# $Id$
# Authors: David Goodger <goodger@python.org>; Ueli Schlaepfer; Dmitry Jemerov
# Copyright: This module has been placed in the public domain.

"""
Transforms related to document parts.
"""

__docformat__ = 'reStructuredText'


import re
import sys
from docutils import nodes, utils
from docutils.transforms import TransformError, Transform


class SectNum(Transform):

    """
    Automatically assigns numbers to the titles of document sections.

    It is possible to limit the maximum section level for which the numbers
    are added.  For those sections that are auto-numbered, the "autonum"
    attribute is set, informing the contents table generator that a different
    form of the TOC should be used.
    """

    default_priority = 710
    """Should be applied before `Contents`."""

    def apply(self):
        self.maxdepth = self.startnode.details.get('depth', None)
        self.startvalue = self.startnode.details.get('start', 1)
        self.prefix = self.startnode.details.get('prefix', '')
        self.suffix = self.startnode.details.get('suffix', '')
        self.startnode.parent.remove(self.startnode)
        if self.document.settings.sectnum_xform:
            if self.maxdepth is None:
                self.maxdepth = sys.maxsize
            self.update_section_numbers(self.document)
        else: # store details for eventual section numbering by the writer
            self.document.settings.sectnum_depth = self.maxdepth
            self.document.settings.sectnum_start = self.startvalue
            self.document.settings.sectnum_prefix = self.prefix
            self.document.settings.sectnum_suffix = self.suffix

    def update_section_numbers(self, node, prefix=(), depth=0):
        depth += 1
        if prefix:
            sectnum = 1
        else:
            sectnum = self.startvalue
        for child in node:
            if isinstance(child, nodes.section):
                numbers = prefix + (str(sectnum),)
                title = child[0]
                # Use &nbsp; for spacing:
                generated = nodes.generated(
                    '', (self.prefix + '.'.join(numbers) + self.suffix
                         +  '\u00a0' * 3),
                    classes=['sectnum'])
                title.insert(0, generated)
                title['auto'] = 1
                if depth < self.maxdepth:
                    self.update_section_numbers(child, numbers, depth)
                sectnum += 1


class Contents(Transform):

    """
    This transform generates a table of contents from the entire document tree
    or from a single branch.  It locates "section" elements and builds them
    into a nested bullet list, which is placed within a "topic" created by the
    contents directive.  A title is either explicitly specified, taken from
    the appropriate language module, or omitted (local table of contents).
    The depth may be specified.  Two-way references between the table of
    contents and section titles are generated (requires Writer support).

    This transform requires a startnode, which contains generation
    options and provides the location for the generated table of contents (the
    startnode is replaced by the table of contents "topic").
    """

    default_priority = 720

    def apply(self):
        try: # let the writer (or output software) build the contents list?
            toc_by_writer = self.document.settings.use_latex_toc
        except AttributeError:
            toc_by_writer = False
        details = self.startnode.details
        if 'local' in details:
            startnode = self.startnode.parent.parent
            while not (isinstance(startnode, nodes.section)
                       or isinstance(startnode, nodes.document)):
                # find the ToC root: a direct ancestor of startnode
                startnode = startnode.parent
        else:
            startnode = self.document
        self.toc_id = self.startnode.parent['ids'][0]
        if 'backlinks' in details:
            self.backlinks = details['backlinks']
        else:
            self.backlinks = self.document.settings.toc_backlinks
        if toc_by_writer:
            # move customization settings to the parent node
            self.startnode.parent.attributes.update(details)
            self.startnode.parent.remove(self.startnode)
        else:
            contents = self.build_contents(startnode)
            if len(contents):
                self.startnode.replace_self(contents)
            else:
                self.startnode.parent.parent.remove(self.startnode.parent)

    def build_contents(self, node, level=0):
        level += 1
        sections = [sect for sect in node if isinstance(sect, nodes.section)]
        entries = []
        autonum = 0
        depth = self.startnode.details.get('depth', sys.maxsize)
        for section in sections:
            title = section[0]
            auto = title.get('auto')    # May be set by SectNum.
            entrytext = self.copy_and_filter(title)
            reference = nodes.reference('', '', refid=section['ids'][0],
                                        *entrytext)
            ref_id = self.document.set_id(reference)
            entry = nodes.paragraph('', '', reference)
            item = nodes.list_item('', entry)
            if ( self.backlinks in ('entry', 'top')
                 and title.next_node(nodes.reference) is None):
                if self.backlinks == 'entry':
                    title['refid'] = ref_id
                elif self.backlinks == 'top':
                    title['refid'] = self.toc_id
            if level < depth:
                subsects = self.build_contents(section, level)
                item += subsects
            entries.append(item)
        if entries:
            contents = nodes.bullet_list('', *entries)
            if auto:
                contents['classes'].append('auto-toc')
            return contents
        else:
            return []

    def copy_and_filter(self, node):
        """Return a copy of a title, with references, images, etc. removed."""
        visitor = ContentsFilter(self.document)
        node.walkabout(visitor)
        return visitor.get_entry_text()


class ContentsFilter(nodes.TreeCopyVisitor):

    def get_entry_text(self):
        return self.get_tree_copy().children

    def visit_citation_reference(self, node):
        raise nodes.SkipNode

    def visit_footnote_reference(self, node):
        raise nodes.SkipNode

    def visit_image(self, node):
        if node.hasattr('alt'):
            self.parent.append(nodes.Text(node['alt']))
        raise nodes.SkipNode

    def ignore_node_but_process_children(self, node):
        raise nodes.SkipDeparture

    visit_interpreted = ignore_node_but_process_children
    visit_problematic = ignore_node_but_process_children
    visit_reference = ignore_node_but_process_children
    visit_target = ignore_node_but_process_children
