import json
import csv
import logging
from pathlib import Path
import argparse
from collections import namedtuple

import requests

logging.basicConfig(level=logging.INFO)

QUANDL_URL = 'https://www.quandl.com/api/v3/datasets/WIKI/{}.json'
DATASTORE = Path('/project/stock-price/data')

Configuration = namedtuple(
    'Configuration',
    ['stock', 'start_date', 'end_date']
)

def fetch_stock_info(stock, start_date, end_date):
    response = requests.get(
        QUANDL_URL.format(stock),
        params={'start_date': start_date, 'end_date': end_date}
    )
    response.raise_for_status()
    json = response.json()
    data = json['dataset']['data']
    stock_price = {}
    for entry in data:
        date = entry[0]
        closing = entry[4]
        stock_price[date] = float(closing)
    return stock_price
    

def read_current_data(store):
    stock_prices = {}
    try:
        with open(store) as f:
            reader = csv.reader(f)
            next(reader)  # skip header
            for row in reader:
                date, price = row
                stock_prices[date] = price
    except FileNotFoundError:
        return {}
    return stock_prices
    
    
def write_data(store, stock_prices):
    sorted_data = sorted(stock_prices.items(), key=lambda it: it[0])
    with open(store, 'w') as f:
        writer = csv.writer(f)
        writer.writerow(['date', 'price'])
        writer.writerows(sorted_data)
    
    
def store_update(store, new_prices):
    stock_prices = read_current_data(store)
    stock_prices.update(new_prices)
    write_data(store, stock_prices)
    
    
def fetch_and_update_stocks(stock, start_date, end_date):
    logging.info(
        f'Fetching stocks for symbol {stock} '
        f'between {start_date} and {end_date}'
    )
    prices = fetch_stock_info(stock, start_date, end_date)
    logging.info(f'Fetched {len(prices)} stock prices.')
    store = DATASTORE / f'{stock}.csv'
    store_update(store, prices)
    logging.info(f'Written information back to data store {store}.')
    
    
def parse_command_line():
    parser = argparse.ArgumentParser(
        description='Fetch and store stock information')
    parser.add_argument('symbol')
    parser.add_argument(
        'start_date',
        help='start date, in format 2018-01-22'
    )
    parser.add_argument(
        'end_date',
        help='end date, in format 2018-01-29'
    )
    args = parser.parse_args()
    return Configuration(
        args.symbol.upper(),
        args.start_date,
        args.end_date
    )
    
    
if __name__ == '__main__':
    configuration = parse_command_line()
    logging.info(f'Using configuration {configuration}.')
    fetch_and_update_stocks(
        configuration.stock, 
        configuration.start_date,
        configuration.end_date
    )