WIP for indexing by multiple tags.

Basically, DODB::Tags#get(tags : Array(String)).

spec/test.cr

@@ -335,6 +335,25 @@ describe "DODB::DataBase" do
 
 			db_ships_by_tags.get("flagship").should eq([] of Ship)
 		end
+
+		it "gets items that have multiple tags" do
+			db = DODB::SpecDataBase.new
+
+			db_ships_by_tags = db.new_tags "tags", &.tags
+
+			Ship.all_ships.each do |ship|
+				db << ship
+			end
+
+			results = db_ships_by_tags.get(["flagship", "name ship"])
+			results.should eq([Ship.yamato])
+
+			results = db_ships_by_tags.get(["name ship", "flagship"])
+			results.should eq([Ship.yamato])
+
+			results = db_ships_by_tags.get(["flagship"])
+			results.should eq([Ship.yamato])
+		end
 	end
 
 	describe "tools" do

src/dodb/tags.cr

@@ -10,27 +10,59 @@ class DODB::Tags(V) < DODB::Indexer(V)
 		::Dir.mkdir_p indexing_directory
 	end
 
+	# FIXME: Too slow. That `uniq` call alone is a perf eater.
+	def tag_combinations(tags)
+		combinations = [] of Array(String)
+
+		previous_tags = [] of String
+		while tag = tags.shift?
+			previous_tags.push tag
+
+			combinations.push previous_tags.clone
+
+			if tags.size > 0
+				combinations.push tags.clone
+			end
+		end
+
+		combinations.uniq
+	end
+
 	def index(key, value)
-		indices = key_proc.call value
+		indices = key_proc.call(value).sort
 
-		indices.each do |index|
-			symlink = get_tagged_entry_path(key, index)
+		tag_combinations(indices).each do |previous_indices|
+			# FIXME: Not on `index`, but on the list of all previous indices.
+			symdir = symlinks_directory previous_indices
+			otdir  = other_tags_directory previous_indices
 
-			Dir.mkdir_p ::File.dirname symlink
+			::Dir.mkdir_p symdir
+			::Dir.mkdir_p otdir
+
+			symlink = get_tagged_entry_path(key, previous_indices)
 
 			::File.delete symlink if ::File.exists? symlink
 
-			::File.symlink get_data_symlink(key), symlink
+			::File.symlink get_data_symlink(key, previous_indices), symlink
 		end
 	end
 
 	def deindex(key, value)
-		indices = key_proc.call value
+		indices = key_proc.call(value).sort
 
-		indices.each do |index_key|
-			symlink = get_tagged_entry_path(key, index_key)
+		tag_combinations(indices).each do |previous_indices|
+			# FIXME: Not on `index`, but on the list of all previous indices.
+			symdir = symlinks_directory previous_indices
+			otdir  = other_tags_directory previous_indices
 
-			::File.delete symlink
+			::Dir.mkdir_p symdir
+			::Dir.mkdir_p otdir
+
+			symlink = get_tagged_entry_path(key, previous_indices)
+
+			::File.delete symlink if ::File.exists? symlink
+
+			# FIXME: Remove directories if empty?
 		end
 	end
 
@@ -38,10 +70,14 @@ class DODB::Tags(V) < DODB::Indexer(V)
 		return true # Tags don’t have collisions or overloads.
 	end
 
-	def get_with_indices(key) : Array(Tuple(V, Int32))
+	def get_with_indices(key : String) : Array(Tuple(V, Int32))
+		get_with_indices [key]
+	end
+
+	def get_with_indices(keys : Array(String)) : Array(Tuple(V, Int32))
 		r_value = Array(Tuple(V, Int32)).new
 
-		partition_directory = "#{indexing_directory}/#{key}"
+		partition_directory = symlinks_directory keys
 
 		return r_value unless Dir.exists? partition_directory
 
@@ -55,20 +91,30 @@ class DODB::Tags(V) < DODB::Indexer(V)
 		r_value
 	end
 
-	def get(key) : Array(V)
+	def get(key : String) : Array(V)
 		get_with_indices(key).map &.[0]
 	end
 
+	def get(keys : Array(String)) : Array(V)
+		get_with_indices(keys.sort).map &.[0]
+	end
+
 	def indexing_directory : String
-		"#{@storage_root}/by_tags/by_#{@name}"
+		"#{@storage_root}/tags/by_#{@name}"
 	end
 
-	private def get_tagged_entry_path(key : String, index_key : String)
-		"#{indexing_directory}/#{index_key}/#{key}.json"
+	private def symlinks_directory(previous_indices : Array(String))
+		"#{indexing_directory}#{previous_indices.map { |i| "/other-tags/#{i}" }.join}/data"
+	end
+	private def other_tags_directory(previous_indices : Array(String))
+		"#{indexing_directory}#{previous_indices.map { |i| "/other-tags/#{i}" }.join}/other-tags"
 	end
 
-	private def get_data_symlink(key : String)
-		"../../../data/#{key}.json"
+	private def get_tagged_entry_path(key : String, indices : Array(String))
+		"#{indexing_directory}#{indices.map { |i| "/other-tags/#{i}" }.join}/data/#{key}.json"
+	end
+	private def get_data_symlink(key : String, indices : Array(String))
+		"../../../#{indices.map { "../../" }.join}/data/#{key}.json"
 	end
 end