#!/usr/bin/env python3
# SPDX-License-Identifier: BSD-3-Clause
#
# new-to-feed - Convert NEWS.adoc to feed.xml
#
# This script converts from "NEWS.adoc" in the main Freedoom repository to
# "feed.xml" on the Freedoom website, which is an RSS feed.
#
# It's possible that there is no need for this script given that GitHub
# generates an Atom feed based on the releases done on GitHub. It can be
# found at:
#   https://github.com/freedoom/freedoom/releases.atom
# Perhaps the website should link to the above in place of the current
# "atom.xml", and "feed.xml" should be abandon.

import datetime
import os
import re
import sys
from xml.dom.minidom import Document

# Globals

channel = None
leading_whitespace = "            "
date = None
desc_lines = []
doc = None
pubdate = None
ver = None

# Regular expressions

# A regular expression that matches version / date lines.
ver_date_patt = re.compile(r'\s*==\s+((?:\d+\.)+\d+)\s+\((\d{4}-\d{2}-\d{2})\)')

# Initial document processing and header prior to the first version.
def add_header():
    global channel
    global doc

    doc = Document()

    rss = doc.createElement('rss')
    rss.setAttribute('version', '2.0')
    doc.appendChild(rss)

    channel = doc.createElement('channel')
    rss.appendChild(channel)

    title = doc.createElement('title')
    title.appendChild(doc.createTextNode('Freedoom Feed'))
    channel.appendChild(title)

    link = doc.createElement('link')
    link.appendChild(doc.createTextNode('https://freedoom.github.io'))
    channel.appendChild(link)

    description = doc.createElement('description')
    description.appendChild(doc.createTextNode('The latest news from Freedoom'))
    channel.appendChild(description)

    language = doc.createElement('language')
    language.appendChild(doc.createTextNode('en-us'))
    channel.appendChild(language)

    image = doc.createElement('image')
    channel.appendChild(image)

    url = doc.createElement('url')
    url.appendChild(doc.createTextNode('https://freedoom.github.io/favicon.ico'))
    image.appendChild(url)


# Called each time we have a complete version section
def add_version():
    item = doc.createElement('item')
    channel.appendChild(item)

    title_elem = doc.createElement('title')
    title_elem.appendChild(doc.createTextNode(date + ": Freedoom " + ver + " released"))
    item.appendChild(title_elem)

    pubdate_elem = doc.createElement('pubDate')
    pubdate_elem.appendChild(doc.createTextNode(pubdate))
    item.appendChild(pubdate_elem)

    link_elem = doc.createElement('link')
    link_elem.appendChild(doc.createTextNode("https://freedoom.github.io/#freedoom-" + ver))
    item.appendChild(link_elem)

    # Avoid join() in order to treat newlines specially.
    nl_ws = "\n" + leading_whitespace
    desc_text = "\n"
    for desc_line in desc_lines:
        if desc_line:
            desc_text += leading_whitespace + desc_line + "\n" + leading_whitespace + "<p/>\n"
        else:
            desc_text += "\n"
    desc_elem = doc.createElement('description')
    desc_elem.appendChild(doc.createTextNode(desc_text))
    item.appendChild(desc_elem)


# Iterates through news_adoc in order to process each version found.
def add_versions():
    global date
    global desc_lines
    global pubdate
    global ver

    first_section = True
    desc_line = ""
    with open(news_adoc) as news_hand:
        line_num = 0
        for line in news_hand:
            line_num += 1
            line = line.rstrip()
            ver_date_match = ver_date_patt.match(line)
            if ver_date_match:
                ver_date_match_groups = ver_date_match.groups()
                if len(ver_date_match_groups) != 2:
                    # Should not happen.
                    print("Line number", line_num, "has", len(ver_date_match_groups),
                        "groups.", file=sys.stderr)
                    sys.exit(1)
                # With the exception of the "HEAD" each new version line indicates
                # that the previous one is complete, so output it before setting
                # "pubdate" to the new value.
                if pubdate:
                    add_version()
                    desc_lines = []
                ver, date = ver_date_match.groups()
                pubdate = datetime.datetime.strptime(date, '%Y-%m-%d').strftime('%d %b %Y')
                first_section = True
            else:
                # Possible description text, but only after the first version date line.
                if not pubdate:
                    continue
                line = line.strip()
                if line.startswith("=== "):
                    # Add the existing line, if any.
                    if desc_line:
                        desc_lines.append(desc_line)
                        desc_line = ""
                    if first_section:
                        first_section = False
                    else:
                        desc_lines.append("")
                    desc_lines.append("> " + line[4:])
                    first_section = False
                elif line.startswith("*"):
                    if desc_line:
                        desc_lines.append(desc_line)
                        desc_line = ""
                    try:
                        space_index = line.index(" ")
                    except ValueError:
                        # Should not happen.
                        print("Line number", line_num, "begins with \"*\", but has no space.")
                        sys.exit(1)
                    desc_line = ("- " * (space_index - 1) if (space_index > 1) \
                                else "") + line[space_index + 1:]
                elif line:
                    # Assume it's a continuation of the previous "*" line.
                    desc_line += (" " + line)
                else:
                    # Blank line marking the end of a bullet.
                    if desc_line:
                        desc_lines.append(desc_line)
                        desc_line = ""
        if not pubdate:
            print("No pubdate at the end.", file=sys.stderr)
            sys.exit(1)
        if desc_line:
            desc_lines.append(desc_line)
            desc_line = ""
        add_version()


# Main enty point.
def main():
    parse_args()
    add_header()
    add_versions()
    output_feed()


# Write the feed to feed_xml.
def output_feed():
    with open(feed_xml, "w") as feed_hand:
        print(doc.toprettyxml(indent="    "), file=feed_hand, end="")


# Parse the command line arguments and store the result in 'args'.
def parse_args():
    global news_adoc
    global feed_xml

    if len(sys.argv) != 3:
        print("Usage:", os.path.basename(sys.argv[0]), \
            "news-file feed-xml", file=sys.stderr)
        sys.exit(1)
    news_adoc = sys.argv[1]
    feed_xml = sys.argv[2]


# So that this script may be accessed as a module.
if __name__ == "__main__":
    main()