from __future__ import annotations

import httpx

from app.market.base import MarketData
from app.schemas import Candle

BASE_URL = "https://api.exchange.coinbase.com"

# Coinbase granularities are in seconds.
GRANULARITIES: dict[str, int] = {
    "1m": 60,
    "5m": 300,
    "15m": 900,
    "1h": 3600,
    "6h": 21600,
    "1d": 86400,
}


def to_product_id(symbol: str) -> str:
    return symbol.replace("/", "-").upper()


class CoinbaseMarketData(MarketData):
    """Public Coinbase Exchange market data over REST (no API key required)."""

    def __init__(self, base_url: str = BASE_URL, timeout: float = 10.0) -> None:
        self._client = httpx.AsyncClient(
            base_url=base_url,
            timeout=timeout,
            headers={"User-Agent": "crypto_trading/0.1"},
        )

    @staticmethod
    def _granularity(timeframe: str) -> int:
        try:
            return GRANULARITIES[timeframe]
        except KeyError:
            raise ValueError(
                f"unsupported timeframe '{timeframe}' for Coinbase; "
                f"use one of {sorted(GRANULARITIES)}"
            ) from None

    async def fetch_candles(self, symbol: str, timeframe: str, limit: int) -> list[Candle]:
        response = await self._client.get(
            f"/products/{to_product_id(symbol)}/candles",
            params={"granularity": self._granularity(timeframe)},
        )
        response.raise_for_status()
        # Coinbase returns newest-first rows: [time, low, high, open, close, volume].
        rows = sorted(response.json(), key=lambda row: row[0])
        candles = [
            Candle(
                ts=int(row[0]) * 1000,
                open=float(row[3]),
                high=float(row[2]),
                low=float(row[1]),
                close=float(row[4]),
                volume=float(row[5]),
            )
            for row in rows
        ]
        return candles[-limit:]

    async def fetch_price(self, symbol: str) -> float:
        response = await self._client.get(f"/products/{to_product_id(symbol)}/ticker")
        response.raise_for_status()
        return float(response.json()["price"])

    async def close(self) -> None:
        await self._client.aclose()