function to generate correct PDF shard path from sha1

1 files changed, 32 insertions, 0 deletions

diff --git a/python/fatcat_web/hacks.py b/python/fatcat_web/hacks.py
index 9e6f6ab5..2415342c 100644
--- a/python/fatcat_web/hacks.py
+++ b/python/fatcat_web/hacks.py
@@ -25,3 +25,35 @@ def wayback_suffix(entity):
             ret = "*/"
         ret += entity.original_url
     return ret
+
+def camp_sha1_path(sha1):
+    assert len(sha1) == 40
+    if sha1[0:2] > 'a9' or (sha1[0:2] == 'a9' and sha1[2:4] >= '48'):
+        shard = 'pdf3'
+    elif sha1[0:2] < '53' or (sha1[0:2] == '53' and sha1[2:4] < 'db'):
+        shard = 'pdf1'
+    else:
+        shard = 'pdf2'
+    return '/{}/pdf/{}/{}/{}.pdf'.format(
+        shard, sha1[0:2], sha1[2:4], sha1)
+
+def test_camp_sha1_path():
+    assert camp_sha1_path('00000088bbc15a03ab89d8da6c356bf25aea9519') == '/pdf1/pdf/00/00/00000088bbc15a03ab89d8da6c356bf25aea9519.pdf'
+    assert camp_sha1_path('53da34b7df640a5065e347ea99e40302154225d5') == '/pdf1/pdf/53/da/53da34b7df640a5065e347ea99e40302154225d5.pdf'
+    assert camp_sha1_path('53db34b7df640a5065e347ea99e40302154225d5') == '/pdf2/pdf/53/db/53db34b7df640a5065e347ea99e40302154225d5.pdf'
+    assert camp_sha1_path('a947d6e2e55dbe649cfde780991f3989e235843d') == '/pdf2/pdf/a9/47/a947d6e2e55dbe649cfde780991f3989e235843d.pdf'
+    assert camp_sha1_path('a948d6e2e55dbe649cfde780991f3989e235843d') == '/pdf3/pdf/a9/48/a948d6e2e55dbe649cfde780991f3989e235843d.pdf'
+    assert camp_sha1_path('ff48d6e2e55dbe649cfde780991f3989e235843d') == '/pdf3/pdf/ff/48/ff48d6e2e55dbe649cfde780991f3989e235843d.pdf'
+
+def get_camp_pdf_path(release):
+    """
+    Assumes the release has been expanded (includes file entities).
+
+    Returns a full local URL to a PDF of the file if one should be available;
+    otherwise returns None.
+    """
+    for f in release.files:
+        for u in f.urls:
+            if '://web.archive.org/' in u.url:
+                return camp_sha1_path(f.sha1)
+    return None