Add view for filling in steps of the tour

Note, we choose to start our urls at step-1 rather than step-0 as this
is consistent when you would enter the first placeholder (excluding the
recipient) for the one off tour.

Also note, we expect a service to allow international sms by default
when it is first created but we keep the check for if the service does
just in case they visit this tour later on.

app/main/views/tour.py

@@ -1,7 +1,15 @@
-from flask import abort, render_template
+from flask import abort, redirect, render_template, session
 
 from app import current_service, current_user, url_for
 from app.main import main
+from app.main.views.send import (
+    all_placeholders_in_session,
+    fields_to_fill_in,
+    get_normalised_placeholders_from_session,
+    get_notification_check_endpoint,
+    get_placeholder_form_instance,
+    get_recipient_and_placeholders_from_session,
+)
 from app.utils import get_template, user_has_permissions
 
 
@@ -21,6 +29,8 @@ def begin_tour(service_id, template_id):
 
     template.values = {"phone_number": current_user.mobile_number}
 
+    session['placeholders'] = {}
+
     return render_template(
         'views/templates/start-tour.html',
         template=template,
@@ -35,4 +45,61 @@ def begin_tour(service_id, template_id):
 )
 @user_has_permissions('send_messages', restrict_admin_usage=True)
 def tour_step(service_id, template_id, step_index):
-    pass
+    db_template = current_service.get_template(template_id)
+
+    if db_template['template_type'] != 'sms':
+        abort(404)
+
+    template = get_template(
+        db_template,
+        current_service,
+        show_recipient=True,
+    )
+
+    placeholders = fields_to_fill_in(template, prefill_current_user=True)
+    try:
+        # user urls are 1 indexed, so start at step-1
+        current_placeholder = placeholders[step_index - 1]
+    except IndexError:
+        if all_placeholders_in_session(placeholders):
+            return get_notification_check_endpoint(service_id, template)
+        return redirect(url_for(
+            '.tour_step', service_id=current_service.id, template_id=db_template['id'], step_index=1
+        ))
+
+    form = get_placeholder_form_instance(
+        current_placeholder,
+        dict_to_populate_from=get_normalised_placeholders_from_session(),
+        template_type=template.template_type,
+        allow_international_phone_numbers=current_service.has_permission('international_sms')
+    )
+
+    if form.validate_on_submit():
+        session['placeholders'][current_placeholder] = form.placeholder_value.data
+
+        if all_placeholders_in_session(placeholders):
+            return get_notification_check_endpoint(service_id, template)
+        return redirect(url_for(
+            '.tour_step', service_id=current_service.id, template_id=db_template['id'], step_index=step_index + 1
+        ))
+
+    back_link = _get_tour_step_back_link(service_id, template_id, step_index)
+
+    template.values = get_recipient_and_placeholders_from_session(db_template['template_type'])
+    template.values[current_placeholder] = None
+
+    return render_template(
+        'views/send-test.html',
+        page_title="Example text message",
+        template=template,
+        form=form,
+        back_link=back_link,
+        help='2'
+    )
+
+
+def _get_tour_step_back_link(service_id, template_id, step_index):
+    if step_index == 1:
+        return url_for('.begin_tour', service_id=service_id, template_id=template_id)
+
+    return url_for('.tour_step', service_id=service_id, template_id=template_id, step_index=step_index - 1)