Module:Road data/parser

-- Export package
local p = {}

-- Local library aliases
local format = string.format
local gsub = mw.ustring.gsub
local trim = mw.text.trim
local upper = mw.ustring.upper

-- Regex substitution patterns
local prepattern = "%[(%w+)%|(.*)%|(.*)%|(.*)%]" -- [arg|equal to (blank for existence)|if true|if false]
local pattern = "%%(%w+)%%" -- %arg%

local function parser(formatStr, args, form)
	local function ifexists(name)
		-- Check whether a page or file named name exists
		if name == '' then return false end -- Page doesn't exist if name is blank
		local title -- mw.title object
		if form == 'shield' then
			title = mw.title.new(name, 'Media') -- Shields are in the Media namespace
		else
			title = mw.title.new(name, 0) -- Links are in the mainspace
		end
		return title.exists -- A boolean for whether the page exists
	end
	local function testArgs(test, equals, ifexists, ifnot)
		-- Implement the if test
		if equals ~= '' then -- Argument equals something
			if args[test] == equals then return ifexists else return ifnot end
		else -- Existence of argument
			if args[test] and args[test] ~= '' then return ifexists else return ifnot end
		end
	end
	local formatTable = {} -- Table with definitions
	-- Recursively dig into tables that could be parser hooks or argument tables.
	local function formatStrInTable(formatStr)
		if type(formatStr) ~= "table" then return formatStr end -- formatStr is a scalar
		formatTable = formatStr
		local hook = formatStr.hook -- Possible hook
		local both = formatStr[2] -- Second shield
		if both then
			local first = formatStrInTable(formatStr[1])
			local second = formatStrInTable(both)
			return {first, second} -- First and second shield
		elseif hook then
			local hooksModule = require "Module:Road data/parser/hooks"
			local hookFunction = hooksModule[hook] or error("Hook '" .. hook .. "' does not exist", 0)
			return formatStrInTable(hookFunction(formatStr, args)) -- Call hook
		else -- Switch on an argument
			local arg = args[formatStr.arg or "route"]
			return formatStrInTable(formatStr[arg] or formatStr.default)
		end
	end
	local function parse(formatStr)
		local preprocessed = gsub(formatStr, prepattern, testArgs) -- If statements
		local parsedStr = gsub(preprocessed, pattern, args) -- Variable interpolation
		local final = trim(parsedStr) -- Trim extra spaces
		if formatTable.ifexists then -- Existence test
			local exists = ifexists(final)
			if exists then
				return final
			else
				return parser(formatTable.otherwise, args, form)
			end
		end
		return final
	end
	formatStr = formatStrInTable(formatStr) -- Get formatStr
	if not formatStr or formatStr == '' then return '' end -- Return empty string for empty formatStr
	if type(formatStr) == 'table' then -- Dual shields
		local first = parse(formatStr[1])
		local second = parse(formatStr[2])
		return first, second
	else
		return parse(formatStr)
	end
end

local function formatString(args, form)
	-- Get format string/table from module based on jurisdiction and type
	local function getTypeData(module, type)
		-- Get data from module for particular type
		local success, moduleData = pcall(mw.loadData, module)
		if not success then return '' end -- Empty string if module cannot be loaded
		local typeTable = moduleData[type] or moduleData[''] -- Type table or empty string default table
		local defaultTable = moduleData[''] or {} -- Default table
		if typeTable then
			local alias = typeTable.alias
			if alias then -- Type is an alias to another module
				local aliasedModule = "Module:Road data/strings/" .. alias.module
				local aliasedType = alias.type
				return getTypeData(aliasedModule, aliasedType)
			end
			return typeTable[form] or defaultTable[form] or ''
		else
			return ''
		end
	end
	
	local stateCountries = {USA = true, CAN = true} -- These countries have state/province modules
	local state = upper(args.state or '')
	local country
	if args.country then
		country = upper(args.country)
	else -- Find country via a mask
		local countryModule = mw.loadData("Module:Road data/countrymask")
		country = countryModule[state] or 'UNK'
	end
	local typeArg = args.type
	local module
	if stateCountries[country] and state ~= '' then
		module = format("Module:Road data/strings/%s/%s", country, state)
	else
		module = format("Module:Road data/strings/%s", country)
	end
	return getTypeData(module, typeArg)
end

function p.parser(passedArgs, form)
	local args = {state = passedArgs.state, type = passedArgs.type, route = passedArgs.route, 
	              denom = passedArgs.denom, county = passedArgs.county, dab = passedArgs.dab,
	              country = passedArgs.country, township = passedArgs.township}
	local formatStr = formatString(args, form)
	if not formatStr or formatStr == '' then return nil end
	return parser(formatStr, args, form)
end

return p