"""Currency exchange rates."""

import json
import os
import typing
from datetime import datetime, timedelta
from decimal import Decimal

import flask
import httpx


async def get_gbpusd(config: flask.config.Config) -> Decimal:
    """Get the current value for GBPUSD, with caching."""
    access_key = config["EXCHANGERATE_ACCESS_KEY"]
    data_dir = config["DATA_DIR"]

    now = datetime.now()
    now_str = now.strftime("%Y-%m-%d_%H:%M")
    fx_dir = os.path.join(data_dir, "fx")
    existing_data = os.listdir(fx_dir)
    existing = [f for f in existing_data if f.endswith("_GBPUSD.json")]
    if existing:
        recent_filename = max(existing)
        recent = datetime.strptime(recent_filename, "%Y-%m-%d_%H:%M_GBPUSD.json")
        delta = now - recent

    if existing and delta < timedelta(hours=6):
        full = os.path.join(fx_dir, recent_filename)
        data = json.load(open(full), parse_float=Decimal)
        if "quotes" in data and "USDGBP" in data["quotes"]:
            return typing.cast(Decimal, 1 / data["quotes"]["USDGBP"])

    url = "http://api.exchangerate.host/live"
    params = {"currencies": "GBP,USD", "access_key": access_key}

    filename = f"{fx_dir}/{now_str}_GBPUSD.json"
    async with httpx.AsyncClient() as client:
        r = await client.get(url, params=params)

    open(filename, "w").write(r.text)
    data = json.loads(r.text, parse_float=Decimal)

    return typing.cast(Decimal, 1 / data["quotes"]["USDGBP"])