scanner.py

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# This file is part of obs_base.
#
# Developed for the LSST Data Management System.
# This product includes software developed by the LSST Project
# (http://www.lsst.org).
# See the COPYRIGHT file at the top-level directory of this distribution
# for details of code ownership.
#
# 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.
#
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"""Interfaces and common code for recursively scanning directories for Gen2
dataset files.
 
The `PathElementHandler` ABC is defined here instead of ``handlers.py`` for
dependency reasons: `DirectoryScanner` uses the ABC, while its concrete
implementations use `DirectorySCanner`.
"""
from __future__ import annotations
 
__all__ = ["PathElementHandler", "DirectoryScanner"]
 
from abc import ABC, abstractmethod
import bisect
import os
from typing import (
    Callable,
    Iterator,
    List,
    Mapping,
    Optional,
)
 
from lsst.log import Log
from lsst.daf.butler import (
    DataCoordinate,
    DatasetType,
    FileDataset,
)
 
 
class PathElementHandler(ABC):
    """An interface for objects that handle a single path element (directory or
    file) in a Gen2 data repository.
 
    Handlers are added to a `DirectoryScanner` instance, which then calls them
    until one succeeds when it processes each element in a directory.
    """
    def __init__(self):
        self.lastDataId2 = {}
 
    __slots__ = ("lastDataId2", "log")
 
    @abstractmethod
    def isForFiles(self) -> bool:
        """Report what kind of path element this object handlers.
 
        Returns
        -------
        Return `True` if this handler is for file entries, or `False` if it
        is for directories.
        """
        raise NotImplementedError()
 
    @abstractmethod
    def __call__(self, path: str, name: str, datasets: Mapping[DatasetType, List[FileDataset]], *,
                 predicate: Callable[[DataCoordinate], bool]) -> bool:
        """Apply the handler to a file path.
 
        Parameters
        ----------
        path : `str`
            Full path of the file or directory.
        name : `str`
            Local name of the file or directory within its parent directory.
        datasets : `dict` [`DatasetType`, `list` [`FileDataset`] ]
            Dictionary that found datasets should be added to.
        predicate : `~collections.abc.Callable`
            A callable taking a single `DataCoordinate` argument and returning
            `bool`, indicating whether that (Gen3) data ID represents one
            that should be included in the scan.'
 
        Returns
        -------
        matched : `bool`
            `True` if this handler was a match for the given path and no other
            handlers need to be tried on it, `False` otherwise.
        """
        raise NotImplementedError()
 
    @property
    @abstractmethod
    def rank(self) -> int:
        """Return a rough indication of how flexible this handler is in terms
        of the path element names it can match.
 
        Handlers that match a constant path element should always return zero.
        """
        raise NotImplementedError()
 
    def translate(self, dataId2: dict, *, partial: bool = False) -> Optional[DataCoordinate]:
        """Translate the given data ID from Gen2 to Gen3.
 
        The default implementation returns `None`.  Subclasses that are able
        to translate data IDs should override this method.
 
        Parameters
        ----------
        dataId2 : `dict`
            Gen2 data ID.
        partial : `bool`, optional
            If `True` (`False` is default) this is a partial data ID for some
            dataset, and missing keys are expected.
 
        Returns
        -------
        dataId3 : `lsst.daf.butler.DataCoordinate` or `None`
            A Gen3 data ID, or `None` if this handler cannot translate data
            IDs.
        """
        return None
 
    def __lt__(self, other: PathElementHandler):
        """Handlers are sorted by rank to reduce the possibility that more
        flexible handlers will have a chance to match something they shouldn't.
        """
        return self.rank < other.rank
 
    lastDataId2: dict
    """The Gen2 data ID obtained by processing parent levels in the directory
    tree.
 
    This attribute should be reset by calling code whenever a new parent
    directory is entered, before invoking `__call__`.
    """
 
    log: Log
    """A logger to use for all diagnostic messages (`lsst.log.Log`).
 
    This attribute is set on a handler in `DirectoryScanner.add`; this avoids
    needing to forward one through all subclass constructors.
    """
 
 
class DirectoryScanner:
    """An object that uses `PathElementHandler` instances to process the files
    and subdirectories in a directory tree.
 
    Parameters
    ----------
    log : `Log`, optional
        Log to use to report warnings and debug information.
    """
    def __init__(self, log: Optional[Log] = None):
        self._files = []
        self._subdirectories = []
        if log is None:
            log = Log.getLogger("obs.base.gen2to3.walker")
        self.log = log
 
    __slots__ = ("_files", "_subdirectories", "log")
 
    def add(self, handler: PathElementHandler):
        """Add a new handler to the scanner.
 
        Parameters
        ----------
        handler : `PathElementHandler`
            The handler to be added.
        """
        handler.log = self.log
        if handler.isForFiles():
            bisect.insort(self._files, handler)
        else:
            bisect.insort(self._subdirectories, handler)
 
    def __iter__(self) -> Iterator[PathElementHandler]:
        """Iterate over all handlers.
        """
        yield from self._files
        yield from self._subdirectories
 
    def scan(self, path: str, datasets: Mapping[DatasetType, List[FileDataset]], *,
             predicate: Callable[[DataCoordinate], bool]):
        """Process a directory.
 
        Parameters
        ----------
        path : `str`
            Full path to the directory to be processed.
        datasets : `dict` [`DatasetType`, `list` [`FileDataset`] ]
            Dictionary that found datasets should be added to.
        predicate : `~collections.abc.Callable`
            A callable taking a single `DataCoordinate` argument and returning
            `bool`, indicating whether that (Gen3) data ID represents one
            that should be included in the scan.
        """
        unrecognized = []
        for entry in os.scandir(path):
            if entry.is_file():
                handlers = self._files
            elif entry.is_dir():
                handlers = self._subdirectories
            else:
                continue
            for handler in handlers:
                if handler(entry.path, entry.name, datasets, predicate=predicate):
                    break
            else:
                unrecognized.append(entry.name)
        if unrecognized:
            self.log.warn("Skipped unrecognized entries in %s: %s", path, unrecognized)