Decide complication pushes from the next appointment's identity

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Sources/CalendarrCore/Transport/WatchPushPolicy.swift

@@ -0,0 +1,35 @@
+import Foundation
+
+/// Identifies the appointment a complication is currently showing.
+///
+/// The start date is part of the identity on purpose: a moved event keeps its
+/// id, and the complication is wrong until it is told.
+public struct NextEventIdentity: Equatable, Sendable, Codable {
+    public let id: String
+    public let start: Date
+
+    public init(id: String, start: Date) {
+        self.id = id
+        self.start = start
+    }
+}
+
+public enum WatchPushPolicy {
+    /// The first event that has not ended yet — which is what every "next
+    /// appointment" complication renders, including one that is running now.
+    public static func nextEventIdentity(in snapshot: CalendarrSnapshot,
+                                         at now: Date) -> NextEventIdentity? {
+        snapshot.events
+            .filter { $0.end > now }
+            .min { $0.start < $1.start }
+            .map { NextEventIdentity(id: $0.id, start: $0.start) }
+    }
+
+    /// Whether this change is worth one of the day's limited complication
+    /// pushes. Only a changed next appointment is — everything else reaches the
+    /// watch on the next application-context delivery.
+    public static func shouldPushComplicationUpdate(previous: NextEventIdentity?,
+                                                    current: NextEventIdentity?) -> Bool {
+        previous != current
+    }
+}

Tests/CalendarrCoreTests/WatchPushPolicyTests.swift

@@ -0,0 +1,76 @@
+import Foundation
+import Testing
+@testable import CalendarrCore
+
+struct WatchPushPolicyTests {
+
+    private static let now = Date(timeIntervalSince1970: 1_789_000_000)
+
+    private static func event(_ id: String, startOffset: TimeInterval,
+                              duration: TimeInterval = 3600) -> SnapshotEvent {
+        SnapshotEvent(id: id, title: id,
+                      start: now.addingTimeInterval(startOffset),
+                      end: now.addingTimeInterval(startOffset + duration),
+                      isAllDay: false, colorHex: "#4285f4", location: "", calendarKey: "local:1")
+    }
+
+    private static func snapshot(_ events: [SnapshotEvent]) -> CalendarrSnapshot {
+        CalendarrSnapshot(writtenAt: now,
+                          coverageStart: now.addingTimeInterval(-86400),
+                          coverageEnd: now.addingTimeInterval(14 * 86400),
+                          isLoggedIn: true, writerVersion: "1.0", events: events,
+                          theme: SnapshotTheme(today: "#1", text: "#2", background: "#3",
+                                               line: "#4", primary: "#5", accent: "#6"),
+                          language: "de")
+    }
+
+    @Test("The next event is the first one that has not ended yet")
+    func picksFirstUnfinished() {
+        let snap = Self.snapshot([Self.event("past", startOffset: -7200),
+                                  Self.event("running", startOffset: -600),
+                                  Self.event("later", startOffset: 3600)])
+
+        #expect(WatchPushPolicy.nextEventIdentity(in: snap, at: Self.now)?.id == "running")
+    }
+
+    @Test("An empty calendar has no next event")
+    func emptyHasNoIdentity() {
+        #expect(WatchPushPolicy.nextEventIdentity(in: Self.snapshot([]), at: Self.now) == nil)
+    }
+
+    @Test("Events are considered in start order regardless of input order")
+    func sortsBeforePicking() {
+        let snap = Self.snapshot([Self.event("late", startOffset: 7200),
+                                  Self.event("soon", startOffset: 1800)])
+
+        #expect(WatchPushPolicy.nextEventIdentity(in: snap, at: Self.now)?.id == "soon")
+    }
+
+    @Test("An unchanged next event does not spend a push")
+    func unchangedDoesNotPush() {
+        let identity = NextEventIdentity(id: "a", start: Self.now)
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: identity, current: identity) == false)
+    }
+
+    @Test("A different event, a moved event, or a first event all spend a push")
+    func changesPush() {
+        let a = NextEventIdentity(id: "a", start: Self.now)
+        let b = NextEventIdentity(id: "b", start: Self.now)
+        let moved = NextEventIdentity(id: "a", start: Self.now.addingTimeInterval(600))
+
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: a, current: b))
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: a, current: moved))
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: nil, current: a))
+    }
+
+    @Test("Losing the last event spends a push, so the watch stops showing it")
+    func clearingPushes() {
+        let a = NextEventIdentity(id: "a", start: Self.now)
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: a, current: nil))
+    }
+
+    @Test("Two empty calendars in a row do not push")
+    func stayingEmptyDoesNotPush() {
+        #expect(WatchPushPolicy.shouldPushComplicationUpdate(previous: nil, current: nil) == false)
+    }
+}