Playbook: Rhai#

The experimental rhai matcher uses the rhai scripting language to evaluate expressions.

Builds#

To use this feature, the rhai feature flag must be enabled at build time.

Locally:

cargo run --features rhai

Container:

docker build --build-arg=CARGO_FEATURES=rhai .

Scripting#

Rhai matchers evaluate a script that returns a Match object or a string containing the AT-URI of the post that has matched. Return values of false or 0 are considered not matched.

The upsert_match(aturi) function is available to create a new Match object. It has one parameter, the AT-URI of the post that is matched.

let condition_thing = true;
// do some stuff ...

if condition_thing {
  return upsert_match();
}

false

Provided Methods#

The following methods are available to rhai scripts:

• build_aturi(event: Event) -> String - Build an AT-URI from an event. For feed posts, this composes an AT-URI from the event DID, commit collection, and commit rkey.

Usage#

The feed matcher type rhai is used with a source attribute that points to an rhai script file.

Rhai scripts are evaluated with scope that includes the following variables:

• event - The event to match against.

An example config file:

feeds:
- uri: "at://did:plc:decafbad/app.bsky.feed.generator/Dcuz0bZP1"
  name: "rhai'ya doing"
  description: "This feed uses the rhai matcher to match against a complex expression."
  matchers:
  - script: "/opt/supercell/rhaiyadoin.rhai"
    type: rhai

An example rhai script:

// Only match events from the bsky feed where the did is "did:plc:cbkjy5n7bk3ax2wplmtjofq2" (@ngerakines.me).
if event.did != "did:plc:cbkjy5n7bk3ax2wplmtjofq2" {
  return false;
}

// If the event has a commit that has a record that has a $type, set rtype. Otherwise the value will be ().
let rtype = event?.commit?.record["$type"];
switch rtype {
  "app.bsky.feed.post" => {
    // Compose the at-uri of the post that has matched.
    return build_aturi(event);
  }
  "app.bsky.feed.like" => {
    // Returns the subject uri of the like event or false if it doesn't exist.
    return event?.commit?.record?.subject?.uri ?? false;
  }
  _ => { }
}

// Nothing else matches
false