From 75b39a2363968a30a80ef4284a0664a4338dae1c Mon Sep 17 00:00:00 2001
From: Jon Bracy <jonbracy@gmail.com>
Date: Thu, 27 Jan 2022 13:34:55 -0600
Subject: [PATCH] Dynamic joins on the same table

---
 lib/active_record/filter.rb                   | 33 +++++----
 .../filter_relationship_test/has_many_test.rb | 69 +++++++++++++++++++
 2 files changed, 85 insertions(+), 17 deletions(-)

diff --git a/lib/active_record/filter.rb b/lib/active_record/filter.rb
index ad0a51f..4d6ae9a 100644
--- a/lib/active_record/filter.rb
+++ b/lib/active_record/filter.rb
@@ -47,6 +47,21 @@ def self.filter_joins(klass, filters)
       custom = []
       [build_filter_joins(klass, filters, [], custom), custom]
     end
+    
+    def self.materialize_joins(filters, js, custom, relations)
+      return if js.nil?
+      
+      case js
+      when Array
+        js.map { |j| materialize_joins(filters, j, custom, relations) }
+      when Proc
+        materialize_joins(filters, js.call(filters), custom, relations)
+      when String
+        custom << js
+      else
+        relations << js
+      end
+    end
 
     def self.build_filter_joins(klass, filters, relations=[], custom=[])
       if filters.is_a?(Array)
@@ -54,23 +69,7 @@ def self.build_filter_joins(klass, filters, relations=[], custom=[])
       elsif filters.is_a?(Hash)
         filters.each do |key, value|
           if klass.filters.has_key?(key.to_sym)
-            js = klass.filters.dig(key.to_sym, :joins)
-
-            if js.is_a?(Array)
-              js.each do |j|
-                if j.is_a?(String)
-                  custom << j
-                else
-                  relations << j
-                end
-              end
-            elsif js
-              if js.is_a?(String)
-                custom << js
-              else
-                relations << js
-              end
-            end
+            materialize_joins(filters[key], klass.filters.dig(key.to_sym, :joins), custom, relations)
           elsif reflection = klass._reflections[key.to_s]
             if value.is_a?(Hash)
               relations << if reflection.polymorphic?
diff --git a/test/filter_relationship_test/has_many_test.rb b/test/filter_relationship_test/has_many_test.rb
index bd0a9ae..1537709 100644
--- a/test/filter_relationship_test/has_many_test.rb
+++ b/test/filter_relationship_test/has_many_test.rb
@@ -22,6 +22,64 @@ class HasManyFilterTest < ActiveSupport::TestCase
 
   class Account < ActiveRecord::Base
     has_many :photos
+    
+    js = -> (filters) do
+      x = if filters.is_a?(Array) && filters.size > 1
+        reflection = self.reflect_on_association(:photos)
+        filters.reduce([]) do |sum, f|
+          if !f.is_a?(String)
+            right_table = reflection.klass.arel_table.alias("photos_#{sum.size}")
+            left_table = reflection.active_record.arel_table
+            on = right_table[reflection.foreign_key].eq(left_table[reflection.klass.primary_key])
+            sum + left_table.join(right_table, Arel::Nodes::OuterJoin).on(on).join_sources
+          else
+            sum
+          end
+        end
+      else
+        :photos
+      end
+    end
+    
+    filter_on :joinalias, js do |klass, table, key, value, relation_trail, alias_tracker|
+      if value.is_a?(Array) && value.size > 1
+        reflection = klass.reflect_on_association(:photos)
+        
+        builder = ActiveRecord::PredicateBuilder.new(ActiveRecord::TableMetadata.new(reflection.klass, reflection.klass.arel_table.alias("photos_0"), reflection))
+        node = builder.build_from_filter_hash(value.shift, relation_trail + [reflection.name], alias_tracker)
+        n = value.shift(2)
+        t = 1
+        while !n.empty?
+          builder = ActiveRecord::PredicateBuilder.new(ActiveRecord::TableMetadata.new(reflection.klass, reflection.klass.arel_table.alias("photos_#{t}"), reflection))
+          t += 1
+          n[1] = builder.build_from_filter_hash(n[1], relation_trail + [reflection.name], alias_tracker)
+          if n[0] == 'AND'
+            if node.is_a?(Arel::Nodes::And)
+              node.children.push(n[1])
+            else
+              node = node.and(n[1])
+            end
+          elsif n[0] == 'OR'
+            node = Arel::Nodes::Grouping.new(node).or(Arel::Nodes::Grouping.new(n[1]))
+          elsif !n[0].is_a?(String)
+            builder = ActiveRecord::PredicateBuilder.new(ActiveRecord::TableMetadata.new(reflection.klass, reflection.klass.arel_table.alias("photos_#{t}"), reflection))
+            t += 1
+            n[0] = builder.build_from_filter_hash(n[0], relation_trail + [reflection.name], alias_tracker)
+            if node.is_a?(Arel::Nodes::And)
+              node.children.push(n[0])
+            else
+              node = node.and(n[0])
+            end
+          else
+            raise 'lll'
+          end
+          n = value.shift(2)
+        end
+        node
+      else
+        expand_filter_for_relationship(relation, value, relation_trail, alias_tracker)
+      end
+    end
   end
 
   class Photo < ActiveRecord::Base
@@ -165,4 +223,15 @@ class Property < ActiveRecord::Base
   #   assert_equal [a2], Property.filter(:listings => { :type => 'sublease'} )
   # end
 
+  test "::filter custom!" do
+    query = Account.filter(joinalias: [{id: 1}, 'AND', {id: 2}])
+
+    assert_equal(<<-SQL.strip.gsub(/\s+/, ' '), query.to_sql.strip.gsub('"', ''))
+      SELECT accounts.* FROM accounts
+      LEFT OUTER JOIN photos photos_0 ON photos_0.account_id = accounts.id
+      LEFT OUTER JOIN photos photos_1 ON photos_1.account_id = accounts.id
+      WHERE photos_0.id = 1
+        AND photos_1.id = 2
+    SQL
+  end
 end