"""Ed25519 key at <project>/.gpu-rent/id_ed25519 (no passphrase)."""

from __future__ import annotations

from pathlib import Path

from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey

from gpu_rent.paths import default_ssh_key_path


def public_path(private: Path) -> Path:
    return private.with_suffix(private.suffix + ".pub") if private.suffix else Path(str(private) + ".pub")


def ensure_ed25519(path: Path | None = None) -> tuple[Path, Path]:
    private = path or default_ssh_key_path()
    pub = public_path(private)
    if private.is_file() and pub.is_file():
        return private, pub

    private.parent.mkdir(parents=True, exist_ok=True)
    key = Ed25519PrivateKey.generate()
    private_bytes = key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.OpenSSH,
        encryption_algorithm=serialization.NoEncryption(),
    )
    public_bytes = key.public_key().public_bytes(
        encoding=serialization.Encoding.OpenSSH,
        format=serialization.PublicFormat.OpenSSH,
    ) + b" gpu-rent\n"

    private.write_bytes(private_bytes)
    try:
        private.chmod(0o600)
    except OSError:
        pass
    pub.write_bytes(public_bytes)
    return private, pub


def key_ready(path: Path | None = None) -> bool:
    private = path or default_ssh_key_path()
    return private.is_file() and public_path(private).is_file()