local CHde = { suite  = "GebietSchweizerHochdeutsch",
               serial = "2023-11-08",
               item   = 123374901 }
--[=[
Gebiet identifizieren, in dem Schweizer Hochdeutsch Amtssprache wäre
]=]


CHde.domains = { CH = true,
                 LI = true,
                 CHE = true,
                 LIE = true,
                 [".ch"] = true,
                 [".li"] = true }
local Failsafe = CHde



CHde.f = function ( at )
    -- Perform task
    -- Parameter:
    --     at  -- string, with code
    -- Returns boolean
    local r
    if type( at ) == "string" then
        local s = mw.text.trim( at )
        r = CHde.domains[ s ]
        if not r then
            s = s:match( "^(%u%u%u?)%-[%u%d]" )
            r = CHde.domains[ s ] or false
        end
    else
        r = false
    end
    return r
end -- CHde.f()



Failsafe.failsafe = function ( atleast )
    -- Retrieve versioning and check for compliance
    -- Precondition:
    --     atleast  -- string, with required version
    --                         or "wikidata" or "~" or "@" 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()



-- Export
local p = { }

p.f = function ( frame )
    return CHde.f( frame.args[ 1 ] )  and "1" or ""
end -- p.f

p.failsafe = function ( frame )
    -- Versioning interface
    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 -- p.failsafe

setmetatable( p,  { __call = function ( func, ... )
                                 setmetatable( p, nil )
                                 return Failsafe
                             end } )

return p