"""Shared helpers for trading pattern scripts."""
from __future__ import annotations

import json
from pathlib import Path
from typing import Any, Dict, List, Optional, Sequence, Tuple
from typing import Dict, List, Optional, Sequence, Tuple

import numpy as np
import pandas as pd
import pyodbc

DEFAULT_CONFIG_PATH = Path("config/pattern_knn_config.json")


def load_config(path: Optional[Path] = None) -> Dict:
    """Load the JSON configuration that holds operational parameters."""
    cfg_path = Path(path or DEFAULT_CONFIG_PATH)
    if not cfg_path.exists():
        raise FileNotFoundError(f"Missing configuration file: {cfg_path}")
    with cfg_path.open("r", encoding="utf-8") as fh:
        return json.load(fh)


def require_section(config: Dict, section: str) -> Dict:
    sect = config.get(section)
    if not isinstance(sect, dict):
        raise KeyError(f"Missing '{section}' section in configuration file")
    return sect


def require_value(section: Dict, key: str, section_name: str) -> Any:
    if key not in section:
        raise KeyError(f"Missing key '{key}' inside '{section_name}' section of configuration file")
    return section[key]


def detect_column(df: pd.DataFrame, candidates: Sequence[str]) -> Optional[str]:
    """Return the first column whose name matches one of the candidates (case insensitive)."""
    low = {c.lower(): c for c in df.columns}
    for cand in candidates:
        cl = cand.lower()
        if cl in low:
            return low[cl]
    for cand in candidates:
        cl = cand.lower()
        for col in df.columns:
            if cl in col.lower():
                return col
    return None


def read_connection_txt(path: Path | str = "connection.txt") -> str:
    params: Dict[str, str] = {}
    path = Path(path)
    if not path.exists():
        raise FileNotFoundError(f"Missing connection.txt at {path}")
    for line in path.read_text(encoding="utf-8").splitlines():
        line = line.strip()
        if not line or line.startswith("#") or "=" not in line:
            continue
        k, v = line.split("=", 1)
        params[k.strip().lower()] = v.strip()

    username = params.get("username")
    password = params.get("password")
    host = params.get("host")
    port = params.get("port", "1433")
    database = params.get("database")

    if not all([username, password, host, database]):
        raise ValueError("connection.txt incompleto: servono username/password/host/database.")

    installed = [d for d in pyodbc.drivers()]
    driver_q = "ODBC+Driver+18+for+SQL+Server" if "ODBC Driver 18 for SQL Server" in installed else "ODBC+Driver+17+for+SQL+Server"
    return f"mssql+pyodbc://{username}:{password}@{host}:{port}/{database}?driver={driver_q}"


def z_norm(arr: np.ndarray) -> Optional[np.ndarray]:
    arr = np.asarray(arr, dtype=float)
    if arr.size == 0:
        return None
    mu = arr.mean()
    sd = arr.std()
    if sd < 1e-12:
        return None
    return (arr - mu) / (sd + 1e-12)


def build_pattern_library(
    ret_series: pd.Series,
    wp: int,
    ha: int,
    embargo: Optional[int] = None,
) -> Tuple[Optional[np.ndarray], Optional[np.ndarray]]:
    """Create the normalized pattern windows and their realized outcomes.

    Args:
        ret_series: Series of returns (ordered oldest→latest).
        wp: Window length for the pattern.
        ha: Holding horizon used to compute the outcome.
        embargo: Optional number of most-recent observations to exclude when
            building the library (useful to avoid leakage when reusing the
            same series for inference).
    """
    x = ret_series.dropna().values
    n = len(x)
    if n < wp + ha + 10:
        return None, None
    embargo = int(embargo or 0)
    usable_n = n - max(0, embargo)
    if usable_n <= wp + ha:
        return None, None
    wins: List[np.ndarray] = []
    outs: List[float] = []
    last_start = usable_n - wp - ha
    if last_start <= 0:
        return None, None
    for t in range(0, last_start + 1):
        win = x[t : t + wp]
        winzn = z_norm(win)
        if winzn is None:
            continue
        outcome = np.sum(x[t + wp : t + wp + ha])
        wins.append(winzn)
        outs.append(outcome)
    if not wins:
        return None, None
    return np.array(wins), np.array(outs)


def predict_from_library(
    curr_win: np.ndarray,
    lib_wins: np.ndarray,
    lib_out: np.ndarray,
    k: int = 25,
) -> Tuple[float, float, np.ndarray]:
    dists = np.linalg.norm(lib_wins - curr_win, axis=1)
    idx = np.argsort(dists)[: min(k, len(dists))]
    return float(np.median(lib_out[idx])), float(np.mean(dists[idx])), idx


def characterize_window(
    ret_series: pd.Series,
    wp: int,
    z_rev: float = 2.0,
    z_vol: float = 2.0,
    std_comp_pct: float = 0.15,
) -> Tuple[Optional[str], float]:
    x = ret_series.dropna().values
    if len(x) < max(wp, 30):
        return None, 0.0
    win = x[-wp:]
    mu, sd = win.mean(), win.std()
    if sd < 1e-12:
        return "compression", 0.5

    last = win[-1]
    z_last = (last - mu) / (sd + 1e-12)
    abs_z_last = abs(z_last)
    last3 = win[-3:] if len(win) >= 3 else win
    sum3 = np.sum(last3)

    if len(x) > 3 * wp:
        roll_std = pd.Series(x).rolling(wp).std().dropna().values
        if len(roll_std) > 20:
            pct = (roll_std < np.std(win)).mean()
        else:
            pct = 0.5
    else:
        pct = 0.5

    if pct < std_comp_pct:
        return "compression", float(1.0 - pct)

    if abs(sum3) > 2 * sd / np.sqrt(3) and np.sign(last3).sum() in (3, -3):
        conf = min(1.0, abs(sum3) / (sd + 1e-12))
        return "momentum_burst", float(conf)

    mean_prev = np.mean(win[:-1]) if len(win) > 1 else 0.0
    if abs_z_last >= z_rev and np.sign(last) != np.sign(mean_prev):
        conf = min(1.0, abs_z_last / 3.0)
        return "reversal_candidate", float(conf)

    if abs_z_last >= z_vol:
        conf = min(1.0, abs_z_last / 3.0)
        return "vol_spike", float(conf)

    return None, 0.0


def hurst_rs(series: pd.Series) -> Optional[float]:
    x = pd.to_numeric(series.dropna(), errors="coerce").astype(float).values
    n = len(x)
    if n < 100:
        return None
    x = x - x.mean()
    z = np.cumsum(x)
    r = z.max() - z.min()
    s = x.std(ddof=1)
    if s <= 0 or r <= 0:
        return None
    h = np.log(r / s) / np.log(n)
    if not np.isfinite(h):
        return None
    return float(h)


def build_hurst_map(returns_long: pd.DataFrame, lookback: int = 252) -> Dict[str, float]:
    if returns_long.empty:
        return {}
    ret_wide = returns_long.pivot(index="Date", columns="ISIN", values="Ret").sort_index()
    hurst_map: Dict[str, float] = {}
    for isin in ret_wide.columns:
        series = ret_wide[isin].dropna().astype(float)
        if len(series) < max(lookback, 100):
            continue
        h_val = hurst_rs(series.iloc[-lookback:])
        if h_val is None or not np.isfinite(h_val):
            continue
        hurst_map[str(isin)] = float(h_val)
    return hurst_map


__all__ = [
    "build_hurst_map",
    "build_pattern_library",
    "characterize_window",
    "detect_column",
    "require_section",
    "require_value",
    "hurst_rs",
    "load_config",
    "predict_from_library",
    "read_connection_txt",
    "z_norm",
]