From 806614d697d011ba3a689ec57fd868cf15bccb63 Mon Sep 17 00:00:00 2001
From: Adam Rybinski <adam.rybins@gmail.com>
Date: Tue, 2 Nov 2021 09:22:06 +0100
Subject: [PATCH] Update paginationMachine.js

---
 paginationMachine.js | 182 +++++++++++++++++++++++++++----------------
 1 file changed, 117 insertions(+), 65 deletions(-)

diff --git a/paginationMachine.js b/paginationMachine.js
index a82fe53..c977adc 100644
--- a/paginationMachine.js
+++ b/paginationMachine.js
@@ -1,71 +1,123 @@
-import { assign, createMachine } from './deps.js';
+import { assign, createMachine } from 'xstate';
+import { choose } from 'xstate/lib/actions';
 
-const infiniteScrollMachine = createMachine({
-  id: 'infiniteScroll',
-  initial: 'fetchingRowOfData',
-  context: {
-    totalEntries: Infinity,
-    data: []
-  },
-  states: {
-    fetchingRowOfData: {
-      on: {
-        RECEIVED_DATA: {
-          target: 'checkingIfThereIsMoreData',
-          actions: ['assignDataToContext']
-        }
-      },
-      invoke: {
-        src: 'fetchRowOfData',
-        onError: {
-          target: 'idle',
-          actions: 'assignErrorMessageToContext'
-        }
-      }
+export interface PaginationMachineContext {
+  totalPages?: number;
+  /**
+   * This page is 1-indexed, not 0-indexed
+   */
+  currentPage: number;
+}
+
+export type PaginationMachineEvent =
+  | {
+      type: 'UPDATE_TOTAL_PAGES';
+      totalPages: number;
+    }
+  | {
+      type: 'NEXT_PAGE';
+    }
+  | {
+      type: 'PREV_PAGE';
+    }
+  | {
+      type: 'GO_TO_TARGET_PAGE';
+      targetPage: number;
+    };
+
+const paginationMachine = createMachine<
+  PaginationMachineContext,
+  PaginationMachineEvent
+>(
+  {
+    id: 'pagination',
+    initial: 'awaitingTotalPages',
+    context: {
+      currentPage: 1,
     },
-    idle: {
-      exit: ['clearErrorMessage'],
-      on: {
-        SCROLL_TO_BOTTOM: 'fetchingRowOfData'
-      }
+    on: {
+      UPDATE_TOTAL_PAGES: {
+        cond: 'newTotalPagesIsValidValue',
+        actions: choose([
+          {
+            cond: 'currentPageIsAboveNewTotalPages',
+            actions: ['assignTotalPagesToContext', 'goToFirstPage'],
+          },
+          {
+            actions: ['assignTotalPagesToContext'],
+          },
+        ]),
+        target: 'idle',
+      },
     },
-    checkingIfThereIsMoreData: {
-      always: [{
-        cond: 'thereIsMoreData',
-        target: 'idle'
-      }, {
-        target: 'noMoreDataToFetch'
-      }]
+    states: {
+      awaitingTotalPages: {},
+      idle: {
+        on: {
+          NEXT_PAGE: {
+            cond: 'canGoToNextPage',
+            actions: 'goToNextPage',
+          },
+          PREV_PAGE: {
+            cond: 'canGoToPrevPage',
+            actions: 'goToPrevPage',
+          },
+          GO_TO_TARGET_PAGE: {
+            actions: 'goToTargetPage',
+            cond: 'targetPageIsWithinBounds',
+          },
+        },
+      },
     },
-    noMoreDataToFetch: {
-      type: 'final'
-    }
-  }
-}, {
-  guards: {
-    thereIsMoreData: context => {
-      return context.totalEntries > context.data.length;
-    }
   },
-  services: {
-    fetchRowOfData: () => send => {}
+  {
+    guards: {
+      newTotalPagesIsValidValue: (context, event) => {
+        if (event.type !== 'UPDATE_TOTAL_PAGES') return false;
+
+        return event.totalPages > 0;
+      },
+      currentPageIsAboveNewTotalPages: (context, event) => {
+        if (event.type !== 'UPDATE_TOTAL_PAGES') return false;
+
+        return context.currentPage > event.totalPages;
+      },
+      canGoToNextPage: (context) => {
+        return context.currentPage < context.totalPages;
+      },
+      canGoToPrevPage: (context) => {
+        return context.currentPage > 1;
+      },
+      targetPageIsWithinBounds: (context, event) => {
+        if (event.type !== 'GO_TO_TARGET_PAGE') return false;
+        return event.targetPage >= 1 && event.targetPage <= context.totalPages;
+      },
+    },
+    actions: {
+      goToFirstPage: assign({
+        currentPage: 1,
+      }),
+      goToPrevPage: assign({
+        currentPage: (context) => context.currentPage - 1,
+      }),
+      goToNextPage: assign({
+        currentPage: (context) => context.currentPage + 1,
+      }),
+      goToTargetPage: assign((context, event) => {
+        if (event.type !== 'GO_TO_TARGET_PAGE') return {};
+
+        return {
+          currentPage: event.targetPage,
+        };
+      }),
+      assignTotalPagesToContext: assign((context, event) => {
+        if (event.type !== 'UPDATE_TOTAL_PAGES') return {};
+        return {
+          totalPages: event.totalPages,
+        };
+      }),
+    },
   },
-  actions: {
-    assignDataToContext: assign((context, event) => {
-      if (event.type !== 'RECEIVED_DATA') return {};
-      return {
-        data: [...context.data, ...event.data],
-        totalEntries: event.totalEntries
-      };
-    }),
-    clearErrorMessage: assign(context => ({
-      errorMessage: undefined
-    })),
-    assignErrorMessageToContext: assign((context, event) => {
-      return {
-        errorMessage: event.data?.message || 'An unknown error occurred'
-      };
-    })
-  }
-});
-export default infiniteScrollMachine;
+);
+
+export default paginationMachine;