import express, { Request, Response } from 'express'
import multer from 'multer'
import path from 'path'
import cors from 'cors'
import http from 'http'
import * as fs from 'fs'
import basicAuth from 'express-basic-auth'
import { Server } from 'socket.io'
import logger from './utils/logger'
import { expressRequestLogger } from './utils/logger'

import {
    IChatFlow,
    IncomingInput,
    IReactFlowNode,
    IReactFlowObject,
    INodeData,
    IDatabaseExport,
    IRunChatflowMessageValue,
    IChildProcessMessage,
    ICredentialReturnResponse
} from './Interface'
import {
    getNodeModulesPackagePath,
    getStartingNodes,
    buildLangchain,
    getEndingNode,
    constructGraphs,
    resolveVariables,
    isStartNodeDependOnInput,
    getAPIKeys,
    addAPIKey,
    updateAPIKey,
    deleteAPIKey,
    compareKeys,
    mapMimeTypeToInputField,
    findAvailableConfigs,
    isSameOverrideConfig,
    replaceAllAPIKeys,
    isFlowValidForStream,
    isVectorStoreFaiss,
    databaseEntities,
    getApiKey,
    transformToCredentialEntity,
    decryptCredentialData,
    clearSessionMemory,
    replaceInputsWithConfig
} from './utils'
import { cloneDeep, omit } from 'lodash'
import { getDataSource } from './DataSource'
import { NodesPool } from './NodesPool'
import { ChatFlow } from './entity/ChatFlow'
import { ChatMessage } from './entity/ChatMessage'
import { Credential } from './entity/Credential'
import { Tool } from './entity/Tool'
import { ChatflowPool } from './ChatflowPool'
import { ICommonObject, INodeOptionsValue } from 'flowise-components'
import { fork } from 'child_process'

export class App {
    app: express.Application
    nodesPool: NodesPool
    chatflowPool: ChatflowPool
    AppDataSource = getDataSource()

    constructor() {
        this.app = express()
    }

    async initDatabase() {
        // Initialize database
        this.AppDataSource.initialize()
            .then(async () => {
                logger.info('📦 [server]: Data Source has been initialized!')

                // Initialize nodes pool
                this.nodesPool = new NodesPool()
                await this.nodesPool.initialize()

                // Initialize chatflow pool
                this.chatflowPool = new ChatflowPool()

                // Initialize API keys
                await getAPIKeys()
            })
            .catch((err) => {
                logger.error('❌ [server]: Error during Data Source initialization:', err)
            })
    }

    async config(socketIO?: Server) {
        // Limit is needed to allow sending/receiving base64 encoded string
        this.app.use(express.json({ limit: '50mb' }))
        this.app.use(express.urlencoded({ limit: '50mb', extended: true }))

        // Allow access from *
        this.app.use(cors())

        // Add the expressRequestLogger middleware to log all requests
        this.app.use(expressRequestLogger)

        if (process.env.FLOWISE_USERNAME && process.env.FLOWISE_PASSWORD) {
            const username = process.env.FLOWISE_USERNAME
            const password = process.env.FLOWISE_PASSWORD
            const basicAuthMiddleware = basicAuth({
                users: { [username]: password }
            })
            const whitelistURLs = [
                '/api/v1/verify/apikey/',
                '/api/v1/chatflows/apikey/',
                '/api/v1/public-chatflows',
                '/api/v1/prediction/',
                '/api/v1/node-icon/',
                '/api/v1/components-credentials-icon/',
                '/api/v1/chatflows-streaming'
            ]
            this.app.use((req, res, next) => {
                if (req.url.includes('/api/v1/')) {
                    whitelistURLs.some((url) => req.url.includes(url)) ? next() : basicAuthMiddleware(req, res, next)
                } else next()
            })
        }

        const upload = multer({ dest: `${path.join(__dirname, '..', 'uploads')}/` })

        // ----------------------------------------
        // Components
        // ----------------------------------------

        // Get all component nodes
        this.app.get('/api/v1/nodes', (req: Request, res: Response) => {
            const returnData = []
            for (const nodeName in this.nodesPool.componentNodes) {
                const clonedNode = cloneDeep(this.nodesPool.componentNodes[nodeName])
                returnData.push(clonedNode)
            }
            return res.json(returnData)
        })

        // Get all component credentials
        this.app.get('/api/v1/components-credentials', async (req: Request, res: Response) => {
            const returnData = []
            for (const credName in this.nodesPool.componentCredentials) {
                const clonedCred = cloneDeep(this.nodesPool.componentCredentials[credName])
                returnData.push(clonedCred)
            }
            return res.json(returnData)
        })

        // Get specific component node via name
        this.app.get('/api/v1/nodes/:name', (req: Request, res: Response) => {
            if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentNodes, req.params.name)) {
                return res.json(this.nodesPool.componentNodes[req.params.name])
            } else {
                throw new Error(`Node ${req.params.name} not found`)
            }
        })

        // Get component credential via name
        this.app.get('/api/v1/components-credentials/:name', (req: Request, res: Response) => {
            if (!req.params.name.includes('&')) {
                if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentCredentials, req.params.name)) {
                    return res.json(this.nodesPool.componentCredentials[req.params.name])
                } else {
                    throw new Error(`Credential ${req.params.name} not found`)
                }
            } else {
                const returnResponse = []
                for (const name of req.params.name.split('&')) {
                    if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentCredentials, name)) {
                        returnResponse.push(this.nodesPool.componentCredentials[name])
                    } else {
                        throw new Error(`Credential ${name} not found`)
                    }
                }
                return res.json(returnResponse)
            }
        })

        // Returns specific component node icon via name
        this.app.get('/api/v1/node-icon/:name', (req: Request, res: Response) => {
            if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentNodes, req.params.name)) {
                const nodeInstance = this.nodesPool.componentNodes[req.params.name]
                if (nodeInstance.icon === undefined) {
                    throw new Error(`Node ${req.params.name} icon not found`)
                }

                if (nodeInstance.icon.endsWith('.svg') || nodeInstance.icon.endsWith('.png') || nodeInstance.icon.endsWith('.jpg')) {
                    const filepath = nodeInstance.icon
                    res.sendFile(filepath)
                } else {
                    throw new Error(`Node ${req.params.name} icon is missing icon`)
                }
            } else {
                throw new Error(`Node ${req.params.name} not found`)
            }
        })

        // Returns specific component credential icon via name
        this.app.get('/api/v1/components-credentials-icon/:name', (req: Request, res: Response) => {
            if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentCredentials, req.params.name)) {
                const credInstance = this.nodesPool.componentCredentials[req.params.name]
                if (credInstance.icon === undefined) {
                    throw new Error(`Credential ${req.params.name} icon not found`)
                }

                if (credInstance.icon.endsWith('.svg') || credInstance.icon.endsWith('.png') || credInstance.icon.endsWith('.jpg')) {
                    const filepath = credInstance.icon
                    res.sendFile(filepath)
                } else {
                    throw new Error(`Credential ${req.params.name} icon is missing icon`)
                }
            } else {
                throw new Error(`Credential ${req.params.name} not found`)
            }
        })

        // load async options
        this.app.post('/api/v1/node-load-method/:name', async (req: Request, res: Response) => {
            const nodeData: INodeData = req.body
            if (Object.prototype.hasOwnProperty.call(this.nodesPool.componentNodes, req.params.name)) {
                try {
                    const nodeInstance = this.nodesPool.componentNodes[req.params.name]
                    const methodName = nodeData.loadMethod || ''

                    const returnOptions: INodeOptionsValue[] = await nodeInstance.loadMethods![methodName]!.call(nodeInstance, nodeData, {
                        appDataSource: this.AppDataSource,
                        databaseEntities: databaseEntities
                    })

                    return res.json(returnOptions)
                } catch (error) {
                    return res.json([])
                }
            } else {
                res.status(404).send(`Node ${req.params.name} not found`)
                return
            }
        })

        // ----------------------------------------
        // Chatflows
        // ----------------------------------------

        // Get all chatflows
        this.app.get('/api/v1/chatflows', async (req: Request, res: Response) => {
            const chatflows: IChatFlow[] = await this.AppDataSource.getRepository(ChatFlow).find()
            return res.json(chatflows)
        })

        // Get specific chatflow via api key
        this.app.get('/api/v1/chatflows/apikey/:apiKey', async (req: Request, res: Response) => {
            try {
                const apiKey = await getApiKey(req.params.apiKey)
                if (!apiKey) return res.status(401).send('Unauthorized')
                const chatflows = await this.AppDataSource.getRepository(ChatFlow)
                    .createQueryBuilder('cf')
                    .where('cf.apikeyid = :apikeyid', { apikeyid: apiKey.id })
                    .orWhere('cf.apikeyid IS NULL')
                    .orWhere('cf.apikeyid = ""')
                    .orderBy('cf.name', 'ASC')
                    .getMany()
                if (chatflows.length >= 1) return res.status(200).send(chatflows)
                return res.status(404).send('Chatflow not found')
            } catch (err: any) {
                return res.status(500).send(err?.message)
            }
        })

        // Get specific chatflow via id
        this.app.get('/api/v1/chatflows/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })
            if (chatflow) return res.json(chatflow)
            return res.status(404).send(`Chatflow ${req.params.id} not found`)
        })

        // Get specific chatflow via id (PUBLIC endpoint, used when sharing chatbot link)
        this.app.get('/api/v1/public-chatflows/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })
            if (chatflow && chatflow.isPublic) return res.json(chatflow)
            else if (chatflow && !chatflow.isPublic) return res.status(401).send(`Unauthorized`)
            return res.status(404).send(`Chatflow ${req.params.id} not found`)
        })

        // Save chatflow
        this.app.post('/api/v1/chatflows', async (req: Request, res: Response) => {
            const body = req.body
            const newChatFlow = new ChatFlow()
            Object.assign(newChatFlow, body)

            const chatflow = this.AppDataSource.getRepository(ChatFlow).create(newChatFlow)
            const results = await this.AppDataSource.getRepository(ChatFlow).save(chatflow)

            return res.json(results)
        })

        // Update chatflow
        this.app.put('/api/v1/chatflows/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })

            if (!chatflow) {
                res.status(404).send(`Chatflow ${req.params.id} not found`)
                return
            }

            const body = req.body
            const updateChatFlow = new ChatFlow()
            Object.assign(updateChatFlow, body)

            this.AppDataSource.getRepository(ChatFlow).merge(chatflow, updateChatFlow)
            const result = await this.AppDataSource.getRepository(ChatFlow).save(chatflow)

            // Update chatflowpool inSync to false, to build Langchain again because data has been changed
            this.chatflowPool.updateInSync(chatflow.id, false)

            return res.json(result)
        })

        // Delete chatflow via id
        this.app.delete('/api/v1/chatflows/:id', async (req: Request, res: Response) => {
            const results = await this.AppDataSource.getRepository(ChatFlow).delete({ id: req.params.id })
            return res.json(results)
        })

        // Check if chatflow valid for streaming
        this.app.get('/api/v1/chatflows-streaming/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })
            if (!chatflow) return res.status(404).send(`Chatflow ${req.params.id} not found`)

            /*** Get Ending Node with Directed Graph  ***/
            const flowData = chatflow.flowData
            const parsedFlowData: IReactFlowObject = JSON.parse(flowData)
            const nodes = parsedFlowData.nodes
            const edges = parsedFlowData.edges
            const { graph, nodeDependencies } = constructGraphs(nodes, edges)

            const endingNodeId = getEndingNode(nodeDependencies, graph)
            if (!endingNodeId) return res.status(500).send(`Ending node ${endingNodeId} not found`)

            const endingNodeData = nodes.find((nd) => nd.id === endingNodeId)?.data
            if (!endingNodeData) return res.status(500).send(`Ending node ${endingNodeId} data not found`)

            if (endingNodeData && endingNodeData.category !== 'Chains' && endingNodeData.category !== 'Agents') {
                return res.status(500).send(`Ending node must be either a Chain or Agent`)
            }

            const obj = {
                isStreaming: isFlowValidForStream(nodes, endingNodeData)
            }
            return res.json(obj)
        })

        // ----------------------------------------
        // ChatMessage
        // ----------------------------------------

        // Get all chatmessages from chatflowid
        this.app.get('/api/v1/chatmessage/:id', async (req: Request, res: Response) => {
            const chatmessages = await this.AppDataSource.getRepository(ChatMessage).find({
                where: {
                    chatflowid: req.params.id
                },
                order: {
                    createdDate: 'ASC'
                }
            })
            return res.json(chatmessages)
        })

        // Add chatmessages for chatflowid
        this.app.post('/api/v1/chatmessage/:id', async (req: Request, res: Response) => {
            const body = req.body
            const newChatMessage = new ChatMessage()
            Object.assign(newChatMessage, body)

            const chatmessage = this.AppDataSource.getRepository(ChatMessage).create(newChatMessage)
            const results = await this.AppDataSource.getRepository(ChatMessage).save(chatmessage)

            return res.json(results)
        })

        // Delete all chatmessages from chatflowid
        this.app.delete('/api/v1/chatmessage/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })
            if (!chatflow) {
                res.status(404).send(`Chatflow ${req.params.id} not found`)
                return
            }
            const flowData = chatflow.flowData
            const parsedFlowData: IReactFlowObject = JSON.parse(flowData)
            const nodes = parsedFlowData.nodes
            let chatId = await getChatId(chatflow.id)
            if (!chatId) chatId = chatflow.id
            clearSessionMemory(nodes, this.nodesPool.componentNodes, chatId, req.query.sessionId as string)
            const results = await this.AppDataSource.getRepository(ChatMessage).delete({ chatflowid: req.params.id })
            return res.json(results)
        })

        // ----------------------------------------
        // Credentials
        // ----------------------------------------

        // Create new credential
        this.app.post('/api/v1/credentials', async (req: Request, res: Response) => {
            const body = req.body
            const newCredential = await transformToCredentialEntity(body)
            const credential = this.AppDataSource.getRepository(Credential).create(newCredential)
            const results = await this.AppDataSource.getRepository(Credential).save(credential)
            return res.json(results)
        })

        // Get all credentials
        this.app.get('/api/v1/credentials', async (req: Request, res: Response) => {
            if (req.query.credentialName) {
                let returnCredentials = []
                if (Array.isArray(req.query.credentialName)) {
                    for (let i = 0; i < req.query.credentialName.length; i += 1) {
                        const name = req.query.credentialName[i] as string
                        const credentials = await this.AppDataSource.getRepository(Credential).findBy({
                            credentialName: name
                        })
                        returnCredentials.push(...credentials)
                    }
                } else {
                    const credentials = await this.AppDataSource.getRepository(Credential).findBy({
                        credentialName: req.query.credentialName as string
                    })
                    returnCredentials = [...credentials]
                }
                return res.json(returnCredentials)
            } else {
                const credentials = await this.AppDataSource.getRepository(Credential).find()
                const returnCredentials = []
                for (const credential of credentials) {
                    returnCredentials.push(omit(credential, ['encryptedData']))
                }
                return res.json(returnCredentials)
            }
        })

        // Get specific credential
        this.app.get('/api/v1/credentials/:id', async (req: Request, res: Response) => {
            const credential = await this.AppDataSource.getRepository(Credential).findOneBy({
                id: req.params.id
            })

            if (!credential) return res.status(404).send(`Credential ${req.params.id} not found`)

            // Decrpyt credentialData
            const decryptedCredentialData = await decryptCredentialData(
                credential.encryptedData,
                credential.credentialName,
                this.nodesPool.componentCredentials
            )
            const returnCredential: ICredentialReturnResponse = {
                ...credential,
                plainDataObj: decryptedCredentialData
            }
            return res.json(omit(returnCredential, ['encryptedData']))
        })

        // Update credential
        this.app.put('/api/v1/credentials/:id', async (req: Request, res: Response) => {
            const credential = await this.AppDataSource.getRepository(Credential).findOneBy({
                id: req.params.id
            })

            if (!credential) return res.status(404).send(`Credential ${req.params.id} not found`)

            const body = req.body
            const updateCredential = await transformToCredentialEntity(body)
            this.AppDataSource.getRepository(Credential).merge(credential, updateCredential)
            const result = await this.AppDataSource.getRepository(Credential).save(credential)

            return res.json(result)
        })

        // Delete all chatmessages from chatflowid
        this.app.delete('/api/v1/credentials/:id', async (req: Request, res: Response) => {
            const results = await this.AppDataSource.getRepository(Credential).delete({ id: req.params.id })
            return res.json(results)
        })

        // ----------------------------------------
        // Tools
        // ----------------------------------------

        // Get all tools
        this.app.get('/api/v1/tools', async (req: Request, res: Response) => {
            const tools = await this.AppDataSource.getRepository(Tool).find()
            return res.json(tools)
        })

        // Get specific tool
        this.app.get('/api/v1/tools/:id', async (req: Request, res: Response) => {
            const tool = await this.AppDataSource.getRepository(Tool).findOneBy({
                id: req.params.id
            })
            return res.json(tool)
        })

        // Add tool
        this.app.post('/api/v1/tools', async (req: Request, res: Response) => {
            const body = req.body
            const newTool = new Tool()
            Object.assign(newTool, body)

            const tool = this.AppDataSource.getRepository(Tool).create(newTool)
            const results = await this.AppDataSource.getRepository(Tool).save(tool)

            return res.json(results)
        })

        // Update tool
        this.app.put('/api/v1/tools/:id', async (req: Request, res: Response) => {
            const tool = await this.AppDataSource.getRepository(Tool).findOneBy({
                id: req.params.id
            })

            if (!tool) {
                res.status(404).send(`Tool ${req.params.id} not found`)
                return
            }

            const body = req.body
            const updateTool = new Tool()
            Object.assign(updateTool, body)

            this.AppDataSource.getRepository(Tool).merge(tool, updateTool)
            const result = await this.AppDataSource.getRepository(Tool).save(tool)

            return res.json(result)
        })

        // Delete tool
        this.app.delete('/api/v1/tools/:id', async (req: Request, res: Response) => {
            const results = await this.AppDataSource.getRepository(Tool).delete({ id: req.params.id })
            return res.json(results)
        })

        // ----------------------------------------
        // Configuration
        // ----------------------------------------

        this.app.get('/api/v1/flow-config/:id', async (req: Request, res: Response) => {
            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: req.params.id
            })
            if (!chatflow) return res.status(404).send(`Chatflow ${req.params.id} not found`)
            const flowData = chatflow.flowData
            const parsedFlowData: IReactFlowObject = JSON.parse(flowData)
            const nodes = parsedFlowData.nodes
            const availableConfigs = findAvailableConfigs(nodes, this.nodesPool.componentCredentials)
            return res.json(availableConfigs)
        })

        // ----------------------------------------
        // Export Load Chatflow & ChatMessage & Apikeys
        // ----------------------------------------

        this.app.get('/api/v1/database/export', async (req: Request, res: Response) => {
            const chatmessages = await this.AppDataSource.getRepository(ChatMessage).find()
            const chatflows = await this.AppDataSource.getRepository(ChatFlow).find()
            const apikeys = await getAPIKeys()
            const result: IDatabaseExport = {
                chatmessages,
                chatflows,
                apikeys
            }
            return res.json(result)
        })

        this.app.post('/api/v1/database/load', async (req: Request, res: Response) => {
            const databaseItems: IDatabaseExport = req.body

            await this.AppDataSource.getRepository(ChatFlow).delete({})
            await this.AppDataSource.getRepository(ChatMessage).delete({})

            let error = ''

            // Get a new query runner instance
            const queryRunner = this.AppDataSource.createQueryRunner()

            // Start a new transaction
            await queryRunner.startTransaction()

            try {
                const chatflows: ChatFlow[] = databaseItems.chatflows
                const chatmessages: ChatMessage[] = databaseItems.chatmessages

                await queryRunner.manager.insert(ChatFlow, chatflows)
                await queryRunner.manager.insert(ChatMessage, chatmessages)

                await queryRunner.commitTransaction()
            } catch (err: any) {
                error = err?.message ?? 'Error loading database'
                await queryRunner.rollbackTransaction()
            } finally {
                await queryRunner.release()
            }

            await replaceAllAPIKeys(databaseItems.apikeys)

            if (error) return res.status(500).send(error)
            return res.status(201).send('OK')
        })

        // ----------------------------------------
        // Prediction
        // ----------------------------------------

        // Send input message and get prediction result (External)
        this.app.post('/api/v1/prediction/:id', upload.array('files'), async (req: Request, res: Response) => {
            await this.processPrediction(req, res, socketIO)
        })

        // Send input message and get prediction result (Internal)
        this.app.post('/api/v1/internal-prediction/:id', async (req: Request, res: Response) => {
            await this.processPrediction(req, res, socketIO, true)
        })

        // ----------------------------------------
        // Marketplaces
        // ----------------------------------------

        // Get all chatflows for marketplaces
        this.app.get('/api/v1/marketplaces/chatflows', async (req: Request, res: Response) => {
            const marketplaceDir = path.join(__dirname, '..', 'marketplaces', 'chatflows')
            const jsonsInDir = fs.readdirSync(marketplaceDir).filter((file) => path.extname(file) === '.json')
            const templates: any[] = []
            jsonsInDir.forEach((file, index) => {
                const filePath = path.join(__dirname, '..', 'marketplaces', 'chatflows', file)
                const fileData = fs.readFileSync(filePath)
                const fileDataObj = JSON.parse(fileData.toString())
                const template = {
                    id: index,
                    name: file.split('.json')[0],
                    flowData: fileData.toString(),
                    description: fileDataObj?.description || ''
                }
                templates.push(template)
            })
            const FlowiseDocsQnA = templates.find((tmp) => tmp.name === 'Flowise Docs QnA')
            if (FlowiseDocsQnA) templates.unshift(FlowiseDocsQnA)
            return res.json(templates)
        })

        // Get all tools for marketplaces
        this.app.get('/api/v1/marketplaces/tools', async (req: Request, res: Response) => {
            const marketplaceDir = path.join(__dirname, '..', 'marketplaces', 'tools')
            const jsonsInDir = fs.readdirSync(marketplaceDir).filter((file) => path.extname(file) === '.json')
            const templates: any[] = []
            jsonsInDir.forEach((file, index) => {
                const filePath = path.join(__dirname, '..', 'marketplaces', 'tools', file)
                const fileData = fs.readFileSync(filePath)
                const fileDataObj = JSON.parse(fileData.toString())
                const template = {
                    ...fileDataObj,
                    id: index,
                    templateName: file.split('.json')[0]
                }
                templates.push(template)
            })
            return res.json(templates)
        })

        // ----------------------------------------
        // API Keys
        // ----------------------------------------

        // Get api keys
        this.app.get('/api/v1/apikey', async (req: Request, res: Response) => {
            const keys = await getAPIKeys()
            return res.json(keys)
        })

        // Add new api key
        this.app.post('/api/v1/apikey', async (req: Request, res: Response) => {
            const keys = await addAPIKey(req.body.keyName)
            return res.json(keys)
        })

        // Update api key
        this.app.put('/api/v1/apikey/:id', async (req: Request, res: Response) => {
            const keys = await updateAPIKey(req.params.id, req.body.keyName)
            return res.json(keys)
        })

        // Delete new api key
        this.app.delete('/api/v1/apikey/:id', async (req: Request, res: Response) => {
            const keys = await deleteAPIKey(req.params.id)
            return res.json(keys)
        })

        // Verify api key
        this.app.get('/api/v1/verify/apikey/:apiKey', async (req: Request, res: Response) => {
            try {
                const apiKey = await getApiKey(req.params.apiKey)
                if (!apiKey) return res.status(401).send('Unauthorized')
                return res.status(200).send('OK')
            } catch (err: any) {
                return res.status(500).send(err?.message)
            }
        })

        // ----------------------------------------
        // Serve UI static
        // ----------------------------------------

        const packagePath = getNodeModulesPackagePath('flowise-ui')
        const uiBuildPath = path.join(packagePath, 'build')
        const uiHtmlPath = path.join(packagePath, 'build', 'index.html')

        this.app.use('/', express.static(uiBuildPath))

        // All other requests not handled will return React app
        this.app.use((req, res) => {
            res.sendFile(uiHtmlPath)
        })
    }

    /**
     * Validate API Key
     * @param {Request} req
     * @param {Response} res
     * @param {ChatFlow} chatflow
     */
    async validateKey(req: Request, res: Response, chatflow: ChatFlow) {
        const chatFlowApiKeyId = chatflow.apikeyid
        const authorizationHeader = (req.headers['Authorization'] as string) ?? (req.headers['authorization'] as string) ?? ''

        if (chatFlowApiKeyId && !authorizationHeader) return res.status(401).send(`Unauthorized`)

        const suppliedKey = authorizationHeader.split(`Bearer `).pop()
        if (chatFlowApiKeyId && suppliedKey) {
            const keys = await getAPIKeys()
            const apiSecret = keys.find((key) => key.id === chatFlowApiKeyId)?.apiSecret
            if (!compareKeys(apiSecret, suppliedKey)) return res.status(401).send(`Unauthorized`)
        }
    }

    /**
     * Start child process
     * @param {ChatFlow} chatflow
     * @param {IncomingInput} incomingInput
     * @param {INodeData} endingNodeData
     */
    async startChildProcess(chatflow: ChatFlow, chatId: string, incomingInput: IncomingInput, endingNodeData?: INodeData) {
        try {
            const controller = new AbortController()
            const { signal } = controller

            let childpath = path.join(__dirname, '..', 'dist', 'ChildProcess.js')
            if (!fs.existsSync(childpath)) childpath = 'ChildProcess.ts'

            const childProcess = fork(childpath, [], { signal })

            const value = {
                chatflow,
                chatId,
                incomingInput,
                componentNodes: cloneDeep(this.nodesPool.componentNodes),
                endingNodeData
            } as IRunChatflowMessageValue
            childProcess.send({ key: 'start', value } as IChildProcessMessage)

            let childProcessTimeout: NodeJS.Timeout

            return new Promise((resolve, reject) => {
                childProcess.on('message', async (message: IChildProcessMessage) => {
                    if (message.key === 'finish') {
                        const { result, addToChatFlowPool } = message.value as ICommonObject
                        if (childProcessTimeout) {
                            clearTimeout(childProcessTimeout)
                        }
                        if (Object.keys(addToChatFlowPool).length) {
                            const { chatflowid, nodeToExecuteData, startingNodes, overrideConfig } = addToChatFlowPool
                            this.chatflowPool.add(chatflowid, nodeToExecuteData, startingNodes, overrideConfig)
                        }
                        resolve(result)
                    }
                    if (message.key === 'start') {
                        if (process.env.EXECUTION_TIMEOUT) {
                            childProcessTimeout = setTimeout(async () => {
                                childProcess.kill()
                                resolve(undefined)
                            }, parseInt(process.env.EXECUTION_TIMEOUT, 10))
                        }
                    }
                    if (message.key === 'error') {
                        let errMessage = message.value as string
                        if (childProcessTimeout) {
                            clearTimeout(childProcessTimeout)
                        }
                        reject(errMessage)
                    }
                })
            })
        } catch (err) {
            logger.error('[server] [mode:child]: Error:', err)
        }
    }

    /**
     * Process Prediction
     * @param {Request} req
     * @param {Response} res
     * @param {Server} socketIO
     * @param {boolean} isInternal
     */
    async processPrediction(req: Request, res: Response, socketIO?: Server, isInternal = false) {
        try {
            const chatflowid = req.params.id
            let incomingInput: IncomingInput = req.body

            let nodeToExecuteData: INodeData

            const chatflow = await this.AppDataSource.getRepository(ChatFlow).findOneBy({
                id: chatflowid
            })
            if (!chatflow) return res.status(404).send(`Chatflow ${chatflowid} not found`)

            let chatId = await getChatId(chatflow.id)
            if (!chatId) chatId = chatflowid

            if (!isInternal) {
                await this.validateKey(req, res, chatflow)
            }

            let isStreamValid = false

            const files = (req.files as any[]) || []

            if (files.length) {
                const overrideConfig: ICommonObject = { ...req.body }
                for (const file of files) {
                    const fileData = fs.readFileSync(file.path, { encoding: 'base64' })
                    const dataBase64String = `data:${file.mimetype};base64,${fileData},filename:${file.filename}`

                    const fileInputField = mapMimeTypeToInputField(file.mimetype)
                    if (overrideConfig[fileInputField]) {
                        overrideConfig[fileInputField] = JSON.stringify([...JSON.parse(overrideConfig[fileInputField]), dataBase64String])
                    } else {
                        overrideConfig[fileInputField] = JSON.stringify([dataBase64String])
                    }
                }
                incomingInput = {
                    question: req.body.question ?? 'hello',
                    overrideConfig,
                    history: []
                }
            }

            /*   Reuse the flow without having to rebuild (to avoid duplicated upsert, recomputation) when all these conditions met:
             * - Node Data already exists in pool
             * - Still in sync (i.e the flow has not been modified since)
             * - Existing overrideConfig and new overrideConfig are the same
             * - Flow doesn't start with nodes that depend on incomingInput.question
             ***/
            const isFlowReusable = () => {
                return (
                    Object.prototype.hasOwnProperty.call(this.chatflowPool.activeChatflows, chatflowid) &&
                    this.chatflowPool.activeChatflows[chatflowid].inSync &&
                    isSameOverrideConfig(
                        isInternal,
                        this.chatflowPool.activeChatflows[chatflowid].overrideConfig,
                        incomingInput.overrideConfig
                    ) &&
                    !isStartNodeDependOnInput(this.chatflowPool.activeChatflows[chatflowid].startingNodes)
                )
            }

            if (process.env.EXECUTION_MODE === 'child') {
                if (isFlowReusable()) {
                    nodeToExecuteData = this.chatflowPool.activeChatflows[chatflowid].endingNodeData
                    logger.debug(
                        `[server] [mode:child]: Reuse existing chatflow ${chatflowid} with ending node ${nodeToExecuteData.label} (${nodeToExecuteData.id})`
                    )
                    try {
                        const result = await this.startChildProcess(chatflow, chatId, incomingInput, nodeToExecuteData)
                        return res.json(result)
                    } catch (error) {
                        return res.status(500).send(error)
                    }
                } else {
                    try {
                        const result = await this.startChildProcess(chatflow, chatId, incomingInput)
                        return res.json(result)
                    } catch (error) {
                        return res.status(500).send(error)
                    }
                }
            } else {
                /*** Get chatflows and prepare data  ***/
                const flowData = chatflow.flowData
                const parsedFlowData: IReactFlowObject = JSON.parse(flowData)
                const nodes = parsedFlowData.nodes
                const edges = parsedFlowData.edges

                if (isFlowReusable()) {
                    nodeToExecuteData = this.chatflowPool.activeChatflows[chatflowid].endingNodeData
                    isStreamValid = isFlowValidForStream(nodes, nodeToExecuteData)
                    logger.debug(
                        `[server]: Reuse existing chatflow ${chatflowid} with ending node ${nodeToExecuteData.label} (${nodeToExecuteData.id})`
                    )
                } else {
                    /*** Get Ending Node with Directed Graph  ***/
                    const { graph, nodeDependencies } = constructGraphs(nodes, edges)
                    const directedGraph = graph
                    const endingNodeId = getEndingNode(nodeDependencies, directedGraph)
                    if (!endingNodeId) return res.status(500).send(`Ending node ${endingNodeId} not found`)

                    const endingNodeData = nodes.find((nd) => nd.id === endingNodeId)?.data
                    if (!endingNodeData) return res.status(500).send(`Ending node ${endingNodeId} data not found`)

                    if (endingNodeData && endingNodeData.category !== 'Chains' && endingNodeData.category !== 'Agents') {
                        return res.status(500).send(`Ending node must be either a Chain or Agent`)
                    }

                    if (
                        endingNodeData.outputs &&
                        Object.keys(endingNodeData.outputs).length &&
                        !Object.values(endingNodeData.outputs).includes(endingNodeData.name)
                    ) {
                        return res
                            .status(500)
                            .send(
                                `Output of ${endingNodeData.label} (${endingNodeData.id}) must be ${endingNodeData.label}, can't be an Output Prediction`
                            )
                    }

                    isStreamValid = isFlowValidForStream(nodes, endingNodeData)

                    /*** Get Starting Nodes with Non-Directed Graph ***/
                    const constructedObj = constructGraphs(nodes, edges, true)
                    const nonDirectedGraph = constructedObj.graph
                    const { startingNodeIds, depthQueue } = getStartingNodes(nonDirectedGraph, endingNodeId)

                    logger.debug(`[server]: Start building chatflow ${chatflowid}`)
                    /*** BFS to traverse from Starting Nodes to Ending Node ***/
                    const reactFlowNodes = await buildLangchain(
                        startingNodeIds,
                        nodes,
                        graph,
                        depthQueue,
                        this.nodesPool.componentNodes,
                        incomingInput.question,
                        chatId,
                        this.AppDataSource,
                        incomingInput?.overrideConfig
                    )

                    const nodeToExecute = reactFlowNodes.find((node: IReactFlowNode) => node.id === endingNodeId)
                    if (!nodeToExecute) return res.status(404).send(`Node ${endingNodeId} not found`)

                    if (incomingInput.overrideConfig)
                        nodeToExecute.data = replaceInputsWithConfig(nodeToExecute.data, incomingInput.overrideConfig)
                    const reactFlowNodeData: INodeData = resolveVariables(nodeToExecute.data, reactFlowNodes, incomingInput.question)
                    nodeToExecuteData = reactFlowNodeData

                    const startingNodes = nodes.filter((nd) => startingNodeIds.includes(nd.id))
                    this.chatflowPool.add(chatflowid, nodeToExecuteData, startingNodes, incomingInput?.overrideConfig)
                }

                const nodeInstanceFilePath = this.nodesPool.componentNodes[nodeToExecuteData.name].filePath as string
                const nodeModule = await import(nodeInstanceFilePath)
                const nodeInstance = new nodeModule.nodeClass()

                isStreamValid = isStreamValid && !isVectorStoreFaiss(nodeToExecuteData)
                logger.debug(`[server]: Running ${nodeToExecuteData.label} (${nodeToExecuteData.id})`)
                const result = isStreamValid
                    ? await nodeInstance.run(nodeToExecuteData, incomingInput.question, {
                          chatHistory: incomingInput.history,
                          socketIO,
                          socketIOClientId: incomingInput.socketIOClientId,
                          logger
                      })
                    : await nodeInstance.run(nodeToExecuteData, incomingInput.question, { chatHistory: incomingInput.history, logger })

                logger.debug(`[server]: Finished running ${nodeToExecuteData.label} (${nodeToExecuteData.id})`)
                return res.json(result)
            }
        } catch (e: any) {
            logger.error('[server]: Error:', e)
            return res.status(500).send(e.message)
        }
    }

    async stopApp() {
        try {
            const removePromises: any[] = []
            await Promise.all(removePromises)
        } catch (e) {
            logger.error(`❌[server]: Flowise Server shut down error: ${e}`)
        }
    }
}

/**
 * Get first chat message id
 * @param {string} chatflowid
 * @returns {string}
 */
export async function getChatId(chatflowid: string) {
    // first chatmessage id as the unique chat id
    const firstChatMessage = await getDataSource()
        .getRepository(ChatMessage)
        .createQueryBuilder('cm')
        .select('cm.id')
        .where('chatflowid = :chatflowid', { chatflowid })
        .orderBy('cm.createdDate', 'ASC')
        .getOne()
    return firstChatMessage ? firstChatMessage.id : ''
}

let serverApp: App | undefined

export async function start(): Promise<void> {
    serverApp = new App()

    const port = parseInt(process.env.PORT || '', 10) || 3000
    const server = http.createServer(serverApp.app)

    const io = new Server(server, {
        cors: {
            origin: '*'
        }
    })

    await serverApp.initDatabase()
    await serverApp.config(io)

    server.listen(port, () => {
        logger.info(`⚡️ [server]: Flowise Server is listening at ${port}`)
    })
}

export function getInstance(): App | undefined {
    return serverApp
}