feat: surface offset fallback browse behavior

client/components/app/LazyBookshelf.vue

@@ -51,6 +51,9 @@ export default {
       routeFullPath: null,
       initialized: false,
       paginationMode: 'offset',
+      deepScrollAllowed: true,
+      deepScrollBlocked: false,
+      maxOffsetPages: Infinity,
       nextCursor: null,
       isCountDeferred: false,
       pageCursors: {},
@@ -338,6 +341,9 @@ export default {
     },
     resetPaginationState() {
       this.paginationMode = 'offset'
+      this.deepScrollAllowed = true
+      this.deepScrollBlocked = false
+      this.maxOffsetPages = Infinity
       this.nextCursor = null
       this.isCountDeferred = false
       this.pageCursors = { 0: null }
@@ -387,6 +393,9 @@ export default {
         }
 
         this.paginationMode = payload.paginationMode || this.paginationMode
+        this.deepScrollAllowed = payload.deepScrollAllowed !== false
+        this.deepScrollBlocked = this.paginationMode === 'offset' && !this.deepScrollAllowed
+        this.maxOffsetPages = this.deepScrollBlocked ? 3 : Infinity
         this.nextCursor = payload.nextCursor || null
         this.isCountDeferred = !!payload.isCountDeferred
 
@@ -426,6 +435,10 @@ export default {
       }
     },
     loadPage(page) {
+      if (this.deepScrollBlocked && page >= this.maxOffsetPages) {
+        return Promise.resolve()
+      }
+
       if (this.pagesLoaded[page]) return this.pagesLoaded[page]
 
       if (this.paginationMode === 'keyset' && page > 0) {

client/cypress/tests/components/app/LazyBookshelf.cy.js

@@ -165,4 +165,37 @@ describe('LazyBookshelf', () => {
       })
     })
   })
+
+  it('keeps offset fallback mode explicit and caps deep endless scroll', () => {
+    const requestUrls = []
+    const getStub = cy.stub().callsFake((url) => {
+      requestUrls.push(url)
+
+      return Promise.resolve({
+        results: [{ id: `item-${requestUrls.length}`, mediaType: 'book', media: { metadata: { title: `Item ${requestUrls.length}` } } }],
+        total: 10,
+        nextCursor: null,
+        paginationMode: 'offset',
+        deepScrollAllowed: false
+      })
+    })
+
+    mountBookshelf(getStub).then(({ wrapper }) => {
+      cy.wrap(null)
+        .then(() => wrapper.vm.loadPage(1))
+        .then(() => wrapper.vm.loadPage(2))
+        .then(() => wrapper.vm.loadPage(3))
+        .then(() => {
+          expect(wrapper.vm.paginationMode).to.equal('offset')
+          expect(wrapper.vm.deepScrollBlocked).to.equal(true)
+          expect(wrapper.vm.maxOffsetPages).to.equal(3)
+          expect(requestUrls).to.have.length(3)
+          expect(requestUrls.some((url) => url.includes('page=0'))).to.equal(true)
+          expect(requestUrls.some((url) => url.includes('page=1'))).to.equal(true)
+          expect(requestUrls.some((url) => url.includes('page=2'))).to.equal(true)
+          expect(requestUrls.some((url) => url.includes('page=3'))).to.equal(false)
+          expect(requestUrls.every((url) => !url.includes('cursor='))).to.equal(true)
+        })
+    })
+  })
 })