# coding: utf-8

from __future__ import unicode_literals
from datetime import datetime
import io
import logging
import os
import time

from jinja2.exceptions import TemplateNotFound
import jinja2
import json

from mkdocs import nav, search, utils
from mkdocs.relative_path_ext import RelativePathExtension
import mkdocs

log = logging.getLogger(__name__)


def convert_markdown(markdown_source, config, site_navigation=None):
    """
    Convert the Markdown source file to HTML as per the config and
    site_navigation. Return a tuple of the HTML as a string, the parsed table
    of contents, and a dictionary of any metadata that was specified in the
    Markdown file.
    """

    extensions = [
        RelativePathExtension(site_navigation, config['strict'])
    ] + config['markdown_extensions']

    return utils.convert_markdown(
        markdown_source=markdown_source,
        extensions=extensions,
        extension_configs=config['mdx_configs']
    )


def get_global_context(nav, config):
    """
    Given the SiteNavigation and config, generate the context which is relevant
    to app pages.
    """

    site_name = config['site_name']

    if config['site_favicon']:
        site_favicon = nav.url_context.make_relative('/' + config['site_favicon'])
    else:
        site_favicon = None

    page_description = config['site_description']

    extra_javascript = utils.create_media_urls(nav, config['extra_javascript'])

    extra_css = utils.create_media_urls(nav, config['extra_css'])

    return {
        'site_name': site_name,
        'site_author': config['site_author'],
        'favicon': site_favicon,
        'page_description': page_description,

        # Note that there's intentionally repetition here. Rather than simply
        # provide the config dictionary we instead pass everything explicitly.
        #
        # This helps ensure that we can throughly document the context that
        # gets passed to themes.
        'repo_url': config['repo_url'],
        'repo_name': config['repo_name'],
        'nav': nav,
        'base_url': nav.url_context.make_relative('/'),
        'homepage_url': nav.homepage.url,
        'site_url': config['site_url'],

        'extra_css': extra_css,
        'extra_javascript': extra_javascript,

        'include_nav': config['include_nav'],
        'include_next_prev': config['include_next_prev'],

        'copyright': config['copyright'],
        'google_analytics': config['google_analytics'],

        'mkdocs_version': mkdocs.__version__,
        'build_date_utc': datetime.utcfromtimestamp(int(os.environ.get('SOURCE_DATE_EPOCH', time.time()))),

        'config': config
    }


def get_page_context(page, content, toc, meta, config):
    """
    Generate the page context by extending the global context and adding page
    specific variables.
    """

    if page.is_homepage or page.title is None:
        page_title = None
    else:
        page_title = page.title

    if page.is_homepage:
        page_description = config['site_description']
    else:
        page_description = None

    if config['site_url']:
        base = config['site_url']
        if not base.endswith('/'):
            base += '/'
        canonical_url = utils.urljoin(
            base, page.abs_url.lstrip('/'))
    else:
        canonical_url = None

    return {
        'page_title': page_title,
        'page_description': page_description,

        'content': content,
        'toc': toc,
        'meta': meta,


        'canonical_url': canonical_url,

        'current_page': page,
        'previous_page': page.previous_page,
        'next_page': page.next_page
    }


def build_template(template_name, env, config, site_navigation=None):

    log.debug("Building template: %s", template_name)

    try:
        template = env.get_template(template_name)
    except TemplateNotFound:
        return False

    if site_navigation is not None:
        context = get_global_context(site_navigation, config)
    else:
        context = {}

    output_content = template.render(context)
    output_path = os.path.join(config['site_dir'], template_name)
    utils.write_file(output_content.encode('utf-8'), output_path)
    return True


def _build_page(page, config, site_navigation, env, dump_json):

    # Read the input file
    input_path = os.path.join(config['docs_dir'], page.input_path)

    try:
        input_content = io.open(input_path, 'r', encoding='utf-8').read()
    except IOError:
        log.error('file not found: %s', input_path)
        raise

    # Process the markdown text
    html_content, table_of_contents, meta = convert_markdown(
        markdown_source=input_content,
        config=config,
        site_navigation=site_navigation
    )

    context = get_global_context(site_navigation, config)
    context.update(get_page_context(
        page, html_content, table_of_contents, meta, config
    ))

    # Allow 'template:' override in md source files.
    if 'template' in meta:
        template = env.get_template(meta['template'][0])
    else:
        template = env.get_template('base.html')

    # Render the template.
    output_content = template.render(context)

    # Write the output file.
    output_path = os.path.join(config['site_dir'], page.output_path)
    if dump_json:
        json_context = {
            'content': context['content'],
            'title': context['current_page'].title,
            'url': context['current_page'].abs_url,
            'language': 'en',
        }
        json_output = json.dumps(json_context, indent=4).encode('utf-8')
        utils.write_file(json_output, output_path.replace('.html', '.json'))
    else:
        utils.write_file(output_content.encode('utf-8'), output_path)

    return html_content, table_of_contents, meta


def build_extra_templates(extra_templates, config, site_navigation=None):

    log.debug("Building extra_templates page")

    for extra_template in extra_templates:

        input_path = os.path.join(config['docs_dir'], extra_template)

        with io.open(input_path, 'r', encoding='utf-8') as template_file:
            template = jinja2.Template(template_file.read())

        if site_navigation is not None:
            context = get_global_context(site_navigation, config)
        else:
            context = {}

        output_content = template.render(context)
        output_path = os.path.join(config['site_dir'], extra_template)
        utils.write_file(output_content.encode('utf-8'), output_path)


def build_pages(config, dump_json=False):
    """
    Builds all the pages and writes them into the build directory.
    """
    site_navigation = nav.SiteNavigation(config['pages'], config['use_directory_urls'])
    loader = jinja2.FileSystemLoader(config['theme_dir'] + [config['mkdocs_templates'], ])
    env = jinja2.Environment(loader=loader)
    search_index = search.SearchIndex()

    build_template('404.html', env, config, site_navigation)

    if not build_template('search.html', env, config, site_navigation):
        log.debug("Search is enabled but the theme doesn't contain a "
                  "search.html file. Assuming the theme implements search "
                  "within a modal.")

    build_template('sitemap.xml', env, config, site_navigation)

    build_extra_templates(config['extra_templates'], config, site_navigation)

    for page in site_navigation.walk_pages():

        try:
            log.debug("Building page %s", page.input_path)
            build_result = _build_page(page, config, site_navigation, env,
                                       dump_json)
            html_content, table_of_contents, _ = build_result
            search_index.add_entry_from_context(
                page, html_content, table_of_contents)
        except Exception:
            log.error("Error building page %s", page.input_path)
            raise

    search_index = search_index.generate_search_index()
    json_output_path = os.path.join(config['site_dir'], 'mkdocs', 'search_index.json')
    utils.write_file(search_index.encode('utf-8'), json_output_path)


def build(config, live_server=False, dump_json=False, clean_site_dir=False):
    """
    Perform a full site build.
    """
    if clean_site_dir:
        log.info("Cleaning site directory")
        utils.clean_directory(config['site_dir'])
    if not live_server:
        log.info("Building documentation to directory: %s", config['site_dir'])
        if not clean_site_dir and site_directory_contains_stale_files(config['site_dir']):
            log.info("The directory contains stale files. Use --clean to remove them.")

    if dump_json:
        build_pages(config, dump_json=True)
        return

    # Reversed as we want to take the media files from the builtin theme
    # and then from the custom theme_dir so the custom versions take take
    # precedence.
    for theme_dir in reversed(config['theme_dir']):
        log.debug("Copying static assets from theme: %s", theme_dir)
        utils.copy_media_files(theme_dir, config['site_dir'])

    log.debug("Copying static assets from the docs dir.")
    utils.copy_media_files(config['docs_dir'], config['site_dir'])

    log.debug("Building markdown pages.")
    build_pages(config)


def site_directory_contains_stale_files(site_directory):
    """
    Check if the site directory contains stale files from a previous build.
    Right now the check returns true if the directory is not empty.
    A more sophisticated approach should be found to trigger only if there are
    files that won't be overwritten anyway.
    """
    if os.path.exists(site_directory):
        if os.listdir(site_directory):
            return True
    return False