//
// Copyright © 2023 Hardcore Engineering Inc.
//
// Licensed under the Eclipse Public License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License. You may
// obtain a copy of the License at https://www.eclipse.org/legal/epl-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//
// See the License for the specific language governing permissions and
// limitations under the License.
//

// uWebSockets.js
// Import should be added: "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.23.0"

import { MeasureContext, generateId } from '@hcengineering/core'
import { Token, decodeToken } from '@hcengineering/server-token'

import { serialize } from '@hcengineering/rpc'
import uWebSockets, { SHARED_COMPRESSOR, WebSocket } from 'uWebSockets.js'
import { getStatistics } from './stats'
import {
  ConnectionSocket,
  HandleRequestFunction,
  LOGGING_ENABLED,
  PipelineFactory,
  Session,
  SessionManager
} from './types'

interface WebsocketUserData {
  wrapper?: ConnectionSocket
  payload: Token
  session?: Promise<Session>
  backPressure?: Promise<void>
  backPressureResolve?: () => void
  unsendMsg: any[]
}

/**
 * @public
 * @param port -
 * @param host -
 */
export function startUWebsocketServer (
  sessions: SessionManager,
  handleRequest: HandleRequestFunction,
  ctx: MeasureContext,
  pipelineFactory: PipelineFactory,
  port: number,
  productId: string
): () => Promise<void> {
  if (LOGGING_ENABLED) console.log(`starting U server on port ${port} ...`)

  const uAPP = uWebSockets.App()

  uAPP
    .ws<WebsocketUserData>('/*', {
    /* There are many common helper features */
    // idleTimeout: 32,
    // maxBackpressure: 1024,
    maxPayloadLength: 50 * 1024 * 1024,
    compression: SHARED_COMPRESSOR,
    maxLifetime: 0,
    sendPingsAutomatically: true,

    upgrade (res, req, context) {
      const url = new URL('http://localhost' + (req.getUrl() ?? ''))
      const token = url.pathname.substring(1)

      try {
        const payload = decodeToken(token ?? '')

        if (payload.workspace.productId !== productId) {
          throw new Error('Invalid workspace product')
        }

        /* This immediately calls open handler, you must not use res after this call */
        res.upgrade<WebsocketUserData>(
          {
            payload,
            session: undefined,
            unsendMsg: []
          },
          /* Spell these correctly */
          req.getHeader('sec-websocket-key'),
          req.getHeader('sec-websocket-protocol'),
          req.getHeader('sec-websocket-extensions'),
          context
        )
      } catch (err) {
        if (LOGGING_ENABLED) console.error('invalid token', err)
        res.writeStatus('401 Unauthorized').end()
      }
    },
    open: (ws: WebSocket<WebsocketUserData>) => {
      const data = ws.getUserData()
      data.wrapper = {
        id: generateId(),
        close: () => {
          try {
            ws.close()
          } catch (err) {
            // Ignore closed
          }
        },
        send: async (ctx, msg): Promise<void> => {
          await ctx.with('backpressure', {}, async () => await data.backPressure)
          const serialized = await ctx.with('serialize', {}, async () => serialize(msg))
          ctx.measure('send-data', serialized.length)
          try {
            const sendR = await ctx.with('backpressure', {}, async () =>
              ws.send(serialized, false, Array.isArray(msg.result))
            )
            if (sendR === 2) {
              data.backPressure = new Promise((resolve) => {
                data.backPressureResolve = resolve
              })
              data.unsendMsg.push(msg)
            }
          } catch (err: any) {
            if (!((err.message ?? '') as string).includes('Invalid access of closed')) {
              console.error(err)
            }
            // Ignore socket is closed
          }
        }
      }

      data.session = sessions.addSession(
        ctx,
        data.wrapper,
        ws.getUserData().payload,
        pipelineFactory,
        productId,
        undefined
      )
    },
    message: (ws, message, isBinary) => {
      const data = ws.getUserData()
      const enc = new TextDecoder('utf-8')
      const tmsg = enc.decode(message)

      void data.session?.then((s) => {
        void handleRequest(ctx, s, data.wrapper as ConnectionSocket, tmsg, data.payload.workspace.name)
      })
    },
    drain: (ws) => {
      console.log(`WebSocket backpressure: ${ws.getBufferedAmount()}`)
      const data = ws.getUserData()
      while (data.unsendMsg.length > 0) {
        if (ws.send(data.unsendMsg[0]) !== 1) {
          data.unsendMsg.shift()
        } else {
          // Wait for next drain.
          return
        }
      }
      data.backPressureResolve?.()
      data.backPressure = undefined
    },
    close: (ws, code, message) => {
      const enc = new TextDecoder('utf-8')
      const data = ws.getUserData()
      try {
        const tmsg = enc.decode(message)
        if (tmsg !== undefined && tmsg !== '') {
          console.error(tmsg)
        }
      } catch (err) {
        console.error(err)
      }
      void data.session?.then((s) => {
        void sessions.close(ctx, data.wrapper as ConnectionSocket, data.payload.workspace, code, '')
      })
    }
  })
    .any('/*', (response, request) => {
      const url = new URL('http://localhost' + (request.getUrl() ?? ''))

      const token = url.pathname.substring(1)
      try {
        const payload = decodeToken(token ?? '')
        console.log(payload.workspace, 'statistics request')

        const json = JSON.stringify(getStatistics(ctx, sessions))

        response
          .writeStatus('200 OK')
          .writeHeader('Content-Type', 'application/json')
          .writeHeader('Access-Control-Allow-Origin', '*')
          .writeHeader('Access-Control-Allow-Methods', 'GET, OPTIONS')
          .writeHeader('Access-Control-Allow-Headers', 'Content-Type')
          .end(json)
      } catch (err) {
        response.writeHead(404, {})
        response.end()
      }
    })
    .listen(port, (s) => {})

  return async () => {
    await sessions.closeWorkspaces(ctx)
  }
}