feat(cargo-elevator): implement high-level functions

Still need the smaller details.

cargo-elevator.lua

@@ -0,0 +1,61 @@
+-- program to manage a cargo elevator
+-- yes, i am aware i could just use the computer to transfer packages at this
+-- point, but where's the fun in that?
+
+local FLOORS = {
+    {
+        match = function (input)
+            local first_char = string.sub(input, 1, 1)
+            return first_char == "A" or first_char == "W"
+        end,
+        detect = function ()
+            -- TODO
+        end,
+        call = function ()
+            -- TODO
+        end
+        storage = "",
+        elevator_storage = "",
+    }
+}
+
+local SLEEP_T = 5
+
+local PKG_STACK = {
+    transfer_all = function (self, src, dest)
+        -- TODO
+    end,
+    transfer_matching = function (self, src, dest, match_f)
+        -- TODO
+    end,
+    get_next_floor = function (self)
+        -- TODO
+    end
+    stack = {},
+}
+
+function run (floors, stack)
+    local next_addr = nil
+    for _, floor in pairs(floors) do
+        if floor.detect() then
+            stack:transfer_all(floor.storage, floor.elevator_storage)
+            stack:transfer_matching(
+                floor.elevator_storage, floor.storage, floor.match
+            )
+            next_addr = stack:get_next_floor()
+        end
+    end
+    if next_addr ~= nil then
+        for _, floor in pairs(floors) do
+            if floor.match(next_addr) then
+                floor.call()
+                break
+            end
+        end
+    end
+end
+
+while true do
+    run(FLOORS)
+    os.sleep(SLEEP_T)
+end