feat(app): gate a collapsing guild header behind an experiment (#2779)

fluxer_admin/src/routes/system_actions.rs

@@ -10,7 +10,8 @@ use crate::{
             CreateRegistrationUrlRequest, DeferredPhoneGateUpdateRequest,
             ExperimentDeliveryConfigUpdateRequest, ExpressionInfoCardConfigUpdateRequest,
             GatewayRolloutConfigUpdateRequest, GatewayRolloutMode,
-            GuildActivityLogPresentationConfigUpdateRequest, InstanceAttachmentDecayUpdateRequest,
+            GuildActivityLogPresentationConfigUpdateRequest,
+            GuildHeaderCollapseConfigUpdateRequest, InstanceAttachmentDecayUpdateRequest,
             InstanceBlueskyIntegrationUpdateRequest, InstanceBlueskyKeyIntegrationUpdateRequest,
             InstanceCaptchaIntegrationUpdateRequest, InstanceConfigUpdateRequest,
             InstanceEmailIntegrationUpdateRequest, InstanceEmailSmtpIntegrationUpdateRequest,
@@ -231,6 +232,10 @@ pub async fn instance_config_post(
             Ok(update) => instance_config_result(client.update_instance_config(&update).await),
             Err(message) => FlashData::error(message),
         },
+        "update_guild_header_collapse" => match build_guild_header_collapse_update(&form) {
+            Ok(update) => instance_config_result(client.update_instance_config(&update).await),
+            Err(message) => FlashData::error(message),
+        },
         "update_experiment_delivery" => match build_experiment_delivery_update(&form) {
             Ok(update) => instance_config_result(client.update_instance_config(&update).await),
             Err(message) => FlashData::error(message),
@@ -805,6 +810,38 @@ fn build_expression_info_card_update(
     })
 }
 
+fn build_guild_header_collapse_update(
+    form: &MultiValueForm,
+) -> Result<InstanceConfigUpdateRequest, String> {
+    Ok(InstanceConfigUpdateRequest {
+        guild_header_collapse: Some(GuildHeaderCollapseConfigUpdateRequest {
+            enabled: Some(form.bool_value("guild_header_collapse_enabled")),
+            rollout_basis_points: parse_form_number(
+                form,
+                "guild_header_collapse_rollout_basis_points",
+                "Rollout basis points",
+                0,
+                EXPERIMENT_ROLLOUT_BASIS_POINTS_MAX,
+            )?,
+            rollout_salt: parse_experiment_rollout_salt(
+                form,
+                "guild_header_collapse_rollout_salt",
+            )?,
+            included_user_ids: Some(parse_experiment_user_ids(
+                form.first("guild_header_collapse_included_user_ids")
+                    .unwrap_or_default(),
+                "Included user IDs",
+            )?),
+            excluded_user_ids: Some(parse_experiment_user_ids(
+                form.first("guild_header_collapse_excluded_user_ids")
+                    .unwrap_or_default(),
+                "Excluded user IDs",
+            )?),
+        }),
+        ..Default::default()
+    })
+}
+
 fn build_experiment_delivery_update(
     form: &MultiValueForm,
 ) -> Result<InstanceConfigUpdateRequest, String> {
@@ -1726,6 +1763,79 @@ mod tests {
         }
     }
 
+    #[test]
+    fn build_guild_header_collapse_update_reads_the_whole_form() {
+        let form = MultiValueForm::parse(
+            b"guild_header_collapse_enabled=true&guild_header_collapse_rollout_basis_points=2500&guild_header_collapse_rollout_salt=%20guild-header-collapse-v2%20&guild_header_collapse_included_user_ids=1500000000000000001%0A1500000000000000001&guild_header_collapse_excluded_user_ids=1500000000000000002%2C%201500000000000000003",
+        );
+        let update = build_guild_header_collapse_update(&form)
+            .expect("valid form")
+            .guild_header_collapse
+            .expect("guild header collapse update");
+        assert_eq!(update.enabled, Some(true));
+        assert_eq!(update.rollout_basis_points, Some(2_500));
+        assert_eq!(
+            update.rollout_salt,
+            Some("guild-header-collapse-v2".to_owned())
+        );
+        assert_eq!(
+            update.included_user_ids,
+            Some(vec!["1500000000000000001".to_owned()])
+        );
+        assert_eq!(
+            update.excluded_user_ids,
+            Some(vec![
+                "1500000000000000002".to_owned(),
+                "1500000000000000003".to_owned()
+            ])
+        );
+    }
+
+    #[test]
+    fn build_guild_header_collapse_update_leaves_the_rollout_inert_when_nothing_is_submitted() {
+        let form = MultiValueForm::parse(b"_csrf=token");
+        let request = build_guild_header_collapse_update(&form).expect("valid form");
+        assert_eq!(
+            serde_json::to_value(request).expect("serializable update"),
+            serde_json::json!({"guild_header_collapse": {
+                "enabled": false,
+                "included_user_ids": [],
+                "excluded_user_ids": [],
+            }})
+        );
+    }
+
+    #[test]
+    fn build_guild_header_collapse_update_rejects_a_rollout_above_the_maximum() {
+        let form = MultiValueForm::parse(b"guild_header_collapse_rollout_basis_points=10001");
+        assert_eq!(
+            build_guild_header_collapse_update(&form).expect_err("invalid rollout"),
+            "Rollout basis points must be a whole number between 0 and 10000"
+        );
+    }
+
+    #[test]
+    fn build_guild_header_collapse_update_reads_only_its_own_prefix() {
+        let form = MultiValueForm::parse(
+            b"guild_header_collapse_enabled=true&guild_header_collapse_rollout_basis_points=2500&guild_header_collapse_rollout_salt=guild-header-collapse-v2&guild_header_collapse_included_user_ids=1500000000000000001&expression_card_rollout_basis_points=750&expression_card_rollout_salt=expression-info-card-v2&expression_card_excluded_user_ids=1500000000000000009",
+        );
+        let update = build_guild_header_collapse_update(&form)
+            .expect("valid form")
+            .guild_header_collapse
+            .expect("guild header collapse update");
+        assert_eq!(update.enabled, Some(true));
+        assert_eq!(update.rollout_basis_points, Some(2_500));
+        assert_eq!(
+            update.rollout_salt,
+            Some("guild-header-collapse-v2".to_owned())
+        );
+        assert_eq!(
+            update.included_user_ids,
+            Some(vec!["1500000000000000001".to_owned()])
+        );
+        assert_eq!(update.excluded_user_ids, Some(Vec::new()));
+    }
+
     #[test]
     fn build_experiment_delivery_update_leaves_both_fields_unchanged_when_absent() {
         let form = MultiValueForm::parse(b"_csrf=token");