sources.py

"""Save DOT code objects, render with Graphviz dot, and open in viewer."""

import locale
import logging
import os
import typing

from .encoding import DEFAULT_ENCODING
from . import _tools
from . import saving
from . import jupyter_integration
from . import piping
from . import rendering
from . import unflattening

__all__ = ['Source']


log = logging.getLogger(__name__)


class Source(rendering.Render, saving.Save,
             jupyter_integration.JupyterIntegration, piping.Pipe,
             unflattening.Unflatten):
    """Verbatim DOT source code string to be rendered by Graphviz.

    Args:
        source: The verbatim DOT source code string.
        filename: Filename for saving the source (defaults to ``'Source.gv'``).
        directory: (Sub)directory for source saving and rendering.
        format: Rendering output format (``'pdf'``, ``'png'``, ...).
        engine: Layout engine used (``'dot'``, ``'neato'``, ...).
        encoding: Encoding for saving the source.

    Note:
        All parameters except ``source`` are optional. All of them
        can be changed under their corresponding attribute name
        after instance creation.
    """

    @classmethod
    @_tools.deprecate_positional_args(supported_number=1, ignore_arg='cls')
    def from_file(cls, filename: typing.Union[os.PathLike, str],
                  directory: typing.Union[os.PathLike, str, None] = None,
                  format: typing.Optional[str] = None,
                  engine: typing.Optional[str] = None,
                  encoding: typing.Optional[str] = DEFAULT_ENCODING,
                  renderer: typing.Optional[str] = None,
                  formatter: typing.Optional[str] = None) -> 'Source':
        """Return an instance with the source string read from the given file.

        Args:
            filename: Filename for loading/saving the source.
            directory: (Sub)directory for source loading/saving and rendering.
            format: Rendering output format (``'pdf'``, ``'png'``, ...).
            engine: Layout command used (``'dot'``, ``'neato'``, ...).
            encoding: Encoding for loading/saving the source.
        """
        directory = _tools.promote_pathlike_directory(directory)
        filepath = (os.path.join(directory, filename) if directory.parts
                    else os.fspath(filename))

        if encoding is None:
            encoding = locale.getpreferredencoding()

        log.debug('read %r with encoding %r', filepath, encoding)
        with open(filepath, encoding=encoding) as fd:
            source = fd.read()

        return cls(source,
                   filename=filename, directory=directory,
                   format=format, engine=engine, encoding=encoding,
                   renderer=renderer, formatter=formatter,
                   loaded_from_path=filepath)

    @_tools.deprecate_positional_args(supported_number=1, ignore_arg='self')
    def __init__(self, source: str,
                 filename: typing.Union[os.PathLike, str, None] = None,
                 directory: typing.Union[os.PathLike, str, None] = None,
                 format: typing.Optional[str] = None,
                 engine: typing.Optional[str] = None,
                 encoding: typing.Optional[str] = DEFAULT_ENCODING, *,
                 renderer: typing.Optional[str] = None,
                 formatter: typing.Optional[str] = None,
                 loaded_from_path: typing.Optional[os.PathLike] = None) -> None:
        super().__init__(filename=filename, directory=directory,
                         format=format, engine=engine,
                         renderer=renderer, formatter=formatter,
                         encoding=encoding)
        self._loaded_from_path = loaded_from_path
        self._source = source

    # work around pytype false alarm
    _source: str
    _loaded_from_path: typing.Optional[os.PathLike]

    def _copy_kwargs(self, **kwargs):
        """Return the kwargs to create a copy of the instance."""
        return super()._copy_kwargs(source=self._source,
                                    loaded_from_path=self._loaded_from_path,
                                    **kwargs)

    def __iter__(self) -> typing.Iterator[str]:
        r"""Yield the DOT source code read from file line by line.

        Yields: Line ending with a newline (``'\n'``).
        """
        lines = self._source.splitlines(keepends=True)
        yield from lines[:-1]
        for line in lines[-1:]:
            suffix = '\n' if not line.endswith('\n') else ''
            yield line + suffix

    @property
    def source(self) -> str:
        """The DOT source code as string.

        Normalizes so that the string always ends in a final newline.
        """
        source = self._source
        if not source.endswith('\n'):
            source += '\n'
        return source

    @_tools.deprecate_positional_args(supported_number=1, ignore_arg='self')
    def save(self, filename: typing.Union[os.PathLike, str, None] = None,
             directory: typing.Union[os.PathLike, str, None] = None, *,
             skip_existing: typing.Optional[bool] = None) -> str:
        """Save the DOT source to file. Ensure the file ends with a newline.

        Args:
            filename: Filename for saving the source (defaults to ``name`` + ``'.gv'``)
            directory: (Sub)directory for source saving and rendering.
            skip_existing: Skip write if file exists (default: ``None``).
                By default skips if instance was loaded from the target path:
                ``.from_file(self.filepath)``.

        Returns:
            The (possibly relative) path of the saved source file.
        """
        skip = (skip_existing is None and self._loaded_from_path
                and os.path.samefile(self._loaded_from_path, self.filepath))
        if skip:
            log.debug('.save(skip_existing=None) skip writing Source.from_file(%r)',
                      self.filepath)
        return super().save(filename=filename, directory=directory,
                            skip_existing=skip)