Stacks API Integrations

HTTP calls within Stacks

Stacks can integrate with APIs exposed over HTTP.

The functions get, post, put and patch do HTTP calls. HTTP calls allow for the following parameters:

card GetCard, then: PostCard do
    get_response = get("https://example.org/endpoint",
    timeout: 5_000,
    cache_ttl: 60_000,
    query: [
      ["name", "@contact.name"],
                ["whatsapp_id", "@contact.whatsapp_id"]
            ])

        log("@get_response")
end

card PostCard, then: PutCard do
    post_response = post("https://example.org/endpoint",
    timeout: 5_000,
    cache_ttl: 60_000,
    body: """
      {"username": @contact.whatsapp_id}
          """,
      headers: [["content-type", "application/json"]]
      )

    log("@post_response")
end

card PutCard, then: PatchCard do
    put_response = put("https://example.org/endpoint",
      timeout: 5_000,
      cache_ttl: 60_000,
      body: """
      {"username": @contact.whatsapp_id}
            """,
      headers: [["content-type", "application/json"]]
      )

    log("@put_response")
end

card PatchCard do
    patch_response = patch("https://example.org/endpoint",
      timeout: 5_000,
      cache_ttl: 60_000,
      body: """
        {"username": @contact.whatsapp_id}
            """,
        headers: [["content-type", "application/json"]]
        )

    log("@patch_response")
end

option	use
body	The body of the HTTP request
cache_ttl	How long to cache a response for, in milliseconds (60_000 or 60000 is 60 seconds)
headers	A list of lists with HTTP headers, [["X-Foo", "Bar"]] would add the X-Foo header to the HTTP request.
mode	"sync" or "async"
query	A list of lists with keys & values to use as query parameters [[key, value]] adds ?key=value to the request
timeout	How long a request is allowed to take, in milliseconds (5_000 or 5000 is 5 seconds)
url	The HTTP endpoint

The HTTP headers and query parameters can be expressions that are evaluated.

HTTP Connection Errors

If the remote side of your HTTP call times out or drops the connection, the status of the response will be set to null and the body attribute of the response will have the error that occurred.

info

It is the stack author's responsibility to make sure connection errors and timeouts are handled gracefully in order to ensure a good user experience.

Here's an example of handling a connection error:

card Webhook, then: Report do
    resp =
      post("https://example.org",
        body: "hello world!",
        timeout: 10,
        query: [["foo", "bar"]],
        headers: [
          ["content-type", "text/plain; charset=utf-8"]
        ]
      )
end

card Report when not resp.status do
    text("""
    Apologies, it looks like we are having some connection errors.
    The response error was ```@resp.body```

    Please try again later!
    """)
end

card Report do
    text("success")
end

RSS feed integration

Here is an example that reads the RSS feed for the BBC's Global News Podcast and allows users to navigate through the episodes and listen to them.

card Init, "⏮ Latest episode", then: Start do
    # Initialize the cursor with a value of zero, this means we always start
    # with the first, most recent, entry from the RSS feed
    cursor = 0
    # Use the public API at rss2json.com to convert the RSS feed that the
    # BBC publishes for their world service podcast to a JSON file that
    # we can read.
    webhook =
      get(
        "https://api.rss2json.com/v1/api.json?rss_url=https%3A%2F%2Fpodcasts.files.bbci.co.uk%2Fp02nq0gn.rss"
      )

    items = webhook.body.items
    # Keep track of the total number of items
    total_items = count(items)
end

card Start do
    # Read the current item
    item = items[cursor]

    # send the audio file first, since this is a _big_ file it takes longer to arrive
    # on the phone than the messages we send later.
    audio("@item.enclosure.link")

    # generate the buttons
    buttons([Init, NextCard]) do
        # send the title as a caption
        text("""
        *@item.title*

        @item.content

        _Episode @(cursor + 1) of @(total_items)_
        _Published at @(item.pubDate)_
        """)
        # The feed unfortunately doesn't have images and so we're just using a static
        # image from the BBC website
        image("https://ichef.bbci.co.uk/images/ic/480x270/p09kz0v5.jpg")
    end
  end

  # We change the text on the button depending on whether or not we have any further
  # episodes. If we do we display "Next episode ➡️", if we don't we display "⏮ First episode"
  #
  # Also if we reach the end of the total number of episodes, we reset the counter to 0
  # which has us starting at the beginning again.
card NextCard, "@IF(cursor + 1 < total_items, \"Next episode ➡️\", \"⏮ First episode\")",
    then: Start do
    cursor = if cursor + 1 < total_items, do: cursor + 1, else: 0
end