Complete the example

Let's add the remaining parts of our client to test different functions.

We start by defining the remaining type we’ll need for querying book reviews:

type BookReview = {
  book: Book;
  reviewer_name: string;
};

Next, we define functions to query for entities and some helper functions to read input from the user:

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

function getInput(query: string): Promise<string> {
  return new Promise((resolve) => {
    rl.question(query, (answer) => {
      resolve(answer);
    });
  });
}

const getReviewsForBook = async (isbn: string) => {
  const bookList = await client.query<BookReview[]>("get_all_reviews_for_book", { isbn: isbn });
  console.log("Book review list\n", bookList);
};

const getAllTransactions = async () => {
  const transactions = await client.query("get_transactions", {});

  console.dir(transactions, {
    depth: null,
    customInspect: true, // This forces Buffer to use hex string output
  });
};

And finally, our complete main function where we add calls to create books, reviews, and fetch data:

async function main() {
  client = await createClient({
    nodeUrlPool: "http://localhost:7740",
    blockchainRid: blockchainRID,
  });

  console.log("Creating a new book transaction");
  await client.signAndSendUniqueTransaction(
    { name: "create_book", args: ["ISBN1", "Chromia 101", "John Doe"] },
    bookKeeperSignatureProvider
  );
  await getInput("Transaction committed!\nPress any key to continue...");

  console.log("Let's fetch and view all books currently in the node");
  await getAllBooks();
  await getInput("Press any key to continue...");

  console.log("We can now add a second book");
  await client.signAndSendUniqueTransaction(
    { name: "create_book", args: ["ISBN2", "Rell 101", "Jane Doe"] },
    bookKeeperSignatureProvider
  );
  await getInput("Transaction committed, press any key to continue...");

  console.log("Let's fetch and view all books currently in the node");
  await getAllBooks();
  await getInput("Press any key to continue...");

  console.log("We can now add two reviews for the book with ISBN = ISBN2");

  await client.signAndSendUniqueTransaction(
    {
      name: "create_book_review",
      args: ["ISBN2", "Bob Doe", "This is a great book!", 5],
    },
    bookKeeperSignatureProvider
  );
  await client.signAndSendUniqueTransaction(
    {
      name: "create_book_review",
      args: ["ISBN2", "Charlie Doe", "It was ok!", 3],
    },
    bookKeeperSignatureProvider
  );
  await getInput("Transaction committed, press any key to continue...");

  console.log("Let's fetch and view all reviews for ISBN2");
  await getReviewsForBook("ISBN2");
  await getInput("Press any key to continue...");

  console.log("Now let's look at all transactions that have been committed to the blockchain");
  await getAllTransactions();
  await getInput("Press any key to continue...");
  rl.close();
}

Now, we have a fully functional example to showcase how straightforward it is to implement a front-end client using Chromia and postchain-client.