Testing LRU cache

terpal-sql-native/src/commonTest/kotlin/io/exoquery/sql/native/LruCacheSpec.kt

@@ -1,10 +1,77 @@
 package io.exoquery.sql.native
 
-// TODO
+import app.cash.sqldelight.internal.currentThreadId
+import io.exoquery.sql.encodingdata.shouldBe
+import io.exoquery.sql.sqlite.LruCache
+import kotlinx.coroutines.CompletableDeferred
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
 class LruCacheSpec {
-  // ------------ This should cover our current use-case of the cache ------------
-  // make a reference map of 1M values (immutable)
-  // launch 1000 tasks to put 1000 random key/values each
-  // make sure all the values are right
-  // (check that evications have only happened due to a trim, never a new-value since the initial values are static)
+
+  data class RemoveData(val wasEvicted: Boolean, val key: String, val oldValue: String, val newValue: String?)
+
+  fun createCacheAndRemovals(cacheSize: Int): Pair<LruCache<String, String>, MutableList<RemoveData>> {
+    val removals = mutableListOf<RemoveData>()
+    val cache = LruCache<String, String>(cacheSize) { wasEvicted, key, oldValue, newValue -> removals.add(RemoveData(wasEvicted, key, oldValue, newValue)) }
+    return Pair(cache, removals)
+  }
+
+  @Test
+  fun testSimple() {
+    val (cache, removals) = createCacheAndRemovals(2)
+    cache.put("a", "1")
+    cache.put("b", "2")
+    cache.put("c", "3")
+    cache.get("a") shouldBe null
+    cache.get("b") shouldBe "2"
+    cache.get("c") shouldBe "3"
+    removals shouldBe listOf(RemoveData(true, "a", "1", null))
+  }
+
+  @Test
+  fun testEviction() {
+    val (cache, removals) = createCacheAndRemovals(3)
+    cache.put("a", "1")
+    cache.put("b", "2")
+    cache.put("a", "11")
+    cache.put("c", "3")
+    cache.get("a") shouldBe "11"
+    cache.get("b") shouldBe "2"
+    cache.get("c") shouldBe "3"
+    cache.get("other") shouldBe null
+    // Note that should be false because the value was updated, not evicted
+    removals shouldBe listOf(RemoveData(false, "a", "1", "11"))
+  }
+
+
+  @Test
+  fun testLRUCacheEvictionInMultithreadedCode(): Unit = runBlocking {
+    val cacheSize = 100
+    val (lruCache, removeList) = createCacheAndRemovals(cacheSize)
+    val countDownLatch = CompletableDeferred<Unit>()
+
+    // Launch multiple coroutines to simulate concurrent cache operations
+    val jobs = (0 until cacheSize).map { key ->
+      val newKey = "value$key"
+      launch {
+        //println("Thread:[${currentThreadId()}], Key=[$newKey], Val=[$key]")
+        lruCache.put(newKey, "$key")
+      }
+    }
+
+    // Wait for all coroutines to finish
+    jobs.forEach { it.join() }
+
+    // Ensure that all keys inserted can be retrieved
+    (0 until cacheSize).forEach { i ->
+      val expectedValue = lruCache.get("value$i")
+      assertEquals("$i", expectedValue, "Expected $i but got $expectedValue for key value$i")
+    }
+
+    countDownLatch.complete(Unit) // Signal that the test has finished
+  }
+
 }