local export = {}
local pos_functions = {}

local en_utilities_module = "Module:en-utilities"

local unpack = unpack or table.unpack -- Lua 5.2 compatibility

local function track(page)
	require("Module:debug").track("hsb-dsb-headword/" .. page)
	return true
end

local function glossary_link(entry, text)
	text = text or entry
	return "]"
end

-- The main entry point.
-- This is the only function that can be invoked from a template.
function export.show(frame)
	local iparams = {
		 = {required = true},
		 = {required = true},
	}

	local iargs = require("Module:parameters").process(frame.args, iparams)
	local poscat = iargs
	langcode = iargs.lang
	if langcode ~= "hsb" and langcode ~= "dsb" then
		error("This module currently only works for lang=hsb and lang=dsb")
	end
	local lang = require("Module:languages").getByCode(langcode)
	local langname = lang:getCanonicalName()

	local params = {
		 = {list = true},
		 = {type = "boolean"},
		 = {type = "boolean", alias_of = "nolink"},
		 = {type = "boolean"},
		 = {type = "boolean"},
		 = {type = "boolean"},
		 = {}, -- for testing
	}

	if pos_functions then
		for key, val in pairs(pos_functions.params) do
			params = val
		end
	end

	local parargs = frame:getParent().args
	local args = require("Module:parameters").process(parargs, params)

	local pagename = args.pagename or mw.loadData("Module:headword/data").pagename

	local user_specified_heads = args.head
	local heads = user_specified_heads
	if args.nolink then
		if #heads == 0 then
			heads = {pagename}
		end
	end

	local data = {
		lang = lang,
		langname = langname,
		pos_category = poscat,
		categories = {},
		heads = heads,
		user_specified_heads = user_specified_heads,
		no_redundant_head_cat = #user_specified_heads == 0,
		genders = {},
		inflections = {},
		categories = {},
		pagename = pagename,
		id = args.id,
		force_cat_output = force_cat,
	}

	data.is_suffix = false
	if args.suffix or (
		not args.nosuffix and pagename:find("^%-") and poscat ~= "suffixes" and poscat ~= "suffix forms"
	) then
		data.is_suffix = true
		data.pos_category = "suffixes"
		local singular_poscat = require(en_utilities_module).singularize(poscat)
		table.insert(data.categories, langname .. " " .. singular_poscat .. "-forming suffixes")
		table.insert(data.inflections, {label = singular_poscat .. "-forming suffix"})
	end

	if pos_functions then
		pos_functions.func(args, data)
	end

	if args.json then
		return require("Module:JSON").toJSON(data)
	end

	return require("Module:headword").full_headword(data)
end

local function get_noun_pos(is_proper)
	local noun_inflection_specs = {
		{"gen", "genitive singular"},
		{"du", "nominative dual"},
		{"pl", "nominative plural"},
		{"genpl", "genitive plural"},
		{"f", "feminine"},
		{"m", "masculine"},
		{"dim", "diminutive"},
		{"pej", "pejorative"},
		{"aug", "augmentative"},
		{"adj", "related adjective"},
		{"dem", "demonym"},
		{"fdem", "female demonym"},
	}
	
	local params = {
		 = {type = "boolean"},
		 = {list = "g"},
	}
	for _, spec in ipairs(noun_inflection_specs) do
		local param, desc = unpack(spec)
		params = {list = true, disallow_holes = true}
		params = {list = true, allow_holes = true}
	end

	return {
		params = params,
		func = function(args, data)
			-- Compute allowed genders, and map incomplete genders to specs with a "?" in them.
			local masc_genders = {"m", "mf", "mfbysense"}
			local non_masc_genders = {false, "f", "n"}
			local hsb_masc_animacies = {false, "in", "anml", "pr"}
			local dsb_masc_animacies = {false, "in", "an"}
			local numbers = {false, "d", "p"}
			local allowed_genders = {}

			local function insert_genders(genders, animacies, numbers, is_masc)
				for _, g in ipairs(genders) do
					for _, an in ipairs(animacies) do
						for _, num in ipairs(numbers) do
							local source_gender_parts = {}
							local dest_gender_parts = {}
							local function ins_part(part, partname)
								if part then
									table.insert(source_gender_parts, part)
									table.insert(dest_gender_parts, part)
								elseif partname == "g" and num == false or partname == "an" and is_masc then
									-- allow incomplete gender duale tantum and plurale tantum nouns; also allow
									-- incomplete animacy for fem/neut; otherwise insert a ? to indicate incomplete
									-- gender spec
									table.insert(dest_gender_parts, "?")
								end
							end
							ins_part(g, "g")
							ins_part(an, "an")
							ins_part(num, "num")
							if #source_gender_parts == 0 then
								allowed_genders = "?"
							else
								allowed_genders =
									table.concat(dest_gender_parts, "-")
							end
						end
					end
				end
			end

			if data.lang:getCode() == "hsb" then
				insert_genders(masc_genders, hsb_masc_animacies, numbers, true)
			else
				insert_genders(masc_genders, dsb_masc_animacies, numbers, true)
			end
			insert_genders(non_masc_genders, {false}, numbers, false)
			-- allow inanimate dual/plural; no gender distinction here
			allowed_genders = "in-d"
			allowed_genders = "in-p"
			
			-- Gather genders
			data.genders = args

			-- Validate and canonicalize genders
			for i, g in ipairs(data.genders) do
				if not allowed_genders then
					error("Unrecognized " .. data.langname .. " gender: " .. g)
				else
					data.genders = allowed_genders
				end
			end

			local function process_inflection(label, infls, qs, frob)
				infls.label = label
				for i, infl in ipairs(infls) do
					if frob then
						infl = frob(infl)
					end
					if qs then
						infls = {term = infl, q = {qs}}
					end
				end
				if #infls > 0 then
					table.insert(data.inflections, infls)
				end
			end

			if args.indecl then
				table.insert(data.inflections, {label = glossary_link("indeclinable")})
			end

			-- Process all inflections.
			for _, spec in ipairs(noun_inflection_specs) do
				local param, desc = unpack(spec)
				process_inflection(desc, args, args)
			end
		end
	}
end

pos_functions = get_noun_pos(false)

pos_functions = get_noun_pos(true)

return export