From fda63a4e873a7e5ce8282b63e30546c2c64e0458 Mon Sep 17 00:00:00 2001
From: Jody Bruchon <jody@jodybruchon.com>
Date: Thu, 17 Sep 2020 21:45:40 -0400
Subject: [PATCH] Randomize archive order before populating search tree

This doesn't result in an elegant, perfectly balanced search tree,
but it's absolutely good enough. This commit completely mitigates
the worst-case scenario where the archive file is sorted.

Signed-off-by: Jody Bruchon <jody@jodybruchon.com>
---
 youtube_dlc/YoutubeDL.py | 47 ++++++++++------------------------------
 1 file changed, 12 insertions(+), 35 deletions(-)

diff --git a/youtube_dlc/YoutubeDL.py b/youtube_dlc/YoutubeDL.py
index 6da32960a..03bb245ba 100644
--- a/youtube_dlc/YoutubeDL.py
+++ b/youtube_dlc/YoutubeDL.py
@@ -122,17 +122,14 @@ def __init__(self, line):
 
     # Tree insertion
     def at_insert(self, line):
-#        print("at_insert: ", line)
         cur = self
         while True:
-#            print("comparing ", line, cur.line)
             if cur.line:
                 if line < cur.line:
                     if cur.left is None:
                         cur.left = ArchiveTree(line)
                         return
                     else:
-#                        print("LEFT")
                         cur = cur.left
                         continue
                 elif line > cur.line:
@@ -140,7 +137,6 @@ def at_insert(self, line):
                         cur.right = ArchiveTree(line)
                         return
                     else:
-#                        print("RIGHT")
                         cur = cur.right
                         continue
                 else:
@@ -426,43 +422,24 @@ def preload_download_archive(self):
                 if ioe.errno != errno.ENOENT:
                     raise
             lmax = len(lines)
-            if lmax >= 4:
+            if lmax > 10:
                 # Populate binary search tree by splitting the archive list in half
                 # and then adding from the outside edges inward
                 # This mitigates the worst case where the archive has been sorted
-                ptrLL = 0
-                ptrLR = lmax // 2
-                ptrRL = ptrLR + 1
-                ptrRR = lmax - 1
-                inserted = 0
-                while True:
-#                    print("ptrs: %d %d %d %d" % (ptrLL, ptrLR, ptrRL, ptrRR))
-                    if ptrLR > ptrLL:
-                        self.archive.at_insert(lines[ptrLR])
-                        inserted += 1
-                        ptrLR -= 1;
-                    if ptrRL < ptrRR:
-                        self.archive.at_insert(lines[ptrRL])
-                        inserted += 1
-                        ptrRL += 1;
-                    if ptrLL < ptrLR:
-                        self.archive.at_insert(lines[ptrLL])
-                        inserted += 1
-                        ptrLL += 1;
-                    if ptrRR > ptrRL:
-                        self.archive.at_insert(lines[ptrRR])
-                        inserted += 1
-                        ptrRR -= 1;
-                    if ptrLL == ptrLR and ptrRL == ptrRR:
-                        print("inserted: %d, lmax: %d" % (inserted, lmax))
+                pos = 0
+                while pos < lmax:
+                    if lmax - pos <= 2:
                         break
-            elif lmax > 0:
-                # Skip multi-line logic for a single line
-                for idx in lines:
-                    self.archive.at_insert(idx)
-            else:
+                    target = random.randrange(pos + 1, lmax - 1)
+                    temp = lines[pos]
+                    lines[pos] = lines[target]
+                    lines[target] = lines[pos]
+                    pos += 1
+            elif lmax < 1:
                 # No lines were loaded
                 return False
+            for x in lines:
+                self.archive.at_insert(x)
             return True
 
         def check_deprecated(param, option, suggestion):