"""Persistent state, in /data (the add-on's only durable volume).

The maintenance cycle is month-scale state: it MUST survive add-on restarts,
HA restarts and power cuts, or the battery quietly stops being maintained and
nothing says so.

Times are stored as ISO-8601 with an explicit UTC offset and parsed back to
aware datetimes. That is not fussiness: the YAML implementation this replaces
was disabled for hours by exactly one naive-vs-aware subtraction, and it failed
silently - the automation never even recorded itself as triggered.
"""

import json
import logging
import os
import tempfile
from datetime import datetime, timezone

_LOG = logging.getLogger("goodwe.store")

DEFAULTS = {
    "phase": "idle",
    "phase_started": None,
    "last_completed": None,
    "last_start_attempt": None,
    "auto": False,
}


class Store:
    def __init__(self, path: str = "/data/state.json"):
        self.path = path
        self.data = dict(DEFAULTS)
        self.load()

    def load(self) -> None:
        try:
            with open(self.path, "r", encoding="utf-8") as fh:
                loaded = json.load(fh)
            if isinstance(loaded, dict):
                self.data = {**DEFAULTS, **loaded}
                _LOG.info("state restored: phase=%s last_completed=%s",
                          self.data.get("phase"), self.data.get("last_completed"))
        except FileNotFoundError:
            _LOG.info("no saved state, starting fresh")
        except (json.JSONDecodeError, OSError) as err:
            # A corrupt state file must not stop the controller: losing the
            # maintenance history is recoverable, refusing to run is not.
            _LOG.warning("state unreadable (%s) - starting fresh", err)

    def save(self) -> None:
        # Atomic replace: a power cut mid-write must not leave a truncated file
        # that reads as "no maintenance ever ran".
        try:
            os.makedirs(os.path.dirname(self.path), exist_ok=True)
            fd, tmp = tempfile.mkstemp(dir=os.path.dirname(self.path))
            with os.fdopen(fd, "w", encoding="utf-8") as fh:
                json.dump(self.data, fh, indent=1)
            os.replace(tmp, self.path)
        except OSError as err:
            _LOG.error("could not persist state: %s", err)

    # -- typed helpers ------------------------------------------------------
    def get_time(self, key: str):
        raw = self.data.get(key)
        if not raw:
            return None
        try:
            parsed = datetime.fromisoformat(raw)
        except (TypeError, ValueError):
            _LOG.warning("unparseable timestamp for %s: %r", key, raw)
            return None
        # Anything that ever escaped without an offset is treated as UTC rather
        # than raising later in an arithmetic expression.
        return parsed if parsed.tzinfo else parsed.replace(tzinfo=timezone.utc)

    def set_time(self, key: str, when: datetime | None) -> None:
        self.data[key] = when.astimezone(timezone.utc).isoformat() if when else None
        self.save()

    def set(self, key: str, value) -> None:
        self.data[key] = value
        self.save()