import threading

import time

import MySQLdb

class Pool:

  def __init__(self, server):

    self.server = server

    self.condition = threading.Condition(threading.Lock())

    self.size  = {

      False: self.server.config['db']['pool']['write'],

      True:  self.server.config['db']['pool']['read'] }

    self.busy  = { False: [], True: [] }

    self.ready = { False: [], True: [] }

  def asquire(self, readonly):

    type_name = "read" if readonly else "write"

    count = 0

    with self.condition:

      while True:

        count = len(self.ready[readonly]) + len(self.busy[readonly])

        if len(self.ready[readonly]) > 0:

          connection = self.ready[readonly][0];

          del self.ready[readonly][0]

          try:

            with connection.cursor() as cursor:

              cursor.execute("SELECT 1")

          except Exception:

            print("close broken %s db connection (count: %s)" % (type_name, count - 1))

            try: connection.close()

            except Exception: pass

            continue

          self.busy[readonly].append(connection)

          return connection

        elif len(self.busy[readonly]) + len(self.ready[readonly]) < self.size[readonly]:

          self.busy[readonly].append(None)

          break

        else:

          self.condition.wait()

    print("open new %s db connection (count: %s)" % (type_name, count + 1))

    connection = None

    for _ in range(1, 10):

      try:

        connection = MySQLdb.connect(**self.server.config['db']['connection'])

      except Exception:

        time.sleep(self.server.config['db']['retrytime'])

    if not connection:

      connection = MySQLdb.connect(**self.server.config['db']['connection'])

    with self.condition:

      self.busy[readonly].remove(None)

      self.busy[readonly].append(connection)

    return connection

  def release(self, connection, readonly):

    with self.condition:

      self.busy[readonly].remove(connection)

      if len(self.busy[readonly]) + len(self.ready[readonly]) < self.size[readonly]:

        connection.rollback()

        self.ready[readonly].append(connection)

        self.condition.notify()

      else:

        type_name = "read" if readonly else "write"

        count = len(self.ready[readonly]) + len(self.busy[readonly])

        print("close extra %s database connection (count: %s)" % (type_name, count - 1))

        try: connection.close()

        except Exception: pass