From 8c8538ff5c8e7e9c654e43a492df5c0236176e4c Mon Sep 17 00:00:00 2001
From: Jon Betts <jon.betts@hypothes.is>
Date: Mon, 7 Sep 2020 14:13:28 +0100
Subject: [PATCH] Add external_link_mode option to open links in a new tab

---
 tests/functional/proxy_test.py         | 16 ++++++++++++++++
 tests/unit/viahtml/hooks/hooks_test.py | 19 +++++++++++++++++++
 viahtml/hooks/hooks.py                 | 11 ++++++++++-
 viahtml/templates/banner.html          |  2 ++
 4 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/tests/functional/proxy_test.py b/tests/functional/proxy_test.py
index d664605c..5ee6b6f1 100644
--- a/tests/functional/proxy_test.py
+++ b/tests/functional/proxy_test.py
@@ -33,3 +33,19 @@ def test_we_do_not_have_a_csp_header(self, proxied_content):
         policy = proxied_content.headers.get("Content-Security-Policy", "*MISSING*")
 
         assert policy == "*MISSING*"
+
+    @pytest.mark.parametrize(
+        "link_mode,expected",
+        (
+            ("new-tab", "new-tab"),
+            (None, "same-tab"),
+        ),
+    )
+    def test_we_set_external_link_mode(self, app, link_mode, expected):
+        url = "/proxy/http://localhost:8080/"
+        if link_mode is not None:
+            url += f"?via.external_link_mode={link_mode}"
+
+        proxied_content = app.get(url)
+
+        assert f'setupExternalLinkHandler("{expected}");' in proxied_content
diff --git a/tests/unit/viahtml/hooks/hooks_test.py b/tests/unit/viahtml/hooks/hooks_test.py
index fdf8e46b..6fbe9321 100644
--- a/tests/unit/viahtml/hooks/hooks_test.py
+++ b/tests/unit/viahtml/hooks/hooks_test.py
@@ -10,6 +10,7 @@ class TestHooks:
     def test_template_vars(self, hooks):
         assert hooks.template_vars == {
             "client_params": Any.function(),
+            "external_link_mode": Any.function(),
             "ignore_prefixes": hooks.ignore_prefixes,
         }
 
@@ -23,6 +24,24 @@ def test_client_params_in_template_vars(self, hooks):
             assert params == "client"
             get_config.assert_called_once_with(sentinel.http_env)
 
+    @pytest.mark.parametrize(
+        "link_mode,expected",
+        (
+            ("new-tab", "new-tab"),
+            ("same-tab", "same-tab"),
+            (None, "same-tab"),
+            ("random", "random"),
+        ),
+    )
+    def test_external_link_mode_in_template_vars(self, hooks, link_mode, expected):
+        http_env = {}
+        if link_mode is not None:
+            http_env["QUERY_STRING"] = f"via.external_link_mode={link_mode}"
+
+        external_link_mode = hooks.template_vars["external_link_mode"]
+
+        assert external_link_mode(http_env) == expected
+
     def test_ignore_prefixes(self, hooks):
         assert hooks.ignore_prefixes == sentinel.prefixes
 
diff --git a/viahtml/hooks/hooks.py b/viahtml/hooks/hooks.py
index ebf099a1..f5779db8 100644
--- a/viahtml/hooks/hooks.py
+++ b/viahtml/hooks/hooks.py
@@ -16,7 +16,16 @@ def __init__(self, config):
     def template_vars(self):
         """Get variables to make available in the global Jinja2 environment."""
 
-        template_vars = {"client_params": lambda http_env: self.get_config(http_env)[1]}
+        def external_link_mode(http_env):
+            via_config, _ = self.get_config(http_env)
+            return via_config.get("external_link_mode", "same-tab").lower()
+
+        template_vars = {
+            # It would be much nicer to calculate this once somehow
+            "client_params": lambda http_env: self.get_config(http_env)[1],
+            "external_link_mode": external_link_mode,
+        }
+
         template_vars.update(self.config)
 
         # This is already in the config, but run through the property just in
diff --git a/viahtml/templates/banner.html b/viahtml/templates/banner.html
index 59ad91b2..2293f8aa 100644
--- a/viahtml/templates/banner.html
+++ b/viahtml/templates/banner.html
@@ -111,5 +111,7 @@
         var embed_script = document.createElement("script");
         embed_script.src = "{{ h_embed_url }}";
         document.head.appendChild(embed_script);
+
+        setupExternalLinkHandler({{external_link_mode(env) | tojson}});
     })();
 </script>
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