#!/usr/bin/python
# Generate an Atom feed from the commit history of a Git repository.
# Adam Sampson <ats@offog.org>
#
# This aims to conform to Atom 1.0 as defined in RFC 4287:
#   https://tools.ietf.org/html/rfc4287

import sys, os, xml.dom.minidom, codecs, argparse
from offog import atomically_updated
from changeparser import get_changes
from atomwriter import add_plain, add_link, add_date

def add_datetime(doc, node, name, dt):
	add_date(doc, node, name, dt.utctimetuple())

def write_atom_feed(commits, f, repo_name, repo_url, feed_url=None):
	doc = xml.dom.minidom.Document()

	feed = doc.createElement("feed")
	feed.setAttribute("xmlns", "http://www.w3.org/2005/Atom")

	add_plain(doc, feed, "title", repo_name)
	add_link(doc, feed, "link", {"rel": "alternate", "href": repo_url})
	# Not having this violates a SHOULD.
	if feed_url is not None:
		add_link(doc, feed, "link", {"rel": "self", "href": feed_url})
	add_plain(doc, feed, "id", feed_url)
	add_plain(doc, feed, "generator", "gitatom")
	# Assumes there's at least one commit -- updated isn't optional.
	add_datetime(doc, feed, "updated", commits[0]["authortime"])

	for commit in commits:
		entry = doc.createElement("entry")

		add_plain(doc, entry, "id", repo_url + "#" + commit["id"])

		add_datetime(doc, entry, "published", commit["authortime"])
		add_datetime(doc, entry, "updated", commit["authortime"])

		add_plain(doc, entry, "title", commit["subject"])
		# This could be <summary> if there was a <link rel="alternate">.
		add_plain(doc, entry, "content", commit["body"])

		author = doc.createElement("author")
		add_plain(doc, author, "name", commit["authorname"])
		add_plain(doc, author, "email", commit["authoremail"])
		entry.appendChild(author)

		feed.appendChild(entry)

	doc.appendChild(feed)
	doc.writexml(codecs.getwriter("UTF-8")(f), "", " ", "\n", "UTF-8")
	doc.unlink()

def main(argv):
	parser = argparse.ArgumentParser(description="Generate an Atom feed from a Git repository.")
	parser.add_argument("--limit", "-n", metavar="N", default=50, type=int,
	                    help="maximum number of commits to include (default: 50)")
	parser.add_argument("--output", "-o", metavar="FILE", required=True,
	                    help="feed output filename")
	parser.add_argument("--feed-url", metavar="URL",
	                    help="public URL for feed (default: none)")
	parser.add_argument("--repo-name", metavar="NAME",
	                    help="name for repository (default: repo basename)")
	parser.add_argument("--repo-url", metavar="URL", required=True,
	                    help="public URL for repository")
	parser.add_argument("repo_path", metavar="REPO-PATH",
	                    help="local path to repository")
	args = parser.parse_args(argv)

	repo_path = args.repo_path
	while repo_path.endswith("/"):
		repo_path = repo_path[:-1]

	repo_url = args.repo_url
	while repo_url.endswith("/"):
		repo_url = repo_url[:-1]

	repo_name = args.repo_name
	if repo_name is None:
		repo_name = os.path.basename(repo_path)
		if repo_name.endswith(".git"):
			repo_name = repo_name[:-4]

	commits = get_changes(repo_path, args.limit)
	with atomically_updated(args.output, "wb") as f:
		write_atom_feed(commits, f, repo_name, repo_url, args.feed_url)

if __name__ == "__main__":
	main(sys.argv[1:])