Feature/sse (#3125)

* Base changes for ServerSide Events (instead of socket.io)

* lint fixes

* adding of interface and separate methods for streaming events

* lint

* first draft, handles both internal and external prediction end points.

* lint fixes

* additional internal end point for streaming and associated changes

* return streamresponse as true to build agent flow

* 1) JSON formatting for internal events
2) other fixes

* 1) convert internal event to metadata to maintain consistency with external response

* fix action and metadata streaming

* fix for error when agent flow is aborted

* prevent subflows from streaming and other code cleanup

* prevent streaming from enclosed tools

* add fix for preventing chaintool streaming

* update lock file

* add open when hidden to sse

* Streaming errors

* Streaming errors

* add fix for showing error message

---------

Co-authored-by: Henry <hzj94@hotmail.com>

packages/components/nodes/tools/ChainTool/core.ts

@@ -1,6 +1,7 @@
 import { DynamicTool, DynamicToolInput } from '@langchain/core/tools'
 import { BaseChain } from 'langchain/chains'
 import { handleEscapeCharacters } from '../../../src/utils'
+import { CustomChainHandler } from '../../../src'
 
 export interface ChainToolInput extends Omit<DynamicToolInput, 'func'> {
     chain: BaseChain
@@ -13,13 +14,42 @@ export class ChainTool extends DynamicTool {
         super({
             ...rest,
             func: async (input, runManager) => {
-                // To enable LLM Chain which has promptValues
+                // prevent sending SSE events of the sub-chain
+                const sseStreamer = runManager?.handlers.find((handler) => handler instanceof CustomChainHandler)?.sseStreamer
+                if (runManager) {
+                    const callbacks = runManager.handlers
+                    for (let i = 0; i < callbacks.length; i += 1) {
+                        if (callbacks[i] instanceof CustomChainHandler) {
+                            ;(callbacks[i] as any).sseStreamer = undefined
+                        }
+                    }
+                }
+
                 if ((chain as any).prompt && (chain as any).prompt.promptValues) {
                     const promptValues = handleEscapeCharacters((chain as any).prompt.promptValues, true)
+
                     const values = await chain.call(promptValues, runManager?.getChild())
+                    if (runManager && sseStreamer) {
+                        const callbacks = runManager.handlers
+                        for (let i = 0; i < callbacks.length; i += 1) {
+                            if (callbacks[i] instanceof CustomChainHandler) {
+                                ;(callbacks[i] as any).sseStreamer = sseStreamer
+                            }
+                        }
+                    }
                     return values?.text
                 }
-                return chain.run(input, runManager?.getChild())
+
+                const values = chain.run(input, runManager?.getChild())
+                if (runManager && sseStreamer) {
+                    const callbacks = runManager.handlers
+                    for (let i = 0; i < callbacks.length; i += 1) {
+                        if (callbacks[i] instanceof CustomChainHandler) {
+                            ;(callbacks[i] as any).sseStreamer = sseStreamer
+                        }
+                    }
+                }
+                return values
             }
         })
         this.chain = chain