feat(seive): new seive used by Channel allows controlled bridging

affects: @tao.js/utils

needed a way to bridge with control info from one network to another so
Channels can bridge ACs back
from Kernels without double/circular AC loops

packages/tao-utils/src/Channel.js

@@ -1,5 +1,6 @@
 // import { Kernel } from '@tao.js/core';
 import { Network } from '@tao.js/core';
+import seive from './seive';
 
 let channelId = 0;
 function newChannelId() {
@@ -108,4 +109,14 @@ export default class Channel {
       handler
     );
   }
+
+  bridgeFrom(TAO, ...trigrams) {
+    return seive(
+      this._channelId,
+      TAO,
+      this,
+      (ac, control) => control.channelId !== this._channelId,
+      ...trigrams
+    );
+  }
 }

packages/tao-utils/src/bridge.js

@@ -1,5 +1,7 @@
 import { Kernel, AppCtx, INTERCEPT, ASYNC, INLINE } from '@tao.js/core';
 
+const NOOP = () => {};
+
 function forwardHandler(destination) {
   return (tao, data) => {
     console.log('bridging::tao', tao);
@@ -25,10 +27,10 @@ function filteredForwardHandler(destination, filter) {
 
 function bridge(type, source, destination, filters) {
   if (type !== INTERCEPT && type !== ASYNC && type !== INLINE) {
-    return;
+    return NOOP;
   }
   if (!(source instanceof Kernel) || !(destination instanceof Kernel)) {
-    return;
+    return NOOP;
   }
   const filterFunction =
     typeof filters[0] === 'function' ? filters.shift() : undefined;

packages/tao-utils/src/index.js

@@ -1,6 +1,7 @@
 import trigramFilter from './trigram-filter';
 import Channel from './Channel';
 import Source from './Source';
+import seive from './seive';
 export * from './bridge';
 
-export { trigramFilter, Channel, Source };
+export { trigramFilter, Channel, Source, seive };

packages/tao-utils/src/seive.js

@@ -0,0 +1,45 @@
+import { Network } from '@tao.js/core';
+import trigramFilter from './trigram-filter';
+
+const NOOP = () => {};
+
+function addControl(name, control) {
+  return { ...control, seive: name };
+}
+
+// filter function signature: (ac:AppCtx, control:Object)
+// filters is: [filterFunc, [exact,]] ...trigrams
+
+export default function seive(name, source, destination, ...filters) {
+  if (
+    !source ||
+    !(source._network instanceof Network) ||
+    !destination ||
+    !(destination._network instanceof Network)
+  ) {
+    return NOOP;
+  }
+  let filterFunction =
+    typeof filters[0] === 'function' ? filters.shift() : undefined;
+  let handleFilter = trigramFilter(...filters);
+
+  let middleware = (handler, ac, forwardAppCtx, control) => {
+    if (filterFunction && !filterFunction(ac, control)) {
+      return;
+    }
+    if (handleFilter(ac)) {
+      destination._channel.setAppCtxControl(
+        ac,
+        addControl(name, control),
+        forwardAppCtx
+      );
+    }
+  };
+  source._network.use(middleware);
+  return () => {
+    source._network.stop(middleware);
+    middleware = null;
+    filterFunction = null;
+    handleFilter = null;
+  };
+}

packages/tao-utils/src/trigram-filter.js

@@ -8,6 +8,9 @@ export default function trigramFilter(...trigrams) {
   if (typeof trigrams[0] === 'boolean') {
     exact = trigrams.shift();
   }
+  if (Array.isArray(trigrams[0])) {
+    trigrams = trigrams[0];
+  }
   return ac => {
     if (!(ac instanceof AppCtx)) {
       return false;