path: root/util/array.lua

-- 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 t_insert, t_sort, t_remove, t_concat
    = table.insert, table.sort, table.remove, table.concat;

local setmetatable = setmetatable;
local getmetatable = getmetatable;
local math_random = math.random;
local math_floor = math.floor;
local pairs, ipairs = pairs, ipairs;
local tostring = tostring;
local type = type;

local array = {};
local array_base = {};
local array_methods = {};
local array_mt = {
	__index = array_methods;
	__name = "array";
	__tostring = function (self) return "{"..self:concat(", ").."}"; end;
};

function array_mt:__freeze() return self; end

local function new_array(self, t, _s, _var)
	if type(t) == "function" then -- Assume iterator
		t = self.collect(t, _s, _var);
	end
	return setmetatable(t or {}, array_mt);
end

function array.new(t)
	return setmetatable(t or {}, array_mt);
end

function array_mt.__add(a1, a2)
	local res = new_array();
	return res:append(a1):append(a2);
end

function array_mt.__eq(a, b)
	if getmetatable(a) ~= array_mt or getmetatable(b) ~= array_mt then
		-- Lua 5.3+ calls this if both operands are tables, even if metatables differ
		return false;
	end
	if #a == #b then
		for i = 1, #a do
			if a[i] ~= b[i] then
				return false;
			end
		end
	else
		return false;
	end
	return true;
end

function array_mt.__div(a1, func)
	local a2 = new_array();
	local o = 0;
	for i = 1, #a1 do
		local new_value = func(a1[i]);
		if new_value ~= nil then
			o = o + 1;
			a2[o] = new_value;
		end
	end
	return a2;
end

setmetatable(array, { __call = new_array });

-- Read-only methods
function array_methods:random()
	return self[math_random(1, #self)];
end

-- Return a random value excluding the one at idx
function array_methods:random_other(idx)
	local max = #self;
	return self[((math.random(1, max-1)+(idx-1))%max)+1];
end

-- These methods can be called two ways:
--   array.method(existing_array, [params [, ...]]) -- Create new array for result
--   existing_array:method([params, ...]) -- Transform existing array into result
--
function array_base.map(outa, ina, func)
	for k, v in ipairs(ina) do
		outa[k] = func(v);
	end
	return outa;
end

function array_base.filter(outa, ina, func)
	local inplace, start_length = ina == outa, #ina;
	local write = 1;
	for read = 1, start_length do
		local v = ina[read];
		if func(v) then
			outa[write] = v;
			write = write + 1;
		end
	end

	if inplace and write <= start_length then
		for i = write, start_length do
			outa[i] = nil;
		end
	end

	return outa;
end

function array_base.slice(outa, ina, i, j)
	if j == nil then
		j = -1;
	end
	if j < 0 then
		j = #ina + (j+1);
	end
	if i < 0 then
		i = #ina + (i+1);
	end
	if i < 1 then
		i = 1;
	end
	if j > #ina then
		j = #ina;
	end
	if i > j then
		for idx = 1, #outa do
			outa[idx] = nil;
		end
		return outa;
	end

	for idx = 1, 1+j-i do
		outa[idx] = ina[i+(idx-1)];
	end
	if ina == outa then
		for idx = 2+j-i, #outa do
			outa[idx] = nil;
		end
	end
	return outa;
end

function array_base.sort(outa, ina, ...)
	if ina ~= outa then
		outa:append(ina);
	end
	t_sort(outa, ...);
	return outa;
end

function array_base.unique(outa, ina)
	local seen = {};
	return array_base.filter(outa, ina, function (item)
		if seen[item] then
			return false;
		else
			seen[item] = true;
			return true;
		end
	end);
end

function array_base.pluck(outa, ina, key, default)
	for i = 1, #ina do
		local v = ina[i][key];
		if v == nil then
			v = default;
		end
		outa[i] = v;
	end
	return outa;
end

function array_base.reverse(outa, ina)
	local len = #ina;
	if ina == outa then
		local middle = math_floor(len/2);
		len = len + 1;
		local o; -- opposite
		for i = 1, middle do
			o = len - i;
			outa[i], outa[o] = outa[o], outa[i];
		end
	else
		local off = len + 1;
		for i = 1, len do
			outa[i] = ina[off - i];
		end
	end
	return outa;
end

--- These methods only mutate the array
function array_methods:shuffle()
	local len = #self;
	for i = 1, #self do
		local r = math_random(i, len);
		self[i], self[r] = self[r], self[i];
	end
	return self;
end

function array_methods:append(ina)
	local len, len2 = #self, #ina;
	for i = 1, len2 do
		self[len+i] = ina[i];
	end
	return self;
end

function array_methods:push(x)
	t_insert(self, x);
	return self;
end

array_methods.pop = t_remove;

function array_methods:concat(sep)
	return t_concat(array.map(self, tostring), sep);
end

function array_methods:length()
	return #self;
end

--- These methods always create a new array
function array.collect(f, s, var)
	local t = {};
	while true do
		var = f(s, var);
		if var == nil then break; end
		t_insert(t, var);
	end
	return setmetatable(t, array_mt);
end

---

-- Setup methods from array_base
for method, f in pairs(array_base) do
	local base_method = f;
	-- Setup global array method which makes new array
	array[method] = function (old_a, ...)
		local a = new_array();
		return base_method(a, old_a, ...);
	end
	-- Setup per-array (mutating) method
	array_methods[method] = function (self, ...)
		return base_method(self, self, ...);
	end
end

return array;