#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""SQLite wrapper with retry logic and WAL mode."""

import time
import random
import sys
import sqlite3


class mysqlite(object):
    """SQLite connection wrapper with automatic retry on lock."""

    def __init__(self, database, factory=None):
        self.handle = sqlite3.connect(database)
        if factory is not None:
            self.handle.text_factory = factory
        self.cursor = self.handle.cursor()
        self.dbname = database
        # Enable WAL mode for better concurrency
        self.cursor.execute('PRAGMA journal_mode=WAL')
        self.cursor.execute('PRAGMA synchronous=NORMAL')

    def _try_op(self, op, query, args=None, rmin=1.5, rmax=7.0):
        """Execute operation with retry on database lock."""
        while True:
            try:
                if query is None:
                    return op()
                elif args is None:
                    return op(query)
                else:
                    return op(query, args)
            except sqlite3.OperationalError as e:
                err_msg = str(e)
                if 'database is locked' in err_msg:
                    sys.stderr.write('zzZzzZZ: db is locked (%s)\n' % self.dbname)
                    time.sleep(random.uniform(rmin, rmax))
                    continue
                else:
                    sys.stderr.write('%s\nquery: %s\nargs: %s\n' % (
                        str(sys.exc_info()), str(query), str(args)))
                    raise

    def execute(self, query, args=None, rmin=1.5, rmax=7.0):
        """Execute a single query with retry."""
        return self._try_op(self.cursor.execute, query, args, rmin, rmax)

    def executemany(self, query, args, rmin=1.5, rmax=7.0):
        """Execute query for multiple argument sets, batched."""
        while args:
            batch = args[:500]
            self._try_op(self.cursor.executemany, query, batch, rmin, rmax)
            args = args[500:]

    def commit(self, rmin=1.5, rmax=7.0):
        """Commit transaction with retry."""
        return self._try_op(self.handle.commit, None, None, rmin, rmax)

    def close(self):
        """Close database connection."""
        self.handle.close()