Editing Module:URLutil

local URLutil = { suite  = "URLutil",
                  serial = "2022-04-05",
                  item   = 10859193 }
--[=[
Utilities for URL etc. on www.
* decode()
* encode()
* getAuthority()
* getFragment()
* getHost()
* getLocation()
* getNormalized()
* getPath()
* getPort()
* getQuery()
* getQueryTable()
* getRelativePath()
* getScheme()
* getSortkey()
* getTLD()
* getTop2domain()
* getTop3domain()
* isAuthority()
* isDomain()
* isDomainExample()
* isDomainInt()
* isHost()
* isHostPathResource()
* isIP()
* isIPlocal()
* isIPv4()
* isIPv6()
* isMailAddress()
* isMailLink()
* isProtocolDialog()
* isProtocolWiki()
* isResourceURL()
* isSuspiciousURL()
* isUnescapedURL()
* isWebURL()
* wikiEscapeURL()
* failsafe()
Only [[dotted decimal]] notation for IPv4 expected.
Does not support dotted hexadecimal, dotted octal, or single-number formats.
IPv6 URL (bracketed) not yet implemented; might need Wikintax escaping anyway.
]=]
local Failsafe  = URLutil



local decodeComponentProtect = { F = "\"#%<>[\]^`{|}",
                                 P = "\"#%<>[\]^`{|}/?",
                                 Q = "\"#%<>[\]^`{|}&=+;,",
                                 X = "\"#%<>[\]^`{|}&=+;,/?" }



local decodeComponentEscape = function ( averse, adapt )
    return  adapt == 20  or  adapt == 127  or
            decodeComponentProtect[ averse ]:find( string.char( adapt ),
                                                   1,
                                                   true )
end -- decodeComponentEscape()



local decodeComponentML = function ( ask )
    local i = 1
    local j, n, s
    while ( i ) do
        i = ask:find( "&#[xX]%x%x+;", i )
        if i then
            j = ask:find( ";",  i + 3,  true )
            s = ask:sub( i + 2,  j - 1 ):upper()
            n = s:byte( 1, 1 )
            if n == 88 then
                n = tonumber( s:sub( 2 ),  16 )
            elseif s:match( "^%d+$" ) then
                n = tonumber( s )
            else
                n = false
            end
            if n then
                if n >= 128 then
                    s = string.format( "&#%d;", n )
                elseif decodeComponentEscape( "X", n ) then
                    s = string.format( "%%%02X", n )
                else
                    s = string.format( "%c", n )
                end
                j = j + 1
                if i == 1 then
                    ask = s .. ask:sub( j )
                else
                    ask = string.format( "%s%s%s",
                                         ask:sub( 1,  i - 1 ),
                                         s,
                                         ask:sub( j ) )
                end
            end
            i = i + 1
        end
    end -- while i
    return ask
end -- decodeComponentML()



local decodeComponentPercent = function ( ask, averse )
    local i = 1
    local j, k, m, n
    while ( i ) do
        i = ask:find( "%%[2-7]%x", i )
        if i then
            j = i + 1
            k = j + 1
            n = ask:byte( k, k )
            k = k + 1
            m = ( n > 96 )
            if m then
                n = n - 32
                m = n
            end
            if n > 57 then
                n = n - 55
            else
                n = n - 48
            end
            n = ( ask:byte( j, j ) - 48 )  *  16   +   n
            if n == 39  and
               ask:sub( i + 3,  i + 5 ) == "%27" then
               j = i + 6
               while ( ask:sub( j,  j + 2 )  ==  "%27" ) do
                  j = j + 3
               end -- while "%27"
            elseif decodeComponentEscape( averse, n ) then
                if m then
                    ask = string.format( "%s%c%s",
                                         ask:sub( 1, j ),
                                         m,
                                         ask:sub( k ) )
                end
            elseif i == 1 then
                ask = string.format( "%c%s",  n,  ask:sub( k ) )
            else
                ask = string.format( "%s%c%s",
                                     ask:sub( 1,  i - 1 ),
                                     n,
                                     ask:sub( k ) )
            end
            i = j
        end
    end -- while i
    return ask
end -- decodeComponentPercent()



local getTopDomain = function ( url, mode )
    local r = URLutil.getHost( url )
    if r then
        local pattern = "[%w%%%-]+%.%a[%w%-]*%a)$"
        if mode == 3 then
            pattern = "[%w%%%-]+%." .. pattern
        end
        r = mw.ustring.match( "." .. r,  "%.(" .. pattern )
        if not r then
            r = false
        end
    else
        r = false
    end
    return r
end -- getTopDomain()



local getHash = function ( url )
    local r = url:find( "#", 1, true )
    if r then
        local i = url:find( "&#", 1, true )
        if i then
            local s
            while ( i ) do
                s = url:sub( i + 2 )
                if s:match( "^%d+;" ) or s:match( "^x%x+;" ) then
                    r = url:find( "#",  i + 4,  true )
                    if r then
                        i = url:find( "&#",  i + 4,  true )
                    else
                        i = false
                    end
                else
                    r = i + 1
                    i = false
                end
            end -- while i
        end
    end
    return r
end -- getHash()



URLutil.decode = function ( url, enctype )
    local r, s
    if type( enctype ) == "string" then
        s = mw.text.trim( enctype )
        if s == "" then
            s = false
        else
            s = s:upper()
        end
    end
    r = mw.text.encode( mw.uri.decode( url, s ) )
    if r:find( "[%[|%]]" ) then
        local k
        r, k = r:gsub( "%[", "&#91;" )
                :gsub( "|", "&#124;" )
                :gsub( "%]", "&#93;" )
    end
    return r
end -- URLutil.decode()



URLutil.encode = function ( url, enctype )
    local k, r, s
    if type( enctype ) == "string" then
        s = mw.text.trim( enctype )
        if s == "" then
            s = false
        else
            s = s:upper()
        end
    end
    r = mw.uri.encode( url, s )
    k = r:byte( 1, 1 )
    if -- k == 35  or      -- #
          k == 42  or      -- *
          k == 58  or      -- :
          k == 59 then     -- ;
        r = string.format( "%%%X%s", k, r:sub( 2 ) )
    end
    if r:find( "[%[|%]]" ) then
        r, k = r:gsub( "%[", "%5B" )
                :gsub( "|",  "%7C" )
                :gsub( "%]", "%5D" )
    end
    return r
end -- URLutil.encode()



URLutil.getAuthority = function ( url )
    local r
    if type( url ) == "string" then
        local colon, host, port
        local pattern = "^%s*%w*:?//([%w%.%%_-]+)(:?)([%d]*)/"
        local s = mw.text.decode( url )
        local i = s:find( "#", 6, true )
        if i then
            s = s:sub( 1,  i - 1 )  ..  "/"
        else
            s = s .. "/"
        end
        host, colon, port = mw.ustring.match( s, pattern )
        if URLutil.isHost( host ) then
            host = mw.ustring.lower( host )
            if colon == ":" then
                if port:find( "^[1-9]" ) then
                    r = ( host .. ":" .. port )
                end
            elseif #port == 0 then
                r = host
            end
        end
    else
        r = false
    end
    return r
end -- URLutil.getAuthority()



URLutil.getFragment = function ( url, decode )
    local r
    if type( url ) == "string" then
        local i = getHash( url )
        if i then
            r = mw.text.trim( url:sub( i ) ):sub( 2 )
            if type( decode ) == "string" then
                local encoding = mw.text.trim( decode )
                local launch
                if encoding == "%" then
                    launch = true
                elseif encoding == "WIKI" then
                    r = r:gsub( "%.(%x%x)", "%%%1" )
                         :gsub( "_", " " )
                    launch = true
                end
                if launch then
                    r = mw.uri.decode( r, "PATH" )
                end
            end
        else
            r = false
        end
    else
        r = nil
    end
    return r
end -- URLutil.getFragment()



URLutil.getHost = function ( url )
    local r = URLutil.getAuthority( url )
    if r then
        r = mw.ustring.match( r, "^([%w%.%%_%-]+):?[%d]*$" )
    end
    return r
end -- URLutil.getHost()



URLutil.getLocation = function ( url )
    local r
    if type( url ) == "string" then
        r = mw.text.trim( url )
        if r == "" then
            r = false
        else
            local i
            i = getHash( r )
            if i then
                if i == 1 then
                    r = false
                else
                    r = r:sub( 1,  i - 1 )
                end
            end
        end
    else
        r = nil
    end
    return r
end -- URLutil.getLocation()



URLutil.getNormalized = function ( url )
    local r
    if type( url ) == "string" then
        r = mw.text.trim( url )
        if r == "" then
            r = false
        else
            r = decodeComponentML( r )
        end
    else
        r = false
    end
    if r then
        local k = r:find( "//", 1, true )
        if k then
            local j = r:find( "/",  k + 2,  true )
            local sF, sP, sQ
            if r:find( "%%[2-7]%x" ) then
                local i = getHash( r )
                if i then
                    sF = r:sub( i + 1 )
                    r  = r:sub( 1,  i - 1 )
                    if sF == "" then
                        sF = false
                    else
                        sF = decodeComponentPercent( sF, "F" )
                    end
                end
                i = r:find( "?", 1, true )
                if i then
                    sQ = r:sub( i )
                    r  = r:sub( 1,  i - 1 )
                    sQ = decodeComponentPercent( sQ, "Q" )
                end
                if j then
                    if #r > j then
                        sP = r:sub( j + 1 )
                        sP = decodeComponentPercent( sP, "P" )
                    end
                    r = r:sub( 1,  j - 1 )
                end
            elseif j then
                local n = #r
                if r:byte( n, n ) == 35 then    -- '#'
                    n = n - 1
                    r = r:sub( 1, n )
                end
                if n > j then
                    sP = r:sub( j + 1 )
                end
                r = r:sub( 1,  j - 1 )
            end
            r = mw.ustring.lower( r ) .. "/"
            if sP then
                r = r .. sP
            end
            if sQ then
                r = r .. sQ
            end
            if sF then
                r = string.format( "%s#%s", r, sF )
            end
        end
        r = r:gsub( " ",  "%%20" )
             :gsub( "%[", "%%5B" )
             :gsub( "|",  "%%7C" )
             :gsub( "%]", "%%5D" )
             :gsub( "%<", "%%3C" )
             :gsub( "%>", "%%3E" )
    end
    return r
end -- URLutil.getNormalized()



URLutil.getPath = function ( url )
    local r = URLutil.getRelativePath( url )
    if r then
        local s = r:match( "^([^%?]*)%?" )
        if s then
            r = s
        end
        s = r:match( "^([^#]*)#" )
        if s then
            r = s
        end
    end
    return r
end -- URLutil.getPath()



URLutil.getPort = function ( url )
    local r = URLutil.getAuthority( url )
    if r then
        r = r:match( ":([1-9][0-9]*)$" )
        if r then
            r = tonumber( r )
        else
            r = false
        end
    end
    return r
end -- URLutil.getPort()



URLutil.getQuery = function ( url, key, separator )
    local r = URLutil.getLocation( url )
    if r then
        r = r:match( "^[^%?]*%?(.+)$" )
        if r then
            if type( key ) == "string" then
                local single = mw.text.trim( key )
                local sep = "&"
                local s, scan
                if type( separator ) == "string" then
                    s = mw.text.trim( separator )
                    if s:match( "^[&;,/]$" ) then
                        sep = s
                    end
                end
                s = string.format( "%s%s%s", sep, r, sep )
                scan = string.format( "%s%s=([^%s]*)%s",
                                      sep, key, sep, sep )
                r = s:match( scan )
            end
        end
        if not r then
            r = false
        end
    end
    return r
end -- URLutil.getQuery()



URLutil.getQueryTable = function ( url, separator )
    local r = URLutil.getQuery( url )
    if r then
        local sep = "&"
        local n, pairs, s, set
        if type( separator ) == "string" then
            s = mw.text.trim( separator )
            if s:match( "^[&;,/]$" ) then
                sep = s
            end
        end
        pairs = mw.text.split( r, sep, true )
        n = #pairs
        r = { }
        for i = 1, n do
            s = pairs[ i ]
            if s:find( "=", 2, true ) then
                s, set = s:match( "^([^=]+)=(.*)$" )
                if s then
                    r[ s ] = set
                end
            else
                r[ s ] = false
            end
        end -- for i
    end
    return r
end -- URLutil.getQueryTable()



URLutil.getRelativePath = function ( url )
    local r
    if type( url ) == "string" then
        local s = url:match( "^%s*[a-zA-Z]*://(.*)$" )
        if s then
            s = s:match( "[^/]+(/.*)$" )
        else
            local x
            x, s = url:match( "^%s*(/?)(/.*)$" )
            if x == "/" then
                s = s:match( "/[^/]+(/.*)$" )
            end
        end
        if s then
            r = mw.text.trim( s )
        elseif URLutil.isResourceURL( url ) then
            r = "/"
        else
            r = false
        end
    else
        r = nil
    end
    return r
end -- URLutil.getRelativePath()



URLutil.getScheme = function ( url )
    local r
    if type( url ) == "string" then
        local pattern = "^%s*([a-zA-Z]*)(:?)(//)"
        local prot, colon, slashes = url:match( pattern )
        r = false
        if slashes == "//" then
            if colon == ":" then
                if #prot > 2 then
                    r = prot:lower() .. "://"
                end
            elseif #prot == 0 then
                r = "//"
            end
        end
    else
        r = nil
    end
    return r
end -- URLutil.getScheme()



URLutil.getSortkey = function ( url )
    local r = url
    if type( url ) == "string" then
        local i = url:find( "//" )
        if i then
            local scheme
            if i == 0 then
                scheme = ""
            else
                scheme = url:match( "^%s*([a-zA-Z]*)://" )
            end
            if scheme then
                local s = url:sub( i + 2 )
                local comps, site, m, suffix
                scheme = scheme:lower()
                i      = s:find( "/" )
                if i  and  i > 1 then
                    suffix = s:sub( i + 1 )            -- mw.uri.encode()
                    s      = s:sub( 1,  i - 1 )
                    suffix = suffix:gsub( "#", " " )
                else
                    suffix = ""
                end
                site, m = s:match( "^(.+)(:%d+)$" )
                if not m then
                    site = s
                    m    = 0
                end
                comps = mw.text.split( site:lower(), ".", true )
                r = "///"
                for i = #comps, 2, -1 do
                    r =  string.format( "%s%s.", r, comps[ i ] )
                end -- for --i
                r = string.format( "%s%s %d %s: %s",
                                   r, comps[ 1 ], m, scheme, suffix )
            end
        end
    end
    return r
end -- URLutil.getSortkey()



URLutil.getTLD = function ( url )
    local r = URLutil.getHost( url )
    if r then
        r = mw.ustring.match( r, "%w+%.(%a[%w%-]*%a)$" )
        if not r then
            r = false
        end
    end
    return r
end -- URLutil.getTLD()



URLutil.getTop2domain = function ( url )
    return getTopDomain( url, 2 )
end -- URLutil.getTop2domain()



URLutil.getTop3domain = function ( url )
    return getTopDomain( url, 3 )
end -- URLutil.getTop3domain()



URLutil.isAuthority = function ( s )
    local r
    if type( s ) == "string" then
        local pattern = "^%s*([%w%.%%_-]+)(:?)(%d*)%s*$"
        local host, colon, port = mw.ustring.match( s, pattern )
        if colon == ":" then
            port = port:match( "^[1-9][0-9]*$" )
            if type( port ) ~= "string" then
                r = false
            end
        elseif port ~= "" then
            r = false
        end
        r = URLutil.isHost( host )
    else
        r = nil
    end
    return r
end -- URLutil.isAuthority()



URLutil.isDomain = function ( s )
    local r
    if type( s ) == "string" then
        local scan = "^%s*([%w%.%%_-]*%w)%.(%a[%w-]*%a)%s*$"
        local scope
        s, scope = mw.ustring.match( s, scan )
        if type( s ) == "string" then
            if mw.ustring.find( s, "^%w" ) then
                if mw.ustring.find( s, "..", 1, true ) then
                    r = false
                else
                    r = true
                end
            end
        end
    else
        r = nil
    end
    return r
end -- URLutil.isDomain()



URLutil.isDomainExample = function ( url )
    -- RFC 2606: example.com example.net example.org example.edu
    local r = getTopDomain( url, 2 )
    if r then
        local s = r:lower():match( "^example%.([a-z][a-z][a-z])$" )
        if s then
            r = ( s == "com" or
                  s == "edu" or
                  s == "net" or
                  s == "org" )
        else
            r = false
        end
    end
    return r
end -- URLutil.isDomainExample()



URLutil.isDomainInt = function ( url )
    -- Internationalized Domain Name (Punycode)
    local r = URLutil.getHost( url )
    if r then
        if r:match( "^[!-~]+$" ) then
            local s = "." .. r
            if s:find( ".xn--", 1, true ) then
                r = true
            else
                r = false
            end
        else
            r = true
        end
    end
    return r
end -- URLutil.isDomainInt()



URLutil.isHost = function ( s )
    return URLutil.isDomain( s ) or URLutil.isIP( s )
end -- URLutil.isHost()



URLutil.isHostPathResource = function ( s )
    local r = URLutil.isResourceURL( s )
    if not r  and s then
        r = URLutil.isResourceURL( "//" .. mw.text.trim( s ) )
    end
    return r
end -- URLutil.isHostPathResource()



URLutil.isIP = function ( s )
    return URLutil.isIPv4( s ) and 4 or URLutil.isIPv6( s ) and 6
end -- URLutil.isIP()



URLutil.isIPlocal = function ( s )
    -- IPv4 according to RFC 1918, RFC 1122; even any 0.0.0.0 (RFC 5735)
    local r = false
    local num = s:match( "^ *([01][0-9]*)%." )
    if num then
        num = tonumber( num )
        if num == 0 then
            r = s:match( "^ *0+%.[0-9]+%.[0-9]+%.[0-9]+ *$" )
        elseif num == 10  or  num == 127 then
            -- loopback; private/local host: 127.0.0.1
            r = URLutil.isIPv4( s )
        elseif num == 169 then
            -- 169.254.*.*
        elseif num == 172 then
            -- 172.(16...31).*.*
            num = s:match( "^ *0*172%.([0-9]+)%." )
            if num then
                num = tonumber( num )
                if num >= 16  and  num <= 31 then
                    r = URLutil.isIPv4( s )
                end
            end
        elseif beg == 192 then
            -- 192.168.*.*
            num = s:match( "^ *0*192%.([0-9]+)%." )
            if num then
                num = tonumber( num )
                if num == 168 then
                    r = URLutil.isIPv4( s )
                end
            end
        end
    end
    if r then
        r = true
    end
    return r
end -- URLutil.isIPlocal()



URLutil.isIPv4 = function ( s )
    local function legal( n )
              return ( tonumber( n ) < 256 )
          end
    local r = false
    if type( s ) == "string" then
        local p1, p2, p3, p4 = s:match( "^%s*([1-9][0-9]?[0-9]?)%.([12]?[0-9]?[0-9])%.([12]?[0-9]?[0-9])%.([12]?[0-9]?[0-9])%s*$" )
        if p1 and p2 and p3 and p4 then
            r = legal( p1 ) and legal( p2 ) and legal( p3 ) and legal( p4 )
        end
    end
    return r
end -- URLutil.isIPv4()



URLutil.isIPv6 = function ( s )
    local dcolon, groups
    if type( s ) ~= "string"
        or s:len() == 0
        or s:find( "[^:%x]" ) -- only colon and hex digits are legal chars
        or s:find( "^:[^:]" ) -- can begin or end with :: but not with single :
        or s:find( "[^:]:$" )
        or s:find( ":::" )
    then
        return false
    end
    s = mw.text.trim( s )
    s, dcolon = s:gsub( "::", ":" )
    if dcolon > 1 then
        return false
    end -- at most one ::
    s = s:gsub( "^:?", ":" ) -- prepend : if needed, upper
    s, groups = s:gsub( ":%x%x?%x?%x?", "" ) -- remove valid groups, and count them
    return ( ( dcolon == 1 and groups < 8 ) or
             ( dcolon == 0 and groups == 8 ) )
        and ( s:len() == 0 or ( dcolon == 1 and s == ":" ) ) -- might be one dangling : if original ended with ::
end -- URLutil.isIPv6()



URLutil.isMailAddress = function ( s )
    if type( s ) == "string" then
        s = mw.ustring.match( s, "^%s*[%w%.%%_-]+@([%w%.%%-]+)%s*$" )
        return URLutil.isDomain( s )
    end
    return false
end -- URLutil.isMailAddress()



URLutil.isMailLink = function ( s )
    if type( s ) == "string" then
        local addr
        s, addr = mw.ustring.match( s, "^%s*([Mm][Aa][Ii][Ll][Tt][Oo]):(%S[%w%.%%_-]*@[%w%.%%-]+)%s*$" )
        if type( s ) == "string" then
            if s:lower() == "mailto" then
                return URLutil.isMailAddress( addr )
            end
        end
    end
    return false
end -- URLutil.isMailLink()



local function isProtocolAccepted( prot, supplied )
    if type( prot ) == "string" then
        local scheme, colon, slashes = mw.ustring.match( prot, "^%s*([a-zA-Z]*)(:?)(/?/?)%s*$" )
        if slashes ~= "/" then
            if scheme == "" then
                if colon ~= ":" and slashes == "//" then
                    return true
                end
             elseif colon == ":" or slashes == "" then
                local s = supplied:match( " " .. scheme:lower() .. " " )
                if type( s ) == "string" then
                    return true
                end
            end
        end
    end
    return false
end -- isProtocolAccepted()



URLutil.isProtocolDialog = function ( prot )
    return isProtocolAccepted( prot, " mailto irc ircs ssh telnet " )
end -- URLutil.isProtocolDialog()



URLutil.isProtocolWiki = function ( prot )
    return isProtocolAccepted( prot,
                               " ftp ftps git http https nntp sftp svn worldwind " )
end -- URLutil.isProtocolWiki()



URLutil.isResourceURL = function ( url )
    local scheme = URLutil.getScheme( url )
    if scheme then
        local s = " // http:// https:// ftp:// sftp:// "
        s = s:find( string.format( " %s ", scheme ) )
        if s then
            if URLutil.getAuthority( url ) then
                if not url:match( "%S%s+%S" ) then
                    local s1, s2 = url:match( "^([^#]+)(#.*)$" )
                    if s2 then
                        if url:match( "^%s*[a-zA-Z]*:?//(.+)/" ) then
                            return true
                        end
                    else
                        return true
                    end
                end
            end
        end
    end
    return false
end -- URLutil.isResourceURL()



URLutil.isSuspiciousURL = function ( url )
    if URLutil.isResourceURL( url ) then
        local s = URLutil.getAuthority( url )
        local pat = "[%[|%]" ..
                    mw.ustring.char( 34,
                                     8201, 45, 8207,
                                     8234, 45, 8239,
                                     8288 )
                    .. "]"
        if s:find( "@" )
           or url:find( "''" )
           or url:find( pat )
           or url:find( "[%.,]$" ) then
            return true
        end
        -- TODO  zero width character ??
        return false
    end
    return true
end -- URLutil.isSuspiciousURL()



URLutil.isUnescapedURL = function ( url, trailing )
    if type( trailing ) ~= "string" then
        if URLutil.isWebURL( url ) then
            if url:match( "[%[|%]]" ) then
                return true
            end
        end
    end
    return false
end -- URLutil.isUnescapedURL()



URLutil.isWebURL = function ( url )
    if URLutil.getScheme( url ) and URLutil.getAuthority( url ) then
        if not url:find( "%S%s+%S" )  and
           not url:find( "''", 1, true ) then
            return true
        end
    end
    return false
end -- URLutil.isWebURL()



URLutil.wikiEscapeURL = function ( url )
    if url:find( "[%[|%]]" ) then
        local n
        url, n = url:gsub( "%[", "&#91;" )
                    :gsub( "|", "&#124;" )
                    :gsub( "%]", "&#93;" )
    end
    return url
end -- URLutil.wikiEscapeURL()



Failsafe.failsafe = function ( atleast )
    -- Retrieve versioning and check for compliance
    -- Precondition:
    --     atleast  -- string, with required version
    --                         or wikidata|item|~|@ or false
    -- Postcondition:
    --     Returns  string  -- with queried version/item, also if problem
    --              false   -- if appropriate
    -- 2020-08-17
    local since = atleast
    local last    = ( since == "~" )
    local linked  = ( since == "@" )
    local link    = ( since == "item" )
    local r
    if last  or  link  or  linked  or  since == "wikidata" then
        local item = Failsafe.item
        since = false
        if type( item ) == "number"  and  item > 0 then
            local suited = string.format( "Q%d", item )
            if link then
                r = suited
            else
                local entity = mw.wikibase.getEntity( suited )
                if type( entity ) == "table" then
                    local seek = Failsafe.serialProperty or "P348"
                    local vsn  = entity:formatPropertyValues( seek )
                    if type( vsn ) == "table"  and
                       type( vsn.value ) == "string"  and
                       vsn.value ~= "" then
                        if last  and  vsn.value == Failsafe.serial then
                            r = false
                        elseif linked then
                            if mw.title.getCurrentTitle().prefixedText
                               ==  mw.wikibase.getSitelink( suited ) then
                                r = false
                            else
                                r = suited
                            end
                        else
                            r = vsn.value
                        end
                    end
                end
            end
        end
    end
    if type( r ) == "nil" then
        if not since  or  since <= Failsafe.serial then
            r = Failsafe.serial
        else
            r = false
        end
    end
    return r
end -- Failsafe.failsafe()



local function Template( frame, action, amount )
    -- Run actual code from template transclusion
    -- Precondition:
    --     frame   -- object
    --     action  -- string, with function name
    --     amount  -- number, of args if > 1
    -- Postcondition:
    --     Return string or not
    local n = amount or 1
    local v = { }
    local r, s
    for i = 1, n do
        s = frame.args[ i ]
        if s then
             s = mw.text.trim( s )
             if s ~= "" then
                 v[ i ] = s
             end
         end
    end -- for i
    if v[ 1 ] then
         r = URLutil[ action ](  v[ 1 ], v[ 2 ], v[ 3 ] )
    end
    return r
end -- Template()



local p = {}

function p.decode( frame )
    return Template( frame, "decode", 2 ) or ""
end
function p.encode( frame )
    return Template( frame, "encode", 2 ) or ""
end
function p.getAuthority( frame )
    return Template( frame, "getAuthority" ) or ""
end
function p.getFragment( frame )
    local r = Template( frame, "getFragment", 2 )
    if r then
        r = "#" .. r
    else
        r = ""
    end
    return r
end
function p.getHost( frame )
    return Template( frame, "getHost" ) or ""
end
function p.getLocation( frame )
    return Template( frame, "getLocation" ) or ""
end
function p.getNormalized( frame )
    return Template( frame, "getNormalized" ) or ""
end
function p.getPath( frame )
    return Template( frame, "getPath" ) or ""
end
function p.getPort( frame )
    return Template( frame, "getPort" ) or ""
end
function p.getQuery( frame )
    local r = Template( frame, "getQuery", 3 )
    if r then
        local key = frame.args[ 2 ]
        if key then
            key = mw.text.trim( key )
            if key == "" then
                key = nil
            end
        end
        if not key then
            r = "?" .. r
        end
    else
        r = ""
    end
    return r
end
function p.getRelativePath( frame )
    return Template( frame, "getRelativePath" ) or ""
end
function p.getScheme( frame )
    return Template( frame, "getScheme" ) or ""
end
function p.getSortkey( frame )
    return Template( frame, "getSortkey" ) or ""
end
function p.getTLD( frame )
    return Template( frame, "getTLD" ) or ""
end
function p.getTop2domain( frame )
    return Template( frame, "getTop2domain" ) or ""
end
function p.getTop3domain( frame )
    return Template( frame, "getTop3domain" ) or ""
end
function p.isAuthority( frame )
    return Template( frame, "isAuthority" ) and "1" or ""
end
function p.isDomain( frame )
    return Template( frame, "isDomain" ) and "1" or ""
end
function p.isDomainExample( frame )
    return Template( frame, "isDomainExample" ) and "1" or ""
end
function p.isDomainInt( frame )
    return Template( frame, "isDomainInt" ) and "1" or ""
end
function p.isHost( frame )
    return Template( frame, "isHost" ) and "1" or ""
end
function p.isHostPathResource( frame )
    return Template( frame, "isHostPathResource" ) and "1" or ""
end
function p.isIP( frame )
    return Template( frame, "isIP" ) or ""
end
function p.isIPlocal( frame )
    return Template( frame, "isIPlocal" ) and "1" or ""
end
function p.isIPv4( frame )
    return Template( frame, "isIPv4" ) and "1" or ""
end
function p.isIPv6( frame )
    return Template( frame, "isIPv6" ) and "1" or ""
end
function p.isMailAddress( frame )
    return Template( frame, "isMailAddress" ) and "1" or ""
end
function p.isMailLink( frame )
    return Template( frame, "isMailLink" ) and "1" or ""
end
function p.isProtocolDialog( frame )
    return Template( frame, "isProtocolDialog" ) and "1" or ""
end
function p.isProtocolWiki( frame )
    return Template( frame, "isProtocolWiki" ) and "1" or ""
end
function p.isResourceURL( frame )
    return Template( frame, "isResourceURL" ) and "1" or ""
end
function p.isSuspiciousURL( frame )
    return Template( frame, "isSuspiciousURL" ) and "1" or ""
end
function p.isUnescapedURL( frame )
    return Template( frame, "isUnescapedURL", 2 ) and "1" or ""
end
function p.isWebURL( frame )
    return Template( frame, "isWebURL" ) and "1" or ""
end
function p.wikiEscapeURL( frame )
    return Template( frame, "wikiEscapeURL" )
end
p.failsafe = function ( frame )
    local s = type( frame )
    local since
    if s == "table" then
        since = frame.args[ 1 ]
    elseif s == "string" then
        since = frame
    end
    if since then
        since = mw.text.trim( since )
        if since == "" then
            since = false
        end
    end
    return Failsafe.failsafe( since ) or ""
end
function p.URLutil()
    return URLutil
end

return p