local p = {}

local floor = math.floor

local function errorf(level, ...)
	if type(level) == "number" then
		return error(string.format(...), level + 1)
	else -- level is actually the format string.
		return error(string.format(level, ...), 2)
	end
end

local function binary_range_search(codepoint, ranges)
	local low, mid, high
	low, high = 1, ranges.length or require "Module:TableTools".length(ranges)
	while low <= high do
		mid = floor((low + high) / 2)
		local range = ranges[mid]
		if codepoint < range[1] then
			high = mid - 1
		elseif codepoint <= range[2] then
			return range, mid
		else
			low = mid + 1
		end
	end
	return nil, mid
end
p.binary_range_search = binary_range_search

--[[
local function linear_range_search(codepoint, ranges)
	for i, range in ipairs(ranges) do
		if range[1] <= codepoint and codepoint <= range[2] then
			return range
		end
	end
end
--]]

-- Load a module by indexing "loader" with the name of the module minus the
-- "Module:Unicode data/" part. For instance, loader.blocks returns
-- [[Module:Unicode data/blocks]]. If a module cannot be loaded, false will be
-- returned.
local loader = setmetatable({}, {
	__index = function (self, key)
		local success, data = pcall(mw.loadData, "Module:Unicode data/" .. key)
		if not success then
			data = false
		end
		self[key] = data
		return data
	end
})

-- For the algorithm used to generate Hangul Syllable names,
-- see "Hangul Syllable Name Generation" in section 3.12 of the
-- Unicode Specification:
-- https://www.unicode.org/versions/Unicode11.0.0/ch03.pdf
local name_hooks = {
	{     0x00,     0x1F, "<control-%04X>" }, -- C0 control characters
	{     0x7F,     0x9F, "<control-%04X>" }, -- DEL and C1 control characters
	{   0x3400,   0x4DBF, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension A
	{   0x4E00,   0x9FFF, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph
	{   0xAC00,   0xD7A3, function (codepoint) -- Hangul Syllables
		local Hangul_data = loader.Hangul
		local syllable_index = codepoint - 0xAC00

		return ("HANGUL SYLLABLE %s%s%s"):format(
			Hangul_data.leads[floor(syllable_index / Hangul_data.final_count)],
			Hangul_data.vowels[floor((syllable_index % Hangul_data.final_count)
				/ Hangul_data.trail_count)],
			Hangul_data.trails[syllable_index % Hangul_data.trail_count]
		)
	end },
	-- High Surrogates, High Private Use Surrogates, Low Surrogates
	{   0xD800,   0xDFFF, "<surrogate-%04X>" },
	{   0xE000,   0xF8FF, "<private-use-%04X>" }, -- Private Use
	-- CJK Compatibility Ideographs
	{   0xF900,   0xFA6D, "CJK COMPATIBILITY IDEOGRAPH-%04X" },
	{   0xFA70,   0xFAD9, "CJK COMPATIBILITY IDEOGRAPH-%04X" },
	{  0x17000,  0x187F7, "TANGUT IDEOGRAPH-%04X" }, -- Tangut Ideograph
	{  0x18800,  0x18AFF, function (codepoint)
		return ("TANGUT COMPONENT-%03d"):format(codepoint - 0x187FF)
	end },
	{  0x18D00,  0x18D08, "TANGUT IDEOGRAPH-%04X" }, -- Tangut Ideograph Supplement
	{  0x1B170,  0x1B2FB, "NUSHU CHARACTER-%04X" }, -- Nushu
	{  0x20000,  0x2A6DF, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension B
	{  0x2A700,  0x2B739, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension C
	{  0x2B740,  0x2B81D, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension D
	{  0x2B820,  0x2CEA1, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension E
	{  0x2CEB0,  0x2EBE0, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension F
	-- CJK Compatibility Ideographs Supplement (Supplementary Ideographic Plane)
	{  0x2F800,  0x2FA1D, "CJK COMPATIBILITY IDEOGRAPH-%04X" },
	{  0xE0100,  0xE01EF, function (codepoint) -- Variation Selectors Supplement
		return ("VARIATION SELECTOR-%d"):format(codepoint - 0xE0100 + 17)
	end},
	{  0x30000,  0x3134A, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension G
	{  0x31350,  0x323AF, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension H
	{  0x2EBF0,  0x2EE5D, "CJK UNIFIED IDEOGRAPH-%04X" }, -- CJK Ideograph Extension I
	{  0xF0000,  0xFFFFD, "<private-use-%04X>" }, -- Plane 15 Private Use
	{ 0x100000, 0x10FFFD, "<private-use-%04X>" }  -- Plane 16 Private Use
}
name_hooks.length = #name_hooks

local name_range_cache

local function generate_name(data, codepoint)
	if type(data) == "string" then
		return data:format(codepoint)
	else
		return data(codepoint)
	end
end

--[[
-- Checks that the code point is a number and in range.
-- Does not check whether code point is an integer.
-- Not used
local function check_codepoint(funcName, argIdx, val)
	require 'libraryUtil'.checkType(funcName, argIdx, val, 'number')
	if codepoint < 0 or 0x10FFFF < codepoint then
		errorf("Codepoint %04X out of range", codepoint)
	end
end
--]]

-- https://www.unicode.org/versions/Unicode11.0.0/ch04.pdf, section 4.8
function p.lookup_name(codepoint)
	-- U+FDD0-U+FDEF and all code points ending in FFFE or FFFF are Unassigned
	-- (Cn) and specifically noncharacters:
	-- https://www.unicode.org/faq/private_use.html#nonchar4
	if 0xFDD0 <= codepoint and (codepoint <= 0xFDEF
			or floor(codepoint % 0x10000) >= 0xFFFE) then
		return ("<noncharacter-%04X>"):format(codepoint)
	end

	if name_range_cache -- Check if previously used "name hook" applies to this code point.
			and codepoint >= name_range_cache[1]
			and codepoint <= name_range_cache[2] then
		return generate_name(name_range_cache[3], codepoint)
	end
	
	local range = binary_range_search(codepoint, name_hooks)
	if range then
		name_range_cache = range
		return generate_name(range[3], codepoint)
	end

	local data = loader[('names/%03X'):format(codepoint / 0x1000)]
	
	if data and data[codepoint] then
		return data[codepoint]
	
	-- Unassigned (Cn) consists of noncharacters and reserved characters.
	-- The character has been established not to be a noncharacter,
	-- and if it were assigned, its name would already been retrieved,
	-- so it must be reserved.
	else
		return ("<reserved-%04X>"):format(codepoint)
	end
end

function p.lookup_image(codepoint)
	local data = loader[('images/%03X'):format(codepoint / 0x1000)]
	
	if data then
		return data[codepoint]
	end
end

local planes = {
	[ 0] = "Basic Multilingual Plane";
	[ 1] = "Supplementary Multilingual Plane";
	[ 2] = "Supplementary Ideographic Plane";
	[ 3] = "Tertiary Ideographic Plane";
	[14] = "Supplementary Special-purpose Plane";
	[15] = "Supplementary Private Use Area-A";
	[16] = "Supplementary Private Use Area-B";
}

-- Load [[Module:Unicode data/blocks]] if needed and assign it to this variable.
local blocks

local function block_iter(blocks, i)
	i = i + 1
	local data = blocks[i]
	if data then
		 -- Unpack doesn't work on tables loaded with mw.loadData.
		return i, data[1], data[2], data[3]
	end
end

-- An ipairs-type iterator generator for the list of blocks.
function p.enum_blocks()
	local blocks = loader.blocks
	return block_iter, blocks, 0
end

function p.lookup_plane(codepoint)
	local i = floor(codepoint / 0x10000)
	return planes[i] or ("Plane %u"):format(i)
end

function p.lookup_block(codepoint)
	local blocks = loader.blocks
	local range = binary_range_search(codepoint, blocks)
	if range then
		return range[3]
	else
		return "No Block"
	end
end

function p.get_block_info(name)
	for i, block in ipairs(loader.blocks) do
		if block[3] == name then
			return block
		end
	end
end

function p.is_valid_pagename(pagename)
	local has_nonws = false

	for cp in mw.ustring.gcodepoint(pagename) do
		if (cp == 0x0023) -- #
		or (cp == 0x005B) -- [
		or (cp == 0x005D) -- ]
		or (cp == 0x007B) -- {
		or (cp == 0x007C) -- |
		or (cp == 0x007D) -- }
		or (cp == 0x180E) -- MONGOLIAN VOWEL SEPARATOR
		or ((cp >= 0x2000) and (cp <= 0x200A)) -- spaces in General Punctuation block
		or (cp == 0xFFFD) -- REPLACEMENT CHARACTER
		then
			return false
		end

		local printable, result = p.is_printable(cp)
		if not printable then
			return false
		end

		if result ~= "space-separator" then
			has_nonws = true
		end
	end

	return has_nonws
end

local function manual_unpack(what, from)
	if what[from + 1] == nil then
		return what[from]
	end
	
	local result = {}
	from = from or 1
	for i, item in ipairs(what) do
		if i >= from then
			table.insert(result, item)
		end
	end
	return unpack(result)
end

local function compare_ranges(range1, range2)
	return range1[1] < range2[1]
end

-- Creates a function to look up data in a module that contains "singles" (a
-- code point-to-data map) and "ranges" (an array containing arrays that contain
-- the low and high code points of a range and the data associated with that
-- range).
-- "loader" loads and returns the "singles" and "ranges" tables.
-- "match_func" is passed the code point and either the data or the "dots", and
-- generates the final result of the function.
-- The varargs ("dots") describes the default data to be returned if there wasn't
-- a match.
-- In case the function is used more than once, "cache" saves ranges that have
-- already been found to match, or a range whose data is the default if there
-- was no match.
local function memo_lookup(data_module_subpage, match_func, ...)
	local dots = { ... }
	local cache = {}
	local singles, ranges

	return function (codepoint)
		if not singles then
			local data_module = loader[data_module_subpage]
			singles, ranges = data_module.singles, data_module.ranges
		end

		if singles[codepoint] then
			return match_func(codepoint, singles[codepoint])
		end

		local range = binary_range_search(codepoint, cache)
		if range then
			return match_func(codepoint, manual_unpack(range, 3))
		end
		
		local range, index = binary_range_search(codepoint, ranges)
		if range then
			table.insert(cache, range)
			table.sort(cache, compare_ranges)
			return match_func(codepoint, manual_unpack(range, 3))
		end
		
		if ranges[index] then
			local dots_range
			if codepoint > ranges[index][2] then
				dots_range = {
					ranges[index][2] + 1,
					ranges[index + 1] and ranges[index + 1][1] - 1 or 0x10FFFF,
					unpack(dots)
				}
			else -- codepoint < range[index][1]
				dots_range = {
					ranges[index - 1] and ranges[index - 1][2] + 1 or 0,
					ranges[index][1] - 1,
					unpack(dots)
				}
			end
			table.sort(cache, compare_ranges)
		end
		
		return match_func(codepoint)
	end
end

-- Get a code point's combining class value in [[Module:Unicode data/combining]],
-- and return whether this value is not zero. Zero is assigned as the default
-- if the combining class value is not found in this data module.
-- That is, return true if character is combining, or false if it is not.
-- See https://www.unicode.org/reports/tr44/#Canonical_Combining_Class_Values for
-- more information.
p.is_combining = memo_lookup(
	"combining",
	function (codepoint, combining_class)
		return combining_class and combining_class ~= 0 or false
	end,
	0)

function p.add_dotted_circle(str)
	return (mw.ustring.gsub(str, ".",
		function(char)
			if p.is_combining(mw.ustring.codepoint(char)) then
				return '◌' .. char
			end
		end))
end

local lookup_control = memo_lookup(
	"control",
	function (codepoint, ccc)
		return ccc or "assigned"
	end,
	"assigned")
p.lookup_control = lookup_control

function p.is_assigned(codepoint)
	return lookup_control(codepoint) ~= "unassigned"
end

function p.is_printable(codepoint)
	local result = lookup_control(codepoint)
	return (result == "assigned") or (result == "space-separator"), result
end

function p.is_whitespace(codepoint)
	local result = lookup_control(codepoint)
	return (result == "space-separator"), result
end

p.lookup_category = memo_lookup(
	"category",
	function (codepoint, category)
		return category
	end,
	"Cn")

local lookup_script = memo_lookup(
	"scripts",
	function (codepoint, script_code)
		return script_code or 'Zzzz'
	end,
	"Zzzz")
p.lookup_script = lookup_script

function p.get_best_script(str)
	-- Check type of argument, because mw.text.decode coerces numbers to strings!
	require "libraryUtil".checkType("get_best_script", 1, str, "string")
	
	-- Convert HTML character references (including named character references,
	-- or character entities) to characters.
	str = mw.text.decode(str, true)
	
	local scripts = {}
	for codepoint in mw.ustring.gcodepoint(str) do
		local script = lookup_script(codepoint)
		
		-- Ignore "Inherited", "Undetermined", or "Uncoded" scripts.
		if not (script == "Zyyy" or script == "Zinh" or script == "Zzzz") then
			scripts[script] = true
		end
	end
	
	-- If scripts does not contain two or more keys,
	-- return first and only key (script code) in table.
	if not next(scripts, next(scripts)) then
		return next(scripts)
	end -- else return majority script, or else "Zzzz"?
end

function p.is_Latin(str)
	require "libraryUtil".checkType("get_best_script", 1, str, "string")
	str = mw.text.decode(str, true)
	
	-- Search for the leading bytes that introduce the UTF-8 encoding of the
	-- code points U+0340-U+10FFFF. If they are not found and there is at least
	-- one Latin-script character, the string counts as Latin, because the rest
	-- of the characters can only be Zyyy, Zinh, and Zzzz.
	-- The only scripts found below U+0370 (the first code point of the Greek
	-- and Coptic block) are Latn, Zyyy, Zinh, and Zzzz.
	-- See the codepage in the [[UTF-8]] article.
	if not str:find "[\205-\244]" then
		for codepoint in mw.ustring.gcodepoint(str) do
			if lookup_script(codepoint) == "Latn" then
				return true
			end
		end
	end
	
	local Latn = false
	
	for codepoint in mw.ustring.gcodepoint(str) do
		local script = lookup_script(codepoint)
		
		if script == "Latn" then
			Latn = true
		elseif not (script == "Zyyy" or script == "Zinh"
				or script == "Zzzz") then
			return false
		end
	end
	
	return Latn
end

-- Checks that a string contains only characters belonging to right-to-left
-- scripts, or characters of ignorable scripts.
function p.is_rtl(str)
	require "libraryUtil".checkType("get_best_script", 1, str, "string")
	str = mw.text.decode(str, true)
	
	-- Search for the leading bytes that introduce the UTF-8 encoding of the
	-- code points U+0580-U+10FFFF. If they are not found, the string can only
	-- have characters from a left-to-right script, because the first code point
	-- in a right-to-left script is U+0591, in the Hebrew block.
	if not str:find "[\214-\244]" then
		return false
	end
	
	local result = false
	local rtl = loader.scripts.rtl
	for codepoint in mw.ustring.gcodepoint(str) do
		local script = lookup_script(codepoint)
		
		if rtl[script] then
			result = true
		elseif not (script == "Zyyy" or script == "Zinh"
				or script == "Zzzz") then
			return false
		end
	end
	
	return result
end


--[[--------------------------< I S _ R T L _ F R A M E >------------------------------------------------------

external entry from an ((#invoke:)) to determine if a string of text is rtl.  Strips html and html-like tags so
that those tags don't corrupt the is-rtl-is-not-rtl determination; this added for the cases where the rtl text
has <br /> tags.

]]

function p.is_rtl_frame (frame)
	local str = frame.args[1];													-- get the string from the ((#invoke:)) frame
	str = str:gsub ('%b<>', '');												-- strip any html and html-like tags
	return p.is_rtl (str);														-- return if whatever remains rtl; false else
end


local function get_codepoint(args, arg)
	local codepoint_string = args[arg]
		or errorf(2, "Parameter %s is required", tostring(arg))
	local codepoint = tonumber(codepoint_string, 16)
		or errorf(2, "Parameter %s is not a code point in hexadecimal base",
			tostring(arg))
	if not (0 <= codepoint and codepoint <= 0x10FFFF) then
		errorf(2, "code point in parameter %s out of range", tostring(arg))
	end
	return codepoint
end

local function get_func(args, arg, prefix)
	local suffix = args[arg]
		or errorf(2, "Parameter %s is required", tostring(arg))
	suffix = mw.text.trim(suffix)
	local func_name = prefix .. suffix
	local func = p[func_name]
		or errorf(2, "There is no function '%s'", func_name)
	return func
end

-- This function allows any of the "lookup" functions to be invoked. The first
-- parameter is the word after "lookup_"; the second parameter is the code point
-- in hexadecimal base.
function p.lookup(frame)
	local func = get_func(frame.args, 1, "lookup_")
	local codepoint = get_codepoint(frame.args, 2)
	local result = func(codepoint)
	if func == p.lookup_name then
		-- Prevent code point labels such as <control-0000> from being
		-- interpreted as HTML tags.
		result = result:gsub("<", "&lt;")
	end
	return result
end

function p.is(frame)
	local func = get_func(frame.args, 1, "is_")
	
	-- is_Latin and is_valid_pagename take strings.
	if func == p.is_Latin or func == p.is_valid_pagename or func == p.is_rtl then
		return (func(frame.args[2]))
	else -- The rest take code points.
		local codepoint = get_codepoint(frame.args, 2)
		return (func(codepoint)) -- Adjust to one result.
	end
end

return p