generate_rss.py

#!/usr/bin/env python3
# This file is placed in the public domain or under the
# CC0-1.0-Universal license, whichever is more permissive.

import argparse
import datetime as dt
import email.utils
from html import escape
from pathlib import Path
import re

import docutils.frontend
from docutils import nodes
from docutils import utils
from docutils.parsers import rst
from docutils.parsers.rst import roles

# get the directory with the PEP sources
PEP_ROOT = Path(__file__).parent


def _format_rfc_2822(datetime: dt.datetime) -> str:
    datetime = datetime.replace(tzinfo=dt.timezone.utc)
    return email.utils.format_datetime(datetime, usegmt=True)


line_cache: dict[Path, dict[str, str]] = {}

# Monkeypatch PEP and RFC reference roles to match Sphinx behaviour
EXPLICIT_TITLE_RE = re.compile(r'^(.+?)\s*(?<!\x00)<(.*?)>$', re.DOTALL)


def _pep_reference_role(role, rawtext, text, lineno, inliner,
                        options={}, content=[]):
    matched = EXPLICIT_TITLE_RE.match(text)
    if matched:
        title = utils.unescape(matched.group(1))
        target = utils.unescape(matched.group(2))
    else:
        target = utils.unescape(text)
        title = "PEP " + utils.unescape(text)
    pep_str, _, fragment = target.partition("#")
    try:
        pepnum = int(pep_str)
        if pepnum < 0 or pepnum > 9999:
            raise ValueError
    except ValueError:
        msg = inliner.reporter.error(
            f'PEP number must be a number from 0 to 9999; "{pep_str}" is invalid.',
            line=lineno)
        prb = inliner.problematic(rawtext, rawtext, msg)
        return [prb], [msg]
    # Base URL mainly used by inliner.pep_reference; so this is correct:
    ref = (inliner.document.settings.pep_base_url
           + inliner.document.settings.pep_file_url_template % pepnum)
    if fragment:
        ref += "#" + fragment
    roles.set_classes(options)
    return [nodes.reference(rawtext, title, refuri=ref, **options)], []


def _rfc_reference_role(role, rawtext, text, lineno, inliner,
                        options={}, content=[]):
    matched = EXPLICIT_TITLE_RE.match(text)
    if matched:
        title = utils.unescape(matched.group(1))
        target = utils.unescape(matched.group(2))
    else:
        target = utils.unescape(text)
        title = "RFC " + utils.unescape(text)
    pep_str, _, fragment = target.partition("#")
    try:
        rfcnum = int(pep_str)
        if rfcnum < 0 or rfcnum > 9999:
            raise ValueError
    except ValueError:
        msg = inliner.reporter.error(
            f'RFC number must be a number from 0 to 9999; "{pep_str}" is invalid.',
            line=lineno)
        prb = inliner.problematic(rawtext, rawtext, msg)
        return [prb], [msg]
    ref = (inliner.document.settings.rfc_base_url + inliner.rfc_url % rfcnum)
    if fragment:
        ref += "#" + fragment
    roles.set_classes(options)
    return [nodes.reference(rawtext, title, refuri=ref, **options)], []


roles.register_canonical_role("pep-reference", _pep_reference_role)
roles.register_canonical_role("rfc-reference", _rfc_reference_role)


def first_line_starting_with(full_path: Path, text: str) -> str:
    # Try and retrieve from cache
    if full_path in line_cache:
        return line_cache[full_path].get(text, "")

    # Else read source
    line_cache[full_path] = path_cache = {}
    for line in full_path.open(encoding="utf-8"):
        if line.startswith("Created:"):
            path_cache["Created:"] = line.removeprefix("Created:").strip()
        elif line.startswith("Title:"):
            path_cache["Title:"] = line.removeprefix("Title:").strip()
        elif line.startswith("Author:"):
            path_cache["Author:"] = line.removeprefix("Author:").strip()

        # Once all have been found, exit loop
        if path_cache.keys == {"Created:", "Title:", "Author:"}:
            break
    return path_cache.get(text, "")


def pep_creation(full_path: Path) -> dt.datetime:
    created_str = first_line_starting_with(full_path, "Created:")
    if full_path.stem == "pep-0102":
        # remove additional content on the Created line
        created_str = created_str.split(" ", 1)[0]
    return dt.datetime.strptime(created_str, "%d-%b-%Y")


def parse_rst(full_path: Path) -> nodes.document:
    text = full_path.read_text(encoding="utf-8")
    settings = docutils.frontend.get_default_settings(rst.Parser)
    document = utils.new_document(f'<{full_path}>', settings=settings)
    rst.Parser(rfc2822=True).parse(text, document)
    return document


def pep_abstract(full_path: Path) -> str:
    """Return the first paragraph of the PEP abstract"""
    for node in parse_rst(full_path).findall(nodes.section):
        if node.next_node(nodes.title).astext() == "Abstract":
            return node.next_node(nodes.paragraph).astext().strip().replace("\n", " ")
    return ""


def main():
    parser = argparse.ArgumentParser(description="Generate RSS feed")
    parser.add_argument(
        "-o",
        "--output-dir",
        default="build",  # synchronise with render.yaml -> deploy step
        help="Output directory, relative to root. Default 'build'.",
    )
    args = parser.parse_args()

    # get list of peps with creation time (from "Created:" string in pep source)
    peps_with_dt = sorted((pep_creation(path), path) for path in PEP_ROOT.glob("pep-????.???"))

    # generate rss items for 10 most recent peps
    items = []
    for datetime, full_path in peps_with_dt[-10:]:
        try:
            pep_num = int(full_path.stem.split("-")[-1])
        except ValueError:
            continue

        title = first_line_starting_with(full_path, "Title:")
        author = first_line_starting_with(full_path, "Author:")
        if "@" in author or " at " in author:
            parsed_authors = email.utils.getaddresses([author])
            joined_authors = ", ".join(f"{name} ({email_address})" for name, email_address in parsed_authors)
        else:
            joined_authors = author
        url = f"https://peps.python.org/pep-{pep_num:0>4}/"

        item = f"""\
    <item>
      <title>PEP {pep_num}: {escape(title, quote=False)}</title>
      <link>{escape(url, quote=False)}</link>
      <description>{escape(pep_abstract(full_path), quote=False)}</description>
      <author>{escape(joined_authors, quote=False)}</author>
      <guid isPermaLink="true">{url}</guid>
      <pubDate>{_format_rfc_2822(datetime)}</pubDate>
    </item>"""
        items.append(item)

    # The rss envelope
    desc = """
    Newest Python Enhancement Proposals (PEPs) - Information on new
    language features, and some meta-information like release
    procedure and schedules.
    """
    last_build_date = _format_rfc_2822(dt.datetime.now(dt.timezone.utc))
    items = "\n".join(reversed(items))
    output = f"""\
<?xml version='1.0' encoding='UTF-8'?>
<rss xmlns:atom="http://www.w3.org/2005/Atom" xmlns:content="http://purl.org/rss/1.0/modules/content/" version="2.0">
  <channel>
    <title>Newest Python PEPs</title>
    <link>https://peps.python.org/peps.rss</link>
    <description>{" ".join(desc.split())}</description>
    <atom:link href="https://peps.python.org/peps.rss" rel="self"/>
    <docs>https://cyber.harvard.edu/rss/rss.html</docs>
    <language>en</language>
    <lastBuildDate>{last_build_date}</lastBuildDate>
{items}
  </channel>
</rss>
"""

    # output directory for target HTML files
    out_dir = PEP_ROOT / args.output_dir
    out_dir.mkdir(exist_ok=True, parents=True)
    out_dir.joinpath("peps.rss").write_text(output)


if __name__ == "__main__":
    main()