"""
Data loading and resampling utilities.
"""

import sqlite3
from pathlib import Path

import pandas as pd

DB_PATH = Path("/home/jonathan/Projects/ForexBots/data/candles.db")

_RESAMPLE_MAP = {
    "open":       "first",
    "high":       "max",
    "low":        "min",
    "close":      "last",
    "tick_volume": "sum",
}


def load_candles(symbol: str, timeframe: str, db_path: Path = DB_PATH) -> pd.DataFrame:
    conn = sqlite3.connect(db_path)
    df = pd.read_sql_query(
        "SELECT time, open, high, low, close, tick_volume "
        "FROM candles WHERE symbol=? AND timeframe=? ORDER BY time",
        conn, params=(symbol, timeframe),
    )
    conn.close()
    df["time"] = pd.to_datetime(df["time"])
    df.set_index("time", inplace=True)
    return df


def resample(df: pd.DataFrame, rule: str) -> pd.DataFrame:
    """Resample an OHLCV dataframe to a coarser timeframe.

    rule follows pandas offset alias (e.g. '1h', '4h', '1D').
    """
    agg = {c: _RESAMPLE_MAP[c] for c in df.columns if c in _RESAMPLE_MAP}
    return df.resample(rule, label="left", closed="left").agg(agg).dropna()