Implement scanner module

scanner/README.md

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+Pipeworks Lua Tube Scanner
+==========================
+
+The scanner script serves as a polyfill for the modern Digiline Detecting
+Pneumatic Tube Segment for use on servers running older versions of Pipeworks.
+It should be a drop-in replacement, so if the server is upgraded, the Lua
+Controlled Sorting Tube can be replaced with an actual Digiline Detecting
+Pneumatic Tube Segment without affecting the rest of the system.
+
+In the current version of Pipeworks, the Digiline Detecting Pneumatic Tube
+Segment sends a Digiline message in table format with details of the itemstack
+passing through the segment. In older versions of Pipeworks, however, the
+segment instead sent a string representation of the itemstack. When playing on
+server running an older version of Pipeworks, this scanner script installed on
+a Lua Controlled Sorting Tube can fill in for the detecting tube, as it sends
+the itemstack information in table format.
+
+
+Configuration
+-------------
+
+The `output_direction` string is the colour of output direction where all items
+should be sent.
+
+The `channel` string is the Digiline channel to which item-passing messages
+will be sent.

scanner/scanner.lua

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+-- Where passing items should be sent.
+local output_direction = "yellow"
+
+-- The channel to which item-passing messages should be sent, each of which is
+-- an itemstack in table form.
+local channel = "scanner:1"
+
+if event.type == "item" then
+	digiline_send(channel, event.item)
+	return output_direction
+end