From df8256f10b94c20eaf1010e158b7cb41605c091e Mon Sep 17 00:00:00 2001
From: Brandon Liu <bdon@bdon.org>
Date: Sun, 20 Mar 2022 18:20:56 +0800
Subject: [PATCH] python writer: fix logical error when a packed leaf directory
 overflows [#37]

---
 python/pmtiles/writer.py   |  3 +--
 python/test/test_writer.py | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/python/pmtiles/writer.py b/python/pmtiles/writer.py
index ca7dd39..185d023 100644
--- a/python/pmtiles/writer.py
+++ b/python/pmtiles/writer.py
@@ -39,14 +39,13 @@ def make_pyramid(tile_entries,start_leaf_offset,max_dir_size=21845):
 
   for group in itertools.groupby(entries_in_leaves,key=by_parent):
     subpyramid_entries = list(group[1])
+    root = subpyramid_entries[0]
     if len(packed_entries) + len(subpyramid_entries) <= max_dir_size:
       # the first item MUST be the root of the pyramid (sorted) - but it may have multiple roots
-      root = subpyramid_entries[0]
       packed_entries.extend(subpyramid_entries)
       packed_roots.append((root.z,root.x,root.y))
     else:
       # flush the current packed entries
-      root = packed_entries[0]
 
       for p in packed_roots:
         root_entries.append(Entry(p[0],p[1],p[2],current_offset,17 * len(packed_entries),True))
diff --git a/python/test/test_writer.py b/python/test/test_writer.py
index b9ab53c..ae3db26 100644
--- a/python/test/test_writer.py
+++ b/python/test/test_writer.py
@@ -31,6 +31,8 @@ class TestTilePyramid(unittest.TestCase):
       ]
       root_entries, leaf_dirs = make_pyramid(entries,0,7)
       self.assertEqual(len(root_entries),7)
+      self.assertEqual(root_entries[5].y,0)
+      self.assertEqual(root_entries[6].y,1)
       self.assertEqual(len(leaf_dirs),1)
       self.assertEqual(len(leaf_dirs[0]),4)
       self.assertEqual(leaf_dirs[0][0].z,2)
@@ -38,6 +40,31 @@ class TestTilePyramid(unittest.TestCase):
       self.assertEqual(leaf_dirs[0][2].z,3)
       self.assertEqual(leaf_dirs[0][3].z,3)
 
+
+    def test_leafdir_overflow(self):
+      entries = [
+        Entry(0,0,0,0,1,False),
+        Entry(1,0,0,1,1,False),
+        Entry(1,0,1,2,1,False),
+        Entry(1,1,0,3,1,False),
+        Entry(1,1,1,4,1,False),
+        Entry(2,0,0,5,1,False),
+        Entry(3,0,0,6,1,False),
+        Entry(3,0,1,7,1,False),
+        Entry(3,1,0,8,1,False),
+        Entry(3,1,1,9,1,False),
+        Entry(2,0,1,10,1,False),
+        Entry(3,0,2,11,1,False),
+        Entry(3,0,3,12,1,False),
+        Entry(3,1,2,13,1,False),
+        Entry(3,1,3,14,1,False)
+      ]
+      root_entries, leaf_dirs = make_pyramid(entries,0,7)
+      print(root_entries)
+      self.assertEqual(len(root_entries),7)
+      self.assertEqual(root_entries[5].y,0)
+      self.assertEqual(root_entries[6].y,1)
+
     def test_full_z7_pyramid(self):
       entries = []
       # create artificial 8 levels