"""
Deterministic Buy/Hold/Sell policy applied to Moirai-MoE's forecast
output (spec sections 31-34, 93, 111-113). This module contains NO
predictive model of its own, hidden or otherwise — only arithmetic over
a forecast object produced by moirai_model.py. Nothing in this file
imports sklearn/xgboost/lightgbm/catboost or any other classifier.
"""
from __future__ import annotations

from dataclasses import dataclass
from typing import Optional

import numpy as np

import config as cfg
from calibration import ProbabilityCalibrator


@dataclass
class Decision:
    action: str  # "BUY" | "SELL" | "HOLD"
    expected_return: float
    expected_edge: float
    p10_return: float
    p90_return: float
    prob_favorable: float          # the probability actually used to gate this decision (calibrated, if a calibrator was supplied)
    raw_prob_favorable: float      # the same event's probability BEFORE calibration -- always shown, never hidden (spec: "do not hide weak signals")
    calibrated: bool               # whether a calibrator was actually applied
    interval_width_pct: float
    rationale: str
    hold_reason: str = None
    reject_stage: str = None  # structured category for diagnostics/counting:
    # "wide_interval" | "no_edge" | "low_confidence_buy" | "low_confidence_sell" | None (BUY/SELL taken)


def _prob_exceeds(levels: list, values: np.ndarray, threshold: float) -> float:
    """P(true return > threshold), estimated by linear interpolation on
    the model's own empirical quantile function — not a fabricated
    number (spec section 32-33)."""
    order = np.argsort(levels)
    lv = np.asarray(levels)[order]
    vv = np.asarray(values)[order]
    if threshold <= vv[0]:
        return 1.0
    if threshold >= vv[-1]:
        return 0.0
    p_below = float(np.interp(threshold, vv, lv))
    return 1.0 - p_below


def decide(forecast, price_now: float, dc: cfg.DecisionConfig = None,
           cost_estimate_frac: float = None,
           calibrator: Optional[ProbabilityCalibrator] = None) -> Decision:
    """`forecast` is a QuantileForecast (see moirai_model.py) with
    .quantile_levels (list of floats incl. 0.1/0.5/0.9) and .quantiles
    of shape (horizon, len(levels)).

    `calibrator`, if given, is applied to prob_favorable/
    prob_favorable_sell BEFORE either is compared against
    dc.min_probability -- real EURUSD 1h testing showed raw quantile-
    derived probabilities of 0.70-0.88 against a realized win rate
    around 0.50, i.e. the raw number is not trustworthy on its own (see
    calibration.py). None (the default) reproduces the previous,
    uncalibrated behavior exactly -- calibration is opt-in via an
    explicitly-supplied, already-fit ProbabilityCalibrator (see
    walk_forward.py for the only leakage-safe way to obtain one)."""
    dc = dc or cfg.DecisionConfig()
    levels = list(forecast.quantile_levels)
    step_prices = np.asarray(forecast.quantiles)[-1]  # final horizon step
    step_returns = step_prices / price_now - 1.0

    p10 = float(step_returns[levels.index(0.1)])
    p50 = float(step_returns[levels.index(0.5)])
    p90 = float(step_returns[levels.index(0.9)])

    cost = cost_estimate_frac if cost_estimate_frac is not None else dc.cost_bps / 10_000
    interval_width_pct = p90 - p10
    raw_prob_favorable = _prob_exceeds(levels, step_returns, threshold=cost)  # P(return > +cost) -- the BUY-side confidence
    # SELL is profitable when return < -cost (shorting profits from a
    # price drop), which is NOT the same event as "return <= +cost" --
    # that includes the whole middle range between -cost and +cost too,
    # so it isn't "1 - prob_favorable" reused. This is its own directional
    # probability, symmetric to prob_favorable but mirrored around
    # -cost instead of +cost, exactly the way min_probability's own
    # definition ("P(return favorable) required to act", config.py) is
    # meant to apply to either direction, not just BUY.
    raw_prob_favorable_sell = 1.0 - _prob_exceeds(levels, step_returns, threshold=-cost)  # P(return < -cost)

    if calibrator is not None:
        prob_favorable = calibrator.apply(raw_prob_favorable)
        prob_favorable_sell = calibrator.apply(raw_prob_favorable_sell)
        calibrated = True
    else:
        prob_favorable = raw_prob_favorable
        prob_favorable_sell = raw_prob_favorable_sell
        calibrated = False

    hold_reason = None
    reject_stage = None
    if interval_width_pct > dc.max_interval_width_pct:
        action = "HOLD"
        hold_reason = "forecast interval too wide relative to expected move (section 93)"
        reject_stage = "wide_interval"
    elif (p50 - cost) > dc.buy_threshold and prob_favorable >= dc.min_probability:
        action = "BUY"
    elif (p50 + cost) < dc.sell_threshold and prob_favorable_sell >= dc.min_probability:
        action = "SELL"
    else:
        action = "HOLD"
        # Distinguish "p50 never even cleared a directional threshold" from
        # "it cleared one, but confidence didn't clear min_probability" --
        # these are very different diagnoses (a fast/low-volatility
        # timeframe where p50 rarely moves enough to matter, vs. a
        # timeframe with real moves but noisy/unreliable ones) and were
        # previously indistinguishable from outside this function, which
        # made "why are there almost no trades" unanswerable without this
        # split (spec section 98: errors/holds must say what failed).
        buy_edge_ok = (p50 - cost) > dc.buy_threshold
        sell_edge_ok = (p50 + cost) < dc.sell_threshold
        if buy_edge_ok:
            hold_reason = "expected edge below threshold after costs — buy-side edge present but confidence below min_probability (section 93)"
            reject_stage = "low_confidence_buy"
        elif sell_edge_ok:
            hold_reason = "expected edge below threshold after costs — sell-side edge present but confidence below min_probability (section 93)"
            reject_stage = "low_confidence_sell"
        else:
            hold_reason = "expected edge below threshold after costs — no directional edge either way (section 93)"
            reject_stage = "no_edge"

    # Report whichever probability is actually relevant to the action taken
    # -- for a SELL, "P(return>cost)" reads as near-zero and looks like the
    # decision has no confidence behind it, when the real (and high)
    # confidence is in the mirrored SELL-side event. BUY/HOLD keep the
    # original P(return>cost) framing.
    if action == "SELL":
        prob_shown, raw_prob_shown, prob_label = prob_favorable_sell, raw_prob_favorable_sell, "P(return<-cost)"
    else:
        prob_shown, raw_prob_shown, prob_label = prob_favorable, raw_prob_favorable, "P(return>cost)"

    cal_note = f"; calibrated (raw={raw_prob_shown:.2f})" if calibrated else ""
    rationale = (
        f"P50 return {p50:+.4%} vs cost {cost:.4%}; {prob_label}={prob_shown:.2f}{cal_note}; "
        f"interval[P10,P90]=[{p10:+.4%},{p90:+.4%}]"
    )
    return Decision(
        action=action, expected_return=p50, expected_edge=p50 - cost,
        p10_return=p10, p90_return=p90, prob_favorable=prob_shown,
        raw_prob_favorable=raw_prob_shown, calibrated=calibrated,
        interval_width_pct=interval_width_pct, rationale=rationale, hold_reason=hold_reason,
        reject_stage=reject_stage,
    )