justjavac / lc-1

Theoretical Deno application for interfacing with a C++ library that launches rockets.

Launch Complex 1

This is a theoretical Deno library for interfacing with a C++ dynamic library. The C++ library does not expose a proper C API but instead implements plain C++ APIs together with some C function pointers for callbacks.

Due to the C++ ABI there are relatively many "return pointer" cases used in the Deno code. These can be found by the UnsafeOwnedPointer class usage, which implements a Deno.UnsafePointer together with an ArrayBuffer that the UnsafePointer references.

The LC-1 library itself (not present in the repo at present) implements a similar class hierarchy as this Deno library. At the core there is a LaunchComplex class, for which a LaunchPad can be built. A LaunchPad can (perhaps illogically) contain many LaunchTowers, and those can then be used to prepare and launch Rockets. A Rocket is suspiciously similar to an HTTP request; it flies off from the LaunchTower and sends telemetry data once it has landed (or eg. destroyed). All other rocket missions except the research missions only send a single packet of telemetry at the end of their missions. Research missions on the other hand will keep sending new data (with varying frequency based on findings) until they're explicitly disposed of.

The telemetry is reported using a callback-turned-stream through the LaunchTower where it launched from. Information about new telemetry being available is delivered to the LaunchTower using a thread safe callback. This comms callback is called whenever new telemetry data is available, but it does not carry any of the telemetry data itself. To get the rocket telemetry data, the LaunchTower must call the processComms API which will then synchronously call a telemetry data callback for those rockets for which new telemetry data is available. This can be thought of as being sort of a crank handle on a C++ side "manual" event loop: The comms callback is a wakeup for the event loop, and it is expected that the event loop will then "turn" the C++ event loop as well.

Future work

There are many unexplored parts of the LC-1 library that I want to incorporate into these theoretical Deno bindings. Some of these include:

• A class used to allow the Launch Complex to create Landing Pads for other Launch Compelexes to send rockets into (including research missions for teaching).
• A class used to receive information and react to the Launch Complex itself moving from place to place and receiving new information that can then be incorporated into Landing Pads, to be then passed onto other rockets.
• A class used to track the profitability and efficiency of the entire Launch Complex.
• A class used to get permissions from the government for rockets to land on other planets and other Launch Complexes' Landing Pads. The rocket does already have provisions for carrying these permissions but they're not properly handled at present.
• A class used to advertise potentially very large caches of valuable data to other Launch Complexes that can be fetched using a series of rockets. The same class can be used to also fetch similar caches from other Launch Complexes that they advertise.