fix(pipelining): enable pipelining of GET, POST

Closes #2

Author: michaelfig

lib/captp.js

@@ -21,8 +21,9 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
   let lastQuestionID = 0;
 
   const valToSlot = new WeakMap();
-  const slotToVal = new Map(); // exports, answers
+  const slotToVal = new Map(); // exports
   const questions = new Map(); // chosen by us
+  const answers = new Map(); // chosen by our peer
   const imports = new Map(); // chosen by our peer
 
   function serializeSlot(val, slots, slotMap) {
@@ -70,23 +71,33 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
     });
   }
 
-  function makeRemote(slot) {
+  function makeQuestion() {
+    lastQuestionID += 1;
+    const questionID = lastQuestionID;
+    const pr = makeRemote(questionID);
+    questions.set(questionID, pr);
+    return [questionID, pr];
+  }
+
+  function makeRemote(target) {
     const handler = {
+      GET(_o, prop) {
+        const [questionID, pr] = makeQuestion();
+        send({
+          type: 'CTP_CALL',
+          questionID,
+          target,
+          method: serialize(harden([prop])),
+        });
+        return harden(pr.p);
+      },
       POST(_o, prop, args) {
         // Support: o~.[prop](...args) remote method invocation
-        // FIXME: Implement a HandledPromise here to support pipelining.
-        const pr = {};
-        pr.p = new Promise((resolve, reject) => {
-          pr.res = resolve;
-          pr.rej = reject;
-        });
-        lastQuestionID += 1;
-        const questionID = lastQuestionID;
-        questions.set(questionID, pr);
+        const [questionID, pr] = makeQuestion();
         send({
           type: 'CTP_CALL',
           questionID,
-          target: slot,
+          target,
           method: serialize(harden([prop, args])),
         });
         return harden(pr.p);
@@ -131,6 +142,7 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
       const bootstrap =
         typeof bootstrapObj === 'function' ? bootstrapObj() : bootstrapObj;
       // console.log('sending bootstrap', bootstrap);
+      answers.set(questionID, bootstrap);
       send({
         type: 'CTP_RETURN',
         answerID: questionID,
@@ -140,15 +152,23 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
     CTP_CALL(obj) {
       const { questionID, target } = obj;
       const [prop, args] = unserialize(obj.method);
-      const val = unserialize({
-        body: JSON.stringify({
-          [QCLASS]: 'slot',
-          index: 0,
-        }),
-        slots: [target],
-      });
-      HandledPromise.applyMethod(val, prop, args)
-        .then(res =>
+      let val;
+      if (answers.has(target)) {
+        val = answers.get(target);
+      } else {
+        val = unserialize({
+          body: JSON.stringify({
+            [QCLASS]: 'slot',
+            index: 0,
+          }),
+          slots: [target],
+        });
+      }
+      const hp = args
+        ? HandledPromise.applyMethod(val, prop, args)
+        : HandledPromise.get(val, prop);
+      answers.set(questionID, hp);
+      hp.then(res =>
           send({
             type: 'CTP_RETURN',
             answerID: questionID,
@@ -198,14 +218,7 @@ export function makeCapTP(ourId, send, bootstrapObj = undefined) {
 
   // Get a reference to the other side's bootstrap object.
   const getBootstrap = () => {
-    const pr = {};
-    pr.p = new Promise((resolve, reject) => {
-      pr.res = resolve;
-      pr.rej = reject;
-    });
-    lastQuestionID += 1;
-    const questionID = lastQuestionID;
-    questions.set(questionID, pr);
+    const [questionID, pr] = makeQuestion();
     send({
       type: 'CTP_BOOTSTRAP',
       questionID,