import logging
import os

from typing import Union, List

from groove import db
from groove.editor import PlaylistEditor, EDITOR_TEMPLATE
from groove.exceptions import PlaylistImportError

from slugify import slugify
from sqlalchemy import func, delete
from sqlalchemy.orm.session import Session
from sqlalchemy.engine.row import Row
from sqlalchemy.exc import NoResultFound, MultipleResultsFound


class Playlist:
    """
    CRUD operations and convenience methods for playlists.
    """
    def __init__(self,
                 slug: str,
                 session: Session,
                 name: str = '',
                 description: str = '',
                 create_ok=True):
        self._session = session
        self._slug = slug
        self._name = name
        self._description = description
        self._entries = None
        self._record = None
        self._create_ok = create_ok
        self._deleted = False
        self._editor = PlaylistEditor()

    @property
    def deleted(self) -> bool:
        return self._deleted

    @property
    def exists(self) -> bool:
        if self.deleted:
            logging.debug("Playlist has been deleted.")
            return False
        if not self._record:
            if self._create_ok:
                return True and self.record
            return False
        return True

    @property
    def editor(self):
        return self._editor

    @property
    def name(self):
        return self._name

    @property
    def description(self):
        return self._description

    @property
    def summary(self):
        return ' :: '.join([
            f"[ {self.record.id} ]",
            self.record.name,
            f"http://{os.environ['HOST']}/{self.slug}",
        ])

    @property
    def slug(self) -> str:
        return self._slug

    @property
    def session(self) -> Session:
        return self._session

    @property
    def record(self) -> Union[Row, None]:
        """
        Cache the playlist row from the database and return it. Optionally create it if it doesn't exist.
        """
        if not self._record:
            self._record = self.get_or_create()
        return self._record

    @property
    def entries(self) -> Union[List, None]:
        """
        Cache the list of entries on this playlist and return it.
        """
        if self.record and not self._entries:
            query = self.session.query(
                db.entry,
                db.track
            ).filter(
                (db.playlist.c.id == self.record.id)
            ).filter(
                db.entry.c.playlist_id == db.playlist.c.id
            ).filter(
                db.entry.c.track_id == db.track.c.id
            ).order_by(
                db.entry.c.track
            )
            self._entries = query.all()
        return self._entries

    @property
    def as_dict(self) -> dict:
        """
        Return a dictionary of the playlist and its entries.
        """
        if not self.exists:
            return {}
        playlist = dict(self.record)
        playlist['entries'] = [dict(entry) for entry in self.entries]
        return playlist

    @property
    def as_string(self) -> str:
        if not self.exists:
            return ''
        text = f"{self.summary}\n"
        for entry in self.entries:
            text += f"  - {entry.track}  {entry.artist} - {entry.title}\n"
        return text

    @property
    def as_yaml(self) -> str:
        template_vars = self.as_dict
        template_vars['entries'] = ''
        for entry in self.entries:
            template_vars['entries'] += f"  - {entry.artist} - {entry.title}\n"
        return EDITOR_TEMPLATE.format(**template_vars)

    def _get_tracks_by_path(self, paths: List[str]) -> List:
        """
        Retrieve tracks from the database that match the specified path fragments. The exceptions NoResultFound and
        MultipleResultsFound are expected in the case of no matches and multiple matches, respectively.
        """
        return [self.session.query(db.track).filter(db.track.c.relpath.ilike(f"%{path}%")).one() for path in paths]

    def edit(self):
        edits = self.editor.edit(self)
        if not edits:
            return
        new = Playlist.from_yaml(edits, self.session)
        if new == self:
            logging.debug("No changes detected.")
            return
        logging.debug(f"Updating {self.slug} with new edits.")
        self._slug = new.slug
        self._name = new.name.strip()
        self._description = new.description.strip()
        self._record = self.save()

    def add(self, paths: List[str]) -> int:
        """
        Add entries to the playlist.  Each path should match one and only one track in the database (case-insensitive).
        If a path doesn't match any track, or if a path matches multiple tracks, nothing is added to the playlist.

        Args:
            paths (list): A list of partial paths to add.

        Returns:
            int: The number of tracks added.
        """
        logging.debug(f"Attempting to add tracks matching: {paths}")
        try:
            return self.create_entries(self._get_tracks_by_path(paths))
        except NoResultFound:
            logging.error("One or more of the specified paths do not match any tracks in the database.")
            return 0
        except MultipleResultsFound:
            logging.error("One or more of the specified paths matches multiple tracks in the database.")
            return 0

    def delete(self) -> Union[int, None]:
        """
        Delete a playlist and its entries from the database, then clear the cached values.
        """
        if not self.record:
            return None
        plid = self.record.id
        stmt = delete(db.entry).where(db.entry.c.playlist_id == plid)
        logging.debug(f"Deleting entries associated with playlist {plid}: {stmt}")
        self.session.execute(stmt)
        stmt = delete(db.playlist).where(db.playlist.c.id == plid)
        logging.debug(f"Deleting playlist {plid}: {stmt}")
        self.session.execute(stmt)
        self.session.commit()
        self._record = None
        self._entries = None
        self._deleted = True
        return plid

    def get_or_create(self, create_ok: bool = False) -> Row:
        try:
            return self._get()
        except NoResultFound:
            logging.debug(f"Could not find a playlist with slug {self.slug}.")
        if self.deleted:
            raise RuntimeError("Object has been deleted.")
        if self._create_ok or create_ok:
            return self.save()

    def _get(self):
        return self.session.query(db.playlist).filter(
            db.playlist.c.slug == self.slug
        ).one()

    def _insert(self, values):
        stmt = db.playlist.insert(values)
        results = self.session.execute(stmt)
        self.session.commit()
        logging.debug(f"Saved playlist with slug {self.slug}")
        return self.session.query(db.playlist).filter(
            db.playlist.c.id == results.inserted_primary_key[0]
        ).one()

    def _update(self, values):
        stmt = db.playlist.update().where(
            db.playlist.c.id == self._record.id
        ).values(values)
        self.session.execute(stmt)
        self.session.commit()
        return self.session.query(db.playlist).filter(
            db.playlist.c.id == self._record.id
        ).one()

    def save(self) -> Row:
        values = {
            'slug': self.slug,
            'name': self.name,
            'description': self.description
        }
        logging.debug(f"Saving values: {values}")
        obj = self._update(values) if self._record else self._insert(values)
        logging.debug(f"Saved playlist {obj.id} with slug {obj.slug}")
        return obj

    def load(self):
        self.get_or_create(create_ok=False)
        return self

    def create_entries(self, tracks: List[Row]) -> int:
        """
        Append a list of tracks to a playlist by populating the entries table with records referencing the playlist and
        the specified tracks.

        Args:
            tracks (list): A list of Row objects from the track table.

        Returns:
            int: The number of tracks added.
        """
        maxtrack = self.session.query(func.max(db.entry.c.track)).filter_by(
            playlist_id=self.record.id
        ).one()[0] or 0

        self.session.execute(
            db.entry.insert(),
            [
                {'playlist_id': self.record.id, 'track_id': obj.id, 'track': idx}
                for (idx, obj) in enumerate(tracks, start=maxtrack+1)
            ]
        )
        self.session.commit()
        self._entries = None
        return len(tracks)

    @classmethod
    def from_row(cls, row, session):
        pl = Playlist(slug=row.slug, session=session)
        pl._record = row
        return pl

    @classmethod
    def from_yaml(cls, source, session):
        try:
            name = list(source.keys())[0].strip()
            description = (source[name]['description'] or '').strip()
            return Playlist(
                slug=slugify(name),
                name=name,
                description=description,
                session=session,
            )
        except (IndexError, KeyError):
            PlaylistImportError("The specified source was not a valid playlist.")

    def __eq__(self, obj):
        for key in ('slug', 'name', 'description'):
            if getattr(obj, key) != getattr(self, key):
                logging.debug(f"{key}: {getattr(obj, key)} != {getattr(self, key)}")
                return False
        return True

    def __repr__(self):
        return self.as_string