--!A cross-platform build utility based on Lua
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
-- Copyright (C) 2015 - 2019, TBOOX Open Source Group.
--
-- @author      OpportunityLiu
-- @file        hashset.lua
--

-- define module
local hashset      = hashset or {}
local hashset_impl = hashset.__index or {}

-- load modules
local table  = require("base/table")

-- representaion for nil key
hashset._NIL = setmetatable({}, {__tostring = function() return "nil" end })

function hashset._to_key(key)
    if key == nil then
        key = hashset._NIL
    end
    return key
end

-- make a new hashset
function hashset.new()
    return setmetatable({ _DATA = {}, _SIZE = 0 }, hashset)
end

-- construct from list of items
function hashset.of(...)
    local result = hashset.new()
    local data = table.pack(...)
    for i = 1, data.n do
        result:insert(data[i])
    end
    return result
end

-- construct from an array
function hashset.from(array)
    assert(array)
    return hashset.of(table.unpack(array))
end

-- check value is in hashset
function hashset_impl:has(value)
    value = hashset._to_key(value)
    return self._DATA[value] or false
end

-- insert value to hashset, returns false if value has already in the hashset
function hashset_impl:insert(value)
    value = hashset._to_key(value)
    local result = not (self._DATA[value] or false)
    if result then
        self._DATA[value] = true
        self._SIZE = self._SIZE + 1
    end
    return result
end

-- remove value from hashset, returns false if value is not in the hashset
function hashset_impl:remove(value)
    value = hashset._to_key(value)
    local result = self._DATA[value] or false
    if result then
        self._DATA[value] = nil
        self._SIZE = self._SIZE - 1
    end
    return result
end

-- convert hashset to an array, nil in the set will be ignored
function hashset_impl:to_array()
    local result = {}
    for k,_ in pairs(self._DATA) do
        if k ~= hashset._NIL then
            table.insert(result, k)
        end
    end
    return result
end

-- get size of hashset
function hashset_impl:size()
    return self._SIZE
end

-- get data of hashset
function hashset_impl:data()
    return self._DATA
end

-- clear hashset
function hashset_impl:clear()
    self._DATA = {}
    self._SIZE = 0
end

-- return module
hashset.__index = hashset_impl
return hashset