--!strict
local Sift = script.Parent.Parent

local Util = require(Sift.Util)

--[=[
  @function filter
  @within Dictionary

  @param dictionary {[K]: V} -- The dictionary to filter.
  @param predicate? (value: V, key: K, dictionary: {[K]: V}) -> any -- The predicate to use to filter the dictionary.
  @return {[K]: V} -- The filtered dictionary.

  Filters a dictionary using a predicate. Any items that do not pass the predicate will be removed from the dictionary.

  ```lua
  local dictionary = { hello = "world", goodbye = "goodbye" }

  local result = Filter(dictionary, function(value, key)
    return value == "world"
  end) -- { hello = "world" }
  ```
]=]
local function filter<K, V>(
	dictionary: { [K]: V },
	predicate: ((value: V, key: K, dictionary: { [K]: V }) -> any)?
): { [K]: V }
	local result = {}

	predicate = if type(predicate) == "function" then predicate else Util.func.truthy

	for key, value in pairs(dictionary) do
		if predicate(value, key, dictionary) then
			result[key] = value
		end
	end

	return result
end

return filter