import hashlib
import psycopg2
import sys
import os
import pandas as pd

def connect_db():
    """Connect to database

    Returns:
        psycopg2 connector: psycopg2 postgresql connector
    """
    conn = None
    try:
        conn = psycopg2.connect(
                    host=os.environ['DB_PATH'],
                    database=os.environ['DB_NAME'],
                    user=os.environ['DB_USERNAME'],
                    password=os.environ['DB_PASSWORD'],
                )
    except (Exception, psycopg2.DatabaseError) as error:
        print(error)
        sys.exit(1)
    return conn

def get_watchlist(username : str):
    """Read list of tickers/descriptions from database

    Args:
        username (str): database table prefix

    Returns:
        Pandas DataFrame: it has two columns - first column is ticker, second column is description
    """
    if username:
        table_name = f"{username + '_watch_list'}"
    else: # username is None, use default table
        table_name = "stock_watch_list"

    QUERY1 = f'''CREATE TABLE IF NOT EXISTS {table_name} 
        (
            tick character varying(5) NOT NULL,
            description text,
            PRIMARY KEY (tick)
        );'''
    QUERY2 = f"INSERT INTO {table_name} SELECT 'SPY', 'SPDR S&P 500 ETF Trust' WHERE NOT EXISTS (SELECT NULL FROM {table_name});"

    QUERY3 = f"SELECT * FROM {table_name};"

    with connect_db() as conn:
        with conn.cursor() as curs:
            curs.execute(QUERY1)
            curs.execute(QUERY2)
            curs.execute(QUERY3)
            tuples_list = curs.fetchall()
    
    df = pd.DataFrame(tuples_list)
    return df

def remove_from_db(username, tick):
    """Remove a row from database table using ticker as key

    Args:
        username (str): database table prefix
        tick (str): ticker
    """
    if username:
        table_name = f"{username + '_watch_list'}"
    else: # username is None, use default table
        table_name = "stock_watch_list"
    
    QUERY = f"DELETE FROM {table_name} WHERE tick = '{tick}';"

    with connect_db() as conn:
        with conn.cursor() as curs:
            curs.execute(QUERY)

def insert_into_db(username : str, tick : str, name : str):
    """Insert ticker and description into database

    Args:
        username (str): database table prefix - each user has its own list of tickers
        tick (str): stock or mutual fund ticker
        name (str): company name for stock, series ID for mutual fund
    """
    if username:
        table_name = f"{username + '_watch_list'}"
    else: # username is None, use default table
        table_name = "stock_watch_list"

    QUERY1 = f'''CREATE TABLE IF NOT EXISTS {table_name} 
        (
            tick character varying(5) NOT NULL,
            description text,
            PRIMARY KEY (tick)
        );'''
    QUERY2 = f"INSERT INTO {table_name} SELECT 'SPY', 'SPDR S&P 500 ETF Trust' WHERE NOT EXISTS (SELECT NULL FROM {table_name});"

    QUERY3 = f"INSERT INTO {table_name} VALUES ('{tick}', '{name}') ON CONFLICT DO NOTHING;"

    with connect_db() as conn:
        with conn.cursor() as curs:
            curs.execute(QUERY1)
            curs.execute(QUERY2)
            curs.execute(QUERY3)

def hash_password(password : str):
    """Generate hash from string using sha256

    Args:
        password (str): any text

    Returns:
        str: hash string
    """
    # Encode the password as bytes
    password_bytes = password.encode('utf-8')
    
    # Use SHA-256 hash function to create a hash object
    hash_object = hashlib.sha256(password_bytes)
    
    # Get the hexadecimal representation of the hash
    password_hash = hash_object.hexdigest()
    
    return password_hash