-- --
-- PAGETYPE --
-- --
-- This is a meta-module intended to replace and similar --
-- templates. It automatically detects namespaces, and allows for a --
-- great deal of customisation. It can easily be ported to other --
-- wikis by changing the values in the Module:Pagetype/config. --
-- --

-- Load config.
local cfg = mw.loadData('Module:Pagetype/config')

-- Load required modules.
local getArgs = require('Module:Arguments').getArgs
local yesno = require('Module:Yesno')
local nsDetectModule = require('Module:Namespace detect')
local nsDetect = nsDetectModule._main
local getParamMappings = nsDetectModule.getParamMappings
local getPageObject = nsDetectModule.getPageObject

local p = {}

local function shallowCopy(t)
	-- Makes a shallow copy of a table.
	local ret = {}
	for k, v in pairs(t) do
		ret[k] = v
	end
	return ret
end

local function checkPagetypeInput
	-- Checks to see whether we need the default value for the given namespace,
	-- and if so gets it from the pagetypes table.
	-- The yesno function returns true/false for "yes", "no", etc., and returns
	-- val for other input.
	local ret = yesno
	if ret and type(ret) ~= 'string' then
		ret = cfg.pagetypes[namespace]
	end
	return ret
end

local function getPagetypeFromClass
	-- Gets the pagetype from a class specified from the first positional
	-- parameter.
	param = yesno
	if param ~= false then -- No check if specifically disallowed.
		for _, alias in ipairs(aliasTable) do
			if class == alias then
				if type(param) == 'string' then
					return param
				else
					return default
				end
			end
		end
	end
end

local function getNsDetectValue(args)
	-- Builds the arguments to pass to Module:Namespace detect and returns
	-- the result.

	-- Get the default values.
	local ndArgs = {}
	local defaultns = args[cfg.defaultns]
	if defaultns == cfg.defaultnsAll then
		ndArgs = shallowCopy(cfg.pagetypes)
	else
		local defaultnsArray
		if defaultns == cfg.defaultnsExtended then
			defaultnsArray = cfg.extendedNamespaces
		elseif defaultns == cfg.defaultnsNone then
			defaultnsArray = {}
		else
			defaultnsArray = cfg.defaultNamespaces
		end
		for _, namespace in ipairs(defaultnsArray) do
			ndArgs[namespace] = cfg.pagetypes[namespace]
		end
	end

	--
	-- Add custom values passed in from the arguments. These overwrite the
	-- defaults. The possible argument names are fetched from
	-- Module:Namespace detect automatically in case new namespaces are
	-- added. Although we accept namespace aliases as parameters, we only pass
	-- the local namespace name as a parameter to Module:Namespace detect.
	-- This means that the "image" parameter can overwrite defaults for the
	-- File: namespace, which wouldn't work if we passed the parameters through
	-- separately.
	--
	local mappings = getParamMappings
	for ns, paramAliases in pairs(mappings) do
		-- Copy the aliases table, as # doesn't work with tables returned from
		-- mw.loadData.
		paramAliases = shallowCopy(paramAliases)
		local paramName = paramAliases[1]
		-- Iterate backwards along the array so that any values for the local
		-- namespace names overwrite those for namespace aliases.
		for i = #paramAliases, 1, -1 do
			local paramAlias = paramAliases[i]
			local ndArg = checkPagetypeInput
			if ndArg == false then
				-- If any arguments are false, convert them to nil to protect
				-- against breakage by future changes to
				-- Module:Namespace detect.
				ndArgs[paramName] = nil
			elseif ndArg then
				ndArgs[paramName] = ndArg
			end
		end
	end
	-- Check for disambiguation-class and N/A-class pages in mainspace.
	if ndArgs.main then
		local class = args[1]
		if type(class) == 'string' then
			-- Put in lower case so e.g. "Dab" and "dab" will both match.
			class = mw.ustring.lower(class)
		end
		local dab = getPagetypeFromClass
		if dab then
			ndArgs.main = dab
		else
			local na = getPagetypeFromClass
			if na then
				ndArgs.main = na
			end
		end
	end
	-- If there is no talk value specified, use the corresponding subject 
	-- namespace for talk pages.
	if not ndArgs.talk then
		ndArgs.subjectns = true
	end
	-- Add the fallback value. This can also be customised, but it cannot be
	-- disabled.
	local other = args[cfg.other]
	-- We will ignore true/false/nil results from yesno here, but using it
	-- anyway for consistency.
	other = yesno
	if type(other) == 'string' then
		ndArgs.other = other
	else
		ndArgs.other = cfg.otherDefault
	end
	-- Allow custom page values.
	ndArgs.page = args.page
	return nsDetect(ndArgs)
end

local function detectRedirects(args)
	local redirect = args[cfg.redirect]
	-- The yesno function returns true/false for "yes", "no", etc., and returns
	-- redirect for other input.
	redirect = yesno
	if redirect == false then
		-- Detect redirects unless they have been explicitly disallowed with
		-- "redirect=no" or similar.
		return
	end
	local pageObject = getPageObject(args.page)
	-- If we are using subject namespaces elsewhere, do so here as well.
	if pageObject
		and not yesno
		and args[cfg.defaultns] ~= cfg.defaultnsAll
	then
		pageObject = getPageObject(
			pageObject.subjectNsText .. ':' .. pageObject.text
		)
	end
	-- Allow custom values for redirects.
	if pageObject and pageObject.isRedirect then
		if type(redirect) == 'string' then
			return redirect
		else
			return cfg.redirectDefault
		end
	end
end

function p._main(args)
	local redirect = detectRedirects(args)
	local pagetype = ""
	if redirect then
		pagetype = redirect
	else
		pagetype = getNsDetectValue(args)
	end
	if yesno then
		if cfg.irregularPlurals[pagetype] then
			pagetype = cfg.irregularPlurals[pagetype]
		else
			pagetype = pagetype .. cfg.plural -- often 's'
		end
	end
	if yesno then
		pagetype = mw.ustring.upper(mw.ustring.sub) ..
			mw.ustring.sub
	end
	return pagetype
end

function p.main(frame)
	local args = getArgs(frame)
	return p._main(args)
end