fix(core): koishijs#630 simplify code

packages/core/src/session.ts

@@ -1,6 +1,6 @@
 import { Channel, Tables, User } from './database'
 import { Command } from './command'
-import { defineProperty, Logger, makeArray, observe, Promisify, Random, remove, segment } from '@koishijs/utils'
+import { defineProperty, Logger, makeArray, observe, Promisify, Random, segment } from '@koishijs/utils'
 import { Argv } from './parser'
 import { Middleware, Next } from './context'
 import { App } from './app'
@@ -94,8 +94,8 @@ export class Session<U extends User.Field = never, G extends Channel.Field = nev
   guild?: Channel.Observed<G>
   parsed?: Parsed
 
-  private _hooks: NodeJS.Timeout[]
   private _promise: Promise<string>
+  private _queued: NodeJS.Timeout
   private _queuedMessages: [string, number][]
 
   constructor(bot: Bot, session: Partial<Session.Payload>) {
@@ -168,21 +168,19 @@ export class Session<U extends User.Field = never, G extends Channel.Field = nev
   }
 
   cancelQueued() {
-    this._hooks.forEach(clearTimeout)
+    clearTimeout(this._queued)
+    this._queued = undefined
     this._queuedMessages = []
   }
 
   private _next() {
     const message = this._queuedMessages.shift()
     if (typeof message === 'undefined') return
-    remove(this._queuedMessages, message)
     this.send(message[0])
-    this._hooks.push(
-      setTimeout(() => {
-        this._hooks.shift()
-        this._next()
-      }, message[1]),
-    )
+    this._queued = setTimeout(() => {
+      this._queued = undefined
+      this._next()
+    }, message[1])
   }
 
   async sendQueued(content: string, delay?: number) {
@@ -192,7 +190,7 @@ export class Session<U extends User.Field = never, G extends Channel.Field = nev
       delay = Math.max(message, character * content.length)
     }
     this._queuedMessages.push([content, delay])
-    if (this._hooks.length === 0) this._next()
+    if (typeof this._queued === 'undefined') this._next()
   }
 
   resolveValue<T>(source: T | ((session: Session) => T)): T {