software/hoardy-web/./tool/hoardy_web/source.py

# Copyright (c) 2024 Jan Malakhovski <oxij@oxij.org>
#
# This file is a part of `hoardy-web` project.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

"""Abstract data sources."""

import abc as _abc
import dataclasses as _dc
import io as _io
import os as _os
import typing as _t

from kisstdlib.failure import *
import kisstdlib.os as _kos


class DeferredSource(metaclass=_abc.ABCMeta):
    @_abc.abstractmethod
    def approx_size(self) -> int:
        raise NotImplementedError()

    @_abc.abstractmethod
    def show_source(self) -> str:
        raise NotImplementedError()

    @_abc.abstractmethod
    def get_fileobj(self) -> _io.BufferedReader:
        raise NotImplementedError()

    def get_bytes(self) -> bytes:
        with self.get_fileobj() as f:
            return f.read()

    def same_as(self, other: _t.Any) -> bool:  # pylint: disable=unused-argument
        return False

    def replaces(self, other: _t.Any) -> bool:  # pylint: disable=unused-argument
        return True


class UnknownSource(DeferredSource):
    def approx_size(self) -> int:
        return 8

    def show_source(self) -> str:
        return f"<UnknownSource {id(self)}>"

    def get_fileobj(self) -> _io.BufferedReader:
        raise NotImplementedError()

    def get_bytes(self) -> bytes:
        raise NotImplementedError()


class _BytesIOReader(_io.BytesIO):
    def peek(self, size: int = 0) -> bytes:
        return self.getvalue()[self.tell() : size]


BytesIOReader = _t.cast(_t.Callable[[bytes], _io.BufferedReader], _BytesIOReader)


@_dc.dataclass
class BytesSource(DeferredSource):
    data: bytes

    def approx_size(self) -> int:
        return 16 + len(self.data)

    def show_source(self) -> str:
        return f"<BytesSource {id(self)} {repr(self.data)}>"

    def get_fileobj(self) -> _io.BufferedReader:
        return BytesIOReader(self.data)

    def get_bytes(self) -> bytes:
        return self.data

    def replaces(self, other: DeferredSource) -> bool:
        if isinstance(other, BytesSource) and self.data == other.data:
            return False
        return True


@_dc.dataclass
class FileSource(DeferredSource):
    path: str | bytes
    st_mtime_ns: int
    st_dev: int
    st_ino: int

    def approx_size(self) -> int:
        return 40 + len(self.path)

    def show_source(self) -> str:
        return _kos.fsdecode_maybe(self.path)

    def get_fileobj(self) -> _io.BufferedReader:
        fobj = open(self.path, "rb")  # pylint: disable=consider-using-with
        try:
            in_stat = _os.fstat(fobj.fileno())
            if self.st_mtime_ns != in_stat.st_mtime_ns:
                raise Failure("`%s` changed between accesses", self.path)
        except Exception:
            try:
                fobj.close()
            except Exception:
                pass
            raise
        return fobj

    def same_as(self, other: DeferredSource) -> bool:
        if (
            isinstance(other, FileSource)
            and self.st_ino != 0
            and other.st_ino != 0
            and self.st_dev == other.st_dev
            and self.st_ino == other.st_ino
        ):
            # same source file inode
            return True
        return False

    def replaces(self, other: DeferredSource) -> bool:
        if isinstance(other, FileSource) and self.path == other.path:
            return False
        return True


def make_FileSource(path: str | bytes, in_stat: _os.stat_result) -> FileSource:
    return FileSource(path, in_stat.st_mtime_ns, in_stat.st_dev, in_stat.st_ino)


DeferredSourceType = _t.TypeVar("DeferredSourceType", bound=DeferredSource)


@_dc.dataclass
class StreamElementSource(DeferredSource, _t.Generic[DeferredSourceType]):
    stream_source: DeferredSourceType
    num: int

    def approx_size(self) -> int:
        return 24 + self.stream_source.approx_size()

    def show_source(self) -> str:
        return self.stream_source.show_source() + "//" + str(self.num)

    def get_fileobj(self) -> _io.BufferedReader:
        raise NotImplementedError()

    def get_bytes(self) -> bytes:
        raise NotImplementedError()

    def replaces(self, other: DeferredSource) -> bool:
        if (
            isinstance(other, StreamElementSource)
            and self.stream_source == other.stream_source
            and self.num == other.num
        ):
            return False
        return True