Module:Table Utility

Taken from LoL's TableUtil Module.

---

local lang = mw.getLanguage('en')

local p = {}

function p.generalLength(tbl)
	local n = 0
	for _, _ in pairs(tbl) do
		n = n + 1
	end
	return n
end

function p.getKeys(tbl, f)
	local ret = {}
	for k, _ in pairs(tbl) do
		ret[#ret+1] = k
	end
	if f then table.sort(ret, f) end
	return ret
end

function p.keyOf(tbl, val)
	for k, v in pairs(tbl) do
		if v == val then
			return k
		end
	end
	return nil
end

function p.hash(tbl)
	if not tbl then return {} end
	local hash = {}
	for k, v in pairs(tbl) do
		hash[v] = k
	end
	return hash
end

function p.appendHash(parent, tbl)
	for k, v in pairs(tbl) do
		parent[v] = k
	end
	return parent
end

-- sorts tblToSort to be in the same order as the elements appear in lookup
function p.sortByKeyOrder(tblToSort,values)
	local lookup = p.hash(values)
	table.sort(tblToSort, function (a,b)
			return (lookup[a] or 0) < (lookup[b] or 0)
		end
	)
	return
end

function p.sortUnique(tbl)
	table.sort(tbl)
	local tbl2 = {}
	local i = 0
	for k, v in ipairs(tbl) do
		if v ~= tbl2[i] then
			i = i + 1
			tbl2[i] = v
		end
	end
	return tbl2
end

function p.mergeArrays(tbl1, ...)
	-- tbl1 is modified to include the elements of tbl2 appended to the end. Order is preserved.
	if not tbl1 then tbl1 = {} end
	local newTables = {...}
	for _, tbl2 in ipairs(newTables) do
		for _, v in ipairs(tbl2) do
			tbl1[#tbl1+1] = v
		end
	end
	return tbl1
end

function p.merge(tbl1, ...)
	-- tbl1 is modified to include all the elements of tbl2.
	if not tbl1 then tbl1 = {} end
	local tables = {...}
	for _, tbl2 in ipairs(tables) do
		for k, v in pairs(tbl2) do
			tbl1[k] = v
		end
	end
	return tbl1
end

function p.mergeDontOverwrite(tbl1, ...)
	-- tbl1 is modified to include all the elements of tbl2.
	if not tbl1 then tbl1 = {} end
	local tables = {...}
	for _, tbl2 in ipairs(tables) do
		for k, v in pairs(tbl2) do
			if tbl1[k] == nil then
				tbl1[k] = v
			end
		end
	end
	return tbl1
end

function p.mergeDicts(tbl1, ...)
	-- tbl1 is modified to include the elements of tbl2 appended to the end. Order is preserved.
	if not tbl1 then tbl1 = {} end
	local newTables = {...}
	for _, tbl2 in ipairs(newTables) do
		for _, v in ipairs(tbl2) do
			tbl1[#tbl1+1] = v
			tbl1[v] = tbl2[v]
		end
	end
	return tbl1
end

-- table.remove for non-integer key
function p.remove(tbl, key)
	local output = tbl[key]
	tbl[key] = nil
	return output
end

function p.removeValue(tbl, val)
	for k, v in pairs(tbl) do
		if val == v then
			tbl[k] = nil
		end
	end
	return tbl
end

function p.removeValueFromArray(tbl, val)
	local len = #tbl
	for i = len, 1, -1 do
		if tbl[i] == val then
			table.remove(i)
		end
	end
end

function p.removeDuplicates(tbl)
	local hash = {}
	local ret = {}
	for _, v in ipairs(tbl) do
		if not hash[v] then
			hash[v] = true
			ret[#ret+1] = v
		end
	end
	return ret
end

-- returns a copy of tbl with the elements in opposite order (not a deep copy)
function p.reverse(tbl)
	local tbl2 = {}
	local len = #tbl
	for i = len, 1, -1 do
		tbl2[len - i + 1] = tbl[i]
	end
	return tbl2
end

function p.reverseInPlace(tbl)
	local len = #tbl
	local stop_at = len / 2
	for i = 1, stop_at do
		local temp = tbl[i]
		tbl[i] = tbl[len - i + 1]
		tbl[len - i + 1] = temp
	end
end

function p.shallowClone(tbl)
	-- mostly to be able to use # operator on something from mw.loadData
	local tbl2 = {}
	for k, v in pairs(tbl) do
		tbl2[k] = v
	end
	return tbl2
end

function p.slice(tbl, s, e)
	if s < 0 then
		s = #tbl + 1 + s
	end
	if e < 0 then
		e = #tbl + 1 + e
	end
	local tbl2 = {}
	for k = s, e do
		tbl2[#tbl2+1] = tbl[k]
	end
	return tbl2
end

-- prints the table as a comma-separated list with and
function p.printList(tbl)
	if #tbl == 1 then
		return tbl[1]
	elseif #tbl == 2 then
		return table.concat(tbl, ' and ')
	else
		last = table.remove(tbl, #tbl)
		list = table.concat(tbl, ', ')
		return list .. ', and ' .. (last or '')
	end
end

function p.removeFalseEntries(tbl, max)
	if not max then max = #tbl end
	local j = 0
	for i = 1, max do
		if tbl[i] then
			j = j + 1
			tbl[j] = tbl[i]
		end
	end
	for i = j+1, max do
		tbl[i] = nil
	end
	return tbl
end

function p.padFalseEntries(tbl, max, default)
	default = default or ''
	for i = 1, max do
		if not tbl[i] then
			tbl[i] = default
		end
	end
	return tbl
end

function p.concat(tbl, sep, f, ...)
	if not tbl then return end
	if not sep then sep = ',' end
	if not f then
		local tbl2 = mw.clone(tbl)
		p.removeFalseEntries(tbl2)
		return table.concat(tbl2, sep)
	end
	local tbl2 = {}
	for k, v in ipairs(tbl) do
		if v then
			tbl2[#tbl2+1] = f(v, ...)
		end
	end
	return table.concat(tbl2, sep)
end

function p.concatDict(tbl, sep, f, ...)
	local tbl2 = {}
	for _, v in ipairs(tbl) do
		tbl2[#tbl2+1] = tbl[v]
	end
	return p.concat(tbl2, sep, f, ...)
end

function p.concatNonempty(tbl, sep, f, ...)
	if not tbl then return end
	if not next(tbl) then return end
	return p.concat(tbl, sep, f, ...)
end

function p.concatFromArgs(args, argname, sep, f)
	-- if fields are saved in args as field1, field2, field3, etc
	local i = 1
	local tbl = {}
	if args[argname] then
		tbl[1] = args[argname]
		i = 2
	end
	while args[argname .. i] do
		tbl[i] = args[argname .. i]
		i = i + 1
	end
	return next(tbl) and p.concat(tbl, sep, f)
end

function p.crop(tbl, max)
	for k, _ in ipairs(tbl) do
		if k > max then
			tbl[k] = nil
		end
	end
end

function p.alphabetize(tbl)
	local hash = {}
	local nocase = {}
	for i, v in ipairs(tbl) do
		nocase[i] = lang:caseFold(v)
		hash[nocase[i]] = v
	end
	table.sort(nocase)
	for i, v in ipairs(nocase) do
		tbl[i] = hash[v]
	end
	return tbl
end

function p.guaranteeTable(c, f, ...)
	if not c then return nil end
	if type(c) == 'table' then
		return f and f(c, ...) or c
	end
	return { f and f(c, ...) or c }
end

function p.guaranteeIndex(tbl, i)
	if type(i) == 'number' then return i end
	return p.keyOf(tbl, i)
end

function p.concatIfTable(tbl, sep)
	if not tbl then return nil end
	return p.concat(p.guaranteeTable(tbl), sep)
end

function p.nextNonFalse(tbl)
	for _, v in pairs(tbl) do
		if v then return v end
	end
end	

function p.interlace(tbl)
	local ret = {}
	local _, keyList = next(tbl)
	for key, _ in pairs(keyList) do
		ret[key] = {}
	end
	for k, v in pairs(tbl) do
		for key, _ in pairs(keyList) do
			ret[key][k] = v[key]
		end
	end
	return ret
end

function p.initTable(tbl, key, val)
	if tbl[key] then return end
	tbl[key] = val or {}
end

function p.initDict(tbl, key, val)
	if tbl[key] then return end
	tbl[key] = val or {}
	tbl[#tbl+1] = key
end

function p.push(tbl, val)
	-- useful just to make code look cleaner when tbl is something like parent[row.key]
	tbl[#tbl+1] = val
end

function p.pushDict(tbl, key, val)
	tbl[#tbl+1] = key
	tbl[key] = val
end

function p.arrayToDict(tbl, key)
	for i, v in ipairs(tbl) do
		tbl[v[key]] = v
		tbl[i] = v
	end
end

function p.extractValueToList(tbl, key)
	local ret = {}
	for _, v in ipairs(tbl) do
		ret[#ret+1] = v[key]
	end
	return ret
end

function p.extractValueFromDictToList(tbl, key)
	local ret = {}
	for _, v in ipairs(tbl) do
		ret[#ret+1] = tbl[v][key]
	end
	return ret
end

function p.arrayFromField(tbl, key)
	local ret = {}
	for k, row in ipairs(tbl) do
		ret[#ret+1] = row[key]
	end
	return ret
end

return p