Added support for a newsletter (#2517)

In reference to idea:
https://github.com/alshedivat/al-folio/discussions/2097
In reference to request:
https://github.com/alshedivat/al-folio/issues/923#issuecomment-2171924663

Added support to integrate a [loops.so](https://loops.so/) mailing list
into the site.

To use, you need to enable `newsletter` in `_config.yml`. You also must
specify a loops endpoint (although I think any mailing list endpoint can
work), which you can get when you set up a mailing list on loops. More
documentation on loops: [here](https://loops.so/docs/forms/custom-form).

Once that is enabled, the behavior is different depending on how you
specified your footer to behave in `_config.yml`. If `footer_fixed:
true`, then the sign up will appear at the bottom of the about page, as
well as at the bottom of blog posts, if you enable `related_posts`.

If `footer_fixed: false`, then the newsletter signup will be in the
footer (on every page), like it is in on [my
website](https://asboyer.com).

I'm not attached to the placement of the signup, and you can choose to
include it wherever you want with `{% include scripts/newsletter.liquid
%}`. Also if you include positional variables into that, you can choose
how you center the signup. So `{% include scripts/newsletter.liquid
left=true %}` positions the signup bar to the left.

Here are some screenshots below:
## Dark version

![image](https://github.com/alshedivat/al-folio/assets/52665298/af7fdb81-6e5f-47a9-958b-4cb93bba9e8f)

## Light version

![image](https://github.com/alshedivat/al-folio/assets/52665298/927f8bc5-b481-448b-ae5e-6f5b1c613243)
I think the input field color should probably change to maybe be light
for both themes? What do you think? I think the dark background looks
cool, but I don't usually see that done like that on other sites.

## Footer fixed

![image](https://github.com/alshedivat/al-folio/assets/52665298/c52f3dc1-0e45-400e-8b71-eeb00d00cb01)


![image](https://github.com/alshedivat/al-folio/assets/52665298/678a2d45-88ab-4d9a-b8cc-9fc6db26d744)

## Footer not fixed

![image](https://github.com/alshedivat/al-folio/assets/52665298/fd2c0228-2bce-4335-ac3c-5cb20a3307e2)


![image](https://github.com/alshedivat/al-folio/assets/52665298/f594b4f2-67e0-4f2b-a3e8-febd579aaf19)
To clarify, if footer isn't fixed, the email signup will appear on every
page.

---------

Co-authored-by: George <31376482+george-gca@users.noreply.github.com>

_config.yml

@@ -174,6 +174,15 @@ external_sources:
       - url: https://blog.google/technology/ai/google-gemini-update-flash-ai-assistant-io-2024/
         published_date: 2024-05-14
 
+# -----------------------------------------------------------------------------
+# Newsletter
+# -----------------------------------------------------------------------------
+
+newsletter:
+  enabled: false
+  endpoint: # your loops endpoint (e.g., https://app.loops.so/api/newsletter-form/YOUR-ENDPOINT)
+  # https://loops.so/docs/forms/custom-form
+
 # -----------------------------------------------------------------------------
 # Collections
 # -----------------------------------------------------------------------------

_includes/footer.liquid

@@ -15,6 +15,10 @@
   </footer>
 {% else %}
   <footer class="sticky-bottom mt-5" role="contentinfo">
+    {% if site.newsletter.enabled %}
+      {% include scripts/newsletter.liquid %}
+    {% endif %}
+
     <div class="container">
       &copy; Copyright {{ site.time | date: '%Y' }}
       {{ site.first_name }}

_includes/related_posts.liquid

@@ -16,3 +16,7 @@
     <a class="text-pink-700 underline font-semibold hover:text-pink-800" href="{{ site.baseurl }}{{ post.url }}">{{ post.title }}</a>
   </li>
 {% endfor %}
+{% if site.newsletter.enabled and site.footer_fixed %}
+  <p class="mb-2" style="margin-top: 1.5rem !important">Subscribe to be notified of future articles:</p>
+  {% include scripts/newsletter.liquid left=true %}
+{% endif %}

_includes/scripts/newsletter.liquid

@@ -0,0 +1,176 @@
+<div
+  class="newsletter-form-container"
+  {% if include.center %}
+    style="margin: 20px"
+  {% endif %}
+>
+  <form
+    class="newsletter-form"
+    action="https://app.loops.so/api/newsletter-form/{{ site.newsletter.endpoint }}"
+    method="POST"
+    style="justify-content: {% if include.left %}flex-start{% elsif include.right %}flex-end{% else %}center{% endif %}"
+  >
+    <input
+      class="newsletter-form-input"
+      name="newsletter-form-input"
+      type="email"
+      placeholder="user@example.com"
+      required=""
+    >
+
+    <button
+      type="submit"
+      class="newsletter-form-button"
+      style="justify-content: {% if include.left %}flex-start{% elsif include.right %}flex-end{% else %}center{% endif %}"
+    >
+      subscribe
+    </button>
+
+    <button
+      type="button"
+      class="newsletter-loading-button"
+      style="justify-content: {% if include.left %}flex-start{% elsif include.right %}flex-end{% else %}center{% endif %}"
+    >
+      Please wait...
+    </button>
+  </form>
+
+  <div
+    class="newsletter-success"
+    style="justify-content: {% if include.left %}flex-start{% elsif include.right %}flex-end{% else %}center{% endif %}"
+  >
+    <p class="newsletter-success-message">You're subscribed!</p>
+  </div>
+
+  <div
+    class="newsletter-error"
+    style="justify-content: {% if include.left %}flex-start{% elsif include.right %}flex-end{% else %}center{% endif %}"
+  >
+    <p class="newsletter-error-message">Oops! Something went wrong, please try again</p>
+  </div>
+
+  <button
+    class="newsletter-back-button"
+    type="button"
+    onmouseout='this.style.textDecoration="none"'
+    onmouseover='this.style.textDecoration="underline"'
+  >
+    &larr; Back
+  </button>
+</div>
+
+<script>
+  function submitHandler(event) {
+    event.preventDefault();
+    var container = event.target.parentNode;
+    var form = container.querySelector('.newsletter-form');
+    var formInput = container.querySelector('.newsletter-form-input');
+    var success = container.querySelector('.newsletter-success');
+    var errorContainer = container.querySelector('.newsletter-error');
+    var errorMessage = container.querySelector('.newsletter-error-message');
+    var backButton = container.querySelector('.newsletter-back-button');
+    var submitButton = container.querySelector('.newsletter-form-button');
+    var loadingButton = container.querySelector('.newsletter-loading-button');
+
+    const rateLimit = () => {
+      errorContainer.style.display = 'flex';
+      errorMessage.innerText = 'Too many signups, please try again in a little while';
+      submitButton.style.display = 'none';
+      formInput.style.display = 'none';
+      backButton.style.display = 'block';
+    };
+
+    // Compare current time with time of previous sign up
+    var time = new Date();
+    var timestamp = time.valueOf();
+    var previousTimestamp = localStorage.getItem('loops-form-timestamp');
+
+    // If last sign up was less than a minute ago
+    // display error
+    if (previousTimestamp && Number(previousTimestamp) + 60000 > timestamp) {
+      rateLimit();
+      return;
+    }
+    localStorage.setItem('loops-form-timestamp', timestamp);
+
+    submitButton.style.display = 'none';
+    loadingButton.style.display = 'flex';
+
+    var formBody = 'userGroup=&email=' + encodeURIComponent(formInput.value);
+    fetch(event.target.action, {
+      method: 'POST',
+      body: formBody,
+      headers: {
+        'Content-Type': 'application/x-www-form-urlencoded',
+      },
+    })
+      .then((res) => [res.ok, res.json(), res])
+      .then(([ok, dataPromise, res]) => {
+        if (ok) {
+          // If response successful
+          // display success
+          success.style.display = 'flex';
+          form.reset();
+        } else {
+          // If response unsuccessful
+          // display error message or response status
+          dataPromise.then((data) => {
+            errorContainer.style.display = 'flex';
+            errorMessage.innerText = data.message ? data.message : res.statusText;
+          });
+        }
+      })
+      .catch((error) => {
+        // check for cloudflare error
+        if (error.message === 'Failed to fetch') {
+          rateLimit();
+          return;
+        }
+        // If error caught
+        // display error message if available
+        errorContainer.style.display = 'flex';
+        if (error.message) errorMessage.innerText = error.message;
+        localStorage.setItem('loops-form-timestamp', '');
+      })
+      .finally(() => {
+        formInput.style.display = 'none';
+        loadingButton.style.display = 'none';
+        backButton.style.display = 'block';
+      });
+  }
+  function resetFormHandler(event) {
+    var container = event.target.parentNode;
+    var formInput = container.querySelector('.newsletter-form-input');
+    var success = container.querySelector('.newsletter-success');
+    var errorContainer = container.querySelector('.newsletter-error');
+    var errorMessage = container.querySelector('.newsletter-error-message');
+    var backButton = container.querySelector('.newsletter-back-button');
+    var submitButton = container.querySelector('.newsletter-form-button');
+
+    success.style.display = 'none';
+    errorContainer.style.display = 'none';
+    errorMessage.innerText = 'Oops! Something went wrong, please try again';
+    backButton.style.display = 'none';
+    formInput.style.display = 'flex';
+    submitButton.style.display = 'flex';
+  }
+
+  var formContainers = document.getElementsByClassName('newsletter-form-container');
+
+  for (var i = 0; i < formContainers.length; i++) {
+    var formContainer = formContainers[i];
+    var handlersAdded = formContainer.classList.contains('newsletter-handlers-added');
+    if (handlersAdded) continue;
+    formContainer.querySelector('.newsletter-form').addEventListener('submit', submitHandler);
+    formContainer.querySelector('.newsletter-back-button').addEventListener('click', resetFormHandler);
+    formContainer.classList.add('newsletter-handlers-added');
+  }
+</script>
+
+<noscript>
+  <style>
+    .newsletter-form-container {
+      display: none;
+    }
+  </style>
+</noscript>

_layouts/about.liquid

@@ -72,5 +72,9 @@ layout: default
         <div class="contact-note">{{ site.contact_note }}</div>
       </div>
     {% endif %}
+
+    {% if site.newsletter.enabled and site.footer_fixed %}
+      {% include scripts/newsletter.liquid center=true %}
+    {% endif %}
   </article>
 </div>

_sass/_base.scss

@@ -1128,13 +1128,127 @@ ninja-keys {
   --ninja-modal-background: var(--global-bg-color);
   --ninja-z-index: 1031;
 }
+
 ninja-keys::part(ninja-input) {
   color: var(--ninja-selected-text-color);
 }
+
 ninja-keys::part(ninja-input-wrapper) {
   background: var(--global-bg-color);
 }
 
+// newsletter
+.newsletter-form-container {
+  margin-bottom: 20px;
+}
+
+.newsletter-form {
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  width: 100%;
+}
+
+.newsletter-form-input {
+  color: var(--global-newsletter-text-color);
+  background: var(--global-newsletter-bg-color);
+  border: 1px solid var(--global-newsletter-text-color);
+  outline: none;
+  margin: 0px 10px 0px 0px;
+  width: 100%;
+  max-width: 350px;
+  min-width: 100px;
+  box-sizing: border-box;
+  box-shadow: rgba(0, 0, 0, 0.05) 0px 1px 2px;
+  border-radius: 6px;
+  padding: 8px 12px;
+}
+
+.newsletter-form-input:focus {
+  border-color: var(--global-theme-color) !important;
+}
+
+.newsletter-form-button {
+  background: var(--global-theme-color);
+  color: var(--global-bg-color);
+  display: flex;
+  width: min-content;
+  max-width: 200px;
+  white-space: nowrap;
+  height: 38px;
+  align-items: center;
+  flex-direction: row;
+  padding: 9px 17px;
+  box-shadow: rgba(0, 0, 0, 0.05) 0px 1px 2px;
+  border-radius: 6px;
+  text-align: center;
+  font-style: normal;
+  font-weight: 500;
+  line-height: 20px;
+  border: none;
+  cursor: pointer;
+}
+
+.newsletter-loading-button {
+  background: var(--global-theme-color);
+  color: var(--global-bg-color);
+  display: none;
+  width: min-content;
+  max-width: 300px;
+  white-space: nowrap;
+  height: 38px;
+  align-items: center;
+  flex-direction: row;
+  padding: 9px 17px;
+  box-shadow: rgba(0, 0, 0, 0.05) 0px 1px 2px;
+  border-radius: 6px;
+  text-align: center;
+  font-style: normal;
+  font-weight: 500;
+  line-height: 20px;
+  border: none;
+  cursor: pointer;
+  margin-right: 20px;
+}
+
+.newsletter-success {
+  color: var(--global-text-color);
+  display: none;
+  align-items: center;
+  width: 100%;
+}
+
+.newsletter-error {
+  color: var(--global-theme-color);
+  display: none;
+  align-items: center;
+  width: 100%;
+}
+
+.newsletter-back-button {
+  color: var(--global-theme-color);
+  margin: 10px auto;
+  text-align: center;
+  display: none;
+  background: transparent;
+  border: none;
+  cursor: pointer;
+}
+
+@media (max-width: 575px) {
+  .newsletter-form-input,
+  .newsletter-form-button,
+  .newsletter-loading-button,
+  .newsletter-success,
+  .newsletter-error {
+    font-size: 16px !important;
+  }
+  .newsletter-form-container {
+    margin-right: 20px;
+    margin-left: 20px;
+  }
+}
+
 // popover is used for annotation in bib.liquid
 .popover {
   background-color: var(--global-bg-color);
@@ -1144,25 +1258,30 @@ ninja-keys::part(ninja-input-wrapper) {
     color: var(--global-text-color); // Header text color
     border-bottom: 1px solid var(--global-divider-color);
   }
+
   .popover-body {
     color: var(--global-text-color); // Body text color
   }
 }
+
 .bs-popover-top {
   // arrow fill color
   .arrow::after {
     border-top-color: var(--global-bg-color);
   }
+
   // arrow border color
   .arrow:before {
     border-top-color: var(--global-divider-color);
   }
 }
+
 .bs-popover-bottom {
   // arrow fill color
   .arrow::after {
     border-bottom-color: var(--global-bg-color);
   }
+
   // arrow border color
   .arrow:before {
     border-bottom-color: var(--global-divider-color);

_sass/_themes.scss

@@ -19,6 +19,8 @@
   --global-highlight-color: #{$red-color-dark};
   --global-back-to-top-bg-color: rgba(#{red($black-color)}, #{green($black-color)}, #{blue($black-color)}, 0.4);
   --global-back-to-top-text-color: #{$white-color};
+  --global-newsletter-bg-color: #{$white-color};
+  --global-newsletter-text-color: #{$black-color};
 
   --global-tip-block: #42b983;
   --global-tip-block-bg: #e2f5ec;
@@ -81,6 +83,8 @@ html[data-theme="dark"] {
   --global-card-bg-color: #{$grey-900};
   --global-back-to-top-bg-color: rgba(#{red($white-color)}, #{green($white-color)}, #{blue($white-color)}, 0.5);
   --global-back-to-top-text-color: #{$black-color};
+  --global-newsletter-bg-color: #{$grey-color-light};
+  --global-newsletter-text-color: #{$grey-color-dark};
 
   --global-tip-block: #42b983;
   --global-tip-block-bg: #e2f5ec;