From 8e0cf9cfa86b16f2d57d5ec7d9fa367a17c299d4 Mon Sep 17 00:00:00 2001
From: James Gill <jamesagill@gmail.com>
Date: Sat, 20 Apr 2013 09:39:45 -0700
Subject: [PATCH] Replacing the insert method in sorting.

It has been replaced with a binary search, instead of
an insertion-sort O(n^2) search.
---
 packages/minimongo/minimongo.js       | 39 +++++++++++++----
 packages/minimongo/minimongo_tests.js | 62 +++++++++++++++++++++++++++
 2 files changed, 92 insertions(+), 9 deletions(-)

diff --git a/packages/minimongo/minimongo.js b/packages/minimongo/minimongo.js
index b8c45951fec..b72370bd56d 100644
--- a/packages/minimongo/minimongo.js
+++ b/packages/minimongo/minimongo.js
@@ -694,21 +694,42 @@ LocalCollection._findInOrderedResults = function (query, doc) {
   throw Error("object missing from query");
 };
 
+//This binary search puts a value between any equal values, and the first 
+//lesser value.  This is to match the previous insertion behaviour of comparing
+//each element and inserting it as soon as it compares less than the
+//encountered value.
+LocalCollection._binarySearch = function (cmp, array, value) {
+  if (array.length == 0) return 0;
+  lower = 0;
+  upper = array.length - 1;
+
+  while (lower <= upper) {
+    idx = Math.floor( (lower + upper) / 2 );
+    comparison = cmp(value, array[idx]);
+    //console.log("lower:"+lower + " upper:" + upper + " idx:"+idx +" c:"+comparison);
+    if (lower == upper) {
+      if (comparison >= 0) idx++;
+      return idx;
+    }
+
+    if ( comparison < 0 )
+      upper = idx;
+    else
+      lower = idx + 1;
+  }
+
+  return idx;
+}
+
 LocalCollection._insertInSortedList = function (cmp, array, value) {
   if (array.length === 0) {
     array.push(value);
     return 0;
   }
 
-  for (var i = 0; i < array.length; i++) {
-    if (cmp(value, array[i]) < 0) {
-      array.splice(i, 0, value);
-      return i;
-    }
-  }
-
-  array.push(value);
-  return array.length - 1;
+  idx = LocalCollection._binarySearch (cmp, array, value)
+  array.splice(idx, 0, value);
+  return idx;
 };
 
 // To track what documents are affected by a piece of code, call saveOriginals()
diff --git a/packages/minimongo/minimongo_tests.js b/packages/minimongo/minimongo_tests.js
index debc0f8f730..3feaf0477f2 100644
--- a/packages/minimongo/minimongo_tests.js
+++ b/packages/minimongo/minimongo_tests.js
@@ -1048,6 +1048,68 @@ Tinytest.add("minimongo - array sort", function (test) {
     _.range(c.find().count()));
 });
 
+Tinytest.add("minimongo - binary search", function (test) {
+  var forward_cmp = function (a, b) {
+    if (a < b)
+      return -1;
+    else if (b < a)
+      return 1;
+    else
+      return 0;
+  };
+
+  var backward_cmp = function (a, b) {
+    return -1 * forward_cmp(a, b);
+  };
+
+  var check_search = function (cmp, array, value, expected, message) {
+    actual = LocalCollection._binarySearch(cmp, array, value);
+    if (expected != actual) {
+      test.fail({type: "minimongo-binary-search",
+                message: message + " : Expected index " + expected +
+                  " but had " + actual
+      });
+    }
+  };
+
+  var check_search_forward = function (array, value, expected, message) {
+    check_search(forward_cmp, array, value, expected, message);
+  }
+  var check_search_backward = function (array, value, expected, message) {
+    check_search(backward_cmp, array, value, expected, message);
+  }
+
+  check_search_forward([1, 2, 5, 7], 4, 2, "Inner insert");
+  check_search_forward([1, 2, 3, 4], 3, 3, "Inner insert, equal value");
+  check_search_forward([1, 2, 5], 4, 2, "Inner insert, odd length");
+  check_search_forward([1, 3, 5, 6], 9, 4, "End insert");
+  check_search_forward([1, 3, 5, 6], 0, 0, "Beginning insert");
+  check_search_forward([1], 0, 0, "Single array, less than.");
+  check_search_forward([1], 1, 1, "Single array, equal.");
+  check_search_forward([1], 2, 1, "Single array, greater than.");
+  check_search_forward([], 1, 0, "Empty array");
+  check_search_forward([1, 1, 1, 2, 2, 2, 2], 1, 3, "Highly degenerate array, lower");
+  check_search_forward([1, 1, 1, 2, 2, 2, 2], 2, 7, "Highly degenerate array, upper");
+  check_search_forward([2, 2, 2, 2, 2, 2, 2], 1, 0, "Highly degenerate array, lower");
+  check_search_forward([2, 2, 2, 2, 2, 2, 2], 2, 7, "Highly degenerate array, equal");
+  check_search_forward([2, 2, 2, 2, 2, 2, 2], 3, 7, "Highly degenerate array, upper");
+
+  check_search_backward([7, 5, 2, 1], 4, 2, "Backward: Inner insert");
+  check_search_backward([4, 3, 2, 1], 3, 2, "Backward: Inner insert, equal value");
+  check_search_backward([5, 2, 1], 4, 1, "Backward: Inner insert, odd length");
+  check_search_backward([6, 5, 3, 1], 9, 0, "Backward: Beginning insert");
+  check_search_backward([6, 5, 3, 1], 0, 4, "Backward: End insert");
+  check_search_backward([1], 0, 1, "Backward: Single array, less than.");
+  check_search_backward([1], 1, 1, "Backward: Single array, equal.");
+  check_search_backward([1], 2, 0, "Backward: Single array, greater than.");
+  check_search_backward([], 1, 0, "Backward: Empty array");
+  check_search_backward([2, 2, 2, 2, 1, 1, 1], 1, 7, "Backward: Degenerate array, lower");
+  check_search_backward([2, 2, 2, 2, 1, 1, 1], 2, 4, "Backward: Degenerate array, upper");
+  check_search_backward([2, 2, 2, 2, 2, 2, 2], 1, 7, "Backward: Highly degenerate array, upper");
+  check_search_backward([2, 2, 2, 2, 2, 2, 2], 2, 7, "Backward: Highly degenerate array, upper");
+  check_search_backward([2, 2, 2, 2, 2, 2, 2], 3, 0, "Backward: Highly degenerate array, upper");
+
+});
 
 Tinytest.add("minimongo - modify", function (test) {
   var modify = function (doc, mod, result) {