import codecs
import fnmatch
import os

import markdown


def neighborhood(iterable, first=None, last=None):
    """
    Yield the (previous, current, next) items given an iterable.

    You can specify a `first` and/or `last` item for bounds.
    """
    iterator = iter(iterable)
    previous = first
    current = iterator.next()  # Throws StopIteration if empty.
    for next in iterator:
        yield (previous, current, next)
        previous = current
        current = next
    yield (previous, current, last)


def parse_markdown(file_path):
    """Extract title, (HTML) content and metadata from a markdown file."""
    parser = markdown.Markdown(extensions=["meta"])
    with codecs.open(file_path, "r") as source:
        content = parser.convert(source.read())
        metadata = parser.Meta if hasattr(parser, "Meta") else None
        title = metadata["title"][0] if metadata is not None else ""
        return title, content, metadata


def each_markdown_from(source_dir, file_name="index.md"):
    """Walk across the `source_dir` and return the md file paths."""
    for root, dirnames, filenames in os.walk(source_dir):
        for filename in fnmatch.filter(filenames, file_name):
            yield os.path.join(root, filename)