import os
from kafka import KafkaConsumer
from datetime import datetime
from collections import defaultdict

from msgcodec.codec import MessageCodec
from msgcodec.messages import SessionEnd
from db.api import DBConnection
from db.models import events_detailed_table_name, events_table_name, sessions_table_name, conf
from db.writer import insert_batch
from handler import handle_message, handle_normal_message, handle_session

DATABASE = os.environ['DATABASE_NAME']
LEVEL = conf[DATABASE]['level']

db = DBConnection(DATABASE)

if LEVEL == 'detailed':
    table_name = events_detailed_table_name
elif LEVEL == 'normal':
    table_name = events_table_name


def main():
    batch_size = 4000
    sessions_batch_size = 400
    batch = []
    sessions = defaultdict(lambda: None)
    sessions_batch = []

    codec = MessageCodec()
    consumer = KafkaConsumer(security_protocol="SSL",
                             bootstrap_servers=[os.environ['KAFKA_SERVER_1'],
                                                os.environ['KAFKA_SERVER_2']],
                             group_id=f"connector_{DATABASE}",
                             auto_offset_reset="earliest",
                             enable_auto_commit=False)

    consumer.subscribe(topics=["events", "messages"])
    print("Kafka consumer subscribed")
    for msg in consumer:
        message = codec.decode(msg.value)
        if message is None:
            print('-')
            continue

        if LEVEL == 'detailed':
            n = handle_message(message)
        elif LEVEL == 'normal':
            n = handle_normal_message(message)

        session_id = decode_key(msg.key)
        sessions[session_id] = handle_session(sessions[session_id], message)
        if sessions[session_id]:
            sessions[session_id].sessionid = session_id

        # put in a batch for insertion if received a SessionEnd
        if isinstance(message, SessionEnd):
            if sessions[session_id]:
                sessions_batch.append(sessions[session_id])

        # try to insert sessions
        if len(sessions_batch) >= sessions_batch_size:
            attempt_session_insert(sessions_batch)
            for s in sessions_batch:
                try:
                    del sessions[s.sessionid]
                except KeyError  as e:
                    print(repr(e))
            sessions_batch = []

        if n:
            n.sessionid = session_id
            n.received_at = int(datetime.now().timestamp() * 1000)
            n.batch_order_number = len(batch)
            batch.append(n)
        else:
            continue

        # insert a batch of events
        if len(batch) >= batch_size:
            attempt_batch_insert(batch)
            batch = []
            consumer.commit()
            print("sessions in cache:", len(sessions))


def attempt_session_insert(sess_batch):
    if sess_batch:
        try:
            print("inserting sessions...")
            insert_batch(db, sess_batch, table=sessions_table_name, level='sessions')
            print("inserted sessions succesfully")
        except TypeError as e:
            print("Type conversion error")
            print(repr(e))
        except ValueError as e:
            print("Message value could not be processed or inserted correctly")
            print(repr(e))
        except Exception as e:
            print(repr(e))


def attempt_batch_insert(batch):
    # insert a batch
    try:
        print("inserting...")
        insert_batch(db=db, batch=batch, table=table_name, level=LEVEL)
        print("inserted succesfully")
    except TypeError as e:
        print("Type conversion error")
        print(repr(e))
    except ValueError as e:
        print("Message value could not be processed or inserted correctly")
        print(repr(e))
    except Exception as e:
        print(repr(e))

def decode_key(b) -> int:
    """
    Decode the message key (encoded with little endian)
    """
    try:
        decoded = int.from_bytes(b, "little", signed=False)
    except Exception as e:
        raise UnicodeDecodeError(f"Error while decoding message key (SessionID) from {b}\n{e}")
    return decoded

if __name__ == '__main__':
    main()