"""Settings and state persistence in the data volume (atomic JSON writes)."""

from __future__ import annotations

import json
import os
import tempfile
import threading
from dataclasses import asdict, dataclass, fields
from pathlib import Path


def atomic_write(path: Path, data: bytes, mode: int = 0o644) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    fd, tmp = tempfile.mkstemp(dir=path.parent, prefix=f".{path.name}.")
    try:
        os.fchmod(fd, mode)
        with os.fdopen(fd, "wb") as f:
            f.write(data)
            f.flush()
            os.fsync(f.fileno())
        os.replace(tmp, path)
    except BaseException:
        try:
            os.unlink(tmp)
        except FileNotFoundError:
            pass
        raise
    try:
        dfd = os.open(path.parent, os.O_DIRECTORY)
        try:
            os.fsync(dfd)
        finally:
            os.close(dfd)
    except OSError:
        pass


def atomic_write_json(path: Path, obj, mode: int = 0o644) -> None:
    atomic_write(path, json.dumps(obj, indent=2, sort_keys=True, ensure_ascii=False).encode(), mode)


def read_json(path: Path, default):
    try:
        return json.loads(path.read_text())
    except FileNotFoundError:
        return default


@dataclass
class Settings:
    printer_host: str = "10.10.2.202"
    ssh_port: int = 22
    ssh_user: str = "root"
    cc2_url: str = "http://10.10.2.202:8081"
    spoolman_url: str = "http://10.10.6.10:7912"
    id_offset: int = 10000
    poll_interval: float = 5.0
    location_slot: str = "CC2 Slot {n}"
    location_storage: str = "Lager"
    empty_grace: float = 20.0  # seconds with tray status 0 before a slot counts as empty
    settle_seconds: float = 60.0  # `used` must be unchanged this long before booking
    dry_run: bool = True

    # environment variable -> field (only used as defaults before settings.json exists)
    ENV = {
        "PRINTER_HOST": "printer_host", "SSH_PORT": "ssh_port", "SSH_USER": "ssh_user",
        "CC2_URL": "cc2_url", "SPOOLMAN_URL": "spoolman_url", "ID_OFFSET": "id_offset",
        "POLL_INTERVAL": "poll_interval", "DRY_RUN": "dry_run",
    }

    @classmethod
    def from_dict(cls, d: dict) -> "Settings":
        s = cls()
        s.update(d)
        return s

    def update(self, d: dict) -> None:
        for f in fields(self):
            if f.name in d and d[f.name] is not None:
                setattr(self, f.name, _coerce(f.type, d[f.name], f.name))
        self.validate()

    def validate(self) -> None:
        if not 1 <= self.ssh_port <= 65535:
            raise ValueError("SSH-Port ungültig")
        if not 0 <= self.id_offset <= 65000:
            raise ValueError("ID-Offset muss zwischen 0 und 65000 liegen")
        if not 1 <= self.poll_interval <= 300:
            raise ValueError("Abfrage-Intervall muss zwischen 1 und 300 s liegen")
        if "{n}" not in self.location_slot:
            raise ValueError("Ortsname für Slots muss {n} enthalten")
        for name in ("cc2_url", "spoolman_url"):
            v = getattr(self, name)
            if not v.startswith(("http://", "https://")):
                raise ValueError(f"{name} muss mit http:// oder https:// beginnen")
            setattr(self, name, v.rstrip("/"))
        if not self.location_storage.strip():
            raise ValueError("Ortsname für das Lager fehlt")

    def to_dict(self) -> dict:
        return asdict(self)

    def slot_location(self, slot: int) -> str:
        return self.location_slot.replace("{n}", str(slot + 1))


def _coerce(typ, value, name):
    typ = typ if isinstance(typ, str) else typ.__name__
    try:
        if typ == "bool":
            if isinstance(value, str):
                return value.strip().lower() in ("1", "true", "yes", "on", "ja")
            return bool(value)
        if typ == "int":
            return int(value)
        if typ == "float":
            return float(value)
        return str(value).strip()
    except (TypeError, ValueError):
        raise ValueError(f"Ungültiger Wert für {name}") from None


class SettingsStore:
    def __init__(self, data_dir: Path, env: dict | None = None):
        self.path = data_dir / "settings.json"
        self._lock = threading.Lock()
        stored = read_json(self.path, None)
        if stored is None:
            env = os.environ if env is None else env
            defaults = {f: env[k] for k, f in Settings.ENV.items() if env.get(k)}
            self.settings = Settings.from_dict(defaults)
        else:
            self.settings = Settings.from_dict(stored)

    def get(self) -> Settings:
        with self._lock:
            return Settings.from_dict(self.settings.to_dict())

    def save(self, changes: dict) -> Settings:
        with self._lock:
            new = Settings.from_dict({**self.settings.to_dict(), **changes})
            atomic_write_json(self.path, new.to_dict())
            self.settings = new
            return Settings.from_dict(new.to_dict())


class StateStore:
    """Bridge state: slot mappings, booked consumption, last record."""

    def __init__(self, data_dir: Path):
        self.path = data_dir / "state.json"
        self.data = read_json(self.path, {})
        self.data.setdefault("version", 1)
        self.data.setdefault("slots", {})
        self.data.setdefault("booked", {})
        self.data.setdefault("locations", {})
        self.data.setdefault("last_record", None)

    def save(self) -> None:
        atomic_write_json(self.path, self.data)