Add form template interface and initial form template

[MAILPOET-2985]

lib/Form/Templates/InitialForm.php

@@ -0,0 +1,123 @@
+<?php
+
+namespace MailPoet\Form\Templates;
+
+class InitialForm implements Template {
+  public function getName(): string {
+    return '';
+  }
+
+  public function getBody(): array {
+    return [
+      [
+        'id' => 'email',
+        'name' => __('Email', 'mailpoet'),
+        'type' => 'text',
+        'params' => [
+          'label' => __('Email', 'mailpoet'),
+          'required' => true,
+          'label_within' => true,
+        ],
+        'styles' => [
+          'full_width' => true,
+        ],
+      ],
+      [
+        'id' => 'submit',
+        'name' => __('Submit', 'mailpoet'),
+        'type' => 'submit',
+        'params' => [
+          'label' => __('Subscribe!', 'mailpoet'),
+        ],
+        'styles' => [
+          'full_width' => true,
+        ],
+      ],
+    ];
+  }
+
+  public function getSettings(): array {
+    return [
+      'on_success' => 'message',
+      'success_message' => '',
+      'segments' => null,
+      'segments_selected_by' => 'admin',
+    ];
+  }
+
+  public function getStyles(): string {
+    return <<<EOL
+/* form */
+.mailpoet_form {
+}
+
+/* columns */
+.mailpoet_column_with_background {
+  padding: 10px;
+}
+/* space between columns */
+.mailpoet_form_column:not(:first-child) {
+  margin-left: 20px;
+}
+
+/* input wrapper (label + input) */
+.mailpoet_paragraph {
+  line-height:20px;
+  margin-bottom: 20px;
+}
+
+/* labels */
+.mailpoet_segment_label,
+.mailpoet_text_label,
+.mailpoet_textarea_label,
+.mailpoet_select_label,
+.mailpoet_radio_label,
+.mailpoet_checkbox_label,
+.mailpoet_list_label,
+.mailpoet_date_label {
+  display:block;
+  font-weight: normal;
+}
+
+/* inputs */
+.mailpoet_text,
+.mailpoet_textarea,
+.mailpoet_select,
+.mailpoet_date_month,
+.mailpoet_date_day,
+.mailpoet_date_year,
+.mailpoet_date {
+  display:block;
+}
+
+.mailpoet_text,
+.mailpoet_textarea {
+  width: 200px;
+}
+
+.mailpoet_checkbox {
+}
+
+.mailpoet_submit {
+}
+
+.mailpoet_divider {
+}
+
+.mailpoet_message {
+}
+
+.mailpoet_form_loading {
+  width: 30px;
+  text-align: center;
+  line-height: normal;
+}
+
+.mailpoet_form_loading > span {
+  width: 5px;
+  height: 5px;
+  background-color: #5b5b5b;
+}
+EOL;
+  }
+}

lib/Form/Templates/Template.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace MailPoet\Form\Templates;
+
+interface Template {
+  public function getName(): string;
+
+  public function getBody(): array;
+
+  public function getSettings(): array;
+
+  public function getStyles(): string;
+}