#!/usr/bin/env python3

from argparse import ArgumentParser
from itertools import chain
import json
from pathlib import Path
from subprocess import run
from tempfile import NamedTemporaryFile

from git import Repo

from helpers import deserialize_directories, pandoc


def parse_arguments():
    parser = ArgumentParser()
    parser.add_argument(
        '--template', help='Pandoc template for HTML output.'
    )
    parser.add_argument(
        '--site-title', help='Prefix to add to <title>.'
    )
    parser.add_argument(
        '--lua-filter', dest='filters', action='append',
        help='Lua filter to run the page through.'
    )
    parser.add_argument(
        'site_tree', help='JSON file describing the page tree.'
    )
    parser.add_argument(
        'target', help='Subfolder to generate an index for.'
    )
    parser.add_argument(
        'output', help='Path to the output file.'
    )
    return parser.parse_args()


def list_files(tree_file, folder):
    with open(tree_file) as tree:
        directories = deserialize_directories(json.load(tree))
    return directories[folder].subfolders, directories[folder].files


def has_title(markdown):
    pandoc = run(
        ('pandoc', '-t', 'json'), input=markdown,
        check=True, text=True, capture_output=True
    )
    ast = json.loads(pandoc.stdout)
    return 'title' in ast['meta']


def format_readme_index(readme, title, items):
    blocks = [
        readme,
        f'# {title}',
        items
    ]

    if not has_title(readme):
        blocks.insert(0, '% README')

    return '\n\n'.join(blocks)


def format_plain_index(title, items):
    return '\n'.join((f'% {title}', items))


def list_pages(files):
    readme = None
    pages = []

    for f in files:
        page = Path(f).stem

        if page == 'README':
            readme = f
        else:
            pages.append(page)

    return pages, readme


# TODO: use pandoc's --include-after-body, so that this works with
# non-markdown READMEs.
def format_index(target, directories, files):
    pages, readme = list_pages(files)

    dir_list = (
        f'- [{d}/]({d}/index.html)' for d in directories
    )
    page_list = (
        f'- [{p}]({p}.html)' for p in pages
    )
    items = '\n'.join(chain(dir_list, page_list))

    title = f'Index for {target}' if target else 'Index'

    if readme is None:
        return format_plain_index(title, items)

    repo_top = Repo(search_parent_directories=True).working_dir
    intro = Path(repo_top, target, readme).read_text()
    return format_readme_index(intro, title, items)


def main(arguments):
    target = arguments.target
    folders, files = list_files(arguments.site_tree, target)

    with NamedTemporaryFile(suffix='.md', mode='w+') as page:
        page.write(format_index(target, folders, files))
        page.flush()

        pandoc(page.name, arguments.output, arguments.template,
               arguments.filters, site_title=arguments.site_title)


if __name__ == '__main__':
    main(parse_arguments())