    ) -> None:
        """
        Initialize the SerieScanner.

        Args:
            basePath: Base directory containing anime series
            loader: Loader instance for fetching series information

        Raises:
            ValueError: If basePath is invalid or doesn't exist
        """
        # Validate basePath to prevent directory traversal attacks
        if not basePath or not basePath.strip():
            raise ValueError("Base path cannot be empty")
        
        # Resolve to absolute path and validate it exists
        abs_path = os.path.abspath(basePath)
        if not os.path.exists(abs_path):
            raise ValueError(f"Base path does not exist: {abs_path}")
        if not os.path.isdir(abs_path):
            raise ValueError(f"Base path is not a directory: {abs_path}")
        
        self.directory: str = abs_path
        self.keyDict: dict[str, AnimeSeries] = {}
        self.loader: Loader = loader
        self._current_operation_id: Optional[str] = None
        self.events = Events()
        
        self.events.on_progress = []
        self.events.on_error = []
        self.events.on_warning = []
        self.events.on_completion = []

        logger.info("Initialized SerieScanner with base path: %s", abs_path)
    
    def _safe_call_event(self, event_handler, data: dict) -> None:
        """Safely call an event handler if it exists.
        
        Args:
            event_handler: Event handler attribute (e.g., self.events.on_progress)
            data: Data dictionary to pass to the event handler
        """
        if event_handler:
            try:
                # Event handlers are stored as lists, iterate over them
                for handler in event_handler:
                    handler(data)
            except Exception as e:
                logger.error("Error calling event handler: %s", e, exc_info=True)

    def subscribe_on_progress(self, handler):
        """
        Subscribe a handler to an event.
        Args:
            handler: Callable to handle the event
        """
        if handler not in self.events.on_progress:
            self.events.on_progress.append(handler)

    def unsubscribe_on_progress(self, handler):
        """
        Unsubscribe a handler from an event.
        Args:
            handler: Callable to remove
        """
        if handler in self.events.on_progress:
            self.events.on_progress.remove(handler)
        
    def _extract_year_from_folder_name(self, folder_name: str) -> int | None:
        """Extract year from folder name if present.
        
        Looks for year in format "(YYYY)" at the end of folder name.
        
        Args:
            folder_name: The folder name to check
            
        Returns:
            int or None: Year if found, None otherwise
            
        Example:
            >>> _extract_year_from_folder_name("Dororo (2025)")
            2025
            >>> _extract_year_from_folder_name("Dororo")
            None
        """
        if not folder_name:
            return None
        
        # Look for year in format (YYYY) - typically at end of name
        match = re.search(r'\((\d{4})\)', folder_name)
        if match:
            try:
                year = int(match.group(1))
                # Validate year is reasonable (between 1900 and 2100)
                if 1900 <= year <= 2100:
                    logger.debug(
                        "Extracted year from folder name: %s -> %d",
                        folder_name,
                        year
                    )
                    return year
            except ValueError:
                pass
        
        return None
    
    def subscribe_on_error(self, handler):
        """
        Subscribe a handler to an event.
        Args:
            handler: Callable to handle the event
        """
        if handler not in self.events.on_error:
            self.events.on_error.append(handler)

    def unsubscribe_on_error(self, handler):
        """
        Unsubscribe a handler from an event.
        Args:
            handler: Callable to remove
        """
        if handler in self.events.on_error:
            self.events.on_error.remove(handler)

    def subscribe_on_warning(self, handler):
        """
        Subscribe a handler to an event.
        Args:
            handler: Callable to handle the event
        """
        if handler not in self.events.on_warning:
            self.events.on_warning.append(handler)

    def unsubscribe_on_warning(self, handler):
        """
        Unsubscribe a handler from an event.
        Args:
            handler: Callable to remove
        """
        if handler in self.events.on_warning:
            self.events.on_warning.remove(handler)

    def subscribe_on_completion(self, handler):
        """
        Subscribe a handler to an event.
        Args:
            handler: Callable to handle the event
        """
        if handler not in self.events.on_completion:
            self.events.on_completion.append(handler)

    def unsubscribe_on_completion(self, handler):
        """
        Unsubscribe a handler from an event.
        Args:
            handler: Callable to remove
        """
        if handler in self.events.on_completion:
            self.events.on_completion.remove(handler)
        
    def reinit(self) -> None:
        """Reinitialize the series dictionary (keyed by anime.key)."""
        self.keyDict: dict[str, AnimeSeries] = {}

    async def _persist_serie_to_db(self, anime: AnimeSeries) -> None:
        """Persist anime to database (create or update).

        Args:
            anime: AnimeSeries model to persist
        """
        try:
            from src.server.database.connection import get_async_session_factory

            db = get_async_session_factory()
            try:
                existing = await AnimeSeriesService.get_by_key(db, anime.key)
                if existing:
                    await AnimeSeriesService.update(
                        db, existing.id,
                        name=anime.name,
                        folder=anime.folder,
                        year=anime.year
                    )
                    await self._sync_episodes_to_db(db, existing.id, anime.episodeDict)
                else:
                    db_anime = await AnimeSeriesService.create(
                        db=db,
                        key=anime.key,
                        name=anime.name,
                        site=anime.site,
                        folder=anime.folder,
                        year=anime.year
                    )
                    for ep in anime.episodes:
                        await EpisodeService.create(
                            db=db,
                            series_id=db_anime.id,
                            season=ep.season,
                            episode_number=ep.episode_number
                        )
                await db.commit()
                logger.debug(
                    "Persisted anime '%s' (key=%s) to database",
                    anime.name, anime.key
                )
            except Exception as e:
                await db.rollback()
                logger.error(
                    "Failed to persist anime '%s' to DB: %s",
                    anime.key, e, exc_info=True
                )
                raise
            finally:
                await db.close()
        except Exception as e:
            logger.error(
                "Could not persist anime '%s' to DB (DB unavailable?): %s",
                anime.key, e
            )

    async def _sync_episodes_to_db(
        self, db, series_id: int, episode_dict: dict[int, list[int]]
    ) -> None:
        """Sync episodes to database, preserving downloaded flags.

        Adds missing episodes, removes episodes no longer missing,
        and preserves is_downloaded=True episodes.

        Args:
            db: Async database session
            series_id: Database ID of the series
            episode_dict: Dict mapping season -> list of episode numbers
        """
        existing_episodes = await EpisodeService.get_by_series(db, series_id)
        existing_map = {
            (ep.season, ep.episode_number): ep for ep in existing_episodes
        }
        new_keys = set()
        for season, eps in episode_dict.items():
            for ep_num in eps:
                new_keys.add((season, ep_num))
        for (season, ep_num), ep in existing_map.items():
            if (season, ep_num) not in new_keys:
                if ep.is_downloaded:
                    logger.debug(
                        "Preserving downloaded episode S%02dE%02d for series_id=%d",
                        season, ep_num, series_id
                    )
                else:
                    await EpisodeService.delete_by_series(
                        db, series_id, season, ep_num
                    )
        for season, eps in episode_dict.items():
            for ep_num in eps:
                if (season, ep_num) not in existing_map:
                    await EpisodeService.create(
                        db=db,
                        series_id=series_id,
                        season=season,
                        episode_number=ep_num
                    )

    def get_total_to_scan(self) -> int:
        """Get the total number of folders to scan.
        
        Returns:
            Total count of folders with MP4 files
        """
        result = self.__find_mp4_files()
        return sum(1 for _ in result)

    def scan(self) -> None:
        """
        Scan directories for anime series and missing episodes.

        Results are stored in self.keyDict and can be retrieved after
        scanning. Data files are also saved to disk for persistence.

        Raises:
            Exception: If scan fails critically
        """
        # Generate unique operation ID
        self._current_operation_id = str(uuid.uuid4())

        logger.info("Starting scan for missing episodes")

        # Notify scan starting
        self._safe_call_event(
            self.events.on_progress,
            {
                "operation_id": self._current_operation_id,
                "phase": "STARTING",
                "current": 0,
                "total": 0,
                "percentage": 0.0,
                "message": "Initializing scan"
            }
        )

        try:
            # Get total items to process
            total_to_scan = self.get_total_to_scan()
            logger.info("Total folders to scan: %d", total_to_scan)

            # The scanner enumerates folders with mp4 files, loads existing
            # metadata, calculates the missing episodes via the provider, and
            # persists the refreshed metadata while emitting progress events.
            result = self.__find_mp4_files()
            counter = 0

            for folder, mp4_files in result:
                try:
                    counter += 1

                    # Calculate progress
                    if total_to_scan > 0:
                        percentage = (counter / total_to_scan) * 100
                    else:
                        percentage = 0.0

                    # Notify progress
                    self._safe_call_event(
                        self.events.on_progress,
                        {
                            "operation_id": self._current_operation_id,
                            "phase": "IN_PROGRESS",
                            "current": counter,
                            "total": total_to_scan,
                            "percentage": percentage,
                            "message": f"Scanning: {folder}",
                            "details": f"Found {len(mp4_files)} episodes"
                        }
                    )

                    serie = self.__read_data_from_file(folder)
                    if serie is None or not serie.key or not serie.key.strip():
                        logger.warning(
                            "No series found in DB for folder '%s', skipping",
                            folder,
                        )
                        continue
                    if (
                        serie is not None
                        and serie.key
                        and serie.key.strip()
                    ):
                        # Delegate the provider to compare local files with
                        # remote metadata, yielding missing episodes per
                        # season. Results are saved back to disk so that both
                        # CLI and API consumers see consistent state.
                        missing_episodes, _site = (
                            self.__get_missing_episodes_and_season(
                                serie.key, mp4_files
                            )
                        )
                        serie.episodeDict = missing_episodes
                        serie.folder = folder

                        # Persist to database (async)
                        try:
                            try:
                                loop = asyncio.get_running_loop()
                            except RuntimeError:
                                # No running loop — safe to use asyncio.run()
                                asyncio.run(self._persist_serie_to_db(serie))
                            else:
                                # Already in async context — schedule as task
                                asyncio.create_task(self._persist_serie_to_db(serie))
                        except Exception as e:
                            logger.warning(
                                "DB persistence failed for '%s', "
                                "continuing without DB: %s",
                                serie.key, e
                            )

                        # Store by key (primary identifier), not folder
                        if serie.key in self.keyDict:
                            existing = self.keyDict[serie.key]
                            logger.warning(
                                "Duplicate series found with key '%s': "
                                "folder '%s' maps to same key as existing folder '%s'. "
                                "Skipping duplicate folder.",
                                serie.key,
                                folder,
                                existing.folder
                            )
                            self._safe_call_event(
                                self.events.on_warning,
                                {
                                    "operation_id": self._current_operation_id,
                                    "warning": "duplicate_key",
                                    "message": f"Duplicate series skipped: '{folder}' maps to key '{serie.key}' already used by '{existing.folder}'",
                                    "metadata": {
                                        "key": serie.key,
                                        "duplicate_folder": folder,
                                        "existing_folder": existing.folder,
                                    }
                                }
                            )
                        else:
                            self.keyDict[serie.key] = serie
                            logger.debug(
                                "Stored series with key '%s' (folder: '%s')",
                                serie.key,
                                folder
                            )
                            no_key_found_logger.info(
                                "Saved Serie: '%s'", str(serie)
                            )

                except Exception as e:
                    # Log error and notify via callback
                    error_msg = (
                        f"Folder: '{folder}' - "
                        f"Unexpected error: {e}"
                    )
                    error_logger.error(
                        "%s\n%s",
                        error_msg,
                        traceback.format_exc()
                    )

                    self._safe_call_event(
                        self.events.on_error,
                        {
                            "operation_id": self._current_operation_id,
                            "error": e,
                            "message": error_msg,
                            "recoverable": True,
                            "metadata": {"folder": folder, "key": None}
                        }
                    )
                    continue

            # Notify scan completion
            self._safe_call_event(
                self.events.on_completion,
                {
                    "operation_id": self._current_operation_id,
                    "success": True,
                    "message": f"Scan completed. Processed {counter} folders.",
                    "statistics": {
                        "total_folders": counter,
                        "series_found": len(self.keyDict)
                    }
                }
            )

            logger.info(
                "Scan completed. Processed %d folders, found %d series",
                counter,
                len(self.keyDict)
            )

        except Exception as e:
            # Critical error - notify and re-raise
            error_msg = f"Critical scan error: {e}"
            logger.error("%s\n%s", error_msg, traceback.format_exc())

            self._safe_call_event(
                self.events.on_error,
                {
                    "operation_id": self._current_operation_id,
                    "error": e,
                    "message": error_msg,
                    "recoverable": False
                }
            )

            self._safe_call_event(
                self.events.on_completion,
                {
                    "operation_id": self._current_operation_id,
                    "success": False,
                    "message": error_msg
                }
            )

            raise

    def __find_mp4_files(self) -> Iterator[tuple[str, list[str]]]:
        """Find all .mp4 files in the directory structure."""
        logger.info("Scanning for .mp4 files")
        for anime_name in os.listdir(self.directory):
            anime_path = os.path.join(self.directory, anime_name)
            if os.path.isdir(anime_path):
                if settings.should_ignore_folder(anime_name):
                    logger.debug("Skipping ignored folder: %s", anime_name)
                    continue
                mp4_files: list[str] = []
                has_files = False
                for root, _, files in os.walk(anime_path):
                    for file in files:
                        if file.endswith(".mp4"):
                            mp4_files.append(os.path.join(root, file))
                            has_files = True
                yield anime_name, mp4_files if has_files else []

    def __read_data_from_file(self, folder_name: str) -> Optional[AnimeSeries]:
        """Load or discover an AnimeSeries for the given folder.

        Strategy:
        1. Query DB by folder name
        2. If not found in DB, return None (no file fallback)

        Args:
            folder_name: Filesystem folder name

        Returns:
            AnimeSeries object if found in DB, None otherwise
        """
        # Step 1: Try DB lookup by folder name
        try:
            session = get_sync_session()
            try:
                anime_series = AnimeSeriesService.get_by_folder_sync(session, folder_name)
                return anime_series
            finally:
                session.close()
        except Exception as exc:
            logger.warning(
                "DB lookup failed for folder '%s': %s",
                folder_name,
                exc
            )

        return None

    def __get_episode_and_season(self, filename: str) -> tuple[int, int]:
        """Extract season and episode numbers from filename.
        
        Args:
            filename: Filename to parse
            
        Returns:
            Tuple of (season, episode) as integers
            
        Raises:
            MatchNotFoundError: If pattern not found
        """
        pattern = r'S(\d+)E(\d+)'
        match = re.search(pattern, filename)
        if match:
            season = match.group(1)
            episode = match.group(2)
            logger.debug(
                "Extracted season %s, episode %s from '%s'",
                season,
                episode,
                filename
            )
            return int(season), int(episode)
        else:
            logger.error(
                "Failed to find season/episode pattern in '%s'",
                filename
            )
            raise MatchNotFoundError(
                "Season and episode pattern not found in the filename."
            )

    def __get_episodes_and_seasons(
        self,
        mp4_files: Iterable[str]
    ) -> dict[int, list[int]]:
        """Get episodes grouped by season from mp4 files.
        
        Args:
            mp4_files: List of MP4 filenames
            
        Returns:
            Dictionary mapping season to list of episode numbers
        """
        episodes_dict: dict[int, list[int]] = {}

        for file in mp4_files:
            season, episode = self.__get_episode_and_season(file)

            if season in episodes_dict:
                episodes_dict[season].append(episode)
            else:
                episodes_dict[season] = [episode]
        return episodes_dict

    def __get_missing_episodes_and_season(
        self,
        key: str,
        mp4_files: Iterable[str]
    ) -> tuple[dict[int, list[int]], str]:
        """Get missing episodes for a serie.
        
        Args:
            key: Series key
            mp4_files: List of MP4 filenames
            
        Returns:
            Tuple of (episodes_dict, site_name)
        """
        # key season , value count of episodes
        expected_dict = self.loader.get_season_episode_count(key)
        filedict = self.__get_episodes_and_seasons(mp4_files)
        episodes_dict: dict[int, list[int]] = {}
        for season, expected_count in expected_dict.items():
            existing_episodes = filedict.get(season, [])
            missing_episodes = [
                ep for ep in range(1, expected_count + 1)
                if ep not in existing_episodes
                and self.loader.is_language(season, ep, key)
            ]

            if missing_episodes:
                episodes_dict[season] = missing_episodes

        return episodes_dict, "aniworld.to"

    def scan_single_series(
        self,
        key: str,
        folder: str,
    ) -> dict[int, list[int]]:
        """
        Scan a single series for missing episodes.
        
        This method performs a targeted scan for only the specified series,
        without triggering a full library rescan. It fetches available
        episodes from the provider and compares with local files.
        
        Args:
            key: The unique provider key for the series
            folder: The filesystem folder name where the series is stored
            
        Returns:
            dict[int, list[int]]: Dictionary mapping season numbers to lists
                of missing episode numbers. Empty dict if no missing episodes.
                
        Raises:
            ValueError: If key or folder is empty
            
        Example:
            >>> scanner = SerieScanner("/path/to/anime", loader)
            >>> missing = scanner.scan_single_series(
            ...     "attack-on-titan",
            ...     "Attack on Titan"
            ... )
            >>> print(missing)
            {1: [5, 6, 7], 2: [1, 2]}
        """
        if not key or not key.strip():
            raise ValueError("Series key cannot be empty")
        if not folder or not folder.strip():
            raise ValueError("Series folder cannot be empty")
        
        logger.info(
            "Starting targeted scan for series: %s (folder: %s)",
            key,
            folder
        )
        
        # Generate unique operation ID for this targeted scan
        operation_id = str(uuid.uuid4())
        # Notify scan starting
        self._safe_call_event(
            self.events.on_progress,
            {
                "operation_id": operation_id,
                "phase": "STARTING",
                "current": 0,
                "total": 1,
                "percentage": 0.0,
                "message": f"Scanning series: {folder}",
                "details": f"Key: {key}"
            }
        )
        
        try:
            # Get the folder path
            folder_path = os.path.join(self.directory, folder)
            
            # Check if folder exists
            if not os.path.isdir(folder_path):
                logger.info(
                    "Series folder does not exist yet: %s - "
                    "will scan for available episodes from provider",
                    folder_path
                )
                mp4_files: list[str] = []
            else:
                # Find existing MP4 files in the folder
                mp4_files = []
                for root, _, files in os.walk(folder_path):
                    for file in files:
                        if file.endswith(".mp4"):
                            mp4_files.append(os.path.join(root, file))
                
                logger.debug(
                    "Found %d existing MP4 files in folder %s",
                    len(mp4_files),
                    folder
                )
            
            # Get missing episodes from provider
            missing_episodes, site = self.__get_missing_episodes_and_season(
                key, mp4_files
            )
            
            # Update progress
            self._safe_call_event(
                self.events.on_progress,
                {
                    "operation_id": operation_id,
                    "phase": "IN_PROGRESS",
                    "current": 1,
                    "total": 1,
                    "percentage": 100.0,
                    "message": f"Scanned: {folder}",
                    "details": f"Found {sum(len(eps) for eps in missing_episodes.values())} missing episodes"
                }
            )
            
            # Create or update AnimeSeries in keyDict
            if key in self.keyDict:
                # Update existing anime - rebuild episodeDict from episodes
                existing = self.keyDict[key]
                existing_ep_dict = existing.episodeDict
                # Merge missing episodes
                for season, eps in missing_episodes.items():
                    if season not in existing_ep_dict:
                        existing_ep_dict[season] = []
                    existing_ep_dict[season].extend(eps)
                logger.debug(
                    "Updated existing series %s with %d missing episodes",
                    key,
                    sum(len(eps) for eps in missing_episodes.values())
                )
            else:
                # Extract year from folder name if present, otherwise leave as None
                year = self._extract_year_from_folder_name(folder)

                # Create new AnimeSeries entry (minimal, fields populated later)
                from src.server.database.models import AnimeSeries
                anime_series = AnimeSeries(
                    key=key,
                    name=folder,  # Use folder as fallback name since we don't have actual name
                    site=site,
                    folder=folder,
                    year=year
                )
                # Set episodeDict cache directly since AnimeSeries doesn't persist missing episodes
                # (they get synced to DB via _persist_serie_to_db later)
                anime_series._episode_dict_cache = missing_episodes.copy()
                self.keyDict[key] = anime_series
                logger.debug(
                    "Created new series entry for %s with %d missing episodes (year=%s)",
                    key,
                    sum(len(eps) for eps in missing_episodes.values()),
                    year
                )
            
            # Notify completion
            self._safe_call_event(
                self.events.on_completion,
                {
                    "operation_id": operation_id,
                    "success": True,
                    "message": f"Scan completed for {folder}",
                    "statistics": {
                        "missing_episodes": sum(
                            len(eps) for eps in missing_episodes.values()
                        ),
                        "seasons_with_missing": len(missing_episodes)
                    }
                }
            )
            
            logger.info(
                "Targeted scan completed for %s: %d missing episodes across %d seasons",
                key,
                sum(len(eps) for eps in missing_episodes.values()),
                len(missing_episodes)
            )
            
            return missing_episodes
            
        except Exception as e:
            error_msg = f"Failed to scan series {key}: {e}"
            logger.error(error_msg, exc_info=True)
            
            # Notify error
            self._safe_call_event(
                self.events.on_error,
                {
                    "operation_id": operation_id,
                    "error": e,
                    "message": error_msg,
                    "recoverable": True,
                    "metadata": {"key": key, "folder": folder}
                }
            )
            # Notify completion with failure
            self._safe_call_event(
                self.events.on_completion,
                {
                    "operation_id": operation_id,
                    "success": False,
                    "message": error_msg
                }
            )
            # Return empty dict on error (scan failed but not critical)
            return {}