// client/app.js: the page's script. It calls the backend on the same
// address, so the browser sends the sign-in cookie with each request.

// The rows' name, and the route that adds and lists the signed-in user's rows.
const PLURAL = 'notes';
const ROUTE = '/api/notes';

// The fields of one row, each with its kind: the form's inputs and the list's columns.
const FIELDS = [{ name: 'title', kind: 'text' }];

// The input each kind of field takes.
const INPUT_TYPES = { text: 'text', integer: 'number', boolean: 'checkbox', timestamp: 'datetime-local' };

// Why the AI model gave no answer, by the error the route answers with 503.
const UNANSWERED = {
  allowance_drawn: "This month's AI allowance is drawn, so the model gives no answer until it resets.",
  allowance_unavailable: 'The platform holds no key for the AI allowance yet, so the model gives no answer now.',
  upstream_quota: 'The AI model is out of capacity now: ask again in a while.',
};

const byId = (id) => document.getElementById(id);

// A field's value as the route takes it: a string, a number, true or false, or an ISO time.
function valueOf(field, input) {
  if (field.kind === 'boolean') return input.checked;
  if (input.value === '') return field.kind === 'text' ? '' : null;
  if (field.kind === 'integer') return Number(input.value);
  if (field.kind === 'timestamp') return new Date(input.value).toISOString();
  return input.value;
}

// The signed-in user, from the platform's own route: null where no one is signed in.
async function signedInUser() {
  const response = await fetch('/__account/me');
  if (response.status === 200) return (await response.json()).user;
  if (response.status === 404) {
    byId('who').textContent = "This address serves no sign-in. Sign-in is on the application's deployed address; a local run's API routes take a session as a Bearer.";
    return undefined;
  }
  return null;
}

async function showRows() {
  const response = await fetch(ROUTE);
  const list = byId('rows');
  list.replaceChildren();
  if (response.status !== 200) return;
  for (const row of await response.json()) {
    const item = document.createElement('li');
    item.textContent = FIELDS.map((field) => (FIELDS.length === 1 ? String(row[field.name]) : `${field.name}: ${row[field.name]}`)).join(', ');
    list.append(item);
  }
}

function buildForm() {
  const inputs = FIELDS.map((field) => {
    const label = document.createElement('label');
    label.textContent = field.name;
    const input = document.createElement('input');
    input.type = INPUT_TYPES[field.kind];
    input.name = field.name;
    if (field.kind !== 'boolean') input.required = true;
    label.append(input);
    byId('fields').append(label);
    return input;
  });
  byId('add').addEventListener('submit', async (event) => {
    event.preventDefault();
    const row = Object.fromEntries(FIELDS.map((field, index) => [field.name, valueOf(field, inputs[index])]));
    const response = await fetch(ROUTE, { method: 'POST', headers: { 'content-type': 'application/json' }, body: JSON.stringify(row) });
    const error = byId('add-error');
    error.hidden = response.status === 201;
    if (response.status !== 201) {
      error.textContent = `The row was not added (status ${response.status}).`;
      return;
    }
    byId('add').reset();
    await showRows();
  });
}

function buildAsk() {
  byId('ask').addEventListener('submit', async (event) => {
    event.preventDefault();
    const answer = byId('answer');
    answer.textContent = 'Asking.';
    const response = await fetch('/api/ask', { method: 'POST', headers: { 'content-type': 'application/json' }, body: JSON.stringify({ question: byId('question').value }) });
    if (response.status === 200) answer.textContent = (await response.json()).answer;
    else if (response.status === 503) answer.textContent = UNANSWERED[(await response.json()).error] ?? 'The AI model gave no answer now.';
    else answer.textContent = `The question was not answered (status ${response.status}).`;
  });
}

async function start() {
  const user = await signedInUser();
  if (user === undefined) return;
  if (user === null) {
    byId('who').textContent = 'No one is signed in.';
    byId('sign-in').hidden = false;
    return;
  }
  const address = user.addresses?.find((held) => held.verified)?.email;
  byId('who').textContent = `Signed in as ${address ?? user.id}.`;
  byId('sign-out').hidden = false;
  byId('rows-title').textContent = `Your ${PLURAL}`;
  byId('signed-in').hidden = false;
  buildForm();
  buildAsk();
  await showRows();
}

start();