From a4bd44de9ed4197366cbcf2360293ea41a01523f Mon Sep 17 00:00:00 2001
From: schroda <50052685+schroda@users.noreply.github.com>
Date: Sat, 25 Nov 2023 15:35:26 +0100
Subject: [PATCH] Correctly merge chapter requests (#474)

A re-fetch wasn't correctly detected which resulted in outdated data to be shown.
The pageInfo was also not correctly merged, which resulted in losing the previous response start cursor and "has previous page" info
---
 src/lib/requests/client/GraphQLClient.ts | 61 ++++++++++++++----------
 1 file changed, 37 insertions(+), 24 deletions(-)

diff --git a/src/lib/requests/client/GraphQLClient.ts b/src/lib/requests/client/GraphQLClient.ts
index 3473fb76..3fb64f85 100644
--- a/src/lib/requests/client/GraphQLClient.ts
+++ b/src/lib/requests/client/GraphQLClient.ts
@@ -6,14 +6,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  */
 
-import {
-    ApolloClient,
-    ApolloClientOptions,
-    InMemoryCache,
-    NormalizedCacheObject,
-    Reference,
-    split,
-} from '@apollo/client';
+import { ApolloClient, ApolloClientOptions, InMemoryCache, NormalizedCacheObject, split } from '@apollo/client';
 import { createUploadLink } from 'apollo-upload-client';
 import { GraphQLWsLink } from '@apollo/client/link/subscriptions';
 import { Client, createClient } from 'graphql-ws';
@@ -33,23 +26,43 @@ const typePolicies: StrictTypedTypePolicies = {
             chapters: {
                 keyArgs: ['condition', 'filter', 'orderBy', 'orderByType'],
                 merge(existing, incoming) {
-                    const merged = {
-                        ...existing,
-                        ...incoming,
-                        nodes: existing?.nodes ?? [],
-                    };
-                    const isRefetch = incoming.nodes.some(
-                        (incomingChapter) =>
-                            existing?.nodes.some(
-                                (existingChapter) =>
-                                    (existingChapter as unknown as Reference).__ref ===
-                                    (incomingChapter as unknown as Reference).__ref,
-                            ),
-                    );
-                    if (!isRefetch) {
-                        merged.nodes = [...(existing?.nodes ?? []), ...incoming.nodes];
+                    if (existing == null) {
+                        return incoming;
                     }
-                    return merged;
+
+                    const isReFetch = !incoming.pageInfo.hasPreviousPage;
+                    const hasLessItems = existing.nodes.length > incoming.nodes.length;
+
+                    const useIncomingResponse = isReFetch && !hasLessItems;
+                    if (useIncomingResponse) {
+                        return incoming;
+                    }
+
+                    const replaceExistingItems = isReFetch && hasLessItems;
+                    if (replaceExistingItems) {
+                        const existingWithReplacedIncoming: typeof incoming = {
+                            ...existing,
+                            pageInfo: {
+                                ...existing.pageInfo,
+                                startCursor: incoming.pageInfo.startCursor,
+                            },
+                            nodes: [...incoming.nodes, ...existing.nodes.slice(incoming.nodes.length)],
+                        };
+
+                        return existingWithReplacedIncoming;
+                    }
+
+                    const existingWithAppendedIncoming: typeof incoming = {
+                        ...existing,
+                        pageInfo: {
+                            ...existing.pageInfo,
+                            endCursor: incoming.pageInfo.endCursor,
+                            hasNextPage: incoming.pageInfo.hasNextPage,
+                        },
+                        nodes: [...existing.nodes, ...incoming.nodes],
+                    };
+
+                    return existingWithAppendedIncoming;
                 },
             },
         },