The translations history

We’re going to store every translation requested, and the result of the translation, so the user can request it back using the / history command.

We’ll also allow the user to clear the history using /clear.

Plus, calling /dnt we’ll disable storing to the history for this particular user, and using /dt we can restore this functionality.

Let’s start by storing every message in the session, with its translation, right after we get it in the message event handler:

const translation = res.data.text[0]
ctx.reply(translation)

let messages = JSON.parse(ctx.session.messages) || []
messages.push({text: ctx.message.text, translation: translation})
ctx.session.messages = JSON.stringify(messages)

Now we can add a /history command handler:

bot.command('history', ctx => {
  try {
    ctx.reply(JSON.parse(ctx.session.messages).map(message => `${message.text}: ${message.translation}`).join('\n'))
  } catch (err) {
    console.error(err)
  }
})

See how we reply to the person. We parse the messages from the session (since they are stored as JSON), then we create a new array which is formatted as text: translation, and we join the array using new lines as separators, so we are pushing a string to the user.

Let’s also add a command to clear the chat history:

bot.command('clear', ctx => {
  ctx.session.messages = JSON.stringify([])
  ctx.reply('✅ history cleared')
})

We simply assign an empty array (as an array JSON-encoded to a string).

Let’s give the user the “do not track” option by typing the /dnt command. We store a dnt flag in the session:

bot.command('dnt', ctx => {
  ctx.session.dnt = true
  ctx.reply('✅ do not track')
})

and we also add a corresponding /dt command that restores the option to the original state. By default, we do track.

bot.command('dt', ctx => {
  ctx.session.dnt = false
  ctx.reply('✅ do track')
})

Let’s now add this flag in the on('message') callback:

//...
if (ctx.session.dnt === true) {
  return
}
let messages = JSON.parse(ctx.session.messages) || []
//...

The code for the project is available at https://glitch.com/edit/#!/node-course-project-telegram-bot-b?path=bot.js

---

Go to the next lesson