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103 lines
2.9 KiB
Python
103 lines
2.9 KiB
Python
"""
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This module provides functionality to generate currency rate charts
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based on historical data retrieved from the database.
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"""
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from datetime import datetime
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from matplotlib import pyplot as plt
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from function.gen_unique_name import generate_unique_name
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from database.server import create_pool
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async def create_chart(
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from_currency: str,
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conv_currency: str,
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start_date: str,
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end_date: str
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) -> (str, None):
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"""
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Generates a line chart of currency rates for a given date range.
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The chart shows the exchange rate trend between `from_currency` and
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`conv_currency` within the specified `start_date` and `end_date` range.
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The generated chart is saved as a PNG file, and the function returns the
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file name. If data is invalid or insufficient, the function returns `None`.
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Args:
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from_currency (str): The base currency (e.g., "USD").
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conv_currency (str): The target currency (e.g., "EUR").
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start_date (str): The start date in the format 'YYYY-MM-DD'.
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end_date (str): The end date in the format 'YYYY-MM-DD'.
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Returns:
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str | None: The name of the saved chart file, or `None` if the operation fails.
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"""
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pool = await create_pool()
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if not validate_date(start_date) or not validate_date(end_date):
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return None
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start_date_obj = datetime.strptime(start_date, '%Y-%m-%d').date()
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end_date_obj = datetime.strptime(end_date, '%Y-%m-%d').date()
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async with pool.acquire() as conn:
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data = await conn.fetch(
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'SELECT date, rate FROM currency '
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'WHERE (date BETWEEN $1 AND $2) AND from_currency = $3 AND conv_currency = $4 ORDER BY date',
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start_date_obj,
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end_date_obj,
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from_currency.upper(),
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conv_currency.upper()
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)
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if not data or len(data) <= 1:
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return None
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date, rate = [], []
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fig = plt.gcf()
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for row in data:
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date.append(str(row['date']))
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rate.append(row['rate'])
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width = 18.5 + (len(date) // 5) * 2
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fig.set_size_inches(width, 9.5)
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if rate[0] < rate[-1]:
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plt.plot(date, rate, color='green', marker='o')
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elif rate[0] > rate[-1]:
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plt.plot(date, rate, color='red', marker='o')
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else:
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plt.plot(date, rate, color='grey')
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plt.xlabel('Date')
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plt.ylabel('Rate')
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name = await generate_unique_name(
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f'{from_currency.upper()}_{conv_currency.upper()}',
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datetime.now()
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)
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fig.savefig(f'../charts/{name}.png')
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fig.clear()
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return name
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def validate_date(date_str: str) -> bool:
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"""
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Validates whether the provided string is a valid date in the format 'YYYY-MM-DD'.
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Args:
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date_str (str): The date string to validate.
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Returns:
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bool: `True` if the string is a valid date, `False` otherwise.
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"""
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try:
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datetime.strptime(date_str, '%Y-%m-%d')
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return True
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except ValueError:
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return False
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