From dec7257eff27f8b525adf22be0aa163b7f07a3bf Mon Sep 17 00:00:00 2001
From: "Phyks (Lucas Verney)" <phyks@phyks.me>
Date: Thu, 14 Jan 2016 00:04:33 +0100
Subject: [PATCH] Add a function to look for updated arXiv versions.

---
 libbmc/repositories/arxiv.py | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/libbmc/repositories/arxiv.py b/libbmc/repositories/arxiv.py
index acf6a6f..79c03d2 100644
--- a/libbmc/repositories/arxiv.py
+++ b/libbmc/repositories/arxiv.py
@@ -2,6 +2,7 @@
 This file contains all the arXiv-related functions.
 """
 import arxiv2bib
+import bibtexparser
 import io
 import re
 import requests
@@ -176,6 +177,36 @@ ARXIV_URL = "http://arxiv.org/abs/{arxiv_id}"
 ARXIV_EPRINT_URL = "http://arxiv.org/e-print/{arxiv_id}"
 
 
+def get_latest_version(arxiv_id):
+    """
+    Find the latest version of a given arXiv eprint.
+
+    :param arxiv_id: The arXiv ID to query.
+    :returns: The latest version on eprint as a string, or ``None``.
+    """
+    # Get updated bibtex
+    # Trick: strip the version from the arXiv id, to query updated BibTeX for
+    # the preprint and not the specific version
+    arxiv_preprint_id = strip_version(arxiv_id)
+    updated_bibtex = bibtexparser.loads(get_bibtex(arxiv_preprint_id))
+    updated_bibtex = next(updated_bibtex.entries_dict)
+
+    try:
+        return updated_bibtex["eprint"]
+    except KeyError:
+        return None
+
+
+def strip_version(arxiv_id):
+    """
+    Remove the version suffix from an arXiv id.
+
+    :param arxiv_id: The arXiv ID to strip.
+    :returns: The arXiv ID without the suffix version
+    """
+    return re.sub(r"v\d+\Z", '', arxiv_id)
+
+
 def is_valid(arxiv_id):
     """
     Check that a given arXiv ID is a valid one.