Update GraphQL Queries with Pagination

Core/Core/Common/CommonModels/API/API.swift

@@ -93,6 +93,24 @@ public class API {
         }
     }
 
+    @discardableResult
+    public func makeRequest<Request: APIRequestable>(
+        _ requestable: Request,
+        refreshToken: Bool = true
+    ) async throws -> Request.Response {
+        return try await withCheckedThrowingContinuation { continuation in
+            makeRequest(requestable) { result, response, error in
+                if let error {
+                    continuation.resume(throwing: APIError.from(data: nil, response: response, error: error))
+                } else if let result {
+                    continuation.resume(returning: result)
+                } else {
+                    continuation.resume(throwing: APIAsyncError.invalidResponse)
+                }
+            }
+        }
+    }
+
     @discardableResult
     public func makeDownloadRequest(_ url: URL,
                                     method: APIMethod? = nil,
@@ -196,6 +214,25 @@ public class API {
             callback(result, urlResponse, error)
         }
     }
+
+    public func exhaust<R>(_ requestable: R, callback: @escaping (R.Response.Page?, URLResponse?, Error?) -> Void) where R: APIPagedRequestable {
+        exhaust(requestable, result: nil, callback: callback)
+    }
+
+    private func exhaust<R>(_ requestable: R, result: R.Response.Page?, callback: @escaping (R.Response.Page?, URLResponse?, Error?) -> Void) where R: APIPagedRequestable {
+        makeRequest(requestable) { response, urlResponse, error in
+            guard let response = response else {
+                callback(nil, urlResponse, error)
+                return
+            }
+            let result = result == nil ? response.page : result! + response.page
+            if let next = requestable.nextPageRequest(from: response) as? R {
+                self.exhaust(next, result: result, callback: callback)
+                return
+            }
+            callback(result, urlResponse, error)
+        }
+    }
 }
 
 public protocol APITask {
@@ -247,3 +284,7 @@ public class FollowRedirect: NSObject, URLSessionTaskDelegate {
         completionHandler(newRequest)
     }
 }
+
+public enum APIAsyncError: Error {
+    case invalidResponse
+}

Core/Core/Common/CommonModels/API/APICombineExtensions.swift

@@ -65,6 +65,23 @@ public extension API {
         }.eraseToAnyPublisher()
     }
 
+    func exhaust<Request: APIPagedRequestable>(
+        _ requestable: Request
+    ) -> AnyPublisher<(body: Request.Response.Page, urlResponse: HTTPURLResponse?), Error> {
+        Future { promise in
+            self.exhaust(requestable, callback: { response, urlResponse, error in
+                if let response {
+                    promise(.success((body: response,
+                                      urlResponse: urlResponse as? HTTPURLResponse)))
+                } else if let error {
+                    promise(.failure(error))
+                } else {
+                    promise(.failure(NSError.instructureError("No response or error received.")))
+                }
+            })
+        }.eraseToAnyPublisher()
+    }
+
     func makeRequest(_ url: URL,
                      method: APIMethod? = nil)
     -> AnyPublisher<URLResponse?, Error> {

Core/Core/Common/CommonModels/API/APIGraphQLRequestable.swift

@@ -24,6 +24,16 @@ public struct GraphQLBody<Variables: Codable & Equatable>: Codable, Equatable {
     let variables: Variables
 }
 
+public protocol PagedResponse: Codable {
+    associatedtype Page: Codable, RangeReplaceableCollection
+    var page: Page { get }
+}
+
+public protocol APIPagedRequestable: APIRequestable where Response: PagedResponse {
+    associatedtype NextRequest = Self
+    func nextPageRequest(from response: Response) -> NextRequest?
+}
+
 protocol APIGraphQLRequestable: APIRequestable {
     associatedtype Variables: Codable, Equatable
 
@@ -46,3 +56,5 @@ extension APIGraphQLRequestable {
         GraphQLBody(query: Self.query, operationName: Self.operationName, variables: variables)
     }
 }
+
+typealias APIGraphQLPagedRequestable = APIGraphQLRequestable & APIPagedRequestable

Core/Core/Common/CommonModels/API/APIMock.swift

@@ -180,7 +180,20 @@ class MockAPITask: APITask {
 }
 
 extension URLRequest {
-    var key: String { "\(httpMethod ?? ""):\(url?.withCanonicalQueryParams?.absoluteString ?? "")" }
+    var key: String {
+        let basicKey = "\(httpMethod ?? ""):\(url?.withCanonicalQueryParams?.absoluteString ?? "")"
+
+        struct BodyHeader: Codable, Equatable {
+            let operationName: String
+        }
+
+        guard
+            let body = httpBody,
+            let header = try? APIJSONDecoder().decode(BodyHeader.self, from: body)
+        else { return basicKey }
+
+        return basicKey + ":\(header.operationName)"
+    }
 }
 
 class APIMock {

Core/Core/Common/CommonUI/Presenter/PagingPresenter.swift

@@ -0,0 +1,160 @@
+//
+// This file is part of Canvas.
+// Copyright (C) 2025-present  Instructure, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+
+import UIKit
+import Combine
+
+public protocol PagingViewController: UIViewController {
+    associatedtype Page: PageModel
+
+    func isMoreRow(at indexPath: IndexPath) -> Bool
+    func loadNextPage()
+}
+
+public protocol PageModel {
+    var nextCursor: String? { get }
+}
+
+public class PagingPresenter<Controller: PagingViewController> {
+
+    private var endCursor: String?
+    private var isLoadingMoreSubject = CurrentValueSubject<Bool, Never>(false)
+    private var loadedCursor: String?
+    private unowned let controller: Controller
+
+    public init(controller: Controller) {
+        self.controller = controller
+    }
+
+    public var hasMore: Bool { endCursor != nil }
+    public var isLoadingMore: Bool { isLoadingMoreSubject.value }
+
+    public func onPageLoaded(_ page: Controller.Page) {
+        endCursor = page.nextCursor
+        isLoadingMoreSubject.send(false)
+    }
+
+    public func onPageLoadingFailed() {
+        isLoadingMoreSubject.send(false)
+    }
+
+    public func willDisplayRow(at indexPath: IndexPath) {
+        guard controller.isMoreRow(at: indexPath), isLoadingMoreSubject.value == false else { return }
+        guard let endCursor, endCursor != loadedCursor else { return }
+        loadMore()
+    }
+
+    public func willSelectRow(at indexPath: IndexPath) {
+        guard controller.isMoreRow(at: indexPath), isLoadingMoreSubject.value == false else { return }
+        loadMore()
+    }
+
+    private func loadMore() {
+        guard let endCursor else { return }
+
+        loadedCursor = endCursor
+        isLoadingMoreSubject.send(true)
+
+        controller.loadNextPage()
+    }
+
+    public func setup(in cell: PageLoadingCell) -> PageLoadingCell {
+        cell.observeLoading(isLoadingMoreSubject.eraseToAnyPublisher())
+        return cell
+    }
+}
+
+public class PageLoadingCell: UITableViewCell {
+    required init?(coder: NSCoder) { nil }
+
+    private let progressView = CircleProgressView()
+    private let label = UILabel()
+
+    private var subscriptions = Set<AnyCancellable>()
+
+    override public func layoutSubviews() {
+        super.layoutSubviews()
+
+        subviews.forEach { subview in
+            guard subview != contentView else { return }
+            subview.isHidden = true
+        }
+    }
+
+    override public init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
+        super.init(style: style, reuseIdentifier: reuseIdentifier)
+
+        contentView.addSubview(progressView)
+
+        progressView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            progressView.widthAnchor.constraint(equalToConstant: 32),
+            progressView.heightAnchor.constraint(equalToConstant: 32),
+            progressView.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
+            progressView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 10),
+            progressView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -10)
+        ])
+
+        contentView.addSubview(label)
+
+        label.text = String(localized: "Load More", bundle: .core)
+        label.textColor = .systemBlue
+        label.font = .scaledNamedFont(.semibold16)
+        label.adjustsFontForContentSizeCategory = true
+        label.translatesAutoresizingMaskIntoConstraints = false
+
+        NSLayoutConstraint.activate([
+            label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
+            label.centerYAnchor.constraint(equalTo: contentView.centerYAnchor),
+            label.topAnchor.constraint(greaterThanOrEqualTo: contentView.topAnchor, constant: 10),
+            label.bottomAnchor.constraint(lessThanOrEqualTo: contentView.bottomAnchor, constant: -10)
+        ])
+    }
+
+    override public func prepareForReuse() {
+        super.prepareForReuse()
+
+        subscriptions.forEach({ $0.cancel() })
+        subscriptions.removeAll()
+    }
+
+    fileprivate func observeLoading(_ loadingPublisher: AnyPublisher<Bool, Never>) {
+        loadingPublisher
+            .receive(on: DispatchQueue.main)
+            .sink { [weak self] isLoading in
+                if isLoading {
+                    self?.setupAsProgressView()
+                } else {
+                    self?.setupAsButton()
+                }
+            }
+            .store(in: &subscriptions)
+    }
+
+    private func setupAsButton() {
+        backgroundConfiguration = UIBackgroundConfiguration.listPlainCell()
+        progressView.isHidden = true
+        label.isHidden = false
+    }
+
+    private func setupAsProgressView() {
+        backgroundConfiguration = UIBackgroundConfiguration.clear()
+        progressView.isHidden = false
+        label.isHidden = true
+    }
+}