Add exchanging tickets to reusable media

libpretixsync/src/main/java/eu/pretix/libpretixsync/api/PretixApi.kt

@@ -129,6 +129,7 @@ open class PretixApi(url: String, key: String, orgaSlug: String, version: Int, h
         body.put("answers", answerbody)
         body.put("questions_supported", questions_supported)
         body.put("canceled_supported", true)
+        body.put("media_exchange_supported", true)
         body.put("secret", secret)
         val jlists = JSONArray()
         for (l in lists) {

libpretixsync/src/main/java/eu/pretix/libpretixsync/check/AsyncCheckProvider.kt

@@ -781,6 +781,15 @@ class AsyncCheckProvider(private val config: ConfigStore, private val db: SyncDa
             return res
         }
 
+        val linkedReusableMedium = db.reusableMediumQueries.selectByLinkedOrderPosition(position.positionId)
+            .executeAsOneOrNull()?.toModel()
+        if (linkedReusableMedium != null) {
+            res.type = TicketCheckProvider.CheckResult.Type.ALREADY_EXCHANGED
+            res.isCheckinAllowed = false
+            storeFailedCheckin(eventSlug, list.serverId, "already_exchanged", position.secret!!, type, position = position.serverId, item = positionItem.serverId, variation = position.variationServerId, subevent = position.subEventServerId, nonce = nonce)
+            return res
+        }
+
         // !!! When extending this, also extend checkOfflineWithoutData !!!
 
         val rules = list.rules

libpretixsync/src/main/java/eu/pretix/libpretixsync/check/OnlineCheckProvider.kt

@@ -163,6 +163,8 @@ class OnlineCheckProvider(
                         res.isCheckinAllowed = includePending && response.has("position") && response.getJSONObject("position").optString("order__status", "n") == "n"
                     } else if ("product" == reason) {
                         res.type = TicketCheckProvider.CheckResult.Type.PRODUCT
+                    } else if ("already_exchanged" == reason) {
+                        res.type = TicketCheckProvider.CheckResult.Type.ALREADY_EXCHANGED
                     } else {
                         res.type = TicketCheckProvider.CheckResult.Type.ERROR
                     }

libpretixsync/src/main/java/eu/pretix/libpretixsync/check/TicketCheckProvider.kt

@@ -57,7 +57,7 @@ interface TicketCheckProvider {
     class CheckResult {
         enum class Type {
             INVALID, VALID, USED, ERROR, UNPAID, BLOCKED, INVALID_TIME, CANCELED, PRODUCT, RULES,
-            ANSWERS_REQUIRED, AMBIGUOUS, REVOKED, UNAPPROVED
+            ANSWERS_REQUIRED, AMBIGUOUS, REVOKED, UNAPPROVED, ALREADY_EXCHANGED
         }
 
         var type: Type? = null

libpretixsync/src/main/sqldelight/common/eu/pretix/libpretixsync/sqldelight/ReusableMedium.sq

@@ -22,6 +22,12 @@ WHERE ReusableMedium.identifier = :identifier
 AND ReusableMedium.type = :type
 AND orders.event_slug IN :event_slugs;
 
+selectByLinkedOrderPosition:
+SELECT ReusableMedium.*
+FROM ReusableMedium
+LEFT JOIN ReusableMedium_OrderPosition ON ReusableMedium_OrderPosition.OrderPositionId = ReusableMedium.id
+WHERE OrderPositionId = :order_position_id;
+
 deleteByServerId:
 DELETE FROM ReusableMedium
 WHERE server_id = ?;