#!/usr/bin/env python3
"""Download historical OHLCV data from Binance and store it as CSV."""
from __future__ import annotations

import argparse
import json
import sys
import time
from pathlib import Path
from typing import Dict, List
from urllib.parse import urlencode
from urllib.request import Request, urlopen

import pandas as pd

BINANCE_REST_BASE = "https://api.binance.com/api/v3/klines"
MAX_LIMIT = 1000
# Interval → milliseconds mapping taken from Binance documentation
INTERVAL_MS: Dict[str, int] = {
    "1m": 60_000,
    "3m": 180_000,
    "5m": 300_000,
    "15m": 900_000,
    "30m": 1_800_000,
    "1h": 3_600_000,
    "2h": 7_200_000,
    "4h": 14_400_000,
    "6h": 21_600_000,
    "8h": 28_800_000,
    "12h": 43_200_000,
    "1d": 86_400_000,
}


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Export OHLCV candles from Binance")
    parser.add_argument("--symbol", default="SOLUSDT", help="Binance symbol, e.g. SOLUSDT")
    parser.add_argument(
        "--interval",
        default="5m",
        choices=sorted(INTERVAL_MS.keys()),
        help="Binance interval (default: 5m)",
    )
    parser.add_argument(
        "--start",
        required=True,
        help="Start timestamp (ISO 8601, e.g. 2024-01-01 or 2024-01-01T00:00:00Z)",
    )
    parser.add_argument(
        "--end",
        required=True,
        help="End timestamp (ISO 8601, inclusive)",
    )
    parser.add_argument(
        "--output",
        type=Path,
        required=True,
        help="Path to output CSV file (directories created automatically)",
    )
    parser.add_argument(
        "--rate-limit-wait",
        type=float,
        default=0.2,
        help="Seconds to sleep between paginated requests (default: 0.2s)",
    )
    return parser.parse_args()


def to_millis(value: str) -> int:
    ts = pd.Timestamp(value)
    if ts.tzinfo is None:
        ts = ts.tz_localize("UTC")
    else:
        ts = ts.tz_convert("UTC")
    return int(ts.timestamp() * 1000)


def fetch_chunk(symbol: str, interval: str, start_ms: int, end_ms: int) -> List[List[float]]:
    params = {
        "symbol": symbol.upper(),
        "interval": interval,
        "startTime": start_ms,
        "endTime": end_ms,
        "limit": MAX_LIMIT,
    }
    query = urlencode(params)
    url = f"{BINANCE_REST_BASE}?{query}"
    req = Request(url, headers={"User-Agent": "binance-export/1.0"})
    with urlopen(req, timeout=30) as resp:
        payload = resp.read()
    data = json.loads(payload)
    if isinstance(data, dict) and data.get("code"):
        raise RuntimeError(f"Binance error {data['code']}: {data.get('msg')}")
    return data  # type: ignore[return-value]


def main() -> int:
    args = parse_args()
    interval = args.interval
    if interval not in INTERVAL_MS:
        raise ValueError(f"Unsupported interval: {interval}")

    start_ms = to_millis(args.start)
    end_ms = to_millis(args.end)
    if end_ms <= start_ms:
        raise ValueError("End time must be after start time")

    interval_ms = INTERVAL_MS[interval]
    cursor = start_ms
    rows: List[List[float]] = []
    request_count = 0

    while cursor < end_ms:
        chunk = fetch_chunk(args.symbol, interval, cursor, end_ms)
        if not chunk:
            break
        rows.extend(chunk)
        request_count += 1
        last_open = chunk[-1][0]
        cursor = last_open + interval_ms
        if len(chunk) < MAX_LIMIT:
            break
        time.sleep(args.rate_limit_wait)

    if not rows:
        raise RuntimeError("No data returned from Binance")

    columns = [
        "open_time",
        "open",
        "high",
        "low",
        "close",
        "volume",
        "close_time",
        "quote_asset_volume",
        "number_of_trades",
        "taker_buy_base",
        "taker_buy_quote",
        "ignore",
    ]
    df = pd.DataFrame(rows, columns=columns)
    df = df.drop(columns=["close_time", "quote_asset_volume", "ignore"])
    df["timestamp"] = pd.to_datetime(df["open_time"], unit="ms", utc=True).dt.tz_convert(None)
    df = df[["timestamp", "open", "high", "low", "close", "volume", "number_of_trades", "taker_buy_base", "taker_buy_quote"]]
    df[["open", "high", "low", "close", "volume"]] = df[["open", "high", "low", "close", "volume"]].astype(float)

    args.output.parent.mkdir(parents=True, exist_ok=True)
    df.to_csv(args.output, index=False)

    first = df.iloc[0].timestamp
    last = df.iloc[-1].timestamp
    duration_days = (last - first).days
    print(f"Saved {len(df):,} candles for {args.symbol} ({interval}) spanning ~{duration_days} days")
    print(f"Requests made: {request_count}")
    print(f"Output: {args.output}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())