SpaceCache/app.js

// load configs and spaces
const config = require("./config.json");
const spaces = require("./spaces.json");

// load modules
const { setInterval } = require("node:timers/promises");
const fetch = require("node-fetch");
const express = require("express");
const { graphqlHTTP } = require('express-graphql');
const { buildSchema } = require('graphql');
const NodeCache = require("node-cache");
const jp = require('jsonpath');
const { PrismaClient } = require('@prisma/client');
const prisma = new PrismaClient();
const cors = require('cors');

// set up things
const cache = new NodeCache({ stdTTL: config.checkperiod * 3 });

let schema = buildSchema(`
  type Space {
    name: String
    id: String!
    open: Boolean!
    updatedAt: String!
  }

  type Query {
    isOpen(id: String): Boolean
    spaces: [Space!]!
  }
`);

let root = {
  isOpen: async ({ id }) => {
    let data = await prisma.space.findUnique({ where: { id: id } });
    return data.open;
  },
  spaces: async () => {
    let data = await prisma.space.findMany();
    return data;
  }
};

let app = express();

/* leaving this here for reference
app.options('/graphql', function (req, res) {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'GET,POST,OPTIONS');
  res.send(200);
});
*/

app.use(cors());

app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true,
}));

app.listen(config.port || 4000);
console.log(`Running a GraphQL API server at localhost:${config.port || 4000}/graphql`);

// CHECK LOOP
(async function () {
  await loop();
  for await (const time of setInterval(config.checkperiod * 1000)) {
    await loop();
  }
})();

async function loop() {
  console.log(new Date(), "Checking for spaces...");
  let changecount = 0;
  for (const space of spaces) {
    //console.log(`Checking ${space.id}...`);
    let response = await checkSpace(space);
    //console.log(`Space ${space.id} is ${o ? "open" : "closed"}`);
    if (typeof response.open === "undefined") {
      console.error(`The space ${space.id} might not be reachable. Please check the endpoint.`);
      continue;
    }
    if (JSON.stringify(response) != JSON.stringify(cache.get(space.id))) {
      cache.set(space.id, response);
      let update = await prisma.space.upsert({
        where: { id: space.id },
        update: { open: response.open, lastChange: response.lastchange },
        create: { id: space.id, open: response.open, lastChange: response.lastchange, name: space.name }
      });
      changecount++;
    }
  }
  console.log(new Date(), "Check complete, updated", changecount, "spaces.");
}

// HELPER FUNCTIONS
async function checkSpace(space) {
  let response, data, open;
  let lastchange = null;
  try {
    response = await fetch(space.endpoint);
    data = await response.json();
  } catch (e) { console.error(`The space ${space.id} might not be reachable. Please check the endpoint. Error: ${e}`); }

  if (!space.path) {
    try {
      open = data.state.open;
      lastchange = new Date(data.state.lastchange*1000);
    }
    catch { console.error(`The space ${space.id} is not using the SpaceAPI standard. Please specify a path.`); }
  } else {
    try { open = (jp.query(data, space.path) == (space.expected ? space.expected : true)); }
    catch { console.error(`The space ${space.id} has an invalid JSONPath to the target value. Please use https://jsonpath.com/ to evaluate the path.`); }
  }
  return { open, lastchange };
}