#!/usr/bin/env python
"""Find and concatenate all the rule files into one readable output.
"""
# n.b.: This shows any file, not just ones committed in git, which would
# require parsing output from git ls-files or something.
# This doesn't show files in subdirectories.
# This won't show anything that doesn't have a .md extension.
# This is supposed to generate valid markdown, but that depends on the
# rule files.
import os
import re


_FILENAME_RE = re.compile(r'(\d+)_(.*)\.md')


def file_paths_under(root):
    """Yield paths of files under the given root.
    """
    for filename in sorted(os.listdir(root)):
        full_path = os.path.join(root, filename)
        # n.b.: lots of checks against filesystem.
        if os.path.isfile(full_path):
            yield full_path


def files(file_paths):
    """Yield file objects for the given file paths.
    """
    # n.b.: no error handling if files don't exist or can't be opened.
    for file_path in file_paths:
        with open(file_path, "r") as file_obj:
            yield file_obj


def parse_path(filename):
    """Extract rule number and title from given path to rule file.
    """
    basename = os.path.basename(filename)
    match = _FILENAME_RE.match(basename)
    if not match:
        return None
    number = match.group(1)
    words = [word.capitalize() for word in match.group(2).split("-")]
    title = " ".join(words)
    return number, title


def render_dir(root):
    """Yield lines presenting rule files in the given directory.
    """
    for file_obj in files(file_paths_under(root)):
        parsed = parse_path(file_obj.name)
        # n.b.: parsed may be None and fail to unpack here.
        number, title = parsed
        content = file_obj.read().rstrip()
        title_line = "{0}. {1}".format(number, title)
        yield ""
        yield title_line
        yield "-" * len(title_line)
        yield ""
        yield content


def render_section(root, title):
    """Add a title to the output of render_dir.
    """
    yield title
    yield "=" * len(title)
    for line in render_dir(root):
        yield line


def main():
    """What happens when the script is run
    """
    this_file = os.path.abspath(__file__)
    here = os.path.dirname(this_file)
    parent = os.path.dirname(here)
    immutable_rule_dir = os.path.join(parent, 'immutable_rules')
    mutable_rule_dir = os.path.join(parent, 'mutable_rules')

    for line in render_section(immutable_rule_dir, "Immutable Rules"):
        print(line)

    print("")

    for line in render_section(mutable_rule_dir, "Mutable Rules"):
        print(line)


# This is a script file, so __name__ stuff is not useful.
main()