stream_data: Add has_content_access function.

This function will be used to check whether a user has access to a
channel's content in future commits.

web/src/stream_data.ts

@@ -519,6 +519,50 @@ export function has_metadata_access(sub: StreamSubscription): boolean {
     return false;
 }
 
+export function has_content_access(sub: StreamSubscription): boolean {
+    if (sub.is_web_public) {
+        return true;
+    }
+
+    if (page_params.is_spectator) {
+        return false;
+    }
+
+    if (sub.subscribed) {
+        return true;
+    }
+
+    if (!has_metadata_access(sub)) {
+        return false;
+    }
+
+    if (current_user.is_guest) {
+        /* istanbul ignore next */
+        return false;
+    }
+
+    // This is after the is_guest check, because this setting has
+    // allow_everyone_group=false.  TODO: Consider adding a
+    // is_user_in_setting_group wrapper abstraction that handles this detail automatically.
+    const can_add_subscribers = user_groups.is_user_in_setting_group(
+        sub.can_add_subscribers_group,
+        people.my_current_user_id(),
+    );
+    if (can_add_subscribers) {
+        return true;
+    }
+
+    if (sub.invite_only) {
+        return false;
+    }
+
+    // We do not do an admin check here since having admin permissions
+    // to a private channel does not give user access to that channel's
+    // content.
+
+    return true;
+}
+
 function can_administer_accessible_channel(sub: StreamSubscription): boolean {
     if (current_user.is_admin) {
         return true;

web/tests/stream_data.test.cjs

@@ -1543,3 +1543,80 @@ test("has_metadata_access", ({override}) => {
     social.subscribed = true;
     assert.equal(stream_data.has_metadata_access(social), true);
 });
+
+test("has_content_access", ({override}) => {
+    const social = {
+        subscribed: false,
+        color: "red",
+        name: "social",
+        stream_id: 2,
+        is_muted: false,
+        invite_only: false,
+        history_public_to_subscribers: false,
+        can_add_subscribers_group: nobody_group.id,
+        can_administer_channel_group: nobody_group.id,
+    };
+
+    assert.equal(stream_data.has_content_access(social), true);
+
+    social.is_web_public = true;
+    assert.equal(stream_data.has_content_access(social), true);
+    page_params.is_spectator = true;
+    assert.equal(stream_data.has_content_access(social), true);
+
+    social.is_web_public = false;
+    page_params.is_spectator = true;
+    assert.equal(stream_data.has_content_access(social), false);
+    page_params.is_spectator = false;
+    assert.equal(stream_data.has_content_access(social), true);
+
+    // Permission to administer a private channel should not give
+    // content access when unsubscribed.
+    assert.equal(stream_data.has_content_access(social), true);
+    social.invite_only = true;
+    social.subscribed = false;
+    assert.equal(stream_data.has_content_access(social), false);
+    override(current_user, "is_admin", true);
+    assert.equal(stream_data.has_content_access(social), false);
+    override(current_user, "is_admin", false);
+
+    // Channel admins should not have content access to a private
+    // channel when unsubscribed.
+    social.can_administer_channel_group = me_group.id;
+    social.subscribed = true;
+    assert.equal(stream_data.has_content_access(social), true);
+    social.subscribed = false;
+    assert.equal(stream_data.has_content_access(social), false);
+    social.can_administer_channel_group = nobody_group.id;
+
+    // Guest should not have content access to a channel they are not
+    // subscribed to.
+    social.invite_only = false;
+    override(current_user, "is_guest", true);
+    social.subscribed = true;
+    assert.equal(stream_data.has_content_access(social), true);
+    social.subscribed = false;
+    assert.equal(stream_data.has_content_access(social), false);
+    // Unless it's a web-public channel
+    social.is_web_public = true;
+    assert.equal(stream_data.has_content_access(social), true);
+    social.is_web_public = false;
+    assert.equal(stream_data.has_content_access(social), false);
+    override(current_user, "is_guest", false);
+    assert.equal(stream_data.has_content_access(social), true);
+    social.invite_only = true;
+
+    assert.equal(stream_data.has_content_access(social), false);
+    social.subscribed = true;
+    assert.equal(stream_data.has_content_access(social), true);
+
+    social.invite_only = true;
+    assert.equal(stream_data.has_content_access(social), true);
+    social.subscribed = false;
+    assert.equal(stream_data.has_content_access(social), false);
+
+    assert.equal(stream_data.has_content_access(social), false);
+    social.can_add_subscribers_group = me_group.id;
+    assert.equal(stream_data.has_content_access(social), true);
+    social.can_add_subscribers_group = nobody_group.id;
+});