Implement PagingKey and PagingData

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

paging/core/src/commonMain/kotlin/org/mobilenativefoundation/paging/core/PagingData.kt

@@ -0,0 +1,49 @@
+package org.mobilenativefoundation.paging.core
+
+
+/**
+ * Represents paging data that can be either a single item or a collection of items.
+ *
+ * @param Id The type of the unique identifier for each item.
+ * @param K The type of the key used for paging.
+ * @param P The type of the parameters associated with each page of data.
+ * @param D The type of the data items.
+ */
+sealed interface PagingData<out Id : Any, out K : Any, out P : Any, out D : Any> {
+
+    /**
+     * Represents a single item of paging data.
+     *
+     * @param Id The type of the unique identifier for the item.
+     * @param K The type of the key used for paging.
+     * @param P The type of the parameters associated with the item.
+     * @param D The type of the data item.
+     * @property id The unique identifier of the item.
+     * @property data The data item.
+     */
+    data class Single<Id : Any, K : Any, P : Any, D : Any>(
+        val id: Id,
+        val data: D
+    ) : PagingData<Id, K, P, D>
+
+    /**
+     * Represents a collection of paging data items.
+     *
+     * @param Id The type of the unique identifier for each item.
+     * @param K The type of the key used for paging.
+     * @param P The type of the parameters associated with each page of data.
+     * @param D The type of the data items.
+     * @property items The list of paging data items in the collection.
+     * @property itemsBefore The number of items before the current collection, if known.
+     * @property itemsAfter The number of items after the current collection, if known.
+     * @property prevKey The paging key of the previous page of data.
+     * @property nextKey The paging key of the next page of data, if available.
+     */
+    data class Collection<Id : Any, K : Any, P : Any, D : Any>(
+        val items: List<Single<Id, K, P, D>>,
+        val itemsBefore: Int?,
+        val itemsAfter: Int?,
+        val prevKey: PagingKey<K, P>,
+        val nextKey: PagingKey<K, P>?,
+    ) : PagingData<Id, K, P, D>
+}

paging/core/src/commonMain/kotlin/org/mobilenativefoundation/paging/core/PagingKey.kt

@@ -0,0 +1,14 @@
+package org.mobilenativefoundation.paging.core
+
+/**
+ * Represents a key used for paging along with its associated parameters.
+ *
+ * @param K The type of the key.
+ * @param P The type of the parameters.
+ * @property key The key value used for paging.
+ * @property params The parameters associated with the key.
+ */
+data class PagingKey<out K : Any, out P : Any>(
+    val key: K,
+    val params: P,
+)