From 73360b7d07c52ecd50c5f4a5595b6e43e31c7912 Mon Sep 17 00:00:00 2001
From: Matthew Beale <matt.beale@madhatted.com>
Date: Sun, 3 Apr 2011 09:23:22 -0400
Subject: [PATCH] Use the whole range of signed integers on MEDIUMINT

---
 lib/ranked-model.rb                   | 1 +
 lib/ranked-model/ranker.rb            | 8 ++++----
 spec/duck-model/lots_of_ducks_spec.rb | 6 +++---
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/lib/ranked-model.rb b/lib/ranked-model.rb
index f6a0383..b46ae2c 100644
--- a/lib/ranked-model.rb
+++ b/lib/ranked-model.rb
@@ -6,6 +6,7 @@ module RankedModel
   # Signed MEDIUMINT in MySQL
   #
   MAX_RANK_VALUE = 8388607
+  MIN_RANK_VALUE = -8388607
 
   def self.included base
 
diff --git a/lib/ranked-model/ranker.rb b/lib/ranked-model/ranker.rb
index 53bc5eb..85a92fa 100644
--- a/lib/ranked-model/ranker.rb
+++ b/lib/ranked-model/ranker.rb
@@ -87,7 +87,7 @@ def update_index_from_position
         case position
           when :first
             if current_first && current_first.rank
-              rank_at( ( current_first.rank.to_f / 2 ).ceil )
+              rank_at( ( RankedModel::MIN_RANK_VALUE + current_first.rank.to_f / 2 ).ceil )
             else
               position_at :middle
             end
@@ -107,7 +107,7 @@ def update_index_from_position
             current = current_at_position(position)
             if current
               previous = position > 0 ? current_at_position(position-1) : nil
-              rank_at( ( ( (previous ? previous.rank : 0) + current.rank ).to_f / 2 ).ceil )
+              rank_at( ( ( (previous ? previous.rank : RankedModel::MIN_RANK_VALUE) + current.rank ).to_f / 2 ).ceil )
             else
               position_at :last
             end
@@ -136,7 +136,7 @@ def rearrange_ranks
             where( instance.class.arel_table[:id].not_eq(instance.id) ).
             where( instance.class.arel_table[ranker.column].gteq(rank) ).
             update_all( "#{ranker.column} = #{ranker.column} + 1" )
-        elsif current_first.rank > 0 && rank > current_first.rank 
+        elsif current_first.rank > RankedModel::MIN_RANK_VALUE && rank > current_first.rank 
           instance.class.
             where( instance.class.arel_table[:id].not_eq(instance.id) ).
             where( instance.class.arel_table[ranker.column].lt(rank) ).
@@ -152,7 +152,7 @@ def rebalance_ranks
         has_set_self = false
         total.times do |index|
           next if index == 0 || index == total
-          rank_value = RankedModel::MAX_RANK_VALUE / total * index
+          rank_value = ((((RankedModel::MAX_RANK_VALUE - RankedModel::MIN_RANK_VALUE).to_f / total) * index ).ceil + RankedModel::MIN_RANK_VALUE)
           index = index - 1
           if has_set_self
             index = index - 1
diff --git a/spec/duck-model/lots_of_ducks_spec.rb b/spec/duck-model/lots_of_ducks_spec.rb
index ab6acd2..865c4c8 100644
--- a/spec/duck-model/lots_of_ducks_spec.rb
+++ b/spec/duck-model/lots_of_ducks_spec.rb
@@ -67,8 +67,8 @@
         @first = Duck.first
         @second = Duck.offset(1).first
         @ordered = Duck.rank(:row).where(Duck.arel_table[:id].not_in([@first.id, @second.id])).collect {|d| d.id }
-        @first.update_attribute :row, 0
-        @second.update_attribute :row, 0
+        @first.update_attribute :row, RankedModel::MIN_RANK_VALUE
+        @second.update_attribute :row, RankedModel::MIN_RANK_VALUE
       }
 
       context {
@@ -96,7 +96,7 @@
           where(Duck.arel_table[:id].not_in([@first.id, @second.id, @third.id, @fourth.id])).
           where(Duck.arel_table[:row].gteq(RankedModel::MAX_RANK_VALUE / 2)).
           collect {|d| d.id }
-        @first.update_attribute :row, 0
+        @first.update_attribute :row, RankedModel::MIN_RANK_VALUE
         @second.update_attribute :row, RankedModel::MAX_RANK_VALUE
         @third.update_attribute :row, (RankedModel::MAX_RANK_VALUE / 2)
         @fourth.update_attribute :row, @third.row