"""Inventory implementation using sqlite"""

import logging
import os
import sqlite3
import threading
import time

from . import shared, structure

sqlite3.threadsafety = 3


class Inventory():
    """sqlite inventory"""
    def __init__(self):
        self._lock = threading.Lock()
        self._deleted = 0
        self._pending = set()
        self._db = sqlite3.connect(
            os.path.join(shared.data_directory, 'objects.dat'),
            check_same_thread=False
        )
        self._db.executescript("""
        BEGIN;
        CREATE TABLE IF NOT EXISTS status
        (key text, value integer, UNIQUE(key) ON CONFLICT REPLACE);
        INSERT INTO status VALUES ('version', 1);
        CREATE TABLE IF NOT EXISTS objects
        (vector unique, expires integer, type integer, version integer,
        stream integer, tag, data, offset integer);
        COMMIT;
        """)
        self.rowid = len(self) or None
        cur = self._db.cursor()
        cur.execute("SELECT value FROM status WHERE key='lastvacuumtime'")
        now = int(time.time())
        try:
            vacuumed = cur.fetchone()[0]
        except TypeError:
            pass
        else:
            if vacuumed < now - 86400:  # 24 hours
                cur.execute('VACUUM')
        cur.execute("INSERT INTO status VALUES ('lastvacuumtime', ?)", (now,))
        self._db.commit()
        self._db.row_factory = self.__object

    @staticmethod
    def __object(cursor, row):
        if len(cursor.description) != 8:
            return row
        vector, expires, obj_type, version, stream, tag, data, offset = row
        return structure.Object(
            expires, obj_type, version, stream, data, offset,
            tag=tag, vector=vector)

    def cleanup(self):
        if len(self._pending) > 100:
            logging.warning(
                'Not cleaning up, %s objects pending', len(self._pending))
            return
        with self._lock:
            cur = self._db.execute(
                'DELETE FROM objects WHERE expires < ?',
                (int(time.time()) - 3 * 3600,)
            )
            self._db.commit()
            self._deleted += cur.rowcount
            # conditional vacuum and validity check
            if self._deleted > 10000:
                logging.info('Doing VACUUM for objects')
                cur.execute('VACUUM')
                cur.execute(
                    "INSERT INTO status VALUES ('lastvacuumtime', ?)",
                    (int(time.time()),))
                self._db.commit()
                self._deleted = 0
        logging.info(
            'Deleted %s expired objects, %s pending',
            cur.rowcount, len(self._pending))

    def filter(self, stream=None, object_type=None, tag=None):
        clauses = []
        if stream:
            clauses.append(('stream = ?', stream))
        if object_type:
            clauses.append(('type = ?', object_type))
        if tag:
            clauses.append(('tag = ?', tag))

        clauses, params = zip(*clauses)

        cur = self._db.execute(
            'SELECT * FROM objects WHERE ' + ' AND '.join(clauses), params)
        return cur

    def select(self, vectors):
        chunk_size = 999
        keys = tuple(vectors)
        with self._lock:
            for i in range(0, len(vectors), chunk_size):
                chunk = keys[i:i+chunk_size]
                cur = self._db.execute(
                    'SELECT vector FROM objects WHERE vector IN ({})'.format(
                        ','.join('?' * len(chunk))), chunk)
                for v, in cur:
                    vectors.remove(v)
        self._pending.update(vectors)
        return vectors

    def vectors_to_send(self, stream=None):
        cur = self._db.execute(
            'SELECT vector FROM objects WHERE expires > ? AND stream = ?'
            ' ORDER BY random()',
            (int(time.time()), stream or shared.stream)
        )
        return [v for v, in cur]

    def get(self, vector, default=None):
        try:
            return self[vector]
        except KeyError:
            return default

    def keys(self):
        cur = self._db.execute('SELECT vector FROM objects')
        return (v for v, in cur)

    def values(self):
        return self._db.execute('SELECT * FROM objects')

    def popitem(self):
        if not self.rowid:
            raise KeyError('empty')
        cur = self._db.execute(
            'SELECT vector FROM objects WHERE ROWID = ?', (self.rowid,))
        vector = cur.fetchone()[0]
        obj = self.get(vector)
        del self[vector]
        return (vector, obj)

    def __contains__(self, vector):
        cur = self._db.execute(
            'SELECT vector FROM objects WHERE vector = ?', (vector,))
        return cur.fetchone()

    def __getitem__(self, vector):
        cur = self._db.execute(
            'SELECT * FROM objects WHERE vector = ?', (vector,))
        cur.row_factory = self.__object
        item = cur.fetchone()
        if item is None:
            raise KeyError(vector)
        return item

    def __delitem__(self, vector):
        with self._lock:  # KeyError
            self._db.execute(
                'DELETE FROM objects WHERE vector = ?', (vector,))
            self._db.commit()
            self.rowid = len(self)

    def __setitem__(self, vector, obj):
        with self._lock:
            try:
                cur = self._db.execute(
                    'INSERT INTO objects VALUES (?,?,?,?,?,?,?,?)', (
                        vector, obj.expires_time, obj.object_type, obj.version,
                        obj.stream_number, obj.tag, obj.data, obj.offset
                    ))
            except (sqlite3.DatabaseError, sqlite3.IntegrityError):
                return
            self._db.commit()
            self.rowid = cur.lastrowid
        self._pending.discard(vector)

    def __bool__(self):
        return self._db.execute(
            'SELECT vector from objects LIMIT 1').fetchone() is not None

    def __len__(self):
        cur = self._db.execute('SELECT count(*) FROM objects')
        return cur.fetchone()[0]

    def __del__(self):
        self._db.close()