"""OPT-11: each battery's mode and on/off switch, as limits and weights.

Pure: no I/O, no clock. main.py reads the store, calls these, and files the
result as a `mode` claim (arbiter.P_MODE) and as the charge weights.
DECISIONS/OPT-11-battery-modes.md has the record; OPT-11-design section 1 has
the modes.

Two rules hold for every mode, and they are what keeps modes safe:

1. A mode range always holds 0 W. A mode may forbid a direction, never force
   one, so batteries never move power in opposite directions because of a mode
   (allocator.unit_interval() drops a range without 0 as a software fault).
2. A mode is a limit, not a weight. A weight of 0 does not keep a battery out:
   allocator._fill()'s last-resort pass still uses it. So "may not" is a range,
   and weights only set the order among batteries that may.

`mode_range()` is the switch alone (Off is [0, 0]). P3 adds the price runs:
`modetrade.decide()` narrows each battery's range by its role this tick
(hold for the expensive hours, charge from the grid, sell), and main.py files
the intersection. Selling is a per-battery choice (`pack_sell`, the owner's
2026-09-27 answer), for Leftover solar and Cheap hours only.
"""

from dataclasses import dataclass

from .store import unit_key

SOLAR_FIRST = "solar_first"
LEFTOVER_SOLAR = "leftover_solar"
CHEAP_HOURS = "cheap_hours"         # OPT-11 P3

# The modes a battery may be set to, in the order the page and the HA select
# list them. The first is the default when the store has no value. A new mode
# is appended, never inserted: automations send the HA labels (P2).
MODES = (SOLAR_FIRST, LEFTOVER_SOLAR, CHEAP_HOURS)
DEFAULT_MODE = SOLAR_FIRST

# Store keys, per battery: `unit/<name>/<key>` (store.unit_key()).
USE_KEY = "pack_use"
MODE_KEY = "pack_mode"
SELL_KEY = "pack_sell"              # OPT-11 P3: sell in the sell run

# Owner decision 2026-09-29 (option A): selling is off until it can be judged
# on the price the grid pays. While False, `read()` answers `sell=False`
# whatever the store holds, the page shows no switch and `pack_sell` is
# refused; the sell code in modetrade/priceruns stays, unreachable.
SELLING_ENABLED = False

# The modes that may charge from the grid in a cheap run with no day plan.
# Leftover solar takes solar only then (owner decision 2026-09-29, option A).
GRID_CHARGE_MODES = (CHEAP_HOURS,)
# OPT-11 P4: with a fresh solar forecast, the day plan (dayplan.py) lets
# Leftover solar charge from the grid, by the shortfall only. Cheap hours only
# ignores the plan (fills to the ceiling); Solar first never grid-charges.
PLAN_CHARGE_MODES = (LEFTOVER_SOLAR,)


def enabled(opts) -> bool:
    """Battery modes are on only when the option is exactly true. One answer,
    read by the controller and by the MQTT announcement."""
    return opts.get("battery_modes_enabled") is True


@dataclass(frozen=True)
class PackMode:
    """One battery's choice: on or off, its mode, and selling."""
    use: bool = True
    mode: str = DEFAULT_MODE
    sell: bool = False

    @property
    def can_sell(self) -> bool:
        """Selling applies to the price modes only; Solar first never sells.
        False for every battery while SELLING_ENABLED is False."""
        return SELLING_ENABLED and self.mode in (LEFTOVER_SOLAR, CHEAP_HOURS)

    @property
    def key(self) -> str:
        """The page's word for this state: a mode, or `off`."""
        return self.mode if self.use else "off"


def read(data: dict, name: str) -> PackMode:
    """Battery `name`'s choice from the store's data. A missing or unknown
    value falls back to the default (on, Solar first), never to Off: a store
    written by a later version must not switch a battery off here."""
    use = data.get(unit_key(name, USE_KEY), True)
    mode = data.get(unit_key(name, MODE_KEY), DEFAULT_MODE)
    return PackMode(use=use is not False,
                    mode=mode if mode in MODES else DEFAULT_MODE,
                    sell=SELLING_ENABLED
                    and data.get(unit_key(name, SELL_KEY)) is True)


def mode_range(pm: PackMode, rating_w: float) -> tuple:
    """`(lo, hi)` in W for this battery's switch. Always holds 0 W.

    Off asks for 0 W both ways; On allows the rating both ways. main.py files
    this intersected with the role range from `modetrade.decide()`.
    """
    if not pm.use:
        return 0.0, 0.0
    r = abs(float(rating_w))
    return -r, r


def charge_weights(base, modes: dict, target_w: float):
    """The allocator's weights with the solar order applied (design 3.5).

    `base` is packshare.weights()' answer (None for "all 1.0"). While the site
    charges (`target_w < 0`), a Leftover solar battery weighs 0 and a Solar
    first battery keeps its weight, so the fill gives the Solar first batteries
    everything they can take before the last-resort pass reaches the others.
    Giving power keeps `base`; `modetrade.weights()` adds the run order.

    When no battery that is on would keep a positive weight (all Leftover
    solar, or every Solar first one at 0), `base` is returned unchanged, so the
    order among equals stays OPT-09's rather than an equal split.
    """
    if float(target_w) >= 0.0 or not modes:
        return base
    names = sorted(modes)
    w = {n: (1.0 if base is None else float(base.get(n, 1.0))) for n in names}
    out = {n: (0.0 if modes[n].mode in (LEFTOVER_SOLAR, CHEAP_HOURS)
               else w[n])
           for n in names}
    if not any(out[n] > 0.0 for n in names if modes[n].use):
        return base
    return out