"""Gestion du fichier known_hosts local (cles d'hotes approuvees via TOFU).

Avec des serveurs en IP dynamique (DHCP), une IP reattribuee a une autre machine
fait apparaitre une "cle d'hote modifiee" lors de la connexion : ce module permet
de retirer facilement l'ancienne entree, en masse ou au cas par cas, sans avoir
a editer le fichier a la main.
"""
from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path

import paramiko

from app.paths import DATA_DIR  # noqa: E402  (chemins valables aussi en .exe)
KNOWN_HOSTS_FILE = DATA_DIR / "known_hosts"


@dataclass
class KnownHostEntry:
    hostname: str
    key_type: str
    fingerprint: str


class KnownHostsStore:
    def __init__(self, path: Path = KNOWN_HOSTS_FILE):
        self.path = path

    def _load(self) -> paramiko.HostKeys:
        hk = paramiko.HostKeys()
        if self.path.exists():
            try:
                hk.load(str(self.path))
            except Exception:
                pass
        return hk

    def list_entries(self) -> list[KnownHostEntry]:
        hk = self._load()
        entries: list[KnownHostEntry] = []
        for hostname in hk.keys():
            for key_type, key in hk[hostname].items():
                entries.append(KnownHostEntry(
                    hostname=hostname,
                    key_type=key_type,
                    fingerprint=key.get_fingerprint().hex(":"),
                ))
        entries.sort(key=lambda e: e.hostname)
        return entries

    def remove_host(self, hostname: str) -> None:
        hk = self._load()
        if hostname in hk:
            del hk[hostname]
            self._save(hk)

    def replace_host_key(self, hostname: str, key: paramiko.PKey) -> None:
        """Retire l'ancienne cle d'un hote et enregistre la nouvelle (cas d'une IP DHCP reattribuee)."""
        hk = self._load()
        if hostname in hk:
            del hk[hostname]
        hk.add(hostname, key.get_name(), key)
        self._save(hk)

    def clear_all(self) -> None:
        DATA_DIR.mkdir(parents=True, exist_ok=True)
        self.path.write_text("", encoding="utf-8")

    def _save(self, hk: paramiko.HostKeys) -> None:
        DATA_DIR.mkdir(parents=True, exist_ok=True)
        hk.save(str(self.path))