currency_api.py

import requests
import configuration as config

currency_data = {}

static_currency_data = {
    "SGD": 1.0,
    "USD": 0.74,
    "EUR": 0.63,
    "JPY": 79.0,
    "GBP": 0.54,
    "AUD": 1.0,
    "CAD": 0.94,
}
"""Global cache for currency exchange rates relative to SGD.

Keys are currency codes (str), values are floats representing how many units
of the keyed currency correspond to 1 SGD. Initially populated with examples,
can be updated by `get_currency_rate`.
"""

def get_currency_rate():
    """Fetches or returns cached currency exchange rates relative to SGD.

    Attempts to fetch live rates from the RapidAPI endpoint if the global
    `currency_data` cache is empty. Updates the cache on success.
    Uses `configuration.RAPIDAPI_KEY`.

    Returns:
        A dictionary mapping currency codes (str) to their exchange rate
        relative to SGD (float: units of currency per 1 SGD), or None if
        fetching or processing fails.
    """
    global currency_data
    if currency_data: 
        return currency_data
    elif config.API_ON:
        url = "https://booking-com15.p.rapidapi.com/api/v1/meta/getExchangeRates"

        querystring = {"base_currency": "SGD"}

        headers = {
            "x-rapidapi-key": config.RAPIDAPI_KEY,
            "x-rapidapi-host": "booking-com15.p.rapidapi.com"
        }

        try:
            response = requests.get(url, headers=headers, params=querystring)
            response.raise_for_status()
            data = response.json()

            for exchange_rate in data["data"]["exchange_rates"]:
                currency_data[exchange_rate["currency"]] = float(exchange_rate["exchange_rate_buy"]) # Use exchange_rate_buy

            return currency_data

        except requests.exceptions.RequestException as e:
            print(f"Error fetching currency rates: {e}")
            return static_currency_data
        except (KeyError, TypeError, ValueError) as e:
            print(f"Error processing API response: {e}")
            return static_currency_data
    else:
        return static_currency_data

def get_list_of_currency():
    """Gets the list of available currency codes from the cache.

    Calls `get_currency_rate()` to ensure rates are loaded/fetched if needed.

    Returns:
        A list of currency code strings (e.g., ['SGD', 'USD', 'EUR']),
        or an empty list if rates are unavailable.
    """
    currency_data = get_currency_rate()
    if currency_data:
        return list(currency_data.keys())
    else:
        return []

def convert_currency_from_SGD(amount, to_currency):
    """Converts an amount from SGD to a target currency.

    Uses the cached exchange rates.

    Args:
        amount: The amount in SGD.
        to_currency: The currency code (str) to convert to.

    Returns:
        The equivalent amount in the target currency, rounded to 2 decimal
        places, or None if the currency rate is not available.
    """
    currency_data = get_currency_rate()
    if currency_data and to_currency in currency_data:
        return round(amount / currency_data["SGD"] * currency_data[to_currency], 2) # Important change here
    else:
        return None

def convert_currency_to_SGD(amount, from_currency):
    """Converts an amount from a specified currency to SGD.

    Uses the cached exchange rates.

    Args:
        amount: The amount in the `from_currency`.
        from_currency: The currency code (str) to convert from.

    Returns:
        The equivalent amount in SGD, rounded to 2 decimal places, or None
        if the currency rate is not available.
    """
    currency_data = get_currency_rate()
    if currency_data and from_currency in currency_data:
        return round(amount / currency_data[from_currency] * currency_data["SGD"], 2) # important change here.
    else:
        return None