index.js

const express = require("express");
const Database = require("better-sqlite3");
const ssbValidate = require("ssb-validate");

const app = express();
const db = new Database("db.sqlite");

const host = "localhost";
const port = 3000;

const externalHost = `http://${host}:${port}`;

const hmacKey = null;

let state = ssbValidate.initial();

db.prepare(
  "CREATE TABLE IF NOT EXISTS messages (value TEXT, author TEXT, sequence INTEGER)"
).run();

// TODO: Check for race condition.
// While this is running I think we might validate a duplicate message.
// I don't think it's a security problem, but it's not a best practice either.
db.prepare("SELECT value FROM messages")
  .all()
  .forEach((row) => {
    ssbValidate.append(state, hmacKey, JSON.parse(row.value));
  });

// JSON support.
app.use(express.json({ limit: "16MB" }));

// Return all messages.
app.get("/", (req, res) => {
  const rows = db
    .prepare(
      "SELECT author, MAX(sequence) as sequence FROM messages GROUP BY author"
    )
    .all();
  const rowsWithLink = rows.map((row) => {
    row.link = `${externalHost}/author/${encodeURIComponent(row.author)}`;
    return row;
  });
  res.send(rowsWithLink);
});

app.get("/author/:id", (req, res) => {
  const rows = db
    .prepare("SELECT value FROM messages WHERE author = ?")
    .all(req.params.id);
  res.send(rows.map((row) => JSON.parse(row.value)));
});

// Accept new messages.
app.post("/", function (req, res) {
  // Handles each message being written. Success returns true, otherwise false.
  const write = (input) => {
    const value = input.value != null ? input.value : input;

    try {
      state = ssbValidate.append(state, hmacKey, value);
      const stringValue = JSON.stringify(value);
      db.prepare(
        "INSERT INTO messages (value, author, sequence) VALUES (?, ?, ?)"
      ).run(stringValue, value.author, value.sequence);
      return true;
    } catch (err) {
      // console.log(err);
      return false;
    }
  };

  // Return number of successful writes.
  let rowsWritten;
  if (Array.isArray(req.body)) {
    rowsWritten = req.body.filter(write).length;
  } else {
    rowsWritten = Number(write(req.body));
  }

  res.send(`${rowsWritten}\n`);
});

app.listen(port, () =>
  console.log(`Example app listening at http://localhost:${port}`)
);