"""strategy/population.py — the ONE definition of the tradeable population.

Every consumer (the live gate in trading_execution, the nightly tuner via
learn_params, the whole-market eod_replay, and future experiment harnesses)
screens sessions through ``population_reject`` so a backtest, a tune, and a live
entry all agree on which names are inside the +EV universe.

UNIT CONTRACT: ``gap_pct`` is a FRACTION (0.12 == 12%), matching the live call
site (``signal.get("gap_pct")``). ``as_of`` documents that every input must be
knowable at evaluation time — ``"open"`` means the static overnight gap
(session open vs prev close) and premarket/at-entry volume. Day-end fields
(full-day volume, close price) are FORBIDDEN: feeding them in re-creates the
outcome-time look-ahead this module exists to kill. The convention is enforced
by review, not at runtime.

Import-clean: no env reads at import time (env parsing lives in ``from_env``),
matching the ``ExitConfig.from_env()`` convention in strategy/exits.py.
"""

from __future__ import annotations

import os
from dataclasses import dataclass


@dataclass(frozen=True)
class PopulationConfig:
    price_min: float = 2.0
    price_max: float = 20.0
    # FRACTION (0.10 == 10%); env TRADING_MIN_ENTRY_GAP_PCT. Code default 0.0 —
    # the whole gap gate is disabled at 0, matching the live default. Production
    # sets 0.10.
    min_entry_gap_pct: float = 0.0
    min_day_volume: float = 0.0  # shares; env TRADING_MIN_DAY_VOLUME
    # Hardcoded in the live gate — module CONSTANTS, no env read. (The
    # TRIGGER_GAP_MAX / TRIGGER_GAP_SQUEEZE_* env keys configure the SEPARATE
    # ArmedTriggerBook watcher gate in runtime/triggers.py, NOT this function.)
    gap_dead_band_lo: float = 0.35
    gap_dead_band_hi: float = 1.50
    squeeze_rvol_min: float = 5.0
    # The >=150% "verified squeeze" exception. Env TRADING_GAP_SQUEEZE_ENABLED (default on).
    # 2026-09-28: under the current exits, live-band ORB breaks with a >=150% gap lost in both
    # halves (Jun-Jul -0.21R n=65, Aug-Sep -0.30R n=53), while the 10-35% band made +0.27R /
    # +0.13R (n=342 / 327). Our own squeeze fills were -0.31R / -0.33R realized (n=16).
    # These are the day's top gainers by the time their opening range breaks: the move has
    # already happened.
    squeeze_enabled: bool = True

    @classmethod
    def from_env(cls, env: dict | None = None) -> "PopulationConfig":
        """Build from environment — SAME keys + defaults as trading_execution's
        ExecutionSettings.from_env today (incl. the [0,1] clamp on the gap floor).
        Reads ONLY the four population keys; the dead-band / squeeze constants are
        never env-driven."""
        v = dict(os.environ)
        if env:
            v.update(env)

        def _qfloat(val: str) -> float:  # mirrors trading_execution._qfloat
            try:
                return max(0.0, min(1.0, float(val)))
            except (TypeError, ValueError):
                return 0.0

        return cls(
            price_min=float(v.get("TRADING_PRICE_MIN", "2.0")),
            price_max=float(v.get("TRADING_PRICE_MAX", "20.0")),
            min_entry_gap_pct=_qfloat(v.get("TRADING_MIN_ENTRY_GAP_PCT", "0.0")),
            min_day_volume=float(v.get("TRADING_MIN_DAY_VOLUME", "0.0")),
            squeeze_enabled=str(v.get("TRADING_GAP_SQUEEZE_ENABLED", "1")).strip().lower()
            not in {"0", "false", "no", "off"},
        )


def population_reject(
    cfg: PopulationConfig,
    *,
    gap_pct,
    price,
    volume,
    rvol,
    as_of: str = "open",
) -> str | None:
    """Return None if inside the tradeable population, else the reject reason.

    UNIT CONTRACT: ``gap_pct`` is a FRACTION (0.12 == 12%), matching the live
    call site (``signal.get("gap_pct")``). CONTRACT: every input must be
    knowable at evaluation time (``as_of="open"`` = static open gap,
    premarket/at-entry volume). Day-end fields are forbidden (see module doc).

    Fail-open: missing values never block (except the dead band, which requires
    a VERIFIED squeeze to re-admit). Logic moved verbatim from the live gate
    ``TradingExecutionService._population_reject``.
    """
    if cfg.min_entry_gap_pct > 0 and gap_pct is not None:
        try:
            g = float(gap_pct)
            if g < cfg.min_entry_gap_pct:
                return f"gap {g:.1%} < {cfg.min_entry_gap_pct:.0%}"
            # dead band (35-150%): +0.02R at year scale — excluded. Above 150%
            # only VOLUME-VERIFIED squeezes re-enter (real ones ran +0.63R;
            # reverse-split fakes show rvol ~0.01).
            if cfg.gap_dead_band_lo < g < cfg.gap_dead_band_hi:
                return f"gap {g:.0%} in dead band 35-150%"
            if g >= cfg.gap_dead_band_hi and not cfg.squeeze_enabled:
                return f"gap {g:.0%} above band (squeeze exception off)"
            if g >= cfg.gap_dead_band_hi and (rvol is None or float(rvol) < cfg.squeeze_rvol_min):
                return f"gap {g:.0%} squeeze unverified (rvol {rvol})"
        except (TypeError, ValueError):
            pass
    if price is not None:
        try:
            px = float(price)
            lo, hi = cfg.price_min, cfg.price_max
            if px > 0 and not (lo <= px <= hi):
                return f"price {px:.2f} outside ${lo:g}-{hi:g} band"
        except (TypeError, ValueError):
            pass
    if cfg.min_day_volume > 0 and volume is not None:
        try:
            if float(volume) < cfg.min_day_volume:
                return (f"day volume {float(volume):,.0f} < "
                        f"{cfg.min_day_volume:,.0f}")
        except (TypeError, ValueError):
            pass
    return None