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