feat: add automatical saving conversation in local storage

[mejsiejdev]

No description provided.

[chewmanji]

May you request review from Maciej King also?

[chewmanji]

I think we'll need list of chats in local storage {"chats" : chat[]} where each one have uuid, prompt and other data related to response from api - it will allow us to generate sidebar items easily

[maciejkrol18]

The amount of code in the onClick callback can be reduced. Notice how this piece of code repeats two times:

localStorage.setItem(
  "chats",
  JSON.stringify([
    ...chats,
    { uuid: newUuid, prompt: text, recommendation: {} },
  ]),
);

I think it's always best to stick to the DRY principle (do not repeat yourself). Here's my take on the callback function - from 17 to 8 lines, and it works the same:

onClick={() => {
  setIsSubmitting(true);
  const newUuid = v4();  
  const chats = localStorage.getItem("chats") == null ? [] : JSON.parse(localStorage.getItem("chats")!) as Chat[]
  localStorage.setItem(
    "chats",
    JSON.stringify([
      ...chats,
      { uuid: newUuid, prompt: text, recommendation: {} },
    ]),
  );
  router.push(`/chat/${newUuid}`);
}}

I'll try my best to explain the thought process behind my changes:

const chats = localStorage.getItem("chats") == null ? [] : JSON.parse(localStorage.getItem("chats")!) as Chat[]

This line removes the need for the entire if block and utilizes a ternary operator instead. If a given local storage key doesn't exist then .getItem() method returns null, otherwise the json string, therefore we explicitly check whether .getItem("chats") is null (this also makes eslint rule @typescript/strict-boolean-expressions happy).

If true ("chats" are null)
it means no chats were saved yet, so we set "chats" variable to an empty array, therefore no type assertions are needed

If false ("chats" are not null)
it means at least one chat is saved, so we set "chats" variable to the parsed json string. Here we still use non-null assertion since typescript still thinks that .getItem("chats") can be null + we do a type assertion since JSON.parse() return type is any

localStorage.setItem(
  "chats",
  JSON.stringify([
    ...chats,
    { uuid: newUuid, prompt: text, recommendation: {} },
  ]),
);

And then we just set the "chats" local storage item to an array consisting of already existing chats and the newly created one. If "chats" variable is an empty array then we can still spread it without a problem.

This solution is compliant with our linter rules and passes all checks

EDIT: This is of course more of a nitpick and such refactor could be done later but since our project won't take that long and it isn't too complex we might as well tweak such things early on