#!/usr/bin/env python3

"""blag's core methods.

"""

# remove when we don't support py38 anymore
from __future__ import annotations
import argparse
import os
import shutil
import logging
import configparser
import sys

from jinja2 import (
    Environment,
    ChoiceLoader,
    FileSystemLoader,
    PackageLoader,
    Template,
)
import feedgenerator

from blag.markdown import markdown_factory, convert_markdown
from blag.devserver import serve
from blag.version import __VERSION__
from blag.quickstart import quickstart

logger = logging.getLogger(__name__)
logging.basicConfig(
        level=logging.INFO,
        format='%(asctime)s %(levelname)s %(name)s %(message)s',
)


def main(arguments: list[str] = None) -> None:
    """Main entrypoint for the CLI.

    This method parses the CLI arguments and executes the respective
    commands.

    Parameters
    ----------
    arguments : list[str]
        optional parameters, used for testing

    """
    args = parse_args(arguments)
    # set loglevel
    if args.verbose:
        logger.setLevel(logging.DEBUG)
    logger.debug(f"This is blag {__VERSION__}.")
    args.func(args)


def parse_args(args: list[str] = None) -> argparse.Namespace:
    """Parse command line arguments.

    Parameters
    ----------
    args : List[str]
        optional parameters, used for testing

    Returns
    -------
    arparse.Namespace

    """
    parser = argparse.ArgumentParser()
    parser.add_argument(
        '--version',
        action='version',
        version='%(prog)s '+__VERSION__,
    )
    parser.add_argument(
        '-v', '--verbose',
        action='store_true',
        help='Verbose output.',
    )

    commands = parser.add_subparsers(dest='command')
    commands.required = True

    build_parser = commands.add_parser(
            'build',
            help='Build website.',
    )
    build_parser.set_defaults(func=build)
    build_parser.add_argument(
            '-i', '--input-dir',
            default='content',
            help='Input directory (default: content)',
    )
    build_parser.add_argument(
            '-o', '--output-dir',
            default='build',
            help='Ouptut directory (default: build)',
    )
    build_parser.add_argument(
            '-t', '--template-dir',
            default='templates',
            help='Template directory (default: templates)',
    )
    build_parser.add_argument(
            '-s', '--static-dir',
            default='static',
            help='Static directory (default: static)',
    )

    quickstart_parser = commands.add_parser(
            'quickstart',
            help="Quickstart blag, creating necessary configuration.",
    )
    quickstart_parser.set_defaults(func=quickstart)

    serve_parser = commands.add_parser(
            'serve',
            help="Start development server.",
    )
    serve_parser.set_defaults(func=serve)
    serve_parser.add_argument(
            '-i', '--input-dir',
            default='content',
            help='Input directory (default: content)',
    )
    serve_parser.add_argument(
            '-o', '--output-dir',
            default='build',
            help='Ouptut directory (default: build)',
    )
    serve_parser.add_argument(
            '-t', '--template-dir',
            default='templates',
            help='Template directory (default: templates)',
    )
    serve_parser.add_argument(
            '-s', '--static-dir',
            default='static',
            help='Static directory (default: static)',
    )

    return parser.parse_args(args)


def get_config(configfile: str) -> configparser.SectionProxy:
    """Load site configuration from configfile.

    Parameters
    ----------
    configfile : str
        path to configuration file


    Returns
    -------
    configparser.SectionProxy

    """
    config = configparser.ConfigParser()
    config.read(configfile)
    # check for the mandatory options
    for value in 'base_url', 'title', 'description', 'author':
        try:
            config['main'][value]
        except Exception:
            print(f'{value} is missing in {configfile}!')
            sys.exit(1)

    if not config['main']['base_url'].endswith('/'):
        logger.warning('base_url does not end with a slash, adding it.')
        config['main']['base_url'] += '/'

    return config['main']


def environment_factory(
    template_dir: str = None,
    globals_: dict = None,
) -> Environment:
    """Environment factory.

    Creates a Jinja2 Environment with the default templates and
    additional templates from `template_dir` loaded. If `globals` are
    provided, they are attached to the environment and thus available to
    all contexts.

    Parameters
    ----------
    template_dir : str
    globals_ : dict

    Returns
    -------
    jinja2.Environment

    """
    # first we try the custom templates, and fall back the ones provided
    # by blag
    loaders: list[FileSystemLoader | PackageLoader] = []
    if template_dir:
        loaders.append(FileSystemLoader([template_dir]))
    loaders.append(PackageLoader('blag', 'templates'))
    env = Environment(loader=ChoiceLoader(loaders))
    if globals_:
        env.globals = globals_
    return env


def build(args: argparse.Namespace) -> None:
    """Build the site.

    This is blag's main method that builds the site, generates the feed
    etc.

    Parameters
    ----------
    args : argparse.Namespace

    """
    os.makedirs(f'{args.output_dir}', exist_ok=True)
    convertibles = []
    for root, dirnames, filenames in os.walk(args.input_dir):
        for filename in filenames:
            rel_src = os.path.relpath(f'{root}/{filename}',
                                      start=args.input_dir)
            # all non-markdown files are just copied over, the markdown
            # files are converted to html
            if rel_src.endswith('.md'):
                rel_dst = rel_src
                rel_dst = rel_dst[:-3] + '.html'
                convertibles.append((rel_src, rel_dst))
            else:
                shutil.copy(f'{args.input_dir}/{rel_src}',
                            f'{args.output_dir}/{rel_src}')
        for dirname in dirnames:
            # all directories are copied into the output directory
            path = os.path.relpath(f'{root}/{dirname}', start=args.input_dir)
            os.makedirs(f'{args.output_dir}/{path}', exist_ok=True)

    # copy static files over
    logger.info('Copying static files.')
    if os.path.exists(args.static_dir):
        shutil.copytree(args.static_dir, args.output_dir, dirs_exist_ok=True)

    config = get_config('config.ini')

    env = environment_factory(args.template_dir, dict(site=config))

    page_template = env.get_template('page.html')
    article_template = env.get_template('article.html')
    archive_template = env.get_template('archive.html')
    tags_template = env.get_template('tags.html')
    tag_template = env.get_template('tag.html')

    articles, pages = process_markdown(
        convertibles,
        args.input_dir,
        args.output_dir,
        page_template,
        article_template,
    )

    generate_feed(
        articles, args.output_dir,
        base_url=config['base_url'],
        blog_title=config['title'],
        blog_description=config['description'],
        blog_author=config['author'],
    )
    generate_archive(articles, archive_template, args.output_dir)
    generate_tags(articles, tags_template, tag_template, args.output_dir)


def process_markdown(
    convertibles: list[tuple[str, str]],
    input_dir: str,
    output_dir: str,
    page_template: Template,
    article_template: Template,
) -> tuple[list[tuple[str, dict]], list[tuple[str, dict]]]:
    """Process markdown files.

    This method processes the convertibles, converts them to html and
    saves them to the respective destination paths.

    If a markdown file has a `date` metadata field it will be recognized
    as article otherwise as page.

    Parameters
    ----------
    convertibles : list[tuple[str, str]]
        relative paths to markdown- (src) html- (dest) files
    input_dir : str
    output_dir : str
    page_template, archive_template : jinja2 template
        templats for pages and articles

    Returns
    -------
    articles, pages : list[tuple[str, dict]]

    """
    logger.info("Converting Markdown files...")
    md = markdown_factory()

    articles = []
    pages = []
    for src, dst in convertibles:
        logger.debug(f'Processing {src}')

        with open(f'{input_dir}/{src}', 'r') as fh:
            body = fh.read()

        content, meta = convert_markdown(md, body)

        context = dict(content=content)
        context.update(meta)

        # if markdown has date in meta, we treat it as a blog article,
        # everything else are just pages
        if meta and 'date' in meta:
            articles.append((dst, context))
            result = article_template.render(context)
        else:
            pages.append((dst, context))
            result = page_template.render(context)
        with open(f'{output_dir}/{dst}', 'w') as fh_dest:
            fh_dest.write(result)

    # sort articles by date, descending
    articles = sorted(articles, key=lambda x: x[1]['date'], reverse=True)
    return articles, pages


def generate_feed(
    articles: list[tuple[str, dict]],
    output_dir: str,
    base_url: str,
    blog_title: str,
    blog_description: str,
    blog_author: str,
) -> None:
    """Generate Atom feed.

    Parameters
    ----------
    articles : list[tuple[str, dict]]
        list of relative output path and article dictionary
    output_dir : str
        where the feed is stored
    base_url : str
        base url
    blog_title : str
        blog title
    blog_description : str
        blog description
    blog_author : str
        blog author

    """
    logger.info('Generating Atom feed.')
    feed = feedgenerator.Atom1Feed(
            link=base_url,
            title=blog_title,
            description=blog_description,
            feed_url=base_url + 'atom.xml',
    )

    for dst, context in articles:
        # if article has a description, use that. otherwise fall back to
        # the title
        description = context.get('description', context['title'])

        feed.add_item(
            title=context['title'],
            author_name=blog_author,
            link=base_url + dst,
            description=description,
            content=context['content'],
            pubdate=context['date'],
        )

    with open(f'{output_dir}/atom.xml', 'w') as fh:
        feed.write(fh, encoding='utf8')


def generate_archive(
    articles: list[tuple[str, dict]],
    template: Template,
    output_dir: str,
) -> None:
    """Generate the archive page.

    Parameters
    ----------
    articles : list[tuple[str, dict]]
        List of articles. Each article has the destination path and a
        dictionary with the content.
    template : jinja2.Template instance
    output_dir : str

    """
    archive = []
    for dst, context in articles:
        entry = context.copy()
        entry['dst'] = dst
        archive.append(entry)

    result = template.render(dict(archive=archive))
    with open(f'{output_dir}/index.html', 'w') as fh:
        fh.write(result)


def generate_tags(
    articles: list[tuple[str, dict]],
    tags_template: Template,
    tag_template: Template,
    output_dir: str,
) -> None:
    """Generate the tags page.

    Parameters
    ----------
    articles : list[tuple[str, dict]]
        List of articles. Each article has the destination path and a
        dictionary with the content.
    tags_template, tag_template : jinja2.Template instance
    output_dir : str

    """
    logger.info("Generating Tag-pages.")
    os.makedirs(f'{output_dir}/tags', exist_ok=True)

    # get tags number of occurrences
    all_tags: dict = {}
    for _, context in articles:
        tags = context.get('tags', [])
        for tag in tags:
            all_tags[tag] = all_tags.get(tag, 0) + 1
    # sort by occurrence
    taglist: list[tuple[str, int]] = sorted(
        all_tags.items(), key=lambda x: x[1], reverse=True
    )

    result = tags_template.render(dict(tags=taglist))
    with open(f'{output_dir}/tags/index.html', 'w') as fh:
        fh.write(result)

    # get tags and archive per tag
    all_tags = {}
    for dst, context in articles:
        tags = context.get('tags', [])
        for tag in tags:
            archive = all_tags.get(tag, [])
            entry = context.copy()
            entry['dst'] = dst
            archive.append(entry)
            all_tags[tag] = archive

    for tag, archive in all_tags.items():
        result = tag_template.render(dict(archive=archive, tag=tag))
        with open(f'{output_dir}/tags/{tag}.html', 'w') as fh:
            fh.write(result)


if __name__ == '__main__':
    main()