# Author: David Goodger
# Contact: goodger@python.org
# Revision: $Revision: 4260 $
# Date: $Date: 2006-01-09 19:28:09 +0100 (Mon, 09 Jan 2006) $
# Copyright: This module has been placed in the public domain.

"""
This is the Docutils (Python Documentation Utilities) package.

Package Structure
=================

Modules:

- __init__.py: Contains component base classes, exception classes, and
  Docutils version information.

- core.py: Contains the ``Publisher`` class and ``publish_*()`` convenience
  functions.

- frontend.py: Runtime settings (command-line interface, configuration files)
  processing, for Docutils front-ends.

- io.py: Provides a uniform API for low-level input and output.

- nodes.py: Docutils document tree (doctree) node class library.

- statemachine.py: A finite state machine specialized for
  regular-expression-based text filters.

- urischemes.py: Contains a complete mapping of known URI addressing
  scheme names to descriptions.

- utils.py: Contains the ``Reporter`` system warning class and miscellaneous
  utilities.

Subpackages:

- languages: Language-specific mappings of terms.

- parsers: Syntax-specific input parser modules or packages.

- readers: Context-specific input handlers which understand the data
  source and manage a parser.

- transforms: Modules used by readers and writers to modify DPS
  doctrees.

- writers: Format-specific output translators.
"""

__docformat__ = 'reStructuredText'

__version__ = '0.4'
"""``major.minor.micro`` version number.  The micro number is bumped for API
changes, for new functionality, and for interim project releases.  The minor
number is bumped whenever there is a significant project release.  The major
number will be bumped when the project is feature-complete, and perhaps if
there is a major change in the design."""

__version_details__ = 'release'
"""Extra version details (e.g. 'snapshot 2005-05-29, r3410', 'repository',
'release'), modified automatically & manually."""

class ApplicationError(StandardError): pass
class DataError(ApplicationError): pass


class SettingsSpec:

    """
    Runtime setting specification base class.

    SettingsSpec subclass objects used by `docutils.frontend.OptionParser`.
    """

    settings_spec = ()
    """Runtime settings specification.  Override in subclasses.

    Defines runtime settings and associated command-line options, as used by
    `docutils.frontend.OptionParser`.  This is a tuple of:

    - Option group title (string or `None` which implies no group, just a list
      of single options).
    
    - Description (string or `None`).
    
    - A sequence of option tuples.  Each consists of:

      - Help text (string)
      
      - List of option strings (e.g. ``['-Q', '--quux']``).
      
      - Dictionary of keyword arguments.  It contains arguments to the
        OptionParser/OptionGroup ``add_option`` method, possibly with the
        addition of a 'validator' keyword (see the
        `docutils.frontend.OptionParser.validators` instance attribute).  Runtime
        settings names are derived implicitly from long option names
        ('--a-setting' becomes ``settings.a_setting``) or explicitly from the
        'dest' keyword argument.  See optparse docs for more details.

    - More triples of group title, description, options, as many times as
      needed.  Thus, `settings_spec` tuples can be simply concatenated.
    """

    settings_defaults = None
    """A dictionary of defaults for settings not in `settings_spec` (internal
    settings, intended to be inaccessible by command-line and config file).
    Override in subclasses."""

    settings_default_overrides = None
    """A dictionary of auxiliary defaults, to override defaults for settings
    defined in other components.  Override in subclasses."""

    relative_path_settings = ()
    """Settings containing filesystem paths.  Override in subclasses.
    Settings listed here are to be interpreted relative to the current working
    directory."""

    config_section = None
    """The name of the config file section specific to this component
    (lowercase, no brackets).  Override in subclasses."""

    config_section_dependencies = None
    """A list of names of config file sections that are to be applied before
    `config_section`, in order (from general to specific).  In other words,
    the settings in `config_section` are to be overlaid on top of the settings
    from these sections.  The "general" section is assumed implicitly.
    Override in subclasses."""


class TransformSpec:

    """
    Runtime transform specification base class.

    TransformSpec subclass objects used by `docutils.transforms.Transformer`.
    """

    def get_transforms(self):
        """Transforms required by this class.  Override in subclasses."""
        if self.default_transforms != ():
            import warnings
            warnings.warn('default_transforms attribute deprecated.\n'
                          'Use get_transforms() method instead.',
                          DeprecationWarning)
            return list(self.default_transforms)
        return []

    # Deprecated; for compatibility.
    default_transforms = ()

    unknown_reference_resolvers = ()
    """List of functions to try to resolve unknown references.  Unknown
    references have a 'refname' attribute which doesn't correspond to any
    target in the document.  Called when FinalCheckVisitor is unable to find a
    correct target.  The list should contain functions which will try to
    resolve unknown references, with the following signature::

        def reference_resolver(node):
            '''Returns boolean: true if resolved, false if not.'''

    If the function is able to resolve the reference, it should also remove
    the 'refname' attribute and mark the node as resolved::

        del node['refname']
        node.resolved = 1

    Each function must have a "priority" attribute which will affect the order
    the unknown_reference_resolvers are run::

        reference_resolver.priority = 100

    Override in subclasses."""


class Component(SettingsSpec, TransformSpec):

    """Base class for Docutils components."""

    component_type = None
    """Name of the component type ('reader', 'parser', 'writer').  Override in
    subclasses."""

    supported = ()
    """Names for this component.  Override in subclasses."""
    
    def supports(self, format):
        """
        Is `format` supported by this component?

        To be used by transforms to ask the dependent component if it supports
        a certain input context or output format.
        """
        return format in self.supported
