first commit

lib/knife/chain.lua

@@ -0,0 +1,31 @@
+local function Invoker (links, index)
+    return function (...)
+        local link = links[index]
+        if not link then
+            return
+        end
+        local continue = Invoker(links, index + 1)
+        local returned = link(continue, ...)
+        if returned then
+            returned(function (_, ...) continue(...) end)
+        end
+    end
+end
+    
+return function (...)
+    local links = { ... }
+
+    local function chain (...)
+        if not (...) then
+            return Invoker(links, 1)(select(2, ...))
+        end
+        local offset = #links
+        for index = 1, select('#', ...) do
+            links[offset + index] = select(index, ...)
+        end
+        return chain
+    end
+
+    return chain
+end
+