--------------------------------------------------------------------------------
--                                                                            --
--                                PAGETYPE                                    --
--                                                                            --
--      This is a meta-module intended to replace ((pagetype)) 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 mDisambiguation = require('Module:Disambiguation')

local p = {}

-- Look up a namespace argument in the args table.
local function lookUpNamespaceArg(args, key)
	local arg = args[key]
	-- Convert "yes", "1" etc. to true, "no", "0" etc. to false, and leave
	-- other values the same.
	return yesno(arg, arg)
end

-- Append multiple values to an array
local function appendMultiple(target, source)
	for _, value in ipairs(source) do
		table.insert(target, value)
	end
end

-- Get argument keys for a title's namespace
local function getNamespaceArgKeys(title, cfg)
	local nsInfo = mw.site.namespaces[title.namespace]
	local customAliases = cfg.customNamespaceAliases[title.namespace] or {}
	local keys = {}
	if nsInfo.name ~= '' then
		table.insert(keys, nsInfo.name)
	end
	if nsInfo.canonicalName ~= nsInfo.name and nsInfo.canonicalName ~= '' then
		table.insert(keys, nsInfo.canonicalName)
	end
	appendMultiple(keys, nsInfo.aliases)
	appendMultiple(keys, customAliases)
	return keys
end

-- Get the argument for a title's namespace, if it was specified in the args
-- table.
local function getNamespaceArg(title, args, cfg)
	if title.isTalkPage then
		return lookUpNamespaceArg(args, cfg.talk)
	end
	for _, key in ipairs(getNamespaceArgKeys(title, cfg)) do
		local arg = lookUpNamespaceArg(args, mw.ustring.lower(key))
		if arg ~= nil then
			return arg
		end
	end
	return nil
end

-- Look up a page type specific to the title's namespace
local function getExplicitPageType(title, cfg)
	if title.isTalkPage then
		return cfg.talkDefault
	else
		return cfg.pagetypes[title.namespace]
	end
end

-- Get a default page type that is not specific to the title's namespace
local function getDefaultPageType(args, cfg)
	local other = lookUpNamespaceArg(args, cfg.other)
	if type(other) == 'string' then
		return other
	else
		return cfg.otherDefault
	end
end

local function detectRedirects(title, args)
	local redirect = lookUpNamespaceArg(args, cfg.redirect)
	if redirect == false then
		-- Don't detect redirects if they have been specifically disallowed.
		return nil
	end

	-- Allow custom values for redirects.
	if not title.isRedirect then
		return nil
	elseif type(redirect) == 'string' then
		return redirect
	else
		return cfg.redirectDefault
	end
end

local function detectDisambiguationPages(title, args, cfg)
	if title.namespace ~= 0 then
		-- Only detect disambiguation pages in mainspace
		return nil
	end

	local dab = lookUpNamespaceArg(args, cfg.dab)
	if dab == false then
		-- Don't detect disambiguation pages if explicitly disallowed
		return nil
	end

	if not mDisambiguation.isDisambiguation(title:getContent()) then
		return nil
	elseif type(dab) == 'string' then
		return dab
	else
		return cfg.dabDefault
	end
end

-- Gets the pagetype from a class specified from the first positional
-- parameter.
local function getPageTypeFromClass(args, class, key, aliasTable, default)
	local arg = lookUpNamespaceArg(args, key)
	if arg == false then
		-- Don't check for this class if it is specifically disallowed.
		return nil
	end
	if aliasTable[class] then
		if type(arg) == 'string' then
			return arg
		else
			return default
		end
	end
	return nil
end

-- Get page types for mainspaces pages with an explicit class specified
local function getMainNamespaceClassPageType(title, args, cfg)
	if title.namespace ~= 0 then
		return nil
	end
	local class = args[1]
	if type(class) == 'string' then
		-- Put in lower case so e.g. "na" and "NA" will both match.
		class = mw.ustring.lower(class)
	end
	return getPageTypeFromClass(
		args,
		class,
		cfg.na,
		cfg.naAliases,
		cfg.naDefault
	)
end

-- Get page type specified by an explicit namespace argument.
local function getNamespaceArgPageType(title, args, cfg)
	local namespaceArg = getNamespaceArg(title, args, cfg)
	if namespaceArg == true then
		-- Namespace has been explicitly enabled, so return the default for
		-- this namespace
		return getExplicitPageType(title, cfg)
	elseif namespaceArg == false then
		-- Namespace has been explicitly disabled
		return getDefaultPageType(args, cfg)
	elseif namespaceArg then
		-- This namespaces uses custom text
		return namespaceArg
	else
		return nil
	end
end

-- Whether the title is in the set of default active namespaces which are
-- looked up in cfg.pagetypes.
local function isInDefaultActiveNamespace(title, args, cfg)
	local defaultNamespacesKey = args[cfg.defaultns]
	if defaultNamespacesKey == cfg.defaultnsAll then
		return true
	end

	local defaultNamespaces
	if defaultNamespacesKey == cfg.defaultnsExtended then
		defaultNamespaces = cfg.extendedNamespaces
	elseif defaultNamespacesKey == cfg.defaultnsNone then
		defaultNamespaces = {}
	else
		defaultNamespaces = cfg.defaultNamespaces
	end
	return defaultNamespaces[title.namespace] or false
end

-- Get page type not specified or detected by other means
local function getOtherPageType(title, args, cfg)
	if isInDefaultActiveNamespace(title, args, cfg) then
		return getExplicitPageType(title, cfg)
	else
		return getDefaultPageType(args, cfg)
	end
end

local function getPageType(title, args, cfg)
	return (
		detectRedirects(title, args, cfg)
		or detectDisambiguationPages(title, args, cfg)
		or getMainNamespaceClassPageType(title, args, cfg)
		or getNamespaceArgPageType(title, args, cfg)
		or getOtherPageType(title, args, cfg)
	)
end

local function shouldUseSubjectTitle(args, cfg)
	return not yesno(args.talk, true) and args[cfg.defaultns] ~= cfg.defaultnsAll
end

-- Get the Scribunto title object to fetch the page type of
local function getTitle(args, cfg)
	local title
	if args.page then
		title = mw.title.new(args.page)
		if not title then
			return nil
		end
	else
		title = mw.title.getCurrentTitle()
	end

	if shouldUseSubjectTitle(args, cfg) then
		return title.subjectPageTitle
	else
		return title
	end
end

local function pluralize(pageType, cfg)
	if cfg.irregularPlurals[pageType] then
		return cfg.irregularPlurals[pageType]
	else
		return pageType .. cfg.plural -- often 's'
	end
end

local function capitalize(pageType)
	local first = mw.ustring.sub(pageType, 1, 1)
	local rest = mw.ustring.sub(pageType, 2)
	return mw.ustring.upper(first) .. rest
end

function p._main(args)
	local title = getTitle(args, cfg)
	local pageType = getPageType(title, args, cfg)
	if yesno(args.plural, false) then
		pageType = pluralize(pageType, cfg)
	end
	if yesno(args.caps, false) then
		pageType = capitalize(pageType)
	end
	return pageType
end

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

return p