import rfeed
from datetime import datetime


from .common import SiteConfig
from .articles import ArticleMetadata, Article, format_article_tags
from .templating import format_html_template, TemplateSelections


def build_tag_index(index: dict[str, Article], wildcard ='*') -> dict[str, list[Article]]:
    '''Creates an inverted index mapping each article tag to a postings list of articles
    with said tag.'''
    tag_index = {}

    # Index the articles in ascending order of original publication date.
    for article in sorted(index.values(), key = lambda a: a.metadata.date):

        # Add all articles to the wildcard tag's postings list.
        if wildcard is not None:
            tag_index[wildcard] = (tag_index.get(wildcard,[])) + [article]

        # Add the article to each of its tags' posting lists.
        for tag in article.metadata.tags:
            tag_index[tag] = (tag_index.get(tag,[])) + [article]
            
    return tag_index


def build_blog_archive(
        site: SiteConfig, 
        index: dict[str, Article],
        template_selections: TemplateSelections,
        **kwargs
    ) -> str:
    '''Converts an index, formatted as filestem: (metadata, contents) dict,
    into an HTML page containing the list of articles, sorted from newest to oldest.
     
    Note: partials must be expanded into the kwargs, as they are needed to generate
    the overall page.
    '''

    # Add each article as a list item to an unordered list.
    archive_html_list = '<ul>'
    for article in sorted(index.values(), key = lambda a: a.metadata.date)[::-1]:
        
        # Generate HTML for the article (including metadata tags).
        archive_html_list += format_html_template(
            template_selections['archive_li'],
            article_filestem = article,
            blog_tags = ' '.join(format_article_tags(article.metadata.tags, template_selections['tag'], site = site)),
            article = article,
            site = site,
            **kwargs 
        )
    archive_html_list +='</ul>'

    tag_index = build_tag_index(index)

    tag_selector_options = []
    tag_selector_css_rules = [f'''
        body:has(input[name="tag-selector"][value="*"]:checked) li:has(.blog-tag){{{{
            display: list-item!important;
        }}}}
    ''']

    # Add tag selector options in descending order of article count.
    for tag, articles in sorted(tag_index.items(), key = lambda item : -len(item[1])):
        tag_selector_options.append(format_html_template(
            template_selections['tag_selector_option'],
            tag_name = tag,
            number_with_tag = len(articles),
            site = site,
            **kwargs
        ))
        if tag == '*':
            continue
        tag_selector_css_rules.append(f'''
            body:has(input[name="tag-selector"]:not([value="{tag}"]):checked) li:has(.blog-tag[data="{tag}"]){{{{
                display: none;
            }}}}
            body:has(input[name="tag-selector"][value="{tag}"]:checked) li:has(.blog-tag[data="{tag}"]){{{{
                display: list-item!important;
            }}}}
        ''')
    
    # For Python 3.9-friendliness.
    newline = '\n'

    # Generate the archive article.
    archive_html_article = format_html_template(
        template_selections['archive_article'], 
        content = archive_html_list,
        tag_selector_options = ' '.join(tag_selector_options),
        tag_selector_css_rules = f'<style>{newline.join(tag_selector_css_rules)}</style>',
        site = site,
        **kwargs
    )

    # Interpolate the article into the overall page template.
    archive_html_page = format_html_template(
        template_selections['page'], 
        content = archive_html_article, 
        site = site,
        **kwargs
    )
        
    with open(f"{site.web_root.rstrip('/')}/archive.html", 'w') as f:
            f.write(archive_html_page)
     

def build_rss_feed(site: SiteConfig, index: dict[str, Article]):
    feed = rfeed.Feed(
        title = site.title,
        link = f"{site.base_url.rstrip('/')}/rss.xml",
        description = site.description,
        language = "en-US",
        lastBuildDate = datetime.now(),
        items = [
            rfeed.Item(
                title = article.metadata.title,
                link = f"{site.base_url.rstrip('/')}/{article.path}", 
                description = article.metadata.description,
                author = article.metadata.author,
                guid = rfeed.Guid(article.path),
                pubDate = datetime(
                    article.metadata.date.year,
                    article.metadata.date.month,
                    article.metadata.date.day
                )
            )
            for article in index.values()
        ]
    )

    with open(f"{site.web_root.rstrip('/')}/rss.xml", 'w') as f:
        f.write(feed.rss())