Transaction Durability and Write Transaction Mutual Exclusion (#137)

* Expose transaction durability, fix write transaction exclusion

* Durability jsValue as extension val

* Use cheaper dummy query for mutex

core/src/jsMain/kotlin/Database.kt

@@ -64,10 +64,12 @@ public class Database internal constructor(internal val database: IDBDatabase) {
      */
     public suspend fun <T> transaction(
         vararg store: String,
+        durability: Durability = Durability.Default,
         action: suspend Transaction.() -> T,
     ): T = withContext(Dispatchers.Unconfined) {
-        @Suppress("UNCHECKED_CAST") // What a silly cast. Apparently `vararg` creates `Array<out String>` instead of `Array<String>`
-        val transaction = Transaction(database.transaction(store as Array<String>, "readonly"))
+        val transaction = Transaction(
+            database.transaction(arrayOf(*store), "readonly", transactionOptions(durability)),
+        )
         val result = transaction.action()
         transaction.awaitCompletion()
         result
@@ -81,10 +83,18 @@ public class Database internal constructor(internal val database: IDBDatabase) {
      */
     public suspend fun <T> writeTransaction(
         vararg store: String,
+        durability: Durability = Durability.Default,
         action: suspend WriteTransaction.() -> T,
     ): T = withContext(Dispatchers.Unconfined) {
-        @Suppress("UNCHECKED_CAST") // What a silly cast. Apparently `vararg` creates `Array<out String>` instead of `Array<String>`
-        val transaction = WriteTransaction(database.transaction(store as Array<String>, "readwrite"))
+        val transaction = WriteTransaction(
+            database.transaction(arrayOf(*store), "readwrite", transactionOptions(durability)),
+        )
+        with(transaction) {
+            // Force overlapping transactions to not call `action` until prior transactions complete.
+            objectStore(store.first())
+                .openKeyCursor(autoContinue = false)
+                .collect { it.close() }
+        }
         val result = transaction.action()
         transaction.awaitCompletion()
         result
@@ -94,3 +104,7 @@ public class Database internal constructor(internal val database: IDBDatabase) {
         database.close()
     }
 }
+
+private fun transactionOptions(durability: Durability): dynamic = jso {
+    this.durability = durability.jsValue
+}

core/src/jsMain/kotlin/Durability.kt

@@ -0,0 +1,19 @@
+package com.juul.indexeddb
+
+import com.juul.indexeddb.Durability.Default
+import com.juul.indexeddb.Durability.Relaxed
+import com.juul.indexeddb.Durability.Strict
+
+/** https://developer.mozilla.org/en-US/docs/Web/API/IDBTransaction/durability */
+public enum class Durability {
+    Default,
+    Strict,
+    Relaxed,
+}
+
+internal val Durability.jsValue: String
+    get() = when (this) {
+        Default -> "default"
+        Strict -> "strict"
+        Relaxed -> "relaxed"
+    }

external/src/jsMain/kotlin/IDBDatabase.kt

@@ -11,5 +11,5 @@ public external class IDBDatabase : EventTarget {
     public fun createObjectStore(name: String): IDBObjectStore
     public fun createObjectStore(name: String, options: dynamic): IDBObjectStore
     public fun deleteObjectStore(name: String)
-    public fun transaction(storeNames: Array<String>, mode: String): IDBTransaction
+    public fun transaction(storeNames: Array<String>, mode: String, options: dynamic): IDBTransaction
 }