history.yaml

name: history
doc: |-
  A machine that remembers what is has seen.

  ToDo: Support changing the limit.

  Warning to developers: Be careful about emitting messages from this
  machine's actions!

  Dev note: Got "TypeError: Cannot extend Go slice" from push(). I
  think that's because the 'hist' value becomes a Go slice (instead of
  an array) at some point in the Go/Goja churning.  Should look into
  that.  For now, I just construct a Javascript array from the slice.

paramspecs:
  limit:
    doc: The maximum number of messages to retain.
    primitiveType: int
patternsyntax: json
nodes:
  start:
    branching:
      branches:
      - target: listen
  listen:
    branching:
      type: message
      branches:
      - pattern: |
          {"from":"history"}
        doc: Skip our own output!
        target: listen
      - pattern: |
          {"query":"?pattern"}
        target: query
      - pattern: |
          "?heard"
        target: heard
  heard:
    action:
      interpreter: ecmascript
      source: |-
        var heard = _.bindings["?heard"];
        delete _.bindings["?heard"];
        var hist = _.bindings.hist;
        if (!hist) {
           hist = [];
        } else {
           hist = [].concat(hist);
        }
        var limit = _.bindings["?limit"]
        if (!limit) {
           limit = 10;
        }
        while (limit <= hist.length) {
           hist.splice(0,1);
        }
        hist.push({ts: new Date(), message: heard});
        _.bindings.hist = hist;
        return _.bindings;
    branching:
      branches:
      - target: listen
  query:
    action:
      interpreter: ecmascript
      source: |-
        var bss = _.match(_.bindings["?pattern"], _.bindings.hist, {});
        delete _.bindings["?pattern"];
        _.out({found: bss, from: "history"});
        return _.bindings;
    branching:
      branches:
      - target: listen