Use kotlinx.datetime for time handling

backend/src/main/kotlin/org/jetbrains/kotlinconf/backend/Api.kt

@@ -1,15 +1,22 @@
 package org.jetbrains.kotlinconf.backend
 
-import io.ktor.http.*
-import io.ktor.server.application.*
-import io.ktor.server.auth.*
-import io.ktor.server.request.*
-import io.ktor.server.response.*
-import io.ktor.server.routing.*
-import io.ktor.util.date.*
-import org.jetbrains.kotlinconf.*
+import io.ktor.http.HttpStatusCode
+import io.ktor.server.application.ApplicationCall
+import io.ktor.server.auth.principal
+import io.ktor.server.request.receive
+import io.ktor.server.response.respond
+import io.ktor.server.routing.Route
+import io.ktor.server.routing.get
+import io.ktor.server.routing.post
+import io.ktor.server.routing.route
+import io.ktor.util.date.GMTDate
+import kotlinx.datetime.toInstant
+import org.jetbrains.kotlinconf.EVENT_TIME_ZONE
+import org.jetbrains.kotlinconf.FeedbackInfo
+import org.jetbrains.kotlinconf.VoteInfo
 import org.jetbrains.kotlinconf.Votes
-import java.time.*
+import java.time.Clock
+import java.time.LocalDateTime
 
 internal fun Route.api(
     store: Store,
@@ -64,8 +71,8 @@ private fun Route.apiVote(
 
             val nowTime = now()
 
-            val startVotesAt = session.startsAt
-            val votingPeriodStarted = nowTime >= startVotesAt.timestamp
+            val startVotesAt = session.startsAt.toInstant(EVENT_TIME_ZONE)
+            val votingPeriodStarted = nowTime >= startVotesAt.toEpochMilliseconds()
 
             if (!votingPeriodStarted) {
                 return@post call.respond(comeBackLater)

backend/src/main/kotlin/org/jetbrains/kotlinconf/backend/SessionizeData.kt

@@ -1,8 +1,8 @@
 package org.jetbrains.kotlinconf.backend
 
+import kotlinx.datetime.LocalDateTime
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
-import org.jetbrains.kotlinconf.GMTDateSerializable
 import org.jetbrains.kotlinconf.SessionId
 import org.jetbrains.kotlinconf.SpeakerId
 
@@ -24,8 +24,8 @@ data class SessionData(
     val speakers: List<SpeakerId>,
     @SerialName("description")
     var descriptionText: String? = "",
-    val startsAt: GMTDateSerializable?,
-    val endsAt: GMTDateSerializable?,
+    val startsAt: LocalDateTime?,
+    val endsAt: LocalDateTime?,
     val title: String,
     val roomId: Int?,
     val questionAnswers: List<QuestionAnswerData> = emptyList(),

shared/src/commonMain/kotlin/org/jetbrains/kotlinconf/APIClient.kt

@@ -23,13 +23,11 @@ import io.ktor.http.isSuccess
 import io.ktor.http.path
 import io.ktor.http.takeFrom
 import io.ktor.serialization.kotlinx.json.json
-import io.ktor.util.date.GMTDate
-import io.ktor.util.date.Month
 import io.ktor.utils.io.core.Closeable
+import kotlinx.datetime.Instant
+import kotlinx.datetime.LocalDateTime
 import org.jetbrains.kotlinconf.utils.appLogger
 
-val HTTP_CLIENT = HttpClient()
-
 /**
  * Adapter to handle backend API and manage auth information.
  */
@@ -38,7 +36,7 @@ class APIClient(
 ) : Closeable {
     var userId: String? = null
 
-    private val client = HTTP_CLIENT.config {
+    private val client = HttpClient {
         install(ContentNegotiation) {
             json()
         }
@@ -135,12 +133,9 @@ class APIClient(
         }.body<Votes>().votes
     }
 
-    /**
-     * Get server time.
-     */
-    suspend fun getServerTime(): GMTDate = client.get {
+    suspend fun getServerTime(): Instant = client.get {
         apiUrl("time")
-    }.bodyAsText().let { response -> GMTDate(response.toLong()) }
+    }.bodyAsText().let { response -> Instant.fromEpochMilliseconds(response.toLong()) }
 
     // TODO real api call https://github.com/JetBrains/kotlinconf-app/issues/268
     suspend fun getNews(): List<NewsItem> = EXAMPLE_NEWS_ITEMS
@@ -171,56 +166,35 @@ private val EXAMPLE_NEWS_ITEMS = listOf(
         id = "0",
         title = "Kotlin 1.9 Released",
         content = "**Exciting news for Kotlin developers!** The latest version of Kotlin brings significant improvements and new features to enhance your development experience.\n\nSome highlights include:\n- *K2 compiler* improvements for faster compilation\n- Enhanced type inference system\n- New stdlib functions\n\nCheck out the detailed release notes at [kotlinlang.org](https://kotlinlang.org) and start exploring these amazing features today! The Kotlin team has been working hard to make this release even more **powerful** and *developer-friendly*.",
-        date = GMTDate(
-            year = 2024,
-            month = Month.APRIL,
-            dayOfMonth = 23,
-            hours = 10,
-            minutes = 24,
-            seconds = 2
-        ),
+        date = LocalDateTime.parse("2024-04-23T10:24:02"),
         photoUrl = "https://picsum.photos/1800/900"
     ),
     NewsItem(
         id = "1",
         title = "KotlinConf 2024 Announced",
         content = "Get ready for the most anticipated Kotlin event of the year! **KotlinConf 2024** brings together developers from around the world for an unforgettable experience.\n\n*What to expect:*\n- Inspiring keynotes from Kotlin leaders\n- In-depth technical sessions\n- Hands-on workshops\n- Networking opportunities\n\nDon't miss the chance to meet fellow Kotlin enthusiasts and learn from industry experts. Early bird tickets are now available at [kotlinconf.com/2024](https://kotlinconf.com/2024).\n\n**Pro tip:** Check out the *conference app* to plan your schedule and connect with other attendees!",
-        date = GMTDate(year = 2024, month = Month.MAY, dayOfMonth = 22, hours = 10, minutes = 24, seconds = 2),
+        date = LocalDateTime.parse("2024-05-22T10:24:02"),
         photoUrl = null
     ),
     NewsItem(
         id = "2",
         title = "Jetpack Compose Updates",
         content = "The world of **Jetpack Compose** continues to evolve with exciting new features for both Android and Desktop development!\n\n*Latest improvements include:*\n- Enhanced performance optimizations\n- New material design components\n- Improved animation APIs\n- Better desktop window management\n\nRead the comprehensive guide on the [Android Developers Blog](https://android-developers.googleblog.com) and explore the [Compose Multiplatform documentation](https://www.jetbrains.com/compose-multiplatform/).\n\n**Did you know?** You can now easily share up to *90% of your UI code* between Android and Desktop applications using Compose Multiplatform!",
-        date = GMTDate(
-            year = 2024,
-            month = Month.JANUARY,
-            dayOfMonth = 22,
-            hours = 10,
-            minutes = 24,
-            seconds = 2
-        ),
+        date = LocalDateTime.parse("2024-01-22T10:24:02"),
         photoUrl = null
     ),
     NewsItem(
         id = "3",
         title = "New Kotlin Multiplatform Features",
         content = "**Kotlin Multiplatform** technology reaches new heights with groundbreaking features and improvements!\n\n*Key highlights of the latest release:*\n- Simplified project setup and configuration\n- Enhanced iOS integration with new Kotlin/Native features\n- Improved dependency management\n- Extended WebAssembly support\n\nStart building your next cross-platform project with [KMP](https://kotlinlang.org/docs/multiplatform.html) today!\n\n**Success Story:** *Philips* recently shared how they achieved a **75% code sharing rate** across platforms using Kotlin Multiplatform. Read their detailed case study on the [Kotlin Blog](https://blog.jetbrains.com/kotlin/).\n\nExplore the [official documentation](https://kotlinlang.org/docs/multiplatform-get-started.html) to learn more about these exciting developments!",
-        date = GMTDate(year = 2024, month = Month.MAY, dayOfMonth = 23, hours = 10, minutes = 24, seconds = 2),
+        date = LocalDateTime.parse("2024-05-23T10:24:02"),
         photoUrl = "https://picsum.photos/1800/900"
     ),
     NewsItem(
         id = "4",
         title = "Kotlin Community Highlights",
         content = "The **Kotlin community** continues to innovate and inspire! Let's celebrate some remarkable community contributions.\n\n*Featured Projects:*\n- **Ktor 2.0**: A powerful framework for building asynchronous servers and clients\n- *Kotlin Native Bridge*: Seamless integration between Kotlin and native platforms\n- **KMP-NativeCoroutines**: Simplified concurrency for multiplatform projects\n\nJoin the community on [Kotlin Slack](https://kotlinlang.slack.com) with over *100,000 members* and share your own projects!\n\n**Want to contribute?** Check out the [Kotlin Contributing Guidelines](https://github.com/JetBrains/kotlin) and help shape the future of Kotlin. The community has already contributed more than *500 patches* to the latest release!\n\nExplore more community projects on [Kotlin Weekly](https://kotlinweekly.net) and get inspired for your next project.",
-        date = GMTDate(
-            year = 2024,
-            month = Month.APRIL,
-            dayOfMonth = 20,
-            hours = 10,
-            minutes = 24,
-            seconds = 2
-        ),
+        date = LocalDateTime.parse("2024-04-20T10:24:02"),
         photoUrl = "https://picsum.photos/1800/900"
     )
 )

shared/src/commonMain/kotlin/org/jetbrains/kotlinconf/ConferenceService.kt

@@ -1,6 +1,5 @@
 package org.jetbrains.kotlinconf
 
-import io.ktor.util.date.GMTDate
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
@@ -14,28 +13,11 @@ import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.toInstant
 import org.jetbrains.kotlinconf.storage.ApplicationStorage
-import org.jetbrains.kotlinconf.utils.time
-
-val UNKNOWN_SESSION_CARD: SessionCardView = SessionCardView(
-    id = SessionId("unknown"),
-    title = "unknown",
-    speakerLine = "unknown",
-    locationLine = "unknown",
-    startsAt = GMTDate.START,
-    endsAt = GMTDate.START,
-    speakerIds = emptyList(),
-    isFavorite = false,
-    description = "unknown",
-    vote = null,
-    tags = emptyList(),
-    startsInMinutes = null,
-    state = SessionState.Upcoming,
-)
-
-val UNKNOWN_SPEAKER: Speaker = Speaker(
-    SpeakerId("unknown"), "unknown", "unknown", "unknown", ""
-)
+import org.jetbrains.kotlinconf.utils.DateTimeFormatting
+import kotlin.time.Duration.Companion.minutes
 
 class ConferenceService(
     private val client: APIClient,
@@ -162,18 +144,14 @@ class ConferenceService(
     suspend fun sendFeedback(sessionId: SessionId, feedbackValue: String): Boolean =
         client.sendFeedback(sessionId, feedbackValue)
 
-    fun speakerById(id: SpeakerId): Speaker = speakers.value[id] ?: UNKNOWN_SPEAKER
+    fun speakerById(id: SpeakerId): Speaker? = speakers.value[id]
 
-    fun sessionById(id: SessionId): SessionCardView =
-        sessionCards.value.find { it.id == id } ?: UNKNOWN_SESSION_CARD
-
-    fun sessionByIdFlow(id: SessionId): Flow<SessionCardView> =
-        sessionCards
-            .map { sessions -> sessions.find { it.id == id } ?: UNKNOWN_SESSION_CARD }
+    fun sessionByIdFlow(id: SessionId): Flow<SessionCardView?> =
+        sessionCards.map { sessions -> sessions.find { it.id == id } }
 
     fun speakersBySessionId(id: SessionId): Flow<List<Speaker>> =
         sessionByIdFlow(id).map { session ->
-            session.speakerIds.map { speakerId -> speakerById(speakerId) }
+            session?.speakerIds?.mapNotNull { speakerId -> speakerById(speakerId) } ?: emptyList()
         }
 
     fun sessionsForSpeaker(id: SpeakerId): List<SessionCardView> =
@@ -204,34 +182,26 @@ class ConferenceService(
             val notificationsAllowed = storage.getNotificationsAllowed().first()
             if (!notificationsAllowed) return@launch
 
-            val startTimestamp = session.startsAt.timestamp
-            val reminderTimestamp = startTimestamp - 5 * 60 * 1000
-            val nowTimestamp = timeProvider.now().timestamp
-            val delay = reminderTimestamp - nowTimestamp
-            val voteTimeStamp = session.endsAt.timestamp
-
-            when {
-                delay >= 0 -> {
-                    notificationManager.schedule(delay, session.title, "Starts in 5 minutes.")
-                }
+            val start = session.startsAt.toInstant(EVENT_TIME_ZONE)
+            val end = session.endsAt.toInstant(EVENT_TIME_ZONE)
+            val now = timeProvider.now().toInstant(EVENT_TIME_ZONE)
 
-                nowTimestamp in reminderTimestamp..<startTimestamp -> {
-                    notificationManager.schedule(0, session.title, "The session is about to start.")
-                }
+            val reminderTime = start - 5.minutes
 
-                nowTimestamp in startTimestamp..<voteTimeStamp -> {
-                    notificationManager.schedule(0, session.title, "Hurry up! The session has already started!")
-                }
+            // Notifications for session start
+            val startsLater = now < reminderTime
+            val startsSoon = now in reminderTime..<start
+            val isLive = now in start..<end
+            when {
+                startsLater -> notificationManager.schedule((reminderTime - now).inWholeMilliseconds, session.title, "Starts in 5 minutes.")
+                startsSoon -> notificationManager.schedule(0, session.title, "The session is about to start.")
+                isLive -> notificationManager.schedule(0, session.title, "Hurry up! The session has already started!")
             }
 
-            if (nowTimestamp > voteTimeStamp) return@launch
-
-            val voteDelay = voteTimeStamp - nowTimestamp
-            notificationManager.schedule(
-                voteDelay,
-                "${session.title} finished",
-                "How was the talk?"
-            )
+            // Notifications for session end
+            if (end > now) {
+                notificationManager.schedule((end - now).inWholeMilliseconds, "${session.title} finished", "How was the talk?")
+            }
         }
     }
 
@@ -247,7 +217,7 @@ class ConferenceService(
 
     private fun mapNewsItemToDisplayItem(
         item: NewsItem,
-        now: GMTDate,
+        now: LocalDateTime,
     ): NewsDisplayItem {
         return NewsDisplayItem(
             id = item.id,
@@ -258,13 +228,12 @@ class ConferenceService(
         )
     }
 
-    private fun GMTDate.toNewsDisplayTime(now: GMTDate): String {
-        return if (year == now.year && dayOfYear == now.dayOfYear) {
-            return time()
-        } else if (year == now.year) {
-            "${month.value} $dayOfMonth"
-        } else {
-            "${month.value} $dayOfMonth, $year"
+    private fun LocalDateTime.toNewsDisplayTime(now: LocalDateTime): String {
+        val isToday = year == now.year && dayOfYear == now.dayOfYear
+        return when {
+            isToday -> DateTimeFormatting.time(this)
+            year == now.year -> DateTimeFormatting.date(this)
+            else -> DateTimeFormatting.dateWithYear(this)
         }
     }
 

shared/src/commonMain/kotlin/org/jetbrains/kotlinconf/Model.kt

@@ -1,12 +1,9 @@
 package org.jetbrains.kotlinconf
 
-import io.ktor.util.date.*
-import kotlinx.serialization.*
-import org.jetbrains.kotlinconf.utils.*
+import kotlinx.datetime.LocalDateTime
+import kotlinx.serialization.Serializable
 import kotlin.jvm.JvmInline
 
-typealias GMTDateSerializable = @Serializable(GMTDateSerializer::class) GMTDate
-
 @Serializable
 @JvmInline
 value class SpeakerId(val id: String) {
@@ -46,12 +43,10 @@ class Session(
     val description: String,
     val speakerIds: List<SpeakerId>,
     val location: String,
-    val startsAt: GMTDateSerializable,
-    val endsAt: GMTDateSerializable,
+    val startsAt: LocalDateTime,
+    val endsAt: LocalDateTime,
     val tags: List<String>? = null
-) {
-    val timeLine get() = startsAt.time() + " - " + endsAt.time()
-}
+)
 
 @Serializable
 class VoteInfo(
@@ -92,7 +87,7 @@ enum class Theme {
 class NewsItem(
     val id: String,
     val photoUrl: String?,
-    val date: GMTDateSerializable,
+    val date: LocalDateTime,
     val title: String,
     val content: String,
 )