-- Prosody IM

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local ipairs, pairs, setmetatable, next, tostring =

      ipairs, pairs, setmetatable, next, tostring;

local getmetatable = getmetatable;

local t_concat = table.concat;

local _ENV = nil;

-- luacheck: std none

local set_mt = { __name = "set" };

function set_mt.__call(set, _, k)

	return next(set._items, k);

end

local items_mt = {};

function items_mt.__call(items, _, k)

	return next(items, k);

end

function set_mt:__freeze()

	local a, i = {}, 1;

	for item in self._items do

		a[i], i = item, i+1;

	end

	return a;

end

local function is_set(o)

	local mt = getmetatable(o);

	return mt == set_mt;

end

local function new(list)

	local items = setmetatable({}, items_mt);

	local set = { _items = items };

	-- We access the set through an upvalue in these methods, so ignore 'self' being unused

	--luacheck: ignore 212/self

	function set:add(item)

		items[item] = true;

	end

	function set:contains(item)

		return items[item];

	end

	function set:contains_set(other_set)

		for item in other_set do

			if not self:contains(item) then

				return false;

			end

		end

		return true;

	end

	function set:items()

		return next, items;

	end

	function set:remove(item)

		items[item] = nil;

	end

	function set:add_list(item_list)

		if item_list then

			for _, item in ipairs(item_list) do

				items[item] = true;

			end

		end

	end

	function set:include(otherset)

		for item in otherset do

			items[item] = true;

		end

	end

	function set:exclude(otherset)

		for item in otherset do

			items[item] = nil;

		end

	end

	function set:empty()

		return not next(items);

	end

	if list then

		set:add_list(list);

	end

	return setmetatable(set, set_mt);

end

local function union(set1, set2)

	local set = new();

	local items = set._items;

	for item in pairs(set1._items) do

		items[item] = true;

	end

	for item in pairs(set2._items) do

		items[item] = true;

	end

	return set;

end

local function difference(set1, set2)

	local set = new();

	local items = set._items;

	for item in pairs(set1._items) do

		items[item] = (not set2._items[item]) or nil;

	end

	return set;

end

local function intersection(set1, set2)

	local set = new();

	local items = set._items;

	set1, set2 = set1._items, set2._items;

	for item in pairs(set1) do

		items[item] = (not not set2[item]) or nil;

	end

	return set;

end

local function xor(set1, set2)

	return union(set1, set2) - intersection(set1, set2);

end

function set_mt.__add(set1, set2)

	return union(set1, set2);

end

function set_mt.__sub(set1, set2)

	return difference(set1, set2);

end

function set_mt.__div(set, func)

	local new_set = new();

	local items, new_items = set._items, new_set._items;

	for item in pairs(items) do

		local new_item = func(item);

		if new_item ~= nil then

			new_items[new_item] = true;

		end

	end

	return new_set;

end

function set_mt.__eq(set1, set2)

	if getmetatable(set1) ~= set_mt or getmetatable(set2) ~= set_mt then

		-- Lua 5.3+ calls this if both operands are tables, even if metatables differ

		return false;

	end

	set1, set2 = set1._items, set2._items;

	for item in pairs(set1) do

		if not set2[item] then

			return false;

		end

	end

	for item in pairs(set2) do

		if not set1[item] then

			return false;

		end

	end

	return true;

end

function set_mt.__tostring(set)

	local s, items = { }, set._items;

	for item in pairs(items) do

		s[#s+1] = tostring(item);

	end

	return "{"..t_concat(s, ", ").."}";

end

return {

	new = new;

	is_set = is_set;

	union = union;

	difference = difference;

	intersection = intersection;

	xor = xor;

};