from __future__ import annotations

from pathlib import Path

from .messages import MAPPER_ENTRY_ALREADY_EXISTS, CANNOT_FIND_DEVICE_PATH
from .commands import CommandInterface
from .misc import DISK_BY_UUID, MAPPER_PATH


class Cryptsetup(CommandInterface):
    class _Subcommands:
        close = "close"
        status = "status"
        open = "open"

    _BINARY = Path("/usr/bin/cryptsetup")

    @classmethod
    def encrypt(cls, mapper_entry: str) -> None:
        """Close a previously open LUKS container."""
        cls._run_command(cls._Subcommands.close, mapper_entry)

    @classmethod
    def _status(cls, name: str) -> str:
        """Return `cryptsetup status` of a device under `/dev/mapper`"""
        return cls._get_output(cls._Subcommands.status, name)

    @classmethod
    def decrypt(cls, path: Path, mapper_entry: str) -> bool:
        """Decrypt a disk, return whether it was already decrypted."""
        if cls._mapper_entry_in_use(mapper_entry):
            if cls._already_decrypted(path, mapper_entry):
                return True
            print(MAPPER_ENTRY_ALREADY_EXISTS)
            raise FileExistsError()
        cls._run_command(cls._Subcommands.open, str(path), mapper_entry)
        return False

    @classmethod
    def _mapper_entry_in_use(cls, mapper_entry: str) -> bool:
        return (MAPPER_PATH / mapper_entry).exists()

    @classmethod
    def _get_device_by_uuid_from_status_output(cls, status: str) -> Path:
        """Given the output of `cryptsetup status [device]`,
        get the unique name of the disk as path in /dev/disk/by-uuid."""
        device = cls._get_device_path(status)
        result = cls._resolve_uuid_of_device(device)
        return result

    @classmethod
    def _resolve_uuid_of_device(cls, device):
        """Given a device like `/dev/sda`, resolve its entry under `/dev/disk/by-uuid`.

        Exit if none can be found."""
        for item in DISK_BY_UUID.iterdir():
            if item.readlink() == device:
                result = item
                break
        else:
            raise FileNotFoundError(
                f"Could not resolve UUID of cryptsetup device {device}"
            )
        return result

    @classmethod
    def _get_device_path(cls, status) -> Path:
        """Given the output of `cryptsetup status`, return the path of the device."""
        for line in status.split("\n"):
            if line.startswith("  device:"):
                device = Path(line.split(":")[-1].strip())
                break
        else:
            raise FileNotFoundError(CANNOT_FIND_DEVICE_PATH)
        # noinspection PyUnboundLocalVariable
        return device

    @classmethod
    def _already_decrypted(cls, path: Path, mapper_entry: str) -> bool:
        """Given a path in `/dev/disk/by-uuid` and the corresponding name under `/dev/mapper`,
        check if the disk is already decrypted."""
        decrypted_disk_path = cls._get_device_by_uuid_from_status_output(
            cls._status(mapper_entry)
        )
        return decrypted_disk_path == path