Module:BookTOC

local p = {}

function p.main(frame)
    local args = frame:getParent().args
    local items = {}
    local levels = {}
    
    -- Collect all TOC items and their levels
    local i = 1
    while args['item' .. i] do
        items[i] = args['item' .. i]
        levels[i] = tonumber(args['level' .. i]) or 2  -- Default to level 2 (==) if not provided
        i = i + 1
    end
    
    -- Generate TOC as wikitext nested list
    if #items == 0 then
        return ''
    end
    
    -- Find the minimum level to use as base
    local min_level = math.min(table.unpack(levels))
    
    local list = {}
    local current_level = min_level
    local list_stack = {min_level}  -- Start with the base level
    
    for idx = 1, #items do
        local level = levels[idx]
        local item = items[idx]
        local normalized_level = level - min_level + 1
        
        -- Close deeper levels
        while #list_stack > 0 and list_stack[#list_stack] > normalized_level do
            table.remove(list_stack)
            table.insert(list, string.rep('#', list_stack[#list_stack]))
        end
        
        -- Open new levels if needed
        while normalized_level > list_stack[#list_stack] do
            table.insert(list, string.rep('#', normalized_level - list_stack[#list_stack]))
            table.insert(list_stack, normalized_level)
        end
        
        -- Add the item
        table.insert(list, string.rep('#', normalized_level - list_stack[#list_stack] + 1))
        table.insert(list, ' ')
        table.insert(list, item)
        table.insert(list, '\n')
        
        current_level = normalized_level
    end
    
    return '<div class="book-toc">\n' .. table.concat(list) .. '</div>'
end

return p