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Please document this module by describing its purpose and usage on the documentation page.

local m_links = require("Module:links")
local m_utils = require("Module:la-utilities")
local m_vl_translit = require("Module:VL-translit")
local title = mw.title.getCurrentTitle()
local lang = require("Module:languages").getByCode("la")

local export = {}

local branch_links = {
	["It-W"] = "[[w:Italo-Western languages|Italo-Western]]",
	["E"] = "[[w:Eastern Romance languages|Eastern]]",
	["S"] = "[[w:Sardinian language|Sardinian]]",
}

local decl_names = {
	["1st"] = "First declension",
	["2nd"] = "Second declension",
	["2nd-er"] = "Second declension, nominative singular in ''-er''",
	["2nd-N"] = "Second declension neuter",
	["3rd"] = "Third declension",
}

local decls = {}

decls["1st"] = {
	params = {
		[1] = {},
		},
}
setmetatable(decls["1st"], {__call = function(self, args, data)
	data.forms["nom-sg"] = args[1] .. "a"
	data.forms["nom-pl"] = args[1] .. "ae"
	
	data.forms["gen-sg"] = args[1] .. "ae"
	data.forms["gen-pl"] = args[1] .. "ārum"
	
	data.forms["dat-sg"] = args[1] .. "ae"
	data.forms["dat-pl"] = args[1] .. "īs"
	
	data.forms["acc-abl-sg"] = args[1] .. "am"
	data.forms["acc-abl-pl"] = args[1] .. "ās"
end
})

decls["2nd"] = {
	params = {
		[1] = {},
		},
}
setmetatable(decls["2nd"], {__call = function(self, args, data)
	data.forms["nom-sg"] = args[1] .. "us"
	data.forms["nom-pl"] = args[1] .. "ī"
	
	data.forms["gen-sg"] = args[1] .. "ī"
	data.forms["gen-pl"] = args[1] .. "ōrum"
	
	data.forms["dat-sg"] = args[1] .. "ō"
	data.forms["dat-pl"] = args[1] .. "īs"
	
	data.forms["acc-abl-sg"] = args[1] .. "um"
	data.forms["acc-abl-pl"] = args[1] .. "ōs"
end
})

decls["2nd-er"] = {
	params = {
		[1] = {},
		[2] = {},
		},
}
setmetatable(decls["2nd-er"], {__call = function(self, args, data)
	data.forms["nom-sg"] = args[1]
	data.forms["nom-pl"] = args[2] .. "ī"
	
	data.forms["gen-sg"] = args[2] .. "ī"
	data.forms["gen-pl"] = args[2] .. "ōrum"
	
	data.forms["dat-sg"] = args[2] .. "ō"
	data.forms["dat-pl"] = args[2] .. "īs"
	
	data.forms["acc-abl-sg"] = args[2] .. "um"
	data.forms["acc-abl-pl"] = args[2] .. "ōs"
end
})

decls["2nd-N"] = {
	params = {
		[1] = {},
		},
}
setmetatable(decls["2nd-N"], {__call = function(self, args, data)
	data.forms["nom-sg"] = args[1] .. "um"
	data.forms["nom-pl"] = args[1] .. "a"
	
	data.forms["gen-sg"] = args[1] .. "ī"
	data.forms["gen-pl"] = args[1] .. "ōrum"
	
	data.forms["dat-sg"] = args[1] .. "ō"
	data.forms["dat-pl"] = args[1] .. "īs"
	
	data.forms["acc-abl-sg"] = args[1] .. "um"
	data.forms["acc-abl-pl"] = args[1] .. "a"
end
})

decls["3rd"] = {
	params = {
		[1] = {},
		[2] = {},
		},
}
setmetatable(decls["3rd"], {__call = function(self, args, data)
	if not args[2] then args[2] = m_utils.make_stem2(args[1]) end
	
	data.forms["nom-sg"] = args[1]
	data.forms["nom-pl"] = args[2] .. "is"
	
	data.forms["gen-sg"] = args[2] .. "is"
	data.forms["gen-pl"] = args[2] .. "um"
	
	data.forms["dat-sg"] = args[2] .. "ī"
	data.forms["dat-pl"] = args[2] .. "ibus"
	
	data.forms["acc-abl-sg"] = args[2] .. "em"
	data.forms["acc-abl-pl"] = args[2] .. "ēs"
end
})

local cases = {
	["nominative"] = {short_form = "nom", link = "''[[nominative case|nominative]]''"},
	["accusative-ablative"] = {short_form = "acc-abl", link = "''[[accusative case|accusative]]-[[ablative case|ablative]]''"},
	["genitive"] = {short_form = "gen", link = "''[[genitive case|genitive]]''"},
	["dative"] = {short_form = "dat", link = "''[[dative case|dative]]''"},
}

local function make_headers(data, wikicode)
	table.insert(wikicode, '|- class="vsHide"\n')
	table.insert(wikicode, '! style="background:#' .. data.latincolour[3] .. '; font-style:italic;" | Number\n')
	table.insert(wikicode, '! style="background:#' .. data.latincolour[3] .. '; font-style:italic;" | Singular\n')
	table.insert(wikicode, '! style="background:#' .. data.latincolour[3] .. '; font-style:italic;" | Plural\n')
end

local function show_form(form, data, branch)
	local function convert_word(form, branch)
		if mw.ustring.find(form, "{{{") then
			return form
		else
			return m_vl_translit.convert_words(form, branch)
		end
	end

	if not form then
		return "—"
	end
	
	
	if title:inNamespace("") then
		return m_links.full_link({lang = lang, alt = convert_word(form, branch), term = form})
	else
		return m_links.full_link({lang = lang, alt = convert_word(form, branch), term = "*" .. form})
	end
end

local function make_case(data, wikicode, case, branch)
	local case_short = cases[case].short_form
	table.insert(wikicode, '|- class="vsHide"\n')
	table.insert(wikicode, '! style="background:#' .. data.latincolour[1] .. ';" | ' .. cases[case].link .. '\n')
	table.insert(wikicode, '| style="background:#' .. data.latincolour[2] .. ';" | ' .. show_form(data.forms[case_short .. '-sg'], data, branch) .. '\n')
	table.insert(wikicode, '| style="background:#' .. data.latincolour[2] .. ';" | ' .. show_form(data.forms[case_short .. '-pl'], data, branch) .. '\n')
end

local function make_table(data, branch)
	local wikicode = {'{| class="prettytable inflection-table vsSwitcher" data-toggle-category="inflection"\n'}
	table.insert(wikicode, '! colspan="5" class="vsToggleElement" style="text-align:left;min-width: 25em;background:#' ..
				 data.latincolour[1] .. '" | ')
	table.insert(wikicode, branch_links[branch] .. ' declension of #head\n')

	make_headers(data, wikicode)
	make_case(data, wikicode, "nominative", branch)
	make_case(data, wikicode, "genitive", branch)
	make_case(data, wikicode, "dative", branch)
	make_case(data, wikicode, "accusative-ablative", branch)

	table.insert(wikicode, "|}")
	
	return table.concat(wikicode)
end

-- The main entry point.
-- This is the only function that can be invoked from a template.
function export.show(frame)
	local parent_args = frame:getParent().args

	local decl_type = (frame.args["decl"] or parent_args["decl"]) or "1st"
	
	if not decls[decl_type] then
		error("Unknown declension type '" .. decl_type .. "'")
	end
	
	local data = {forms = {}}
	data.head = parent_args["head"] or nil
	
	data.latincolour = {
		frame:expandTemplate({title = "Latincolour1"}),
		frame:expandTemplate({title = "Latincolour2"}),
		frame:expandTemplate({title = "Latincolour3"}),
	}

	local args = require("Module:parameters").process(parent_args, decls[decl_type].params, true)
	
	if not args[1] then
		setmetatable(args, {__index = function(self, key)
			return "{{{" .. key .. "}}}"
		end
		})
	end
	
	-- Generate the forms
	decls[decl_type](args, data)
	data["decl"] = decl_type
	
	-- Make the table
	t = decl_names[data.decl] .. '.\n\n'
	if parent_args.family then
		t = t .. make_table(data, parent_args.family)
		if parent_args.family2 then
			t = t .. "\n" .. make_table(data, parent_args.family2)
		end
	else
		t = t .. make_table(data, "It-W") .. "\n" .. make_table(data, "E") .. "\n" .. make_table(data, "S")
	end
	if title:inNamespace("") then
		t = mw.ustring.gsub(t, "#head", m_links.full_link({lang = lang, alt = data.forms["nom-sg"]}, "term"))
	else
		t = mw.ustring.gsub(t, "#head", m_links.full_link({lang = lang, alt = "*" .. data.forms["nom-sg"]}, "term"))
	end
	return t
end

return export