"""Handles all file writing and post-installation processing."""

import io
import os
from collections.abc import Collection, Iterable
from dataclasses import dataclass
from pathlib import Path
from typing import (
    TYPE_CHECKING,
    BinaryIO,
    Union,
)

from installer.records import Hash, RecordEntry
from installer.scripts import Script
from installer.utils import (
    _WINDOWS,
    Scheme,
    construct_record_file,
    copyfileobj_with_hashing,
    fix_shebang,
    make_file_executable,
)

if TYPE_CHECKING:
    from installer.scripts import LauncherKind, ScriptSection


class WheelDestination:
    """Handles writing the unpacked files, script generation and ``RECORD`` generation.

    Subclasses provide the concrete script generation logic, as well as the RECORD file
    (re)writing.
    """

    def write_script(
        self, name: str, module: str, attr: str, section: "ScriptSection"
    ) -> RecordEntry:
        """Write a script in the correct location to invoke given entry point.

        :param name: name of the script
        :param module: module path, to load the entry point from
        :param attr: final attribute access, for the entry point
        :param section: Denotes the "entry point section" where this was specified.
            Valid values are ``"gui"`` and ``"console"``.
        :type section: str

        Example usage/behaviour::

            >>> dest.write_script("pip", "pip._internal.cli", "main", "console")

        """
        raise NotImplementedError

    def write_file(
        self,
        scheme: Scheme,
        path: Union[str, "os.PathLike[str]"],
        stream: BinaryIO,
        is_executable: bool,
    ) -> RecordEntry:
        """Write a file to correct ``path`` within the ``scheme``.

        :param scheme: scheme to write the file in (like "purelib", "platlib" etc).
        :param path: path within that scheme
        :param stream: contents of the file
        :param is_executable: whether the file should be made executable

        The stream would be closed by the caller, after this call.

        Example usage/behaviour::

            >>> with open("__init__.py") as stream:
            ...     dest.write_file("purelib", "pkg/__init__.py", stream)

        """
        raise NotImplementedError

    def finalize_installation(
        self,
        scheme: Scheme,
        record_file_path: str,
        records: Iterable[tuple[Scheme, RecordEntry]],
    ) -> None:
        """Finalize installation, after all the files are written.

        Handles (re)writing of the ``RECORD`` file.

        :param scheme: scheme to write the ``RECORD`` file in
        :param record_file_path: path of the ``RECORD`` file with that scheme
        :param records: entries to write to the ``RECORD`` file

        Example usage/behaviour::

            >>> dest.finalize_installation("purelib")

        """
        raise NotImplementedError


@dataclass
class SchemeDictionaryDestination(WheelDestination):
    """Destination, based on a mapping of {scheme: file-system-path}."""

    scheme_dict: dict[str, str]
    """A mapping of {scheme: file-system-path}"""

    interpreter: str
    """The interpreter to use for generating scripts."""

    script_kind: "LauncherKind"
    """The "kind" of launcher script to use."""

    hash_algorithm: str = "sha256"
    """
    The hashing algorithm to use, which is a member of
    :any:`hashlib.algorithms_available` (ideally from
    :any:`hashlib.algorithms_guaranteed`).
    """

    bytecode_optimization_levels: Collection[int] = ()
    """
    Compile cached bytecode for installed .py files with these optimization
    levels. The bytecode is specific to the minor version of Python (e.g. 3.10)
    used to generate it.
    """

    destdir: str | None = None
    """
    A staging directory in which to write all files. This is expected to be the
    filesystem root at runtime, so embedded paths will be written as though
    this was the root.
    """

    overwrite_existing: bool = False
    """Silently overwrite existing files."""

    def _path_with_destdir(self, scheme: Scheme, path: str) -> Path:
        target_dir = Path(self.scheme_dict[scheme]).resolve()
        file = (target_dir / path).resolve()

        if not file.is_relative_to(target_dir):
            raise ValueError(
                f"Attempting to write {path} outside of the target directory"
            )

        if self.destdir is not None:
            rel_path = file.relative_to(file.anchor)
            return Path(self.destdir) / rel_path
        return file

    def write_to_fs(
        self,
        scheme: Scheme,
        path: str,
        stream: BinaryIO,
        is_executable: bool,
    ) -> RecordEntry:
        """Write contents of ``stream`` to the correct location on the filesystem.

        :param scheme: scheme to write the file in (like "purelib", "platlib" etc).
        :param path: path within that scheme
        :param stream: contents of the file
        :param is_executable: whether the file should be made executable

        - Ensures that an existing file is not being overwritten.
        - Hashes the written content, to determine the entry in the ``RECORD`` file.
        """
        target_path = self._path_with_destdir(scheme, path)
        if not self.overwrite_existing and target_path.exists():
            message = f"File already exists: {target_path!s}"
            raise FileExistsError(message)

        parent_folder = target_path.parent
        if not parent_folder.exists():
            parent_folder.mkdir(parents=True)

        with target_path.open("wb") as f:
            hash_, size = copyfileobj_with_hashing(stream, f, self.hash_algorithm)

        if is_executable:
            make_file_executable(target_path)

        return RecordEntry(path, Hash(self.hash_algorithm, hash_), size)

    def write_file(
        self,
        scheme: Scheme,
        path: Union[str, "os.PathLike[str]"],
        stream: BinaryIO,
        is_executable: bool,
    ) -> RecordEntry:
        """Write a file to correct ``path`` within the ``scheme``.

        :param scheme: scheme to write the file in (like "purelib", "platlib" etc).
        :param path: path within that scheme
        :param stream: contents of the file
        :param is_executable: whether the file should be made executable

        - Changes the shebang for files in the "scripts" scheme.
        - Uses :py:meth:`SchemeDictionaryDestination.write_to_fs` for the
          filesystem interaction.
        """
        path_ = os.fspath(path)

        if scheme == "scripts":
            with fix_shebang(stream, self.interpreter) as stream_with_different_shebang:
                return self.write_to_fs(
                    scheme, path_, stream_with_different_shebang, is_executable
                )

        return self.write_to_fs(scheme, path_, stream, is_executable)

    def write_script(
        self, name: str, module: str, attr: str, section: "ScriptSection"
    ) -> RecordEntry:
        """Write a script to invoke an entrypoint.

        :param name: name of the script
        :param module: module path, to load the entry point from
        :param attr: final attribute access, for the entry point
        :param section: Denotes the "entry point section" where this was specified.
            Valid values are ``"gui"`` and ``"console"``.
        :type section: str

        - Generates a launcher using :any:`Script.generate`.
        - Writes to the "scripts" scheme.
        - Uses :py:meth:`SchemeDictionaryDestination.write_to_fs` for the
          filesystem interaction.
        """
        script = Script(name, module, attr, section)
        script_name, data = script.generate(self.interpreter, self.script_kind)

        with io.BytesIO(data) as stream:
            entry = self.write_to_fs(
                Scheme("scripts"), script_name, stream, is_executable=True
            )

            path = self._path_with_destdir(Scheme("scripts"), script_name)
            mode = path.stat().st_mode
            mode |= (mode & 0o444) >> 2
            path.chmod(mode)

            return entry

    def _compile_bytecode(self, scheme: Scheme, record: RecordEntry) -> None:
        """Compile bytecode for a single .py file."""
        if scheme not in ("purelib", "platlib"):
            return

        import compileall

        target_path = self._path_with_destdir(scheme, record.path)
        dir_path_to_embed = (Path(self.scheme_dict[scheme]) / record.path).parent

        for level in self.bytecode_optimization_levels:
            compileall.compile_file(
                target_path, optimize=level, quiet=1, ddir=dir_path_to_embed
            )

    def finalize_installation(
        self,
        scheme: Scheme,
        record_file_path: str,
        records: Iterable[tuple[Scheme, RecordEntry]],
    ) -> None:
        """Finalize installation, by writing the ``RECORD`` file & compiling bytecode.

        :param scheme: scheme to write the ``RECORD`` file in
        :param record_file_path: path of the ``RECORD`` file with that scheme
        :param records: entries to write to the ``RECORD`` file
        """

        def prefix_for_scheme(file_scheme: str) -> str | None:
            if file_scheme == scheme:
                return None
            if _WINDOWS:  # pragma: no cover
                path = os.path.abspath(self.scheme_dict[file_scheme])  # noqa: PTH100
            else:  # pragma: no cover
                path = os.path.relpath(
                    self.scheme_dict[file_scheme],
                    start=self.scheme_dict[scheme],
                )
            return path + "/"

        record_list = list(records)
        with construct_record_file(record_list, prefix_for_scheme) as record_stream:
            self.write_to_fs(
                scheme, record_file_path, record_stream, is_executable=False
            )

        for scheme, record in record_list:
            self._compile_bytecode(scheme, record)