splice: Script for complex splices

[ddustin]

PR reviewers: It might be good to start here to learn the splice script syntax: https://github.com/ddustin/lightning/blob/ddustin/splice_script/doc/lightning-splice.7.md

New compiler for splice scripts that parses splice scripts, validates them, converts them to json and back again.

A test is included that puts some advanced and complex scripts into the parser and validates the results that come out.

Changelog-Added: Splice script parser — takes a custom splice query language to bundle multiple complex splices into a single task in a simple way.

[vincenzopalazzo]

Mh What do you mean by "Scripts"? and why now we need a "compiler" for splicing? 😕

I feel that I am missing somethings?

[ddustin]

Mh What do you mean by "Scripts"? and why now we need a "compiler" for splicing? 😕

I feel that I am missing somethings?

Proper documentation is coming but here's a quick summary:

The script isn't required to be used -- there will also be a json option and, of course, the lower level api is available.

When doing splices across multiple channels it quickly becomes unwieldy for users. Using the script is a nice shorthand to make it easier -- and also allows you to do "dry runs" and confirm it's doing what you'd like.

Say you wanted to take 50% of funds and splice them into three other channels, in splice script it's quite simple:

84ff50 -> 50%;
* -> cecf35;
* -> 4fe310;
* -> c14f60;

While working on it, it made sense to add a bunch of other useful things like being able to specify amounts as whole numbers, percentages, or * (split amount among all *s); channel queries; onchain bitcoin addresses; and the onchain wallet.

By building this more powerful part first it becomes trivial to implement the simpler splice commands. For instance:

Splice out 10 million sats

84ff50 -> 10M;

Splice in 10 million sats

wallet -> 10M;
* -> 84ff50;

Cross splice 10 million sats

84ff50 -> 10M;
* -> cecf35;

Pay 10M sats onchain using channel funds

84ff50 -> 10M+fee;
10M -> 1JfbZRwdDHKZmuiZgYArJZhcuuzuw2HuMu;