Define Middleware, Reducer, and Effect

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

@@ -0,0 +1,20 @@
+package org.mobilenativefoundation.paging.core
+
+/**
+ * Represents an effect that can be triggered after reducing a specific [PagingAction] and [PagingState] combination.
+ *
+ * Effects are side effects or additional actions that need to be performed after the state has been reduced based on a dispatched action.
+ * They can be used for tasks such as loading more data, updating the UI, triggering network requests, or any other side effects that depend on the current state and action.
+ *
+ * @param Id The type of the unique identifier for each item in the paged data.
+ * @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.
+ * @param E The type of errors that can occur during the paging process.
+ * @param A The type of custom actions that can be dispatched to modify the paging state.
+ * @param PA The specific type of [PagingAction] that triggers this effect.
+ * @param S The specific type of [PagingState] that triggers this effect.
+ */
+interface Effect<Id : Comparable<Id>, K : Any, P : Any, D : Any, E : Any, A : Any, PA : PagingAction<Id, K, P, D, E, A>, S : PagingState<Id, K, P, D, E>> {
+    operator fun invoke(action: PA, state: S, dispatch: (PagingAction<Id, K, P, D, E, A>) -> Unit)
+}

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

@@ -0,0 +1,29 @@
+package org.mobilenativefoundation.paging.core
+
+/**
+ * Represents a middleware that intercepts and modifies paging actions before they reach the reducer.
+ *
+ * [Middleware] allows for pre-processing, logging, or any other custom logic to be applied to actions before they are handled by the [Reducer].
+ * It can also modify or replace the action before passing it to the next [Middleware] or [Reducer].
+ *
+ * @param Id The type of the unique identifier for each item in the paged data.
+ * @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.
+ * @param E The type of errors that can occur during the paging process.
+ * @param A The type of custom actions that can be dispatched to modify the paging state.
+ */
+interface Middleware<Id : Comparable<Id>, K : Any, P : Any, D : Any, E : Any, A : Any> {
+
+    /**
+     * Applies the middleware logic to the given [action].
+     *
+     * The middleware can perform any necessary pre-processing, logging, or modification of the action
+     * before invoking the [next] function to pass the action to the next middleware or the reducer.
+     *
+     * @param action The paging action to be processed by the middleware.
+     * @param next A suspending function that should be invoked with the processed action to pass it to the next middleware or the reducer.
+     * If the middleware does not want to pass the action further, it can choose not to invoke this function.
+     */
+    suspend fun apply(action: PagingAction<Id, K, P, D, E, A>, next: suspend (PagingAction<Id, K, P, D, E, A>) -> Unit)
+}

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

@@ -0,0 +1,29 @@
+package org.mobilenativefoundation.paging.core
+
+/**
+ * The [Reducer] is responsible for taking the current [PagingState] and a dispatched [PagingAction],
+ * and producing a new [PagingState] based on the action and the current state.
+ *
+ * @param Id The type of the unique identifier for each item in the paged data.
+ * @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.
+ * @param E The type of errors that can occur during the paging process.
+ * @param A The type of custom actions that can be dispatched to modify the paging state.
+ */
+interface Reducer<Id : Comparable<Id>, K : Any, P : Any, D : Any, E : Any, A : Any> {
+    /**
+     * Reduces the current [PagingState] based on the dispatched [PagingAction] and returns a new [PagingState].
+     *
+     * This function is called whenever a [PagingAction] is dispatched to update the paging state.
+     * It should handle the action and produce a new state based on the current state and the action.
+     *
+     * @param action The dispatched [PagingAction] to be reduced.
+     * @param state The current [PagingState] before applying the action.
+     * @return The new [PagingState] after applying the action to the current state.
+     */
+    suspend fun reduce(
+        action: PagingAction<Id, K, P, D, E, A>,
+        state: PagingState<Id, K, P, D, E>
+    ): PagingState<Id, K, P, D, E>
+}