import ISC
import pickle
import signal
    
class ConfigData:
    def __init__(self):
        self.zones = {}

    def add_zone(self, zone_name, zone_file):
        self.zones[zone_name] = zone_file

    def remove_zone(self, zone_name):
        del self.zones[zone_name]

class ConfigManager:
    def __init__(self):
        self.cc = ISC.CC.Session()
        self.cc.group_subscribe("ConfigManager")
        self.cc.group_subscribe("Boss", "ConfigManager")
        self.config = ConfigData()
        self.db_filename = "/tmp/parkinglot.db"
        self.running = False

    def notify_boss(self):
        self.cc.group_sendmsg({"running": "configmanager"}, "Boss")

    def add_zone(self, zone_name):
        self.config.add_zone(zone_name, "todo")
        self.write_config()
        print("sending update zone add")
        self.cc.group_sendmsg({"zone_added": zone_name }, "ParkingLot")

    def remove_zone(self, zone_name):
        self.config.remove_zone(zone_name)
        print("sending update zone del")
        self.cc.group_sendmsg({"zone_deleted": zone_name }, "ParkingLot")

    def read_config(self):
        print("Reading config")
        try:
            file = open(self.db_filename, 'rb');
            self.config = pickle.load(file)
            file.close()
        except IOError as ioe:
            print("No config file found, starting with empty config")
        except EOFError as eofe:
            print("Config file empty, starting with empty config")

    def write_config(self):
        print("Writing config")
        try:
            file = open(self.db_filename, 'wb');
            pickle.dump(self.config, file)
            file.close()
        except IOError as ioe:
            print("Unable to write config file; configuration not stored")

    def handle_msg(self, msg):
        """return answer message"""
        answer = {}
        if "command" in msg:
            cmd = msg["command"]
            try:
                if cmd[0] == "zone" and cmd[1] == "add":
                    self.add_zone(cmd[2])
                    answer["result"] = [ 0 ]
                elif cmd[0] == "zone" and cmd[1] == "remove":
                    try:
                        self.remove_zone(cmd[2])
                        answer["result"] = [ 0 ]
                    except KeyError:
                        # zone wasn't there, should we make
                        # a separate exception for that?
                        answer["result"] = [ 1, "Unknown zone" ]
                elif cmd[0] == "zone" and cmd[1] == "list":
                    answer["result"]     = list(self.config.zones.keys())
                elif cmd == "shutdown":
                    print("[bind-cfgd] Received shutdown command")
                    self.running = False
                else:
                    print("[bind-cfgd] unknown command: " + str(cmd))
                    answer["result"] = [ 1, "Unknown command: " + str(cmd) ]
            except IndexError as ie:
                print("[bind-cfgd] missing argument")
                answer["result"] = [ 1, "Missing argument in command" ]
        else:
            print("[bind-cfgd] unknown message: " + str(msg))
            answer["result"] = [ 1, "Unknown module: " + str(msg) ]
        return answer
        
    def run(self):
        self.running = True
        while (self.running):
            msg, env = self.cc.group_recvmsg(False)
            if msg:
                print("[bind-cfgd] received message: ")
                print(msg)
                answer = self.handle_msg(msg);
                print("[bind-cfgd] sending answer: ")
                print(answer)
                self.cc.group_reply(env, answer)
                print("[bind-cfgd] answer sent")
            else:
                self.running = False

cm = None

def signal_handler(signal, frame):
    global cm
    if cm:
        cm.running = False

if __name__ == "__main__":
    try:
        cm = ConfigManager()
        signal.signal(signal.SIGINT, signal_handler)
        signal.signal(signal.SIGTERM, signal_handler)
        cm.read_config()
        # do loading here if necessary
        cm.notify_boss()
        cm.run()
        cm.write_config()
    except ISC.CC.SessionError as se:
        print("[bind-cfgd] Error creating config manager, "
              "is the command channel daemon running?")
    except KeyboardInterrupt as kie:
        print("Got ctrl-c, save config and exit")
        cm.write_config()