feat(searchbox): query debouncing (#297)

Cartfile

@@ -1,3 +1,3 @@
 github "apple/swift-log" ~> 1.4
-github "algolia/algoliasearch-client-swift" ~> 8.17
+github "algolia/algoliasearch-client-swift" ~> 8.18
 github "algolia/instantsearch-telemetry-native" ~> 0.1.3

Examples/Examples/DemoListViewController.swift

@@ -44,7 +44,7 @@ final class DemoListViewController<Demo: DemoProtocol & Codable>: UITableViewCon
     navigationItem.searchController = searchController
     tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellIdentifier)
     hitsInteractor.onResultsUpdated.subscribe(with: self) { viewController, results in
-      let demos = (try? results.extractHits() as [Demo]) ?? []
+      let demos = (try? results.extractHits(jsonDecoder: JSONDecoder()) as [Demo]) ?? []
       viewController.updateDemos(demos)
     }
   }

InstantSearch.podspec

@@ -15,7 +15,7 @@ Pod::Spec.new do |s|
 
   s.subspec "Insights" do |ss|
       ss.source_files = 'Sources/InstantSearchInsights/**/*.{swift}'
-      ss.dependency 'AlgoliaSearchClient', '~> 8.17'
+      ss.dependency 'AlgoliaSearchClient', '~> 8.18'
       ss.ios.deployment_target = '9.0'
       ss.osx.deployment_target = '10.10'
       ss.watchos.deployment_target = '2.0'
@@ -24,7 +24,7 @@ Pod::Spec.new do |s|
 
   s.subspec "Core" do |ss|
       ss.source_files = 'Sources/InstantSearchCore/**/*.{swift}'
-      ss.dependency 'AlgoliaSearchClient', '~> 8.17'
+      ss.dependency 'AlgoliaSearchClient', '~> 8.18'
       ss.dependency 'InstantSearch/Insights'
       ss.dependency 'InstantSearchTelemetry', '~> 0.1.3'
       ss.ios.deployment_target = '9.0'

Package.swift

@@ -32,7 +32,7 @@ let package = Package(
   dependencies: [
     .package(name: "AlgoliaSearchClient",
              url: "https://github.com/algolia/algoliasearch-client-swift",
-             from: "8.17.0"),
+             from: "8.18.2"),
     .package(name: "InstantSearchTelemetry",
              url: "https://github.com/algolia/instantsearch-telemetry-native",
              from: "0.1.3")

Sources/InstantSearchCore/Common/Debouncer.swift

@@ -0,0 +1,64 @@
+import Foundation
+
+/// `Debouncer` helps in reducing the frequency of execution for a given set of operations.
+/// It ensures that a function does not get called until after a certain amount of time has passed
+/// since the last time it was called. This is especially useful for actions that get triggered often,
+/// like UI input events, to avoid unnecessary work and improve performance.
+///
+/// Type parameter `T` is the type of the value you're monitoring. It should be `Equatable` to check
+/// for changes.
+///
+/// Usage:
+///
+/// ```swift
+/// let debouncer = Debouncer<String>(delay: 0.5)
+/// searchBar.onChange = { searchText in
+///     debouncer.debounce(value: searchText) { debouncedSearchText in
+///         // perform an action with debouncedSearchText
+///     }
+/// }
+/// ```
+class Debouncer<T: Equatable> {
+  /// The delay, in seconds, after which the action should be taken.
+  private let delay: TimeInterval
+  /// Keeps track of the last value passed to the `debounce` function.
+  private var lastValue: T?
+  /// The work item that's scheduled to run after the debounce delay.
+  private var workItem: DispatchWorkItem?
+  /// The execute queue of the completion block.
+  private var queue: DispatchQueue
+
+  /// Initializes a new debouncer with the given delay.
+  ///
+  /// - Parameter delay: The amount of time to wait before executing the action.
+  /// - Parameter queue: The execute queue of the completion block.
+  init(delay: TimeInterval,
+       queue: DispatchQueue = .main) {
+    self.delay = delay
+    self.queue = queue
+  }
+
+  /// Debounces the execution of a function.
+  ///
+  /// If this method is called again with the same value before the delay has elapsed,
+  /// the previously scheduled work will be canceled, effectively "debouncing" the calls.
+  ///
+  /// - Parameters:
+  ///   - value: The new value to check against the previous one.
+  ///   - completion: The completion block to execute after the delay, if the value has changed.
+  func debounce(value: T, completion: @escaping (T) -> Void) {
+    // Cancel the previously scheduled work item if it hasn't run yet
+    workItem?.cancel()
+    // If the new value is different from the last one, schedule the completion block to run after the delay
+    if lastValue != value {
+      lastValue = value
+
+      workItem = DispatchWorkItem { [weak self] in
+        self?.lastValue = nil
+        completion(value)
+      }
+
+      DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: workItem!)
+    }
+  }
+}

Sources/InstantSearchCore/SearchBox/SearchBoxInteractor+Controller.swift

@@ -16,24 +16,32 @@ public extension SearchBoxInteractor {
     /// Controller interfacing with a concrete query input view
     public let controller: Controller
 
+    /// Debouncer that manages the debounce delay for successive query inputs to optimize performance.
+    private let queryDebouncer: Debouncer<String?>
+
     /**
      - Parameters:
-       - interactor: Business logic component that handles textual query input
-       - controller: Controller interfacing with a concrete query input view
+     - interactor: Business logic component that handles textual query input
+     - controller: Controller interfacing with a concrete query input view
+     - debounceInterval: The delay (in seconds) after which the query input is processed, allowing for debounced input. Default value is 100ms (0.1 seconds).
      */
     public init(interactor: SearchBoxInteractor,
-                controller: Controller) {
+                controller: Controller,
+                debounceInterval: TimeInterval = 0.1) {
       self.interactor = interactor
       self.controller = controller
+      self.queryDebouncer = Debouncer(delay: debounceInterval)
     }
 
     public func connect() {
       interactor.onQueryChanged.subscribePast(with: controller) { controller, query in
         controller.setQuery(query)
       }.onQueue(.main)
 
-      controller.onQueryChanged = { [weak interactor] in
-        interactor?.query = $0
+      controller.onQueryChanged = { [weak interactor, queryDebouncer] query in
+        queryDebouncer.debounce(value: query) { query in
+          interactor?.query = query
+        }
       }
 
       controller.onQuerySubmitted = { [weak interactor] in
@@ -52,10 +60,10 @@ public extension SearchBoxInteractor {
 
 public extension SearchBoxInteractor {
   /**
-    Establishes a connection with a controller
-    - Parameters:
-      - controller: Controller interfacing with a concrete query input view
-    - Returns: Established connection
+   Establishes a connection with a controller
+   - Parameters:
+   - controller: Controller interfacing with a concrete query input view
+   - Returns: Established connection
    */
   @discardableResult func connectController<Controller: SearchBoxController>(_ controller: Controller) -> ControllerConnection<Controller> {
     let connection = ControllerConnection(interactor: self,

Sources/InstantSearchSwiftUI/DataModel/SearchBoxObservableController.swift

@@ -17,29 +17,32 @@ import InstantSearchTelemetry
   @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
   public class SearchBoxObservableController: ObservableObject, SearchBoxController {
     /// Textual query
-    @Published public var query: String {
-      didSet {
-        onQueryChanged?(query)
-      }
-    }
+    @Published public var query: String
 
     public var onQueryChanged: ((String?) -> Void)?
 
     public var onQuerySubmitted: ((String?) -> Void)?
 
+    private var querySubscription: AnyCancellable?
+
     public func setQuery(_ query: String?) {
+      guard query != self.query else { return }
       self.query = query ?? ""
     }
 
     public init(query: String = "") {
       self.query = query
       InstantSearchTelemetry.shared.traceDeclarative(type: .searchBox)
+      querySubscription = $query.removeDuplicates().sink { [weak self] value in
+        self?.onQueryChanged?(value)
+      }
     }
 
     /// Trigger query submit event
     public func submit() {
       onQuerySubmitted?(query)
     }
+
   }
 
   /// QueryInputController implementation adapted for usage with SwiftUI views

Tests/InstantSearchCoreTests/Unit/QueryInput/SearchBoxControllerConnectionTests.swift

@@ -36,7 +36,9 @@ class SearchBoxControllerConnectionTests: XCTestCase {
     let presetQuery = "q1"
     interactor.query = presetQuery
 
-    let connection = SearchBoxInteractor.ControllerConnection(interactor: interactor, controller: controller)
+    let connection = SearchBoxInteractor.ControllerConnection(interactor: interactor,
+                                                              controller: controller,
+                                                              debounceInterval: 0)
 
     connection.connect()
 
@@ -99,23 +101,32 @@ class SearchBoxControllerConnectionTester {
     XCTAssertEqual(controller.query, presetQuery, file: file, line: line)
 
     controller.query = "q2"
-
-    if isConnected {
-      XCTAssertEqual(interactor.query, "q2", file: file, line: line)
-    } else {
-      XCTAssertNil(interactor.query, file: file, line: line)
+
+    let queryChangedExpectation = source.expectation(description: "query changed")
+    queryChangedExpectation.isInverted = !isConnected
+    let subscription = interactor.onQueryChanged.subscribe(with: self) { _, query in
+      if isConnected {
+        XCTAssertEqual(query, "q2", file: file, line: line)
+      } else {
+        XCTAssertNil(query, file: file, line: line)
+      }
+      queryChangedExpectation.fulfill()
     }
-
+    source.waitForExpectations(timeout: 2)
+    subscription.cancel()
+
     controller.query = "q3"
 
     let querySubmittedExpectation = source.expectation(description: "query submitted")
     querySubmittedExpectation.isInverted = !isConnected
-
     interactor.onQuerySubmitted.subscribe(with: self) { _, query in
-      XCTAssertEqual(query, "q3", file: file, line: line)
+      if isConnected {
+        XCTAssertEqual(query, "q3", file: file, line: line)
+      } else {
+        XCTAssertNil(query, file: file, line: line)
+      }
       querySubmittedExpectation.fulfill()
     }
-
     controller.submitQuery()
 
     source.waitForExpectations(timeout: 2, handler: nil)