import json
import os
import tempfile
import fcntl
from typing import List, Dict, Any, Optional
from fastapi.encoders import jsonable_encoder
#Import logiche e schemi
from schemas.reslevis import GatewayItem
from .config import GATEWAY_JSON_PATH


# ============================================================
#  Utility per lock e scrittura atomica
# ============================================================
class _LockedFile:
    """Gestisce l'accesso concorrente al file JSON con lock a livello OS."""
    def __init__(self, path: str, mode: str):
        self.path = path
        self.mode = mode
        self.fp = None

    def __enter__(self):
        os.makedirs(os.path.dirname(self.path), exist_ok=True)
        if "r" in self.mode and not os.path.exists(self.path):
            open(self.path, "w").write("[]")
        self.fp = open(self.path, self.mode)
        lock_type = (
            fcntl.LOCK_SH
            if ("r" in self.mode and "w" not in self.mode and "+" not in self.mode)
            else fcntl.LOCK_EX
        )
        fcntl.flock(self.fp.fileno(), lock_type)
        return self.fp

    def __exit__(self, exc_type, exc, tb):
        try:
            fcntl.flock(self.fp.fileno(), fcntl.LOCK_UN)
        finally:
            self.fp.close()



def _atomic_write(path: str, data: str) -> None:
    """Scrive su file in modo atomico (evita corruzione in caso di crash)."""
    dirpath = os.path.dirname(path)
    os.makedirs(dirpath, exist_ok=True)

    with tempfile.NamedTemporaryFile("w", dir=dirpath, delete=False) as tmp:
        tmp.write(data)
        tmp.flush()
        os.fsync(tmp.fileno())
        temp_name = tmp.name

    os.replace(temp_name, path)

    try:
        os.chmod(path, 0o664)
    except Exception as e:
        print(f"Warning: impossibile impostare i permessi su {path}: {e}")

def _norm_str(v: Any) -> str:
    """Normalizza un valore per confronti case-insensitive e safe su None."""
    return str(v).strip().lower() if v is not None else ""

def _index_by_id(rows: List[Dict[str, Any]], gateway_id: str) -> Optional[int]:
    gid = _norm_str(gateway_id)
    for i, r in enumerate(rows):
        if _norm_str(r.get("id")) == gid:
            return i
    return None


class GatewayJsonRepository:
    """Gestisce lettura e scrittura dei Gateway nel file JSON."""
    def __init__(self, json_path: str = GATEWAY_JSON_PATH):
        self.path = json_path

    def _read_all(self) -> List[Dict[str, Any]]:
        """Legge tutti i record dal file JSON."""
        with _LockedFile(self.path, "r") as fp:
            try:
                fp.seek(0)
                data = fp.read().strip()
                return json.loads(data) if data else []
            except json.JSONDecodeError:
                return []

    def _write_all(self, rows: List[Dict[str, Any]]) -> None:
        """Sovrascrive completamente il file JSON con la lista fornita."""
        payload = json.dumps(rows, ensure_ascii=False, indent=2)
        _atomic_write(self.path, payload)

    def list(self, search_string: Optional[str] = None) -> List[Dict[str, Any]]:
        """Ritorna tutti i Gateway, eventualmente filtrati per testo."""
        rows = self._read_all()
        if search_string:
            s = search_string.lower()
            rows = [
                r for r in rows
                if any(
                    (isinstance(r.get(k), str) and s in (r.get(k) or "").lower())
                    for k in ("name", "mac", "model", "status", "ip", "notes")
                )
            ]
        return rows

    def add(self, item: GatewayItem) -> None:
        """Aggiunge un nuovo gateway con controllo duplicati su ID e MAC."""
        rows = self._read_all()
        obj = jsonable_encoder(item)  # UUID -> str
        obj_id = _norm_str(obj.get("id"))
        mac = _norm_str(obj.get("mac"))

        if any(_norm_str(r.get("id")) == obj_id for r in rows):
            raise ValueError(f"Gateway con id '{obj_id}' già presente")

        if mac and any(_norm_str(r.get("mac")) == mac for r in rows):
            raise ValueError(f"Gateway con mac '{mac}' già presente")

        rows.append(obj)
        self._write_all(rows)

    def update(self, item: GatewayItem) -> None:
        """Sostituisce il gateway esistente con stesso ID. Controlla MAC duplicato su altri record."""
        rows = self._read_all()
        obj = jsonable_encoder(item)
        obj_id = _norm_str(obj.get("id"))
        mac = _norm_str(obj.get("mac"))

        idx = _index_by_id(rows, obj_id)
        if idx is None:
            raise ValueError(f"Gateway con id '{obj_id}' non trovato")

        if mac and any(_norm_str(r.get("mac")) == mac and _norm_str(r.get("id")) != obj_id for r in rows):
            raise ValueError(f"Gateway con mac '{mac}' già presente")

        rows[idx] = obj
        self._write_all(rows)

    def remove(self, gateway_id: str) -> None:
        """Rimuove un gateway per ID, altrimenti solleva ValueError."""
        rows = self._read_all()
        idx = _index_by_id(rows, gateway_id)
        if idx is None:
            raise ValueError(f"Gateway con id '{gateway_id}' non trovato")
        del rows[idx]
        self._write_all(rows)