import platform
import re
import subprocess
from argparse import Namespace
from dataclasses import dataclass
from enum import Enum
from pathlib import Path
from typing import Any, ClassVar, Self, TypedDict, override

from . import nix
from .process import Remote, run_wrapper
from .utils import Args

type ImageVariants = dict[str, str]


class NixOSRebuildError(Exception):
    "nixos-rebuild general error."

    def __init__(self, message: str) -> None:
        self.message = message

    @override
    def __str__(self) -> str:
        return f"error: {self.message}"


class Action(Enum):
    SWITCH = "switch"
    BOOT = "boot"
    TEST = "test"
    BUILD = "build"
    EDIT = "edit"
    REPL = "repl"
    DRY_BUILD = "dry-build"
    DRY_RUN = "dry-run"
    DRY_ACTIVATE = "dry-activate"
    BUILD_IMAGE = "build-image"
    BUILD_VM = "build-vm"
    BUILD_VM_WITH_BOOTLOADER = "build-vm-with-bootloader"
    LIST_GENERATIONS = "list-generations"

    @override
    def __str__(self) -> str:
        return self.value

    @staticmethod
    def values() -> list[str]:
        return [a.value for a in Action]


@dataclass(frozen=True)
class BuildAttr:
    path: str | Path
    attr: str | None

    def to_attr(self, *attrs: str) -> str:
        return f"{self.attr + '.' if self.attr else ''}{'.'.join(attrs)}"

    @classmethod
    def from_arg(cls, attr: str | None, file: str | None) -> Self:
        # We use, in this order:
        #   1. the --file argument (can be a directory, implying /system.nix)
        #   2. system.nix in the cwd, but only if --attr is used
        #   3. the <nixos-system> Nix path entry
        #   4. /etc/nixos/system.nix
        #   5. the <nixpkgs/nixos> Nix path entry (uses configuration.nix)

        if file:
            fpath = Path(file)
            if fpath.is_dir() and (fpath / "system.nix").exists():
                return cls(fpath / "system.nix", attr)
            # Backward compatibility
            elif fpath.is_dir() and (fpath / "default.nix").exists():
                return cls(fpath / "default.nix", attr)
            return cls(fpath, attr)
        elif attr and Path("system.nix").exists():
            return cls(Path("system.nix"), attr)
        elif attr and Path("default.nix").exists():
            # Backward compatibility
            return cls(Path("default.nix"), attr)
        elif nix.find_file("nixos-system"):
            return cls("<nixos-system>", attr)
        elif Path("/etc/nixos/system.nix").exists():
            return cls(Path("/etc/nixos/system.nix"), attr)
        return cls("<nixpkgs/nixos>", attr)


@dataclass(frozen=True)
class Flake:
    path: str
    attr: str
    _re: ClassVar = re.compile(r"^(?P<path>[^\#]*)\#?(?P<attr>[^\#\"]*)$")

    def to_attr(self, *attrs: str) -> str:
        return f"{self}.{'.'.join(attrs)}"

    @override
    def __str__(self) -> str:
        return f"{self.path}#{self.attr}"

    @classmethod
    def parse(cls, flake_str: str, target_host: Remote | None = None) -> Self:
        m = cls._re.match(flake_str)
        assert m is not None, f"got no matches for {flake_str}"
        attr = m.group("attr")
        nixos_attr = f'nixosConfigurations."{attr or cls._get_hostname(target_host) or "default"}"'
        path = m.group("path")
        return cls(path, nixos_attr)

    @classmethod
    def from_arg(cls, flake_arg: Any, target_host: Remote | None) -> Self | None:  # noqa: ANN401
        match flake_arg:
            case str(s):
                return cls.parse(s, target_host)
            case True:
                return cls.parse(".", target_host)
            case False:
                return None
            case _:
                # Use /etc/nixos/flake.nix if it exists.
                default_path = Path("/etc/nixos/flake.nix")
                if default_path.exists():
                    # It can be a symlink to the actual flake.
                    default_path = default_path.resolve()
                    return cls.parse(str(default_path.parent), target_host)
                else:
                    return None

    def resolve_path_if_exists(self) -> str:
        try:
            return str(Path(self.path).resolve(strict=True))
        except FileNotFoundError:
            return self.path

    @staticmethod
    def _get_hostname(target_host: Remote | None) -> str | None:
        if target_host:
            try:
                return run_wrapper(
                    ["uname", "-n"],
                    capture_output=True,
                    remote=target_host,
                ).stdout.strip()
            except (AttributeError, subprocess.CalledProcessError):
                return None
        else:
            return platform.node()


@dataclass(frozen=True)
class Generation:
    id: int
    timestamp: str  # we may want to have a proper timestamp type in future
    current: bool


# camelCase since this will be used as output for `--json` flag
class GenerationJson(TypedDict):
    generation: int
    date: str
    nixosVersion: str
    kernelVersion: str
    configurationRevision: str
    specialisations: list[str]
    current: bool


class FlakeMetadataJson(TypedDict):
    resolvedUrl: str


@dataclass(frozen=True)
class GroupedNixArgs:
    build_flags: Args
    common_flags: Args
    copy_flags: Args
    flake_eval_flags: Args
    flake_build_flags: Args

    @classmethod
    def from_parsed_args_groups(cls, args_groups: dict[str, Namespace]) -> Self:
        common_flags = vars(args_groups["common_flags"])
        common_build_flags = common_flags | vars(args_groups["common_build_flags"])
        build_flags = common_build_flags | vars(args_groups["classic_build_flags"])
        flake_common_flags = common_flags | vars(args_groups["flake_common_flags"])
        flake_eval_flags = vars(args_groups["flake_eval_flags"])
        flake_build_flags = common_build_flags | flake_common_flags
        copy_flags = common_flags | vars(args_groups["copy_flags"])
        # --no-build-output -> --no-link
        if build_flags.get("no_build_output"):
            flake_build_flags["no_link"] = True

        return cls(
            build_flags=build_flags,
            common_flags=common_flags,
            copy_flags=copy_flags,
            flake_eval_flags=flake_eval_flags,
            flake_build_flags=flake_build_flags,
        )


@dataclass(frozen=True)
class Profile:
    name: str
    path: Path

    @classmethod
    def from_arg(cls, name: str) -> Self:
        match name:
            case "system":
                return cls(name, Path("/nix/var/nix/profiles/system"))
            case _:
                path = Path("/nix/var/nix/profiles/system-profiles") / name
                path.parent.mkdir(mode=0o755, parents=True, exist_ok=True)
                return cls(name, path)