publish.py

"""
Blog publisher: reads all posts/*.md (with YAML frontmatter), renders HTML for each
post, regenerates index.html, and regenerates feed.rss.

Usage:
    python publish.py            # build everything
    python publish.py <post.md>  # build a single post only (no index/feed update)

Each post must have a YAML frontmatter block with at least:
    ---
    title: "Post Title"
    date: YYYY-MM-DD
    ---
"""

import os
import re
import sys

from email import utils
from datetime import datetime, date, timezone

import pystache
import pypandoc
import yaml


POSTS_DIR = "posts"
OUT_DIR = "out"
FM_RE = re.compile(r"\A---\s*\n(.*?)\n---\s*\n", re.DOTALL)


# ---------------------------------------------------------------------------
# Frontmatter parsing
# ---------------------------------------------------------------------------

def split_frontmatter(md):
    m = FM_RE.match(md)
    if not m:
        return {}, md
    meta = yaml.safe_load(m.group(1)) or {}
    return meta, md[m.end():]


# ---------------------------------------------------------------------------
# Post helpers
# ---------------------------------------------------------------------------

def stem(filename):
    """'Some_Post.md' → 'Some_Post'"""
    return os.path.basename(filename)[:-3]


def out_file(filename):
    return stem(filename) + ".html"


def to_date(value):
    """Coerce a frontmatter date value to a Python date."""
    if isinstance(value, date):
        return value
    if isinstance(value, str):
        return date.fromisoformat(value)
    raise ValueError(f"Cannot parse date: {value!r}")


def rfc2822(d):
    """Format a date as RFC 2822 for RSS pubDate."""
    dt = datetime(d.year, d.month, d.day, tzinfo=timezone.utc)
    return utils.format_datetime(dt)


def get_post(filename):
    path = os.path.join(POSTS_DIR, filename)
    with open(path) as f:
        contents = f.read()

    meta, body = split_frontmatter(contents)

    post_date = to_date(meta["date"]) if "date" in meta else date.fromtimestamp(os.stat(path).st_mtime)
    title = meta.get("title") or stem(filename).replace("_", " ")

    return {
        "filename": filename,
        "out_file": out_file(filename),
        "title": title,
        "date": str(post_date),           # YYYY-MM-DD, used in post template
        "date_and_time": rfc2822(post_date),  # RFC 2822, used in RSS
        "post": pypandoc.convert_text(body, "html", format="md"),
        "_date_obj": post_date,
    }


def get_posts():
    today = date.today()
    filenames = [f for f in os.listdir(POSTS_DIR) if f.endswith(".md")]
    posts = [get_post(f) for f in filenames]
    posts = [p for p in posts if p["_date_obj"] <= today]
    posts.sort(key=lambda p: p["_date_obj"], reverse=True)
    return posts


# ---------------------------------------------------------------------------
# Rendering
# ---------------------------------------------------------------------------

def render_post(tpl, post):
    html = pystache.render(tpl, post)
    with open(os.path.join(OUT_DIR, post["out_file"]), "w+") as f:
        f.write(html)


def render_index(tpl, posts):
    html = pystache.render(tpl, {"posts": posts})
    with open(os.path.join(OUT_DIR, "index.html"), "w+") as f:
        f.write(html)


def render_feed(tpl, posts):
    build_date = rfc2822(date.today())
    xml = pystache.render(tpl, {"date": build_date, "posts": posts})
    with open(os.path.join(OUT_DIR, "feed.rss"), "w+") as f:
        f.write(xml)


# ---------------------------------------------------------------------------
# Entry points
# ---------------------------------------------------------------------------

def build_all():
    os.makedirs(OUT_DIR, exist_ok=True)
    posts = get_posts()
    print(f"Building {len(posts)} posts into {OUT_DIR}/...")

    with open("layout.html") as f:
        post_tpl = f.read()
    for post in posts:
        render_post(post_tpl, post)

    with open("index_layout.html") as f:
        index_tpl = f.read()
    render_index(index_tpl, posts)
    print("  index.html written")

    with open("feed_tpl.rss") as f:
        feed_tpl = f.read()
    render_feed(feed_tpl, posts)
    print("  feed.rss written")


def build_one(target):
    """Render a single post file (path or bare filename inside posts/)."""
    os.makedirs(OUT_DIR, exist_ok=True)
    filename = os.path.basename(target)
    if not filename.endswith(".md"):
        filename += ".md"
    post = get_post(filename)

    with open("layout.html") as f:
        tpl = f.read()
    render_post(tpl, post)
    print(f"  {OUT_DIR}/{post['out_file']} written")


if __name__ == "__main__":
    if len(sys.argv) == 1:
        build_all()
    elif len(sys.argv) == 2:
        build_one(sys.argv[1])
    else:
        print(__doc__)
        sys.exit(1)