Module:alternative forms

local export = {}

local labels_module = "Module:labels"
local links_module = "Module:links"
local parameter_utilities_module = "Module:parameter utilities"

local function track(page)
	require("Module:debug/track")("alter/" .. page)
end

--[==[
Main function for displaying alternative forms. Extracted out from the template-callable function so this can be
called by other modules (in particular, ]). `allow_self_link` causes terms the same as the
pagename to be shown normally; otherwise they are displayed unlinked. `default_separator` controls the separator between
terms when the user didn't use a special separator term like ";" (defaulting to ", ").
]==]
function export.display_alternative_forms(parent_args, pagename, allow_self_link, default_separator)
	local params = {
		 = {required = true, type = "language", default = "en"},
		 = {list = true, allow_holes = true},
	}

    local m_param_utils = require(parameter_utilities_module)

	local param_mods = m_param_utils.construct_param_mods {
		{group = {"link", "ref"}},
		-- For compatibility, we need to turn off separate_no_index for q= and qq=.
		{group = "q", separate_no_index = false},
		-- We currently don't support unindexed l= and ll=.
		{group = "l", require_index = true},
	}

	local items, args = m_param_utils.process_list_arguments {
		params = params,
		param_mods = param_mods,
		raw_args = parent_args,
		termarg = 2,
		parse_lang_prefix = true,
		track_module = "alter",
		lang = 1,
		sc = "sc.default",
		stop_when = function(data)
			local stop = not data.any_param_at_index
			if stop and parent_args == nil then
				track("actual hole in params")
			end
			return stop
		end,
		default_separator = default_separator,
	}

	if not items then
		error("No items found!")
	end

	local lang = args
	local raw_labels = {}

	-- Extract the labels and make sure none are blank or omitted.
	local last_item_index = items.orig_index
	if last_item_index < args.maxindex then
		for i = last_item_index + 2, args.maxindex do
			if not args then
				-- Indices in i start at 1 but parameters start at 2 to add 1 to shown index.
				error("Missing/blank item not allowed in ] labels, but saw such an item in parameter "
					.. (i + 1))
			end
			table.insert(raw_labels, args)
		end
	end

	-- Make sure there aren't property parameters after the last item (i.e. corresponding to labels).
	for k, v in pairs(args) do
		-- Look for named list parameters. We check:
		-- (1) key is a string (excludes the term param, which is a number);
		-- (2) value is a table, i.e. a list;
		-- (3) v.maxindex is set (i.e. allow_holes was used);
		-- (4) v.maxindex is past the index of the last term.
		if type(k) == "string" and type(v) == "table" and v.maxindex and v.maxindex > last_item_index then
			local set_values = {}
			for i = last_item_index + 1, v.maxindex do
				if v then
					table.insert(set_values, i)
				end
			end
			error(("Extraneous values for %s= (set at position%s %s)"):format(k, #set_values > 1 and "s" or "",
				table.concat(set_values, ",")))
		end
	end

	if not allow_self_link then
		-- If the to-be-linked term is the same as the pagename, display it unlinked.
		for _, item in ipairs(items) do
			if not item.term and (lang:makeEntryName(item.term)) == pagename then
				track("term is pagename")
				item.alt = item.alt or item.term
				item.term = nil
			end
		end
	end

	local labels
	if #raw_labels > 0 then
		labels = require(labels_module).process_raw_labels { labels = raw_labels, lang = lang, nocat = true }
	end

	local parts = {}
	local function ins(part)
		table.insert(parts, part)
	end

	-- Construct the final output.

	-- First the items, including separators, left and right regular qualifiers and left and right per-item labels.
	for _, item in ipairs(items) do
		ins(item.separator)
		local text = require(links_module).full_link(item, nil, allow_self_link, "show qualifiers")
		ins(text)
	end

	-- If there are labels, construct them now and append to final output.
	if labels then
		if lang:hasTranslit() then
			ins(" &mdash; " .. require(labels_module).format_processed_labels {
				labels = labels, lang = lang
			})
		else
			ins(" " .. require(labels_module).format_processed_labels {
				labels = labels, lang = lang, open = "(", close = ")"
			})
		end
	end

	return table.concat(parts)
end

--[==[
Template-callable function for displaying alternative forms.
]==]
function export.create(frame)
	local parent_args = frame:getParent().args
	local title = mw.title.getCurrentTitle()
	local PAGENAME = title.text
	return export.display_alternative_forms(parent_args, title)
end

return export