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--
-- All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
-- its licensors.
--
-- For complete copyright and license terms please see the LICENSE at the root of this
-- distribution (the "License"). All use of this software is governed by the License,
-- or, if provided, by the license below or the license accompanying this file. Do not
-- remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
--
-- Original file Copyright Crytek GMBH or its affiliates, used under license.
--
--
--	Description: Containers for Lua
--  Docs:
--
----------------------------------------------------------------------------------------------------
local countTable = Set and Set.countTable or {};

-- Create factory and management table
Set = {};
Set.countTable = countTable;

-- All tables are registered in Set.countTable, therefore won't GCed!
-- Unless we make their entries weak references. See Lua docs.
-- The effect is that these references are ignored by the garbage collector.
setmetatable(Set.countTable, { __mode="kv" });


-- Create and return a new Set table
Set.New = function()
	local nt = {}
	Set.countTable[nt] = 0
	return nt
end

Set.SerializeValues = function(tbl)
	local result = {}
	for k,v in pairs(tbl) do
	  local item = {}
	  table.insert( item, 1, k );
	  table.insert( item, 2, v );
	  table.insert( result, item );
	end
	return result
end


Set.DeserializeValues = function(tbl)
	local result = Set.New()
	for i,item in ipairs(tbl) do
	  Set.Add( result, item[1], item[2] );
	end
	return result;
end



Set.DeserializeEntities = function(tbl)
	local result = Set.New()
	for i,entityID in ipairs(tbl) do
		Set.Add(result, entityID)
	end
	return result
end


Set.SerializeEntities = function(tbl)
	local result = {};
	for entityID,v in pairs(tbl) do
		table.insert(result, entityID)
	end
	return result;
end


Set.DeserializeItems = function(tbl)
	local result = Set.New();
	for i,item in ipairs(tbl) do
		if (item) then
			Set.Add(result, item);
		end
	end
	return result;
end


Set.SerializeItems = function(tbl)
	local result = {};
	local index = 1;
	for item,v in pairs(tbl) do
		result[index] = item;
		index = index + 1;
	end
	return result;
end


-- Is this table registered as a Set?
-- When performance and best-effort execution are required, this function
-- can easily be reduced to a stub or even all calls to it removed with regexp
Set.Check = function(table)
	-- Run-time checking
	if (not Set.countTable[table]) then
		-- Throwing an error here would be preferable
		if (print) then 
			print(tostring(table).."is not registered as a Set"); 
		else 
			System.Log(tostring(table).."is not registered as a Set");
		end
		System.ShowDebugger()
		Set.throwAnError.throwAnError = true;
	end
end


-- Add an entry into a Set iff it does not already exist
-- if v == nil, we set it to true - leaving it nil would break things
-- Returns true on success, false if entry already exists
Set.Add = function(table, k, v)
	v = v or true;
	Set.Check(table);
	if (not table[k]) then
		table[k] = v;
		Set.countTable[table] = Set.countTable[table] + 1;
		return true;
	end
	return false;
end
	 
-- Removes an entry from a Set
-- if k == nil, does nothing, which is debatable semantics
-- Returns true on success, false if entry did not exist
Set.Remove = function(table, k)
	Set.Check(table);
	if (table[k]) then
		table[k] = nil;
		Set.countTable[table] = Set.countTable[table] - 1;
		return true;
	end
	return false;
end

	 
-- Get a value from a Set
-- Return the value or nil if none
Set.Get = function(table, k)
	Set.Check(table);
	return table[k]
end


-- Set the value associated with a key, even if it already exists
-- if v == nil, we set it to true - leaving it nil would break things
-- Returns true if it did already exist, false if not
Set.Set = function(table, k, v)
	v = v or true;
	Set.Check(table);
	if (not table[k]) then
		table[k] = v;
		Set.countTable[table] = Set.countTable[table] + 1;
		return false;
	else
		-- Replace, no need to change count
		table[k] = v;
		return true;
	end
end


-- Get the number of entries in the Set
Set.Size = function(table)
	Set.Check(table);
	return Set.countTable[table];
end


-- Remove all entries
-- No return value
Set.RemoveAll = function(table)
	Set.Check(table);
	for k,v in pairs(table) do
		table[k] = nil;
	end
	Set.countTable[table] = 0;
end
	
	
-- Add entries of one Set into another
-- Keys shared by both will not be overwritten
-- Returns true iff keys were disjoint, none shared
Set.Merge = function(dest, source)
	local disjoint = true;
	Set.Check(dest);
	Set.Check(source);
	for k,v in pairs(source) do
		if (not Set.Add(dest, k, v)) then
			disjoint = false;
		end
	end
	return disjoint;
end
	

-- Iterating:
-- For now, treat a Set as any table.
-- This should change.
	

-- Utility/debugging function:
-- Sanity check a suspicious Set
-- Tries to find evidence of tampering
-- Returns true iff it passes
Set.SanityCheck = function(table) 
	-- Check this was created as a Set
	Set.Check(table);  
	-- Find as many things as you can in the Set
	local count = 0;
	for i,v in pairs(table) do
		count = count + 1;
	end
	local size = Set.Size(table);
	if (count ~= size) then
		System.Log("[Set] Sanity check failed - Set size is "..tostring(size)..", counted "..count);
		return false;
	end
	-- Check that all entries have the same type
	-- This is just good practice, rather than an error
	local indexType = nil;
	local valueType = nil;
	for i,v in pairs(table) do
		-- Check index
		if (indexType) then
			if (indexType ~= type(i)) then
				System.Log("[Set] Sanity check failed - Found indices of both types "..indexType.." and "..type(i));
				return false;
			end
		else
			indexType = type(i);
		end
		-- Check value
		if (valueType) then
			if (valueType ~= type(v)) then
				System.Log("[Set] Sanity check failed - Found values of both types "..valueType.." and "..type(v));
				return false;
			end
		else
			valueType = type(v);
		end
	end
	return true;
end



-- Unit test
-- Return true for success or false on failure
Set.Test = function(fullTest)

	local A = Set.New();
	local B = Set.New();

	if ( Set.Add(A, "key1", 1) == false ) then return false; end
	if ( Set.Add(A, "key2") == false ) then return false; end
	if ( Set.Add(A, "key3", 3) == false ) then return false; end
	if ( Set.Add(A, "key1", 1) == true  ) then return false; end
	if ( Set.Remove(A, "key1") == false ) then return false; end
	if ( Set.Get(A, "key2")== false )			then return false; end
	if ( Set.Get(A, "key1") ~= nil )			then return false; end
	if ( Set.Get(A, "key3") ~= 3 )				then return false; end
	if ( Set.Size(A) ~= 2 ) 							then return false; end
	Set.RemoveAll(A);
	if ( Set.Size(A) ~= 0 )								then return false; end  
	if ( Set.Add(A, "key1", 1) == false ) then return false; end
	
	if ( Set.Set(A, "key1", 9) == false ) 		then return false; end
	if ( Set.Set(A, "key0", 9) == true  ) then return false; end
	if ( Set.Add(A, "keyF", 3) == false ) then return false; end
	if ( Set.Size(A) ~= 3 ) 							then return false; end
	
	
	if ( Set.Add(B, "key3", 3) == false ) then return false; end
	if ( Set.Add(B, "key4", 4) == false ) then return false; end
	if ( Set.Add(B, "key5", 5) == false ) then return false; end
	if ( Set.Add(B, "key3", 3) == true  ) then return false; end
	
	if ( Set.Set(B, "key9") == true  ) then return false; end
	if ( Set.Get(B, "key9") == nil  ) then return false; end

	if (not Set.Merge(A,B)) then return false; end
	if (Set.Size(A) ~= 7) then return false; end
	
	if (Set.Merge(A,B)) then return false; end
	if (Set.Size(A) ~= 7) then return false; end
	
	if (fullTest) then
		-- Check countTable and GC (slow)
	
		-- Shouldn't assume there are no Sets when testing
	
		collectgarbage();
	
		local baseCount = 0;
		for i,v in pairs(Set.countTable) do
				baseCount = baseCount + 1;
		end
	
		B = nil;
		collectgarbage();
	
		local count = 0;
		for i,v in pairs(Set.countTable) do
				count = count + 1;
		end
		if (baseCount - count ~= 1) then return false; end
	end

	-- Move this line around for testing
	do return true; end 
	
	return true;
end

-- Perform quick version of unit test
if (not Set.Test()) then
	System.Log("Containers: ... Error - Failed Unit Test");
else
	--System.Log("Containers: ... End loading!");
end

-- Useful testing lines in Editor:
-- #Script.ReloadScript("Scripts/Utils/Containers.lua");
-- #System.Log(tostring(Set.Test(true)))