from __future__ import annotations

import os
import pickle
from pathlib import Path

import numpy as np
import pandas as pd

# Pre-computed forecasts for the three demo datasets live here.

# Check local (inside backend/) first, then project root (parent.parent)
_HERE = Path(__file__).parent
CACHE_DIR = _HERE / "demo_cache" if (_HERE / "demo_cache").exists() else _HERE.parent / "demo_cache"
DEMO_DIR  = _HERE / "demo_data"  if (_HERE / "demo_data").exists()  else _HERE.parent / "demo_data"

_CACHE: dict[str, dict] = {}   # in-memory after first load


# ─── Public API ───────────────────────────────────────────────────────────────

def load_all() -> None:
    """
    Called once at FastAPI startup after the model is loaded.
    Reads all .pkl files from demo_cache/ into memory.
    Missing files are skipped silently — demo still works, just slower.
    """
    CACHE_DIR.mkdir(parents=True, exist_ok=True)
    for pkl_file in CACHE_DIR.glob("*.pkl"):
        key = pkl_file.stem
        try:
            with open(pkl_file, "rb") as f:
                _CACHE[key] = pickle.load(f)
        except Exception:
            pass


def get(key: str) -> dict | None:
    return _CACHE.get(key)


def has(key: str) -> bool:
    return key in _CACHE


# ─── Pre-compute script ───────────────────────────────────────────────────────

def build_all() -> None:
    """
    Generates and saves pre-computed forecasts for all demo datasets.
    Requires the model to already be loaded (call forecaster.load_model() first).
    """
    import forecaster
    from preprocessor import ingest, prepare_series
    from calibrator import calibrate
    from detector import build_detector
    from confidence import compute as confidence_score
    from decision import get_decision
    from baseline import select_and_run

    CACHE_DIR.mkdir(parents=True, exist_ok=True)

    demos = {
        "bakery":   ("bakery_sales.csv",         "date", "weekly_sales_inr"),
        "crop":     ("crop_prices_sample.csv",    "date", "wheat_price_inr_per_quintal"),
        "m5":       ("walmart_m5_sample.csv",     "date", "FOODS_1"),
    }

    for key, (filename, date_col, value_col) in demos.items():
        csv_path = DEMO_DIR / filename
        if not csv_path.exists():
            print(f"  skip {key} — {csv_path} not found")
            continue

        try:
            print(f"  building {key}...")

            with open(csv_path, "rb") as f:
                file_bytes = f.read()

            session_data = ingest(file_bytes, filename)
            session_id   = session_data["session_id"]
            prepared     = prepare_series(session_id, date_col, value_col)
            series       = prepared["series"]

            result = forecaster.run_forecast(series, horizon=4, frequency=prepared["frequency"])

            cal = calibrate(series, result["low"], result["high"])
            cal_low  = cal["calibrated_low"]
            cal_high = cal["calibrated_high"]

            hist_std = float(np.std(series))
            score, label = confidence_score(cal_low, cal_high, hist_std)

            last_val = float(series[-1])
            first_fc = float(result["median"][0])
            trend_pct = ((first_fc - last_val) / (last_val + 1e-9)) * 100

            decision = get_decision(
                trend_pct=trend_pct,
                confidence=score,
                cusum_alert="NONE",
                is_financial=prepared["is_financial"],
                is_intermittent=prepared["is_intermittent"],
            )

            detector  = build_detector(series)
            dates     = prepared["dates"]
            fc_dates  = _future_dates(dates[-1], 4, prepared["frequency"])

            payload = {
                "forecast": [
                    {
                        "date":   fc_dates[i],
                        "low":    float(cal_low[i]),
                        "median": float(result["median"][i]),
                        "high":   float(cal_high[i]),
                    }
                    for i in range(4)
                ],
                "baseline": [
                    {"date": fc_dates[i], "value": float(result["baseline"][i])}
                    for i in range(4)
                ],
                "baseline_type":    result["baseline_type"],
                "confidence_score": score,
                "confidence_label": label,
                "decision":         decision,
                "trend_pct":        round(trend_pct, 2),
                "fallback_bands":   cal["fallback"],
                "is_financial":     prepared["is_financial"],
                "is_intermittent":  prepared["is_intermittent"],
                "history_dates":    dates[-52:],
                "history_values":   [float(v) for v in series[-52:]],
                "series_name":      value_col.replace("_", " "),
                "frequency":        prepared["frequency"],
                "_detector":        detector,
                "_alpha":           cal["alpha"],
                "_hist_std":        hist_std,
                "_series":          series,
            }

            pkl_path = CACHE_DIR / f"{key}.pkl"
            with open(pkl_path, "wb") as f:
                pickle.dump(payload, f)

            print(f"  ✓ {key} → {pkl_path.name}  "
                  f"(conf={score}, trend={trend_pct:+.1f}%)")

        except Exception as e:
            print(f"  ✗ {key} failed: {e}")

    print("Cache build complete.")


def _future_dates(last_date_str: str, horizon: int, frequency: str) -> list[str]:
    last = pd.Timestamp(last_date_str)
    freq_map = {"hourly": "h", "daily": "D", "weekly": "W", "monthly": "MS", "quarterly": "QS", "annually": "YS"}
    offset   = freq_map.get(frequency, "W")
    dates    = pd.date_range(start=last, periods=horizon + 1, freq=offset)[1:]
    return [d.strftime("%Y-%m-%d") for d in dates]


# ─── CLI entry point ──────────────────────────────────────────────────────────

if __name__ == "__main__":
    import forecaster
    print("Loading Chronos-Bolt-Small...")
    forecaster.load_model()
    print("Model ready. Building demo cache...\n")
    build_all()