Merge pull request #73 from madscience/fixed-offset

Support fixed offset pagination (page = 1...n)
equalogic · Jun 1, 2020 · 5c017ec · 5c017ec
2 parents e84152f + dd1c91b
commit 5c017ec
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Showing 3 changed files with 57 additions and 5 deletions.
diff --git a/src/cursor/OffsetCursorPaginator.spec.ts b/src/cursor/OffsetCursorPaginator.spec.ts
@@ -51,4 +51,23 @@ describe('OffsetCursorPaginator', () => {
     expect(pageInfo.endCursor).toBeDefined();
     expect(OffsetCursor.create(pageInfo.endCursor!).parameters.offset).toStrictEqual(49);
   });
+
+  test('PageInfo is correct for fixed offset pagination', () => {
+    const paginator = OffsetCursorPaginator.createFromConnectionArgs(
+      {
+        first: 20,
+        page: 4,
+      },
+      100,
+    );
+    const pageInfo = paginator.createPageInfo(20);
+
+    expect(pageInfo.totalEdges).toBe(100);
+    expect(pageInfo.hasPreviousPage).toBe(true);
+    expect(pageInfo.hasNextPage).toBe(true);
+    expect(pageInfo.startCursor).toBeDefined();
+    expect(OffsetCursor.create(pageInfo.startCursor!).parameters.offset).toStrictEqual(60);
+    expect(pageInfo.endCursor).toBeDefined();
+    expect(OffsetCursor.create(pageInfo.endCursor!).parameters.offset).toStrictEqual(79);
+  });
 });
diff --git a/src/cursor/OffsetCursorPaginator.ts b/src/cursor/OffsetCursorPaginator.ts
@@ -36,6 +36,11 @@ export class OffsetCursor extends Cursor {
   }
 }
 
+interface CreateFromConnectionArgsOptions {
+  defaultEdgesPerPage?: number;
+  maxEdgesPerPage?: number;
+}
+
 export class OffsetCursorPaginator {
   public take: number = 20;
   public skip: number = 0;
@@ -62,21 +67,41 @@ export class OffsetCursorPaginator {
   }
 
   public static createFromConnectionArgs(
-    { first, last, before, after }: ConnectionArgs,
+    { page, first, last, before, after }: ConnectionArgs,
     totalEdges: number,
+    options: CreateFromConnectionArgsOptions = {},
   ): OffsetCursorPaginator {
-    let take: number = 20;
+    const { defaultEdgesPerPage = 20, maxEdgesPerPage = 100 } = options;
+    let take: number = defaultEdgesPerPage;
     let skip: number = 0;
 
     if (first != null) {
-      if (first > 100 || first < 1) {
-        throw new ConnectionArgsValidationError('The "first" argument accepts a value between 1 and 100, inclusive.');
+      if (first > maxEdgesPerPage || first < 1) {
+        throw new ConnectionArgsValidationError(
+          `The "first" argument accepts a value between 1 and ${maxEdgesPerPage}, inclusive.`,
+        );
       }
 
       take = first;
       skip = 0;
     }
 
+    if (page != null) {
+      if (last != null || after != null || before != null) {
+        throw new ConnectionArgsValidationError(
+          `The "page" argument cannot be used together with "last", "after" or "before".`,
+        );
+      }
+
+      if (page < 1) {
+        throw new ConnectionArgsValidationError(
+          `The "page" argument accepts only a positive integer greater than zero.`,
+        );
+      }
+
+      skip = take * (page - 1);
+    }
+
     if (last != null) {
       if (first != null) {
         throw new ConnectionArgsValidationError(
@@ -85,7 +110,9 @@ export class OffsetCursorPaginator {
       }
 
       if (last > 100 || last < 1) {
-        throw new ConnectionArgsValidationError('The "last" argument accepts a value between 1 and 100, inclusive.');
+        throw new ConnectionArgsValidationError(
+          `The "last" argument accepts a value between 1 and ${maxEdgesPerPage}, inclusive.`,
+        );
       }
 
       take = last;

diff --git a/src/type/ConnectionArgs.ts b/src/type/ConnectionArgs.ts
@@ -2,6 +2,12 @@ import * as GQL from '@nestjs/graphql';
 
 @GQL.ArgsType()
 export class ConnectionArgs {
+  @GQL.Field(_type => GQL.Int, {
+    nullable: true,
+    description: 'Retrieve page of edges by fixed offset page number.',
+  })
+  public page?: number;
+
   @GQL.Field(_type => String, {
     nullable: true,
     description: 'Retrieve page of edges before opaque cursor.',