Define QueueManager and Implement RealQueueManager

Signed-off-by: mramotar <[email protected]>

paging/core/src/commonMain/kotlin/org/mobilenativefoundation/paging/core/impl/QueueManager.kt

@@ -0,0 +1,18 @@
+package org.mobilenativefoundation.paging.core.impl
+
+import org.mobilenativefoundation.paging.core.PagingKey
+
+/**
+ * Represents a manager for the queue of pages to be loaded.
+ *
+ * @param K The type of the key used for paging.
+ * @param P The type of the parameters associated with each page of data.
+ */
+interface QueueManager<K : Any, P : Any> {
+    /**
+     * Enqueues a page key to be loaded.
+     *
+     * @param key The [PagingKey] representing the page to be loaded.
+     */
+    fun enqueue(key: PagingKey<K, P>)
+}

paging/core/src/commonMain/kotlin/org/mobilenativefoundation/paging/core/impl/RealQueueManager.kt

@@ -0,0 +1,59 @@
+package org.mobilenativefoundation.paging.core.impl
+
+import kotlinx.coroutines.flow.StateFlow
+import org.mobilenativefoundation.paging.core.FetchingStrategy
+import org.mobilenativefoundation.paging.core.Logger
+import org.mobilenativefoundation.paging.core.PagingAction
+import org.mobilenativefoundation.paging.core.PagingBuffer
+import org.mobilenativefoundation.paging.core.PagingConfig
+import org.mobilenativefoundation.paging.core.PagingKey
+
+class RealQueueManager<Id : Comparable<Id>, K : Any, P : Any, D : Any, E : Any, A : Any>(
+    pagingConfigInjector: Injector<PagingConfig>,
+    loggerInjector: OptionalInjector<Logger>,
+    dispatcherInjector: Injector<Dispatcher<Id, K, P, D, E, A>>,
+    private val fetchingStrategy: FetchingStrategy<Id, K, P, D>,
+    private val pagingBuffer: PagingBuffer<Id, K, P, D>,
+    private val anchorPosition: StateFlow<PagingKey<K, P>>,
+    private val stateManager: StateManager<Id, K, P, D, E>,
+) : QueueManager<K, P> {
+
+    private val logger = lazy { loggerInjector.inject() }
+    private val pagingConfig = lazy { pagingConfigInjector.inject() }
+    private val dispatcher = lazy { dispatcherInjector.inject() }
+
+    private val queue: ArrayDeque<PagingKey<K, P>> = ArrayDeque()
+
+    override fun enqueue(key: PagingKey<K, P>) {
+        logger.value?.log(
+            """
+            Enqueueing:
+                Key: $key
+        """.trimIndent()
+        )
+
+        queue.addLast(key)
+
+        processQueue()
+    }
+
+    private fun processQueue() {
+        while (queue.isNotEmpty() && fetchingStrategy.shouldFetch(
+                anchorPosition = anchorPosition.value,
+                prefetchPosition = stateManager.state.value.prefetchPosition,
+                pagingConfig = pagingConfig.value,
+                pagingBuffer = pagingBuffer,
+            )
+        ) {
+            val nextKey = queue.removeFirst()
+
+            logger.value?.log(
+                """Dequeued:
+                    Key: $nextKey
+                """.trimMargin(),
+            )
+
+            dispatcher.value.dispatch(PagingAction.Load(nextKey))
+        }
+    }
+}