--!nonstrict
--[=[
	NumberLocalizationUtils script from Roblox's player scripts in handling the leaderboard.

	Example locale-sensitive number formatting:
	https://docs.oracle.com/cd/E19455-01/806-0169/overview-9/index.html

	Locale specification:
	[DECIMAL_SEPARATOR] = string for decimal point, if needed
	[GROUP_DELIMITER] = string for groupings of numbers left of the decimal
	List section = abbreviations for language, in increasing order

	Missing features in this code:
	- No support for differences in number of digits per GROUP_DELIMITER.
	Some Chinese dialects group by 10000 instead of 1000.
	- No support for variable differences in number of digits per GROUP_DELIMITER.
	Indian natural language groups the first 3 to left of decimal, then every 2 after that.

	See https://en.wikipedia.org/wiki/Decimal_separator#Digit_grouping


	@class NumberLocalizationUtils
]=]

local require = require(script.Parent.loader).load(script)

local RoundingBehaviourTypes = require("RoundingBehaviourTypes")

local NumberLocalizationUtils = {}

local DEFAULT_LOCALE = "en-us"

-- Separator aliases to help avoid spelling errors
local DECIMAL_SEPARATOR = "decimalSeparator"
local GROUP_DELIMITER = "groupDelimiter"

local localeInfos = {}

localeInfos["en-us"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, "K" },
	{ 1e6, "M" },
	{ 1e9, "B" },
}

localeInfos["es-es"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = ".",
	{ 1, "" },
	{ 1e3, " mil" },
	{ 1e6, " M" },
}

localeInfos["fr-fr"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = " ",
	{ 1, "" },
	{ 1e3, " k" },
	{ 1e6, " M" },
	{ 1e9, " Md" },
}

localeInfos["de-de"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = " ",
	{ 1, "" },
	{ 1e3, " Tsd." },
	{ 1e6, " Mio." },
	{ 1e9, " Mrd." },
}

localeInfos["pt-br"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = ".",
	{ 1, "" },
	{ 1e3, " mil" },
	{ 1e6, " mi" },
	{ 1e9, " bi" },
}

localeInfos["zh-cn"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",", -- Chinese commonly uses 3 digit groupings, despite 10000s rule
	{ 1, "" },
	{ 1e3, "千" },
	{ 1e4, "万" },
	{ 1e8, "亿" },
}

localeInfos["zh-cjv"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, "千" },
	{ 1e4, "万" },
	{ 1e8, "亿" },
}

localeInfos["zh-tw"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, "千" },
	{ 1e4, "萬" },
	{ 1e8, "億" },
}

localeInfos["ko-kr"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, "천" },
	{ 1e4, "만" },
	{ 1e8, "억" },
}

localeInfos["ja-jp"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, "千" },
	{ 1e4, "万" },
	{ 1e8, "億" },
}

localeInfos["it-it"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = " ",
	{ 1, "" },
	{ 1e3, " mila" },
	{ 1e6, " Mln" },
	{ 1e9, " Mld" },
}

localeInfos["ru-ru"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = ".",
	{ 1, "" },
	{ 1e3, " тыс" },
	{ 1e6, " млн" },
	{ 1e9, " млрд" },
}

localeInfos["id-id"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = ".",
	{ 1, "" },
	{ 1e3, " rb" },
	{ 1e6, " jt" },
	{ 1e9, " M" },
}

localeInfos["vi-vn"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = " ",
	{ 1, "" },
	{ 1e3, " N" },
	{ 1e6, " Tr" },
	{ 1e9, " T" },
}

localeInfos["th-th"] = {
	[DECIMAL_SEPARATOR] = ".",
	[GROUP_DELIMITER] = ",",
	{ 1, "" },
	{ 1e3, " พ" },
	{ 1e4, " ม" },
	{ 1e5, " ส" },
	{ 1e6, " ล" },
}

localeInfos["tr-tr"] = {
	[DECIMAL_SEPARATOR] = ",",
	[GROUP_DELIMITER] = ".",
	{ 1, "" },
	{ 1e3, " B" },
	{ 1e6, " Mn" },
	{ 1e9, " Mr" },
}

-- Aliases for languages that use the same mappings.
localeInfos["en"] = localeInfos["en-us"]
localeInfos["en-gb"] = localeInfos["en-us"]
localeInfos["es-mx"] = localeInfos["es-es"]

local function findDecimalPointIndex(numberStr: string)
	return string.find(numberStr, "%.") or #numberStr + 1
end

-- Find the base 10 offset needed to make 0.1 <= abs(number) < 1
local function findDecimalOffset(number: number)
	if number == 0 then
		return 0
	end

	local offsetToOnesRange = math.floor(math.log10(math.abs(number)))
	return -(offsetToOnesRange + 1) -- Offset one more (or less) digit
end

local function roundToSignificantDigits(
	number: number,
	significantDigits: number,
	roundingBehaviourType: RoundingBehaviourTypes.RoundingBehaviourType
)
	local offset = findDecimalOffset(number)
	local multiplier = 10 ^ (significantDigits + offset)
	local significand
	if roundingBehaviourType == RoundingBehaviourTypes.TRUNCATE then
		significand = math.modf(number * multiplier)
	else
		significand = math.floor(number * multiplier + 0.5)
	end
	return significand / multiplier
end

local function addGroupDelimiters(numberStr, delimiter: string): string
	local formatted = numberStr
	local delimiterSubStr = string.format("%%1%s%%2", delimiter)
	while true do
		local lFormatted, k = string.gsub(formatted, "^(-?%d+)(%d%d%d)", delimiterSubStr)
		formatted = lFormatted
		if k == 0 then
			break
		end
	end
	return formatted
end

local function findDenominationEntry(
	localeInfo,
	number: number,
	roundingBehaviourType: RoundingBehaviourTypes.RoundingBehaviourType
)
	local denominationEntry = localeInfo[1] -- Default to base denominations
	local absOfNumber = math.abs(number)
	for i = #localeInfo, 2, -1 do
		local entry = localeInfo[i]
		local baseValue
		if roundingBehaviourType == RoundingBehaviourTypes.TRUNCATE then
			baseValue = entry[1]
		else
			baseValue = entry[1] - localeInfo[i - 1][1] / 2
		end
		if baseValue <= absOfNumber then
			denominationEntry = entry
			break
		end
	end
	return denominationEntry
end

function NumberLocalizationUtils.localize(number: number, locale: string): string
	if number == 0 then
		return "0"
	end

	local localeInfo = localeInfos[locale]
	if not localeInfo then
		localeInfo = localeInfos[DEFAULT_LOCALE]
		warn(
			string.format(
				"[NumberLocalizationUtils] - Locale not found: '%s', reverting to '%s' instead.",
				tostring(locale),
				DEFAULT_LOCALE
			)
		)
	end

	if localeInfo.groupDelimiter then
		return addGroupDelimiters(number, localeInfo.groupDelimiter)
	end

	return tostring(number)
end

--[=[
	Abbreviates the number to a truncated amount in a localized way.

	```lua
	print(NumberLocalizationUtils.abbreviate(2500, "en-us", RoundingBehaviourTypes.ROUND_TO_CLOSEST, 3)) --> 2.5k
	```

	@param number number
	@param locale string
	@param roundingBehaviourType RoundingBehaviourType?
	@param numSignificantDigits number?
	@return string
]=]
function NumberLocalizationUtils.abbreviate(
	number: number,
	locale: string,
	roundingBehaviourType: RoundingBehaviourTypes.RoundingBehaviourType?,
	numSignificantDigits: number?
): string
	assert(type(number) == "number", "Bad number")
	local roundingBehavior = roundingBehaviourType or RoundingBehaviourTypes.ROUND_TO_CLOSEST
	local significantDigits = numSignificantDigits or 3

	if roundingBehavior == RoundingBehaviourTypes.NONE then
		return NumberLocalizationUtils.localize(number, locale)
	end

	if number == 0 then
		return "0"
	end

	local localeInfo = localeInfos[locale]
	if not localeInfo then
		localeInfo = localeInfos[DEFAULT_LOCALE]
		warn(
			string.format(
				"[NumberLocalizationUtils] - Locale not found: '%s', reverting to '%s' instead.",
				tostring(locale),
				DEFAULT_LOCALE
			)
		)
	end

	-- select which denomination we are going to use
	local denominationEntry = findDenominationEntry(localeInfo, number, roundingBehavior)
	local baseValue = denominationEntry[1]
	local symbol = denominationEntry[2]

	-- Round to required significant digits
	local significantQuotient = roundToSignificantDigits(number / baseValue, significantDigits, roundingBehavior)

	-- trim decimal points
	local trimmedQuotientString
	local symbolsAboveDecimal = math.ceil(math.log10(significantQuotient))
	local maxDecimals = math.max(1, significantDigits - symbolsAboveDecimal)
	local trimmedQuotient
	local roundingFactor = 10 ^ maxDecimals
	if roundingBehavior == RoundingBehaviourTypes.TRUNCATE then
		trimmedQuotient = math.modf(significantQuotient * roundingFactor) / roundingFactor
	elseif roundingBehavior == RoundingBehaviourTypes.ROUND_TO_CLOSEST then
		trimmedQuotient = math.floor(significantQuotient * roundingFactor + 0.5) / roundingFactor
	else
		error(
			string.format(
				"[NumberLocalizationUtils.abbreviate] - Unknown roundingBehaviourType %q",
				tostring(roundingBehavior)
			)
		)
	end

	trimmedQuotientString = tostring(trimmedQuotient)

	-- Split the string into integer and fraction parts
	local decimalPointIndex = findDecimalPointIndex(trimmedQuotientString)
	local integerPart = string.sub(trimmedQuotientString, 1, decimalPointIndex - 1)
	local fractionPart = string.sub(trimmedQuotientString, decimalPointIndex + 1, #trimmedQuotientString)

	-- Add group delimiters to integer part
	if localeInfo.groupDelimiter then
		integerPart = addGroupDelimiters(integerPart, localeInfo.groupDelimiter)
	end

	if #fractionPart > 0 then
		return integerPart .. localeInfo.decimalSeparator .. fractionPart .. symbol
	else
		return integerPart .. symbol
	end
end

return NumberLocalizationUtils