Editing Module:Array

local Array = {}
local array_constructor

-- Copy table library so as not to unexpectedly change the behavior of code that
-- uses it.
local array_methods = mw.clone(table)

-- Create version of table.sort that returns the table.
array_methods.sort = function (t, comp)
	table.sort(t, comp)
	return t
end

-- ipairs and unpack operate on arrays.
array_methods.ipairs = ipairs
array_methods.unpack = unpack

function array_methods:type()
	local mt = getmetatable(self)
	return type(mt) == "table" and mt.__type or nil
end

function array_methods:adjustIndex(index)
	index = math.floor(index)
	if index < 0 then
		index = #self + index + 1
	end
	return index
end

-- string.sub-style slicing.
function array_methods:slice(i, j)
	if i == nil then
		i = 1
	elseif type(i) == "number" then
		i = self:adjust_index(i)
	else
		error("Expected number, got " .. type(i))
	end
	
	if j == nil or type(j) == "number" then
		j = self:adjust_index(j or -1)
	else
		error("Expected number, got " .. type(j))
	end
	
	local new_arr = array_constructor()
	local k = 0
	for index = i, j do
		k = k + 1
		new_arr[k] = self[index]
	end
	return new_arr
end

-- A function to convert string key-table modules such
-- as [[Module:languages/data/2]] into arrays.
-- "from" is a bad name.
-- field_for_key supplies the field name in which the
-- key will be stored.
local function to_array(map, field_for_key)
	m_table = m_table or require "Module:table"
	
	local arr = {}
	local i = 0
	for key, val in pairs(map) do
		i = i + 1
		local new_val = m_table.shallowcopy(val)
		if field_for_key then
			new_val[field_for_key] = key
		end
		arr[i] = new_val
	end
	
	return array_constructor(arr)
end

-- Functions from [[Module:table]] that operate on arrays or sparse arrays.
-- List copied from [[Module:table/documentation]].
local operate_on_array = {
	-- non-sparse
	"removeDuplicates", "length", "contains", "serialCommaJoin",
	"reverseIpairs", "reverse", "invert", "listToSet", "isArray",
	-- sparse
	"numKeys", "maxIndex", "compressSparseArray", "sparseIpairs",
	-- tables in general
	"shallowcopy", "deepcopy",
}

-- Not all of these operate on arrays.
local create_new_array = {
	-- Functions from [[Module:table]] that create an array.
	-- List copied from [[Module:table/documentation]].
	"removeDuplicates", "numKeys", "compressSparseArray",
	"keysToList", "reverse",
	-- Functions from [[Module:table]] that create an table.
	"shallowcopy", "deepcopy",
	-- Functions from [[Module:fun]] that create an array.
	"map", "filter",
}

-- Functions from [[Module:fun]] that take an array in the second argument.
-- They just have to have the argument order reversed to work as methods of the
-- array object.
local second_argument_is_array = { "map", "some", "all", "filter" }

-- Add aliases for the functions from [[Module:table]] whose names
-- contain "array" or "list", which is redundant, and whose names don't conform
-- to the usual camel case.
-- The key redirects to the value.
local alias_of = {
	compress = "compressSparseArray", keys = "keysToList", toSet = "listToSet",
	deepCopy = "deepcopy", shallowCopy = "shallowcopy",
}

local function get_module_function(key, module, module_name)
	return module[key] 
		or error("No function named " .. tostring(key) .. " in Module:" .. module_name)
end

local function wrap_in_array_constructor(func)
	return function (...)
		return array_constructor(func(...))
	end
end

local function create_array_generating_func(key, module, module_name)
	return wrap_in_array_constructor(get_module_function(key, module, module_name))
end

local function reverse_arguments(func)
	return function (a, b)
		return func(b, a, true)
	end
end

local function underscore_to_camel_case(str)
	if type(str) ~= "string" then return str end
	str = str:gsub("_(.)", string.upper)
	return str
end

local m_table, m_fun
local Array = {}
Array.__type = "array"
function Array:__index(key)
	if type(key) ~= "string" then
		return nil
	end
	
	-- Convert underscores to camel case: num_keys -> numKeys.
	key = underscore_to_camel_case(key)
	
	local val = array_methods[key]
	if val then
		return val
	end
	
	key = alias_of[key] or key
	
	local func
	m_table = m_table or require "Module:table"
	if m_table.contains(operate_on_array, key) then
		if m_table.contains(create_new_array, key) then
			func = create_array_generating_func(key, m_table, "table")
		else
			func = m_table[key]
		end
	elseif m_table.contains(second_argument_is_array, key) then
		m_fun = m_fun or require "Module:fun"
		
		local raw_func = reverse_arguments(get_module_function(key, m_fun, "fun"))
		if m_table.contains(create_new_array, key) then
			func = wrap_in_array_constructor(raw_func)
		else
			func = raw_func
		end
	elseif key == "fold" then
		m_fun = m_fun or require "Module:fun"
		
		local raw_func = get_module_function(key, m_fun, "fun")
		func = function(t, func, accum)
			return raw_func(func, t, accum)
		end
	end
	
	if func then
		array_methods[key] = func
		return func
	end
end

function Array.__add(a, b)
	if type(a) == 'table' and type(b) == 'table' then
		m_table = m_table or require "Module:table"
		
		local new_arr = array_constructor(m_table.shallowcopy(a))
		
		for _, val in ipairs(b) do
			new_arr:insert(val)
		end
		
		return new_arr
	end
end

function Array:new(...)
	local arr
	if select("#", ...) == 1 and type((...)) == "table" then
		arr = ...
		
		local mt = getmetatable(arr)
		-- If table has been loaded with mw.loadData, copy it to avoid the
		-- limitations of it being a virtual table.
		if mt and mt.mw_loadData then
			m_table = m_table or require "Module:table"
			arr = m_table.shallowcopy(arr)
		end
	else
		arr = { ... }
	end
	return setmetatable(arr, self)
end

-- Declared as local above.
function array_constructor(...)
	return Array:new(...)
end

local array_generating_funcs = { from = to_array }
local Array_library_mt = {
	__call = Array.new, __index = array_generating_funcs
}
setmetatable(Array, Array_library_mt)

function Array_library_mt:__index(key)
	key = underscore_to_camel_case(key)
	key = alias_of[key] or key
	
	if array_generating_funcs[key] then
		return array_generating_funcs[key]
	end
	
	m_table = m_table or require "Module:table"
	
	if m_table.contains(create_new_array, key) then
		local func = create_array_generating_func(key, m_table, "table")
		array_generating_funcs[key] = func
		return func
	end
end

return Array