Add UI for exporting user account data

snikket_web/templates/user_home.html

@@ -30,6 +30,7 @@
 			<div>
 				<div>{% call standard_button("edit", url_for(".profile"), class="primary") %}{% trans %}Edit profile{% endtrans %}{% endcall %}</div>
 				<div>{% call standard_button("passwd", url_for(".change_pw"), class="secondary") %}{% trans %}Change password{% endtrans %}{% endcall %}</div>
+				<div>{% call standard_button("folder", url_for(".manage_data"), class="secondary") %}{% trans %}Manage your data{% endtrans %}{% endcall %}</div>
 			</div>
 			{#- -#}
 		</li>

snikket_web/templates/user_manage_data.html

@@ -0,0 +1,23 @@
+{% extends "app.html" %}
+{% from "library.j2" import standard_button, form_button, render_errors, avatar with context %}
+{% block content %}
+<h1>{% trans %}Manage your data{% endtrans %}</h1>
+<p>{% trans user_name=user_info.display_name %}Welcome home, {{ user_name }}.{% endtrans %}</p>
+<nav class="welcome">
+	<ul>
+		<li>
+			<h2>{% trans %}Export account{% endtrans %}</h2>
+			<p>{% trans %}Download your account data as a file for backup purposes or to move your account to another service.{% endtrans %}</p>
+
+			{% call render_errors(form) %}{% endcall %}
+
+			<div class="f-bbox">
+				<form method="POST">
+					{{ form.csrf_token }}
+					{%- call form_button("download", form.action_export, class="primary") %}{% endcall -%}
+				</form>
+			</div>
+		</li>
+	</ul>
+</nav>
+{% endblock %}

snikket_web/user.py

@@ -1,9 +1,12 @@
+import aiohttp
 import asyncio
 import typing
+import urllib
 
 import quart.flask_patch
 from quart import (
     Blueprint,
+    Response,
     render_template,
     request,
     redirect,
@@ -168,6 +171,50 @@ async def profile() -> typing.Union[str, quart.Response]:
                                  avatar_too_big_warning=EAVATARTOOBIG)
 
 
+class DataExportForm(BaseForm):
+    action_export = wtforms.SubmitField(
+        _l("Export")
+    )
+
+
+@bp.route("/manage_data", methods=["GET", "POST"])
+@client.require_session()
+async def manage_data() -> typing.Union[str, quart.Response]:
+    form = DataExportForm()
+
+    if form.validate_on_submit():
+        user_info = await client.get_user_info()
+        # The UTF-8 version of the filename needs to be percent-encoded
+        encoded_address = urllib.parse.quote(
+            user_info["address"].encode(encoding='utf-8', errors='strict')
+        )
+        try:
+            account_data = await client.export_account_data()
+        except aiohttp.ClientResponseError as e:
+            if e.status == 404:
+                await flash(
+                    _("You currently have no account data to export."),
+                    "alert"
+                )
+            else:
+                raise e
+        else:
+            return Response(account_data,
+                            mimetype="application/xml",
+                            headers={
+                                # We provide the UTF-8 filename, but the ASCII
+                                # one will be used as a fallback for legacy
+                                # browsers (RFC 5987)
+                                "Content-Disposition": (
+                                    'attachment; filename="account-data.xml"; '
+                                    'filename*="UTF-8\'\'account-data-{}.xml"'
+                                ).format(encoded_address)
+                            })
+    return await render_template("user_manage_data.html",
+                                 form=form,
+                                 )
+
+
 @bp.route("/logout", methods=["GET", "POST"])
 @client.require_session()
 async def logout() -> typing.Union[quart.Response, str]: