Module:TableTools

------------------------------------------------------------------------------------
--                                   TableTools                                   --
--                                                                                --
-- This module includes a number of functions for dealing with Lua tables.        --
-- It is a meta-module, meant to be called from other Lua modules, and should not --
-- be called directly from #invoke.                                               --
------------------------------------------------------------------------------------

local libraryUtil = require('libraryUtil')

local p = {}

-- Define often-used variables and functions.
local floor = math.floor
local infinity = math.huge
local checkType = libraryUtil.checkType
local checkTypeMulti = libraryUtil.checkTypeMulti

------------------------------------------------------------------------------------
-- isPositiveInteger
--
-- This function returns true if the given value is a positive integer, and false
-- if not. Although it doesn't operate on tables, it is included here as it is
-- useful for determining whether a given table key is in the array part or the
-- hash part of a table.
------------------------------------------------------------------------------------
function p.isPositiveInteger(v)
 return type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity
end

------------------------------------------------------------------------------------
-- isNan
--
-- This function returns true if the given number is a NaN value, and false if
-- not. Although it doesn't operate on tables, it is included here as it is useful
-- for determining whether a value can be a valid table key. Lua will generate an
-- error if a NaN is used as a table key.
------------------------------------------------------------------------------------
function p.isNan(v)
 return type(v) == 'number' and v ~= v
end

------------------------------------------------------------------------------------
-- shallowClone
--
-- This returns a clone of a table. The value returned is a new table, but all
-- subtables and functions are shared. Metamethods are respected, but the returned
-- table will have no metatable of its own.
------------------------------------------------------------------------------------
function p.shallowClone(t)
 checkType('shallowClone', 1, t, 'table')
 local ret = {}
 for k, v in pairs(t) do
  ret[k] = v
 end
 return ret
end

------------------------------------------------------------------------------------
-- removeDuplicates
--
-- This removes duplicate values from an array. Non-positive-integer keys are
-- ignored. The earliest value is kept, and all subsequent duplicate values are
-- removed, but otherwise the array order is unchanged.
------------------------------------------------------------------------------------
function p.removeDuplicates(arr)
 checkType('removeDuplicates', 1, arr, 'table')
 local isNan = p.isNan
 local ret, exists = {}, {}
 for _, v in ipairs(arr) do
  if isNan(v) then
   -- NaNs can't be table keys, and they are also unique, so we don't need to check existence.
   ret[#ret + 1] = v
  elseif not exists[v] then
   ret[#ret + 1] = v
   exists[v] = true
  end
 end
 return ret
end

------------------------------------------------------------------------------------
-- numKeys
--
-- This takes a table and returns an array containing the numbers of any numerical
-- keys that have non-nil values, sorted in numerical order.
------------------------------------------------------------------------------------
function p.numKeys(t)
 checkType('numKeys', 1, t, 'table')
 local isPositiveInteger = p.isPositiveInteger
 local nums = {}
 for k in pairs(t) do
  if isPositiveInteger(k) then
   nums[#nums + 1] = k
  end
 end
 table.sort(nums)
 return nums
end

------------------------------------------------------------------------------------
-- affixNums
--
-- This takes a table and returns an array containing the numbers of keys with the
-- specified prefix and suffix. For example, for the table
-- {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix "a", affixNums will return
-- {1, 3, 6}.
------------------------------------------------------------------------------------
function p.affixNums(t, prefix, suffix)
 checkType('affixNums', 1, t, 'table')
 checkType('affixNums', 2, prefix, 'string', true)
 checkType('affixNums', 3, suffix, 'string', true)

 local function cleanPattern(s)
  -- Cleans a pattern so that the magic characters ()%.[]*+-?^$ are interpreted literally.
  return s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
 end

 prefix = prefix or ''
 suffix = suffix or ''
 prefix = cleanPattern(prefix)
 suffix = cleanPattern(suffix)
 local pattern = '^' .. prefix .. '([1-9]%d*)' .. suffix .. '$'

 local nums = {}
 for k in pairs(t) do
  if type(k) == 'string' then
   local num = mw.ustring.match(k, pattern)
   if num then
    nums[#nums + 1] = tonumber(num)
   end
  end
 end
 table.sort(nums)
 return nums
end

------------------------------------------------------------------------------------
-- numData
--
-- Given a table with keys like {"foo1", "bar1", "foo2", "baz2"}, returns a table
-- of subtables in the format
-- {[1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'}}.
-- Keys that don't end with an integer are stored in a subtable named "other". The
-- compress option compresses the table so that it can be iterated over with
-- ipairs.
------------------------------------------------------------------------------------
function p.numData(t, compress)
 checkType('numData', 1, t, 'table')
 checkType('numData', 2, compress, 'boolean', true)
 local ret = {}
 for k, v in pairs(t) do
  local prefix, num = mw.ustring.match(tostring(k), '^([^0-9]*)([1-9][0-9]*)$')
  if num then
   num = tonumber(num)
   local subtable = ret[num] or {}
   if prefix == '' then
    -- Positional parameters match the blank string; put them at the start of the subtable instead.
    prefix = 1
   end
   subtable[prefix] = v
   ret[num] = subtable
  else
   local subtable = ret.other or {}
   subtable[k] = v
   ret.other = subtable
  end
 end
 if compress then
  local other = ret.other
  ret = p.compressSparseArray(ret)
  ret.other = other
 end
 return ret
end

------------------------------------------------------------------------------------
-- compressSparseArray
--
-- This takes an array with one or more nil values, and removes the nil values
-- while preserving the order, so that the array can be safely traversed with
-- ipairs.
------------------------------------------------------------------------------------
function p.compressSparseArray(t)
 checkType('compressSparseArray', 1, t, 'table')
 local ret = {}
 local nums = p.numKeys(t)
 for _, num in ipairs(nums) do
  ret[#ret + 1] = t[num]
 end
 return ret
end

------------------------------------------------------------------------------------
-- sparseIpairs
--
-- This is an iterator for sparse arrays. It can be used like ipairs, but can
-- handle nil values.
------------------------------------------------------------------------------------
function p.sparseIpairs(t)
 checkType('sparseIpairs', 1, t, 'table')
 local nums = p.numKeys(t)
 local i = 0
 local lim = #nums
 return function ()
  i = i + 1
  if i <= lim then
   local key = nums[i]
   return key, t[key]
  else
   return nil, nil
  end
 end
end

------------------------------------------------------------------------------------
-- size
--
-- This returns the size of a key/value pair table. It will also work on arrays,
-- but for arrays it is more efficient to use the # operator.
------------------------------------------------------------------------------------
function p.size(t)
 checkType('size', 1, t, 'table')
 local i = 0
 for _ in pairs(t) do
  i = i + 1
 end
 return i
end

local function defaultKeySort(item1, item2)
 -- "number" < "string", so numbers will be sorted before strings.
 local type1, type2 = type(item1), type(item2)
 if type1 ~= type2 then
  return type1 < type2
 elseif type1 == 'table' or type1 == 'boolean' or type1 == 'function' then
  return tostring(item1) < tostring(item2)
 else
  return item1 < item2
 end
end
------------------------------------------------------------------------------------
-- keysToList
--
-- Returns an array of the keys in a table, sorted using either a default
-- comparison function or a custom keySort function.
------------------------------------------------------------------------------------
function p.keysToList(t, keySort, checked)
 if not checked then
  checkType('keysToList', 1, t, 'table')
  checkTypeMulti('keysToList', 2, keySort, {'function', 'boolean', 'nil'})
 end

 local arr = {}
 local index = 1
 for k in pairs(t) do
  arr[index] = k
  index = index + 1
 end

 if keySort ~= false then
  keySort = type(keySort) == 'function' and keySort or defaultKeySort
  table.sort(arr, keySort)
 end

 return arr
end

------------------------------------------------------------------------------------
-- sortedPairs
--
-- Iterates through a table, with the keys sorted using the keysToList function.
-- If there are only numerical keys, sparseIpairs is probably more efficient.
------------------------------------------------------------------------------------
function p.sortedPairs(t, keySort)
 checkType('sortedPairs', 1, t, 'table')
 checkType('sortedPairs', 2, keySort, 'function', true)

 local arr = p.keysToList(t, keySort, true)

 local i = 0
 return function ()
  i = i + 1
  local key = arr[i]
  if key ~= nil then
   return key, t[key]
  else
   return nil, nil
  end
 end
end

------------------------------------------------------------------------------------
-- isArray
--
-- Returns true if the given value is a table and all keys are consecutive
-- integers starting at 1.
------------------------------------------------------------------------------------
function p.isArray(v)
 if type(v) ~= 'table' then
  return false
 end
 local i = 0
 for _ in pairs(v) do
  i = i + 1
  if v[i] == nil then
   return false
  end
 end
 return true
end

------------------------------------------------------------------------------------
-- isArrayLike
--
-- Returns true if the given value is iterable and all keys are consecutive
-- integers starting at 1.
------------------------------------------------------------------------------------
function p.isArrayLike(v)
 if not pcall(pairs, v) then
  return false
 end
 local i = 0
 for _ in pairs(v) do
  i = i + 1
  if v[i] == nil then
   return false
  end
 end
 return true
end

------------------------------------------------------------------------------------
-- invert
--
-- Transposes the keys and values in an array. For example, {"a", "b", "c"} ->
-- {a = 1, b = 2, c = 3}. Duplicates are not supported (result values refer to
-- the index of the last duplicate) and NaN values are ignored.
------------------------------------------------------------------------------------
function p.invert(arr)
 checkType("invert", 1, arr, "table")
 local isNan = p.isNan
 local map = {}
 for i, v in ipairs(arr) do
  if not isNan(v) then
   map[v] = i
  end
 end

 return map
end

------------------------------------------------------------------------------------
-- listToSet
--
-- Creates a set from the array part of the table. Indexing the set by any of the
-- values of the array returns true. For example, {"a", "b", "c"} ->
-- {a = true, b = true, c = true}. NaN values are ignored as Lua considers them
-- never equal to any value (including other NaNs or even themselves).
------------------------------------------------------------------------------------
function p.listToSet(arr)
 checkType("listToSet", 1, arr, "table")
 local isNan = p.isNan
 local set = {}
 for _, v in ipairs(arr) do
  if not isNan(v) then
   set[v] = true
  end
 end

 return set
end

------------------------------------------------------------------------------------
-- deepCopy
--
-- Recursive deep copy function. Preserves identities of subtables.
------------------------------------------------------------------------------------
local function _deepCopy(orig, includeMetatable, already_seen)
 if type(orig) ~= "table" then
  return orig
 end
 
 -- already_seen stores copies of tables indexed by the original table.
 local copy = already_seen[orig]
 if copy ~= nil then
  return copy
 end
 
 copy = {}
 already_seen[orig] = copy -- memoize before any recursion, to avoid infinite loops
 
 for orig_key, orig_value in pairs(orig) do
  copy[_deepCopy(orig_key, includeMetatable, already_seen)] = _deepCopy(orig_value, includeMetatable, already_seen)
 end
 
 if includeMetatable then
  local mt = getmetatable(orig)
  if mt ~= nil then
   setmetatable(copy, _deepCopy(mt, true, already_seen))
  end
 end
 
 return copy
end

function p.deepCopy(orig, noMetatable, already_seen)
 checkType("deepCopy", 3, already_seen, "table", true)
 return _deepCopy(orig, not noMetatable, already_seen or {})
end

------------------------------------------------------------------------------------
-- sparseConcat
--
-- Concatenates all values in the table that are indexed by a number, in order.
-- sparseConcat{a, nil, c, d}  =>  "acd"
-- sparseConcat{nil, b, c, d}  =>  "bcd"
------------------------------------------------------------------------------------
function p.sparseConcat(t, sep, i, j)
 local arr = {}

 local arr_i = 0
 for _, v in p.sparseIpairs(t) do
  arr_i = arr_i + 1
  arr[arr_i] = v
 end

 return table.concat(arr, sep, i, j)
end

------------------------------------------------------------------------------------
-- length
--
-- Finds the length of an array, or of a quasi-array with keys such as "data1",
-- "data2", etc., using an exponential search algorithm. It is similar to the
-- operator #, but may return a different value when there are gaps in the array
-- portion of the table. Intended to be used on data loaded with mw.loadData. For
-- other tables, use #.
-- Note: #frame.args in frame object always be set to 0, regardless of  the number
-- of unnamed template parameters, so use this function for frame.args.
------------------------------------------------------------------------------------
function p.length(t, prefix)
 -- requiring module inline so that [[Module:Exponential search]] which is
 -- only needed by this one function doesn't get millions of transclusions
 local expSearch = require("Module:Exponential search")
 checkType('length', 1, t, 'table')
 checkType('length', 2, prefix, 'string', true)
 return expSearch(function (i)
  local key
  if prefix then
   key = prefix .. tostring(i)
  else
   key = i
  end
  return t[key] ~= nil
 end) or 0
end

------------------------------------------------------------------------------------
-- inArray
--
-- Returns true if valueToFind is a member of the array, and false otherwise.
------------------------------------------------------------------------------------
function p.inArray(arr, valueToFind)
 checkType("inArray", 1, arr, "table")
 -- if valueToFind is nil, error?

 for _, v in ipairs(arr) do
  if v == valueToFind then
   return true
  end
 end
 return false
end

------------------------------------------------------------------------------------
-- merge
--
-- Given the arrays, returns an array containing the elements of each input array
-- in sequence.
------------------------------------------------------------------------------------
function p.merge(...)
 local arrays = {...}
 local ret = {}
 for i, arr in ipairs(arrays) do
  checkType('merge', i, arr, 'table')
  for _, v in ipairs(arr) do
   ret[#ret + 1] = v
  end
 end
 return ret
end

------------------------------------------------------------------------------------
-- extend
--
-- Extends the first array in place by appending all elements from the second
-- array.
------------------------------------------------------------------------------------
function p.extend(arr1, arr2)
 checkType('extend', 1, arr1, 'table')
 checkType('extend', 2, arr2, 'table')

 for _, v in ipairs(arr2) do
  arr1[#arr1 + 1] = v
 end
end

return p