move the 'getOlderHistory' call into the database worker

lib/workers/compute-index.js

@@ -144,9 +144,53 @@ const computeMetadata = function (data, cb, errorHandler) {
     });
 };
 
+/*  getOlderHistory
+    * allows clients to query for all messages until a known hash is read
+    * stores all messages in history as they are read
+      * can therefore be very expensive for memory
+      * should probably be converted to a streaming interface
+
+    Used by:
+    * GET_HISTORY_RANGE
+*/
+
+const getOlderHistory = function (data, cb) {
+    const oldestKnownHash = data.hash;
+    const channelName = data.channel;
+
+    //const store = Env.store;
+    //const Log = Env.Log;
+    var messageBuffer = [];
+    var found = false;
+    store.getMessages(channelName, function (msgStr) {
+        if (found) { return; }
+
+        let parsed = tryParse(Env, msgStr);
+        if (typeof parsed === "undefined") { return; }
+
+        // identify classic metadata messages by their inclusion of a channel.
+        // and don't send metadata, since:
+        // 1. the user won't be interested in it
+        // 2. this metadata is potentially incomplete/incorrect
+        if (HK.isMetadataMessage(parsed)) { return; }
+
+        var content = parsed[4];
+        if (typeof(content) !== 'string') { return; }
+
+        var hash = HK.getHash(content);
+        if (hash === oldestKnownHash) {
+            found = true;
+        }
+        messageBuffer.push(parsed);
+    }, function (err) {
+        cb(err, messageBuffer);
+    });
+};
+
 const COMMANDS = {
     COMPUTE_INDEX: computeIndex,
     COMPUTE_METADATA: computeMetadata,
+    GET_OLDER_HISTORY: getOlderHistory,
 };
 
 process.on('message', function (data) {