reorder citations in Vectara response

packages/components/nodes/chains/VectaraChain/VectaraChain.ts

@@ -5,6 +5,42 @@ import { Document } from 'langchain/document'
 import { VectaraStore } from 'langchain/vectorstores/vectara'
 import fetch from 'node-fetch'
 
+// functionality based on https://github.com/vectara/vectara-answer
+const reorderCitations = (unorderedSummary: string) => {
+    const allCitations = unorderedSummary.match(/\[\d+\]/g) || [];
+  
+    const uniqueCitations = [...new Set(allCitations)];
+    const citationToReplacement: { [key: string]: string } = {};
+    uniqueCitations.forEach((citation, index) => {
+      citationToReplacement[citation] = `[${index + 1}]`;
+    });
+  
+    return unorderedSummary.replace(
+      /\[\d+\]/g,
+      (match) => citationToReplacement[match]
+    );
+};
+const applyCitationOrder = (
+    searchResults: any[],
+    unorderedSummary: string
+  ) => {
+    const orderedSearchResults: any[] = [];
+    const allCitations = unorderedSummary.match(/\[\d+\]/g) || [];
+  
+    const addedIndices = new Set<number>();
+    for (let i = 0; i < allCitations.length; i++) {
+      const citation = allCitations[i];
+      const index = Number(citation.slice(1, citation.length - 1)) - 1;
+  
+      if (addedIndices.has(index)) continue;
+      orderedSearchResults.push(searchResults[index]);
+      addedIndices.add(index);
+    }
+  
+    return orderedSearchResults;
+};
+        
+
 class VectaraChain_Chains implements INode {
     label: string
     name: string
@@ -254,7 +290,7 @@ class VectaraChain_Chains implements INode {
             const result = await response.json()
             const responses = result.responseSet[0].response
             const documents = result.responseSet[0].document
-            let summarizedText = ''
+            let rawSummarizedText = ''
 
             for (let i = 0; i < responses.length; i += 1) {
                 const responseMetadata = responses[i].metadata
@@ -287,9 +323,12 @@ class VectaraChain_Chains implements INode {
                 throw new Error(`BAD REQUEST: summarizer ${summarizerPromptName} is invalid for this account.`)
             }
 
-            summarizedText = result.responseSet[0].summary[0]?.text
+            rawSummarizedText = result.responseSet[0].summary[0]?.text
 
-            const sourceDocuments: Document[] = responses.map(
+            let summarizedText = reorderCitations(rawSummarizedText);
+            let summaryResponses = applyCitationOrder(responses, rawSummarizedText);            
+        
+            const sourceDocuments: Document[] = summaryResponses.map(
                 (response: { text: string; metadata: Record<string, unknown>; score: number }) =>
                     new Document({
                         pageContent: response.text,