Module:Interwiki extra

-- This is the interwiki library. It is not meant to be used directly in articles, but to be used by other Lua modules.

local interwikiTable = mw.loadData( 'Module:InterwikiTable' )
local libraryUtil = require( 'libraryUtil' )

local iw = {}

local function getProjectCode( prefix )
    for code, t in pairs( interwikiTable ) do
        for _, interwikiPrefix in ipairs( t.iw_prefix ) do
            if prefix == interwikiPrefix then
                return code
            end
        end
    end
    return nil
end

function iw.isKnownPrefix( prefix )
    return getProjectCode( prefix ) and true or false
end

function iw.isValidLanguageCode( code )
    return mw.language.isKnownLanguageTag( code )
end

function iw.new( prefix )
    local obj = {}
    local data = {}
    local checkSelf = libraryUtil.makeCheckSelfFunction( 'Module:Interwiki', 'interwiki', obj, 'interwiki object' )
    
    local code = interwikiTable[ prefix ] and prefix or getProjectCode( prefix )
    if not code then
        return nil
    end
    
    local iwTable = interwikiTable[ code ]
    
    data.domain = iwTable.domain
    data.titlePrefix = iwTable.title_prefix
    data.takesLanguagePrefix = iwTable.takesLanguagePrefix
    
    function data:getPrefixes()
        checkSelf( self, 'getPrefixes' )
        local t = {}
        for i, iwPrefix in ipairs( iwTable.iw_prefix ) do
            table.insert( t, iwPrefix )
        end
        return t
    end
    
    -- Specify which fields are read-only, and prepare the metatable.
    local readOnlyFields = {
        domain = true,
        titlePrefix = true,
        takesLanguagePrefix = true,
        getPrefixes = true,
    }
 
    local function pairsfunc( t, k )
        local v
        repeat
            k = next( readOnlyFields, k )
            if k == nil then
                return nil
            end
            v = t[ k ]
        until v ~= nil
        return k, v
    end
 
    return setmetatable( obj, {
        __pairs = function ( t )
            return pairsfunc, t, nil
        end,
        __index = data,
        __newindex = function( t, key, value )
            if readOnlyFields[ key ] then
                error( 'index "' .. key .. '" is read-only', 2 )
            else
                rawset( t, key, value )
            end
        end,
        __tostring = function( t )
            return t:getPrefixes()[ 1 ]
        end
    } )
end

function iw.test()
    local new = iw.new( 'wikibooks' )
    return tostring( new )
end

return iw
Usage
