Lua Min-Heap, w/Actions

heap = {
    new = function()
        return {
            size = 0,
            elements = {}
    }
    end,

    _exch = function(h, x, y)
        assert(type(x) == "number")
        assert(type(y) == "number")

        local temp = h.elements[x]
        h.elements[x] = h.elements[y]
        h.elements[y] = temp
    end,

    _sink = function(h, parentIndex)
        local N = h.size

        while (parentIndex*2) <= N do
            local childIndex = parentIndex * 2

            if childIndex < N and lowerPriority(h.elements[childIndex],
                                                                                                        h.elements[childIndex+1]) then
                childIndex = childIndex + 1
            end

            if not lowerPriority(h.elements[parentIndex], h.elements[childIndex]) then
                break
            else
                heap._exch(h, parentIndex, childIndex)
                parentIndex = childIndex
            end
        end
    end,

    _swim = function(h, childIndex)
        while childIndex > 1 and lowerPriority(h.elements[math.floor(childIndex/2)],
                                                                                                            h.elements[childIndex]) do
            local parentIndex = math.floor(childIndex / 2)
            heap._exch(h, childIndex, parentIndex)
            childIndex = parentIndex
        end
    end,

    insert = function(h, element)
        table.insert(h.elements, element)
        h.size = h.size + 1

        heap._swim(h, h.size)
    end,

    extract = function(h)
        heap._exch(h, 1, h.size)
        h.size = h.size - 1
        local ret = table.remove(h.elements)

        heap._sink(h, 1)

        return ret
    end,

    head = function(h)
        local element = h.elements[1]
        return element
    end
}

function action(name, balance, priority, command)
  assert(type(name) == "string")
  assert(type(balance) == "string")
  assert(type(priority) == "number")
  assert(type(command) == "function" or type(command) == "string")

    local actionCommand = function() end

  if type(command) == "string" then
    actionCommand = function()
      send(command)
    end
  else
    actionCommand = command
  end

  local action = {
    name = name,
    balance = balance,
    priority = priority,
    command = actionCommand
    }

    setmetatable(action, {
        __lt = function(a, b)
            return a.priority < b.priority
        end
    })

    return action
end

function lowerPriority(x, y)
    assert(type(x) == "table")
    assert(type(y) == "table")

    assert(type(x.priority) == "number")
    assert(type(y.priority) == "number")

    return x.priority >= y.priority
end