local export = {}

local m_str_utils = require("Module:string utilities")

local byte = string.byte
local codepoint = m_str_utils.codepoint
local concat = table.concat
local convert_iteration_marks = require("Module:Hani").convert_iteration_marks
local explode = m_str_utils.explode_utf8
local format = string.format
local gmatch = string.gmatch
local gsub = string.gsub
local insert = table.insert
local sub = string.sub
local u = m_str_utils.char
local ugsub = mw.ustring.gsub
local umatch = mw.ustring.match
local upper = m_str_utils.upper

local m_data = require("Module:Hani-sortkey/data/serialized")
local m_data_core = mw.loadData("Module:Hani-sortkey/data/core")
local cache = {}

--[[
	Returns the index in the string where the ideographic description sequence
	(IDS) ends, or the index of the end of the string. Iterates whenever
	another ideographic description character (IDC) is found.
]]
local function findEndOfIDS(text, IDchar, i)
	if not (text and IDchar and i) then
		return nil
	end
	
	local j = i
	local component = 1
	
	-- Number of components expected after current IDC.
	local components = m_data_core.ids[IDchar]
	
	while component <= components do
		j = j + 1
		
		local char = text[j]
		
		if not char then
			break
		elseif m_data_core.ids[char] then
			j = findEndOfIDS(text, char, j)
		end
		
		component = component + 1
	end
	
	--[[
		If the expected number of components has been found,
		return the current index in the text.
	]]
	if component - components == 1 then
		return j
	else
		return nil
	end
end

local function unserialize(a, b)
	return m_data_core.radicals[byte(a)] .. format("%02d", byte(b) - 10)
end

-- The data is stored in [[Module:Hani-sortkey/data]]. This data is not accessed directly (due to the large amount of memory this would consume), but is instead stored in a serialized form as [[Module:Hani-sortkey/data/serialized]]. If the data is changed, the new serialized data can be generated with [[Module:Hani-sortkey/data/serializer]].
function export.getData(char)
	if type(char) == "string" then
		char = codepoint(char)
	elseif type(char) ~= "number" then
		error("getData must operate on a single character or codepoint.")
	end
	local offset, s, f, lookup = 0
	for i = 2, m_data_core.ranges.n, 2 do
		s, f = m_data_core.ranges[i - 1], m_data_core.ranges[i]
		if char > f then
			offset = offset + f - s + 1
		elseif char >= s and char <= f then
			lookup = 2 * (offset + char - s + 1)
			return (gsub(sub(m_data, lookup - 1, lookup), "(.)(.)", unserialize))
		end
	end
	return u(char)
end

function export.makeSortKey(text, lang, sc)
-- Convert any iteration marks into full characters, and remove any spaces. Also remove punctuation if the term contains non-punctuation (so that entries for punctuation characters can still be sorted properly).
	text = ugsub(convert_iteration_marks(text), "%s+", "")
	if not umatch(text, "^%p+$") then
		text = ugsub(text, "%p+", "")
	end
	
	text = explode(text)
	local sort, text_len, i = {}, #text, 0
	while i < text_len do
		i = i + 1
		local char = text[i]
		
		if m_data_core.preconvert[char] then
			local j = 0
			for c in gmatch(m_data_core.preconvert[char], ".[\128-\191]*") do
				if j == 0 then
					text[i] = c
				else
					insert(text, i + j, c)
				end
				j = j + 1
			end
			char = text[i]
			text_len = #text
		end
		--[=[
			If we encounter an ideographic description character (IDC),
			find out if it begins a valid ideographic description sequence (IDS).
			
			If the IDS is valid and a sortkey for it is listed in
			[[Module:Hani-sortkey/data/unsupported]], then return
			the sortkey, and move to the next character after the
			IDS.
			
			Otherwise, insert the IDC into the sortkey and move to the next
			character after the IDC.
			
			If the IDS is valid and no sortkey for it is found, track it.
		]=]
		if m_data_core.ids[char] then
			local j = findEndOfIDS(text, char, i)
			local IDS, data
			if j then
				IDS = concat(text, nil, i, j)
				data = m_data_core.unsupported[IDS]
			end
			
			if not data then
				if IDS then
					require("Module:debug").track("Hani-sortkey/IDS-without-sortkey")
					mw.log("ideographic description sequence without sortkey: '"
						.. IDS .. "'")
				else
					require("Module:debug").track("Hani-sortkey/invalid-IDS")
					mw.log("invalid ideographic description sequence at the beginning of '"
						.. text[i] .. "'")
				end
			end
			if IDS and data then
				insert(sort, data)
				i = j
			else
				insert(sort, char)
			end
		else
			if not cache[char] then
				cache[char] = export.getData(char)
			end
			insert(sort, cache[char])
		end
	end
	
	return concat(sort)
end

return export