From c6fd334387753a3e6636f3ae37eb78e1bb6bde36 Mon Sep 17 00:00:00 2001
From: Nicolas Thouvenin <nthouvenin@gmail.com>
Date: Sun, 13 Dec 2020 23:12:33 +0100
Subject: [PATCH] feat: [exchange] can use one pipeline per chunk (or not)

---
 packages/analytics/src/expand.js | 71 +++++++++++++++++++++++---------
 1 file changed, 51 insertions(+), 20 deletions(-)

diff --git a/packages/analytics/src/expand.js b/packages/analytics/src/expand.js
index 4cc1a284..bbd47149 100644
--- a/packages/analytics/src/expand.js
+++ b/packages/analytics/src/expand.js
@@ -64,17 +64,37 @@ async function mergeWith(data, feed) {
  * @param {String} [script] the external pipeline is described in a string of characters
  * @param {String} [commands] the external pipeline is described in a object
  * @param {String} [command] the external pipeline is described in a URL-like command
+ * @param {String} [persistent=false] The internal database will be reused until it is deleted
+ * @param {String} [cache] Use a specific ezs statement to run commands (advanced)
  * @returns {Object}
  */
 export default async function expand(data, feed) {
-    const { ezs } = this;
+    if (this.isLast()) {
+        if (this.input) {
+            this.whenFinish.finally(() => feed.close());
+            return this.input.end();
+        }
+        return feed.close();
+    }
+
     const path = this.getParam('path');
-    if (this.isFirst()) {
-        debug('ezs')('[expand] with sub pipeline.');
+    const id = this.getIndex().toString().padStart(20, '0');
+    const value = get(data, path);
+    const { ezs } = this;
+    const persistent = this.getParam('persistent', false);
+
+    if (value === undefined) {
+        return feed.send(data);
+    }
+
+    if (!this.store) {
         const location = this.getParam('location');
         this.store = createStore(ezs, 'expand', location);
         this.store.reset();
-        const commands = ezs.createCommands({
+    }
+
+    if (!this.commands) {
+        this.commands = ezs.createCommands({
             file: this.getParam('file'),
             script: this.getParam('script'),
             command: this.getParam('command'),
@@ -82,26 +102,37 @@ export default async function expand(data, feed) {
             prepend: this.getParam('prepend'),
             append: this.getParam('append'),
         });
-        const statements = ezs.compileCommands(commands, this.getEnv());
-        this.input = ezs.createStream(ezs.objectMode());
-        const output = ezs.createPipeline(this.input, statements)
-            .pipe(ezs(mergeWith, { path }, this.store))
-            .pipe(ezs.catch());
-        this.whenFinish = feed.flow(output);
-    }
-    if (this.isLast()) {
-        this.whenFinish.finally(() => feed.close());
-        return this.input.end();
     }
     try {
-        const id = this.getIndex().toString().padStart(20, '0');
         await this.store.put(id, data);
-        const value = get(data, path);
-        if (value !== undefined) {
-            return ezs.writeTo(this.input, core(id, value), () => feed.end());
-        }
-        return feed.send(data);
     } catch (e) {
         return feed.stop(e);
     }
+
+    if (persistent) {
+        if (!this.input) {
+            debug('ezs')('[expand] with sub pipeline.');
+            this.input = ezs.createStream(ezs.objectMode());
+            const statements = ezs.compileCommands(this.commands, this.getEnv());
+            const output = ezs.createPipeline(this.input, statements)
+                .pipe(ezs(mergeWith, { path }, this.store))
+                .pipe(ezs.catch());
+            this.whenFinish = feed.flow(output);
+        }
+        return ezs.writeTo(this.input, core(id, value), () => feed.end());
+    }
+    const cache = this.getParam('cache');
+    let statements;
+    const { commands } = this;
+    if (cache) {
+        statements = [ezs(cache, { commands }, this.getEnv())];
+    } else {
+        statements = ezs.compileCommands(commands, this.getEnv());
+    }
+    const stream = ezs.createStream(ezs.objectMode());
+    const output = ezs.createPipeline(stream, statements)
+        .pipe(ezs(mergeWith, { path }, this.store))
+        .pipe(ezs.catch());
+    ezs.writeTo(stream, core(id, value), () => stream.end());
+    feed.flow(output);
 }