#!/bin/python3

from contextlib import contextmanager
import colorama

import time
import datetime
import dateutil.tz

import bs4
import urllib.parse

import re

import lxml.etree as ET


@contextmanager
def init_colorama():
    """Set global foreground modifying ANSI codes.

    BLACK, BLUE, CYAN, GREEN, MAGENTA, RED, WHITE, YELLOW, and RESET.

    """

    # pylint: disable=exec-used,invalid-name

    colorama.init()
    for color, ansi in colorama.Fore.__dict__.items():
        exec("global {0}; {0} = '{1}'".format(color, ansi))
    yield
    for color in colorama.Fore.__dict__:
        exec("global {0}; {0} = ''".format(color))
    colorama.deinit()


def current_datetime():
    """Return the current datetime, complete with tzinfo.

    Precision is one second. Timezone is the local timezone.
    """
    return datetime.datetime.fromtimestamp(round(time.time()),
                                           dateutil.tz.tzlocal())


def absolutify_links(soup, baseurl):
    """Make links in an article absolute.

    Parameters
    ----------
    soup : bs4.BeautifulSoup
    baseurl : str

    """
    for tag in soup.find_all(lambda tag: tag.has_attr("href")):
        tag["href"] = urllib.parse.urljoin(baseurl, tag["href"])
    for tag in soup.find_all(lambda tag: tag.has_attr("src")):
        tag["src"] = urllib.parse.urljoin(baseurl, tag["src"])

# MARKDOWN EXTENSION!
#
# See docstring of process_image_sizes for documentation.

# If matched, 1st group is width, 3rd group (optional) is height, and
# 4th group is actual text.
IMAGESIZE_EXTRACTOR = re.compile(r'\|(\d+)(x(\d+))?\|\s*(.*)')

def process_image_sizes(soup):
    """Process the image size Markdown extension.

    Allows specifying image size in a Markdown image construct
    ![](). The syntax is:

        ![|width(xheight)?| alt](src)

    where width and height are positive integers (xheight is optional),
    and alt is the regular alt string (either plain or with some
    Markdown formatting). alt string, as usual, is optional.

    Examples:

        ![|1920x1080| Hello, world!](http://example.com/hello.png)
        ![|1920| *Hey!*](http://example.com/hey.png)
        ![|1280x800|](http://example.com/noalt.png)

    """
    if not soup.article:
        return
    for img_tag in soup.article.find_all("img"):
        if img_tag.has_attr("alt"):
            match = IMAGESIZE_EXTRACTOR.match(img_tag["alt"])
            if match:
                width, _, height, realalt = match.groups()
                img_tag["width"] = width
                if height:
                    img_tag["height"] = height
                img_tag["alt"] = realalt

    # strip image specs from captions, if any
    for caption in soup.article.select(".figure .caption"):
        if hasattr(caption, "contents") and isinstance(caption.contents[0], str):
            match = IMAGESIZE_EXTRACTOR.match(caption.contents[0])
            if match:
                caption.contents[0].replace_with(match.group(4))


def make_sitemap_url_element(link, updated=None, changefreq=None, priority=None):
    """Make a sitemap <url> element.

    Parameters
    ----------
    link : str or xml.etree.ElementTree.Element
        If using an xml.etree.ElementTree.Element element, then it shall
        be an atom:link element, e.g., <link href="http://zmwangx.github.io/"/>.
    updated : datetime or xml.etree.ElementTree.Element, optional
        If using an xml.etree.ElementTree.Element element, then it shall
        be an atom:updated element, e.g.,
        <updated>2015-05-05T22:38:42-07:00</updated>.
    changefreq : {"always", "hourly", "daily", "weekly", "monthly", "yearly", "never"}, optional
    priority : {1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1}, optional

    """

    urlelem = ET.Element("url")
    loc = ET.Element("loc")
    loc.text = link.attrib["href"] if isinstance(link, ET._Element) else link
    urlelem.append(loc)
    if updated is not None:
        lastmod = ET.Element("lastmod")
        lastmod.text = (updated.text if isinstance(updated, ET._Element)
                        else updated.isoformat())
        urlelem.append(lastmod)
    if changefreq is not None:
        changefreq_elem = ET.Element("changefreq")
        changefreq_elem.text = changefreq
        urlelem.append(changefreq_elem)
    if priority is not None:
        priority_elem = ET.Element("priority")
        priority_elem.text = "%.1f" % priority
        urlelem.append(priority_elem)
    return urlelem

def link_img_tags(soup):
    """Convert each <img> tag in <article> to a link to its original."""
    if not soup.article:
        return
    for img_tag in soup.article.find_all("img"):
        a_tag = soup.new_tag("a", href=img_tag["src"], target="_blank")
        a_tag.insert(0, copy.copy(img_tag))
        img_tag.replace_with(a_tag)


def _pre_tag_insert_line_numbers(soup, pre_tag):
    """Insert line numbers to a pre tag."""
    num_lines = len(pre_tag.text.split("\n"))
    for line_number in range(1, num_lines + 1):
        # line number divs will look like:
        # <span class="line-number" data-line="1" style="top: 0em"><!----></span>
        # <span class="line-number" data-line="2" style="top: 1.35em"><!----></span>
        ln_tag = soup.new_tag("span")
        ln_tag["class"] = "line-number"
        ln_tag["data-line"] = line_number
        ln_tag["style"] = "top: %.2fem" % ((line_number - 1) * 1.35)
        # add a comment to the content of the span to suppress tidy5
        # empty <span> tag warning
        ln_tag.append(soup.new_string("", bs4.Comment))
        pre_tag.code.append(ln_tag)


def process_footnote_backlinks(soup):
    """Add class attribute "footnotes-backlink" to each footnote backlink."""
    for footnotes in soup.find_all("div", attrs={"class": "footnotes"}):
        for fn_a_tag in footnotes.find_all(lambda tag:
                                           tag.name == "a" and
                                           tag.has_attr("href") and
                                           tag["href"].startswith("#fnref") and
                                           tag.string == "\u21A9"):  # U+21A9: LEFTWARDS ARROW WITH HOOK
            fn_a_tag["class"] = "footnotes-backlink"
            fn_a_tag.string = "\u21A9\uFE0E" # U+FE0E: VARIATION SELECTOR-15


def postprocess_html_file(htmlfilepath):
    """Perform a series of postprocessing to an HTML file."""
    with open(htmlfilepath, "r+", encoding="utf-8") as htmlfileobj:
        soup = bs4.BeautifulSoup(htmlfileobj.read(), "lxml")

        # a series of postprocessing (extensible)
        process_image_sizes(soup)
        link_img_tags(soup)
        process_footnote_backlinks(soup)

        # write back
        htmlfileobj.seek(0)
        htmlfileobj.write(str(soup))
        htmlfileobj.truncate()