compute metadata in the same child process that builds indexes

lib/workers/compute-index.js

@@ -5,6 +5,7 @@ const HK = require("../hk-util");
 const Store = require("../storage/file");
 const Util = require("../common-util");
 const nThen = require("nthen");
+const Meta = require("../metadata");
 
 const Env = {};
 
@@ -46,7 +47,13 @@ const tryParse = function (Env, str) {
             * including the initial metadata line, if it exists
 
 */
-const computeIndex = function (channelName, cb) {
+const computeIndex = function (data, cb) {
+    if (!data || !data.channel) {
+        return void cb('E_NO_CHANNEL');
+    }
+
+    const channelName = data.channel;
+
     const cpIndex = [];
     let messageBuf = [];
     let i = 0;
@@ -125,45 +132,60 @@ const computeIndex = function (channelName, cb) {
     });
 };
 
+const computeMetadata = function (data, cb, errorHandler) {
+    const ref = {};
+    const lineHandler = Meta.createLineHandler(ref, errorHandler);
+    return void store.readChannelMetadata(data.channel, lineHandler, function (err) {
+        if (err) {
+            // stream errors?
+            return void cb(err);
+        }
+        cb(void 0, ref.meta);
+    });
+};
+
+const COMMANDS = {
+    COMPUTE_INDEX: computeIndex,
+    COMPUTE_METADATA: computeMetadata,
+};
+
 process.on('message', function (data) {
     if (!data || !data.txid) {
         return void process.send({
             error:'E_INVAL'
         });
     }
-    const txid = data.txid;
 
-    if (!ready) {
-        return void init(data.config, function (err) {
-            if (err) {
-                return void process.send({
-                    txid: txid,
-                    error: err,
-                });
-            }
-            ready = true;
-            process.send({txid: txid,});
-        });
-    }
-
-    const channel = data.args;
-    if (!channel) {
-        return void process.send({
-            error: 'E_NO_CHANNEL',
-        });
-    }
-
-    // computeIndex
-    computeIndex(channel, function (err, index) {
+    const cb = function (err, value) {
         if (err) {
             return void process.send({
-                txid: txid,
+                txid: data.txid,
                 error: err,
             });
         }
-        return void process.send({
-            txid: txid,
-            value: index,
+        process.send({
+            txid: data.txid,
+            value: value,
+        });
+    };
+
+    if (!ready) {
+        return void init(data.config, function (err) {
+            if (err) { return void cb(err); }
+            ready = true;
+            cb();
+        });
+    }
+
+    const command = COMMANDS[data.command];
+    if (typeof(command) !== 'function') {
+        return void cb("E_BAD_COMMAND");
+    }
+    command(data, cb, function (label, info) {
+        // for streaming errors
+        process.send({
+            error: label,
+            value: info,
         });
     });
 });