Module:Chapter Infobox

For Previous Chapter:

num must be the current chapter number, this removes the need for all the #expr calls {{#invoke:Chapter Infobox|prev_chapter|num}}

For Next Chapter:

num must be the current chapter number, this removes the need for all the #expr calls {{#invoke:Chapter Infobox|next_chapter|num}}

Code uses/calls Module:Which_Chapter

---

local mod = {}

---@return string
function mod.prev_chapter(frame)
    local args = frame.args
    local parent = frame:getParent()
    local pargs={}
    if parent then pargs=parent.args end
    local num = args[1] or pargs[1] or 0
    if num - 1 <= 0 then
        return "N/A"
    else
        return frame:expandTemplate{title = "Which Chapter", args = {tostring(num - 1)}}
    end
end

---@return string
function mod.next_chapter(frame)
    local args = frame.args
    local parent = frame:getParent()
    local pargs={}
    if parent then pargs=parent.args end
    local num = args[1] or pargs[1] or 0
    return frame:expandTemplate{title = "Which Chapter", args = {tostring(num + 1)}}
end

return mod