local p = {} -- Package to be exported  
-- Change to "" upon deployment.
local moduleSuffix = ""  
local parserHooksModuleName = "Module:Road data/parser/hooks" .. moduleSuffix  
-- Local library aliases
local format = string.format
local gsub = mw.ustring.gsub
local upper = mw.ustring.upper  
---
-- Substitution pattern based on passed arguments
-- Syntax: [param|value|match|mismatch]
-- where
-- param is the parameter name to be tested
-- value is the value to test against argument; if empty, the argument is
-- tested for existence
-- match is the string to be substituted if the argument matches value
-- mismatch is the string to be substituted if the argument does not match
-- the value
-- These arguments may not contain "[", "|", or "]".
local prepattern = "%[(%w+)%|([^%[|%]]*)%|([^%[|%]]*)%|([^%[|%]]*)%]"
---
-- Parameter substitution pattern
-- Syntax: %param%
-- where param is the name of the parameter whose value is to be substituted
-- in place of %param%.
local pattern = "%%(%w+)%%"  
---
-- Perform substitutions.
-- @param #string formatStr The string the be substituted
-- @param #table args The arguments passed to this module
local function subst(formatStr, args)
---
-- Perform a substitution based on passed argument.
-- @param #string param The parameter name to be tested
-- @param #string value The value to test against argument; if empty,
-- the argument is tested for existence
-- @param #string ifmatch The resulting string if the argument matches
-- `value`
-- @param #string ifmismatch The resulting string if the argument does not
-- match `value`
-- @return #string either `ifmatch` or `ifmismatch`, based on the test
local function testArgs(param, value, ifmatch, ifmismatch)
local arg = args[param] or ''
if value ~= '' then
return arg == value and ifmatch or ifmismatch
else
return arg ~= '' and ifmatch or ifmismatch
end
end
-- argument-test substitutions
local preprocessed = gsub(formatStr, prepattern, testArgs)
-- parameter substitutions
return (gsub(preprocessed, pattern, args))
-- gsub returns number of matches as second value.
-- The enclosing parens discards it.
end  
---
-- Determine whether a given title exists on Wikipedia.
-- @param #string name The title, e.g., article name and file name,
-- without namespace prefix
-- @param #string key The name of the entry being translated.
-- @return #boolean `true` if the title exists, false otherwise
local function titleExists(name, key)
if name == '' then return false end
local namespaceModule = mw.loadData('Module:Road data/parser/namespace')
-- Retrieve the namespace for `key`.
local namespace = namespaceModule[key] or 0
local title = mw.title.new(name, namespace);
return title.exists
end  
---
-- Determine whether titles exist on Wikipedia.
-- @param value A string or a table containing strings of titles to be checked
-- against
-- @param #string key The name of the entry being translated.
-- @return #boolean `true` if all titles exist, false otherwise
local function ifexists(value, key)
local valueType = type(value)
if valueType == "table" then
-- If `value` is a table, recursively check the existence
-- for each element within the table.
for _,entry in pairs(value) do
if not ifexists(entry, key) then return false end
end
return true
end
-- Otherwise, `value` is a string, so check the existence for that string.
return titleExists(value, key)
end  
---
-- Perform a translation on a given entry.
-- @param entry An entry to be translated; may be any non-function type.
-- A table may be a parser hook specification, a switch table, or an
-- ordinary value table. Translations are applied recursively.
-- @param #table args The arguments passed to this module
-- @param #string key The name of the entry being translated.
-- @return The translated entry
local function translate(entry, args, key)
if type(entry) == "string" then
return subst(entry, args) -- Substitute arguments as necessary.
elseif type(entry) ~= "table" then
return entry
elseif entry.hook then
-- This entry is a parser hook.
-- Requires: Parser hook must have hook field.
local hook = entry.hook
local parserHooksModule = require(parserHooksModuleName)
local hookFunction = parserHooksModule[hook]
or error("Hook '" .. hook .. "' does not exist", 0)
return translate(hookFunction(entry, args), args, key)
elseif entry.arg or entry.undefined or entry.default then
-- This entry is a switch table.
-- Requires: Switch table must have
-- arg, undefined, or default fields
-- but not hook field.
local arg = args[entry.arg or "route"]
if entry[arg] then return translate(entry[arg], args, key) end
if arg == nil and entry.undefined ~= nil then
-- result for unspecified argument
return translate(entry.undefined, args, key)
end
-- default result for mismatch
local defaultValue = translate(entry.default, args, key)
if defaultValue and entry.ifexists and not args.ignoreifexists then
-- Check existence.
if ifexists(defaultValue, key) then return defaultValue end
-- Failed existence check results in fallback value (default to nil).
return entry.otherwise and translate(entry.otherwise, args, key) or nil
else
return defaultValue
end
else
-- This entry is a value table.
-- Process each table element.
local result = {}
for key,elem in pairs(entry) do
result[key] = translate(elem, args, key)
end
return result
end
end  
---
-- Retrieve an entry from a data module based on a given type and key.
-- @param #string module The name of the data module to be fetched
-- @param type The key for the type table within the loaded table
-- @param key The key for the entry within the type table
-- @return fetchedTable[type][key] if specified, where `fetchedTable` is the
-- table fetched from `module`, nil otherwise
local function getTypeData(module, type, key)
-- Attempt to fetch the given data module.
local success, moduleData = pcall(mw.loadData, module)
if not success then return false, moduleData end -- Module could not be loaded
-- The type table defaults to empty-key table if undefined.
local typeTable = moduleData[type] or moduleData['']
-- Fallback table is the empty-key table, with the empty table as default.
local defaultTable = moduleData[''] or {}
if typeTable then
local alias = typeTable.alias
if alias and alias.module and alias.type then
-- The type table is an alias table.
-- Recursively fetch the aliased type data.
local aliasedModule = "Module:Road data/strings/" .. alias.module
local aliasedType = alias.type
return getTypeData(aliasedModule, aliasedType, key)
end
return true, typeTable[key] or defaultTable[key] or nil
else
return true, nil
end
end  
---
-- Determine the module name for the lookup by country and state.
-- @param #table args The arguments passed to this module
-- @return #string The module name to be fetched
local function getModuleName(args)
-- countries with submodules for states or provinces
local stateCountries = {USA = true, CAN = true}
local state = upper(args.state or args.province or '')
local country
if args.country then
country = upper(args.country)
else
-- Recover the country from the given state or province.
local countryModule = mw.loadData("Module:Road data/countrymask")
country = countryModule[state] or 'UNK'
end
if stateCountries[country] and state ~= '' then
-- Submodule within the country exists.
return format("Module:Road data/strings/%s/%s", country, state)
end
return format("Module:Road data/strings/%s", country)
end  
---
-- Fetch the entry from the appropriate module, and return that entry
-- substituted with appropriate values.
-- @param #table args The arguments to be used for lookup and substitutions
-- @param #string key The key for the entry within the type table
-- @param #string type (optional) The key for the type table within the fetched
-- module; defaults to args.type
-- @param #string moduleName (optional) The name of the module to be fetched;
-- defaults to the module determined by country and state
-- @return The substituted entry
function p.parser(args, key, type, moduleName)