Started working on Cache Database

backend/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'com.android.library'
     id 'org.jetbrains.kotlin.android'
+    id 'io.realm.kotlin'
 }
 
 android {
@@ -46,6 +47,9 @@ dependencies {
     implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
     implementation 'com.google.code.gson:gson:2.9.0'
 
+    // Realm
+    implementation 'io.realm.kotlin:library-base:1.10.0'
+
     // https://mvnrepository.com/artifact/org.jetbrains.kotlinx/kotlinx-coroutines-core
     implementation group: 'org.jetbrains.kotlinx', name: 'kotlinx-coroutines-core', version: '1.7.3', ext: 'pom'
     testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3'

backend/src/main/java/net/buzzert/kordophone/backend/db/CachedChatDatabase.kt

@@ -0,0 +1,46 @@
+package net.buzzert.kordophone.backend.db
+
+import io.realm.kotlin.Realm
+import io.realm.kotlin.RealmConfiguration
+import net.buzzert.kordophone.backend.db.model.Conversation
+import net.buzzert.kordophone.backend.db.model.toDatabaseConversation
+import net.buzzert.kordophone.backend.model.Conversation as ModelConversation
+
+internal class CachedChatDatabase (private val realmConfig: RealmConfiguration) {
+    companion object {
+        private val schema = setOf(Conversation::class)
+
+        fun liveDatabase(): CachedChatDatabase {
+            return CachedChatDatabase(
+                RealmConfiguration.Builder(schema = schema)
+                    .name("chat-cache")
+                    .build()
+            )
+        }
+
+        fun testDatabase(): CachedChatDatabase {
+            return CachedChatDatabase(
+                RealmConfiguration.Builder(schema = schema)
+                    .name("chat-cache-test")
+                    .inMemory()
+                    .build()
+            )
+        }
+    }
+
+    private val realm = Realm.open(realmConfig)
+
+    fun writeConversations(conversations: List<ModelConversation>) {
+        val dbConversations = conversations.map { it.toDatabaseConversation() }
+        realm.writeBlocking {
+            dbConversations.forEach {
+                copyToRealm(it)
+            }
+        }
+    }
+
+    fun fetchConversations(): List<ModelConversation> {
+        val items = realm.query(Conversation::class).find()
+        return items.map { it.toConversation() }
+    }
+}

backend/src/main/java/net/buzzert/kordophone/backend/db/model/Conversation.kt

@@ -0,0 +1,63 @@
+package net.buzzert.kordophone.backend.db.model
+
+import io.realm.kotlin.Realm
+import io.realm.kotlin.ext.realmListOf
+import io.realm.kotlin.ext.toRealmList
+import io.realm.kotlin.types.RealmInstant
+import io.realm.kotlin.types.RealmList
+import io.realm.kotlin.types.RealmObject
+import io.realm.kotlin.types.annotations.PrimaryKey
+import net.buzzert.kordophone.backend.model.GUID
+import org.mongodb.kbson.ObjectId
+import java.time.Instant
+import net.buzzert.kordophone.backend.model.Conversation as ModelConversation
+import java.util.Date
+
+open class Conversation(
+    @PrimaryKey
+    var _id: String,
+
+    var displayName: String?,
+    var participants: RealmList<String>,
+    var date: RealmInstant,
+    var unreadCount: Int,
+    var lastMessagePreview: String,
+    var guid: GUID,
+
+    // TODO: Not sure how to do this yet...
+    // var messages: RealmList<Message>,
+): RealmObject
+{
+    constructor(): this(
+        _id = ObjectId().toString(),
+        displayName = null,
+        participants = realmListOf(),
+        date = RealmInstant.now(),
+        unreadCount = 0,
+        lastMessagePreview = "",
+        guid = "",
+    )
+
+    fun toConversation(): ModelConversation {
+        return ModelConversation(
+            displayName = displayName,
+            participants = participants!!.toList(),
+            date = Date.from(date.toInstant()),
+            unreadCount = unreadCount,
+            guid = guid,
+            lastMessagePreview = lastMessagePreview
+        )
+    }
+}
+
+fun ModelConversation.toDatabaseConversation(): Conversation {
+    val from = this
+    return Conversation().apply {
+        displayName = from.displayName
+        participants = from.participants.toRealmList()
+        date = from.date.toInstant().toRealmInstant()
+        unreadCount = from.unreadCount
+        lastMessagePreview = from.lastMessagePreview
+        guid = from.guid
+    }
+}

backend/src/main/java/net/buzzert/kordophone/backend/db/model/Date+Instant.kt

@@ -0,0 +1,37 @@
+package net.buzzert.kordophone.backend.db.model
+
+import io.realm.kotlin.types.RealmInstant
+import java.time.Instant
+
+// Copied from Realm's documentation
+// https://www.mongodb.com/docs/realm/sdk/kotlin/realm-database/schemas/supported-types/
+
+fun RealmInstant.toInstant(): Instant {
+    val sec: Long = this.epochSeconds
+    // The value always lies in the range `-999_999_999..999_999_999`.
+    // minus for timestamps before epoch, positive for after
+    val nano: Int = this.nanosecondsOfSecond
+    return if (sec >= 0) { // For positive timestamps, conversion can happen directly
+        Instant.ofEpochSecond(sec, nano.toLong())
+    } else {
+        // For negative timestamps, RealmInstant starts from the higher value with negative
+        // nanoseconds, while Instant starts from the lower value with positive nanoseconds
+        // TODO This probably breaks at edge cases like MIN/MAX
+        Instant.ofEpochSecond(sec - 1, 1_000_000 + nano.toLong())
+    }
+}
+
+fun Instant.toRealmInstant(): RealmInstant {
+    val sec: Long = this.epochSecond
+    // The value is always positive and lies in the range `0..999_999_999`.
+    val nano: Int = this.nano
+
+    return if (sec >= 0) { // For positive timestamps, conversion can happen directly
+        RealmInstant.from(sec, nano)
+    } else {
+        // For negative timestamps, RealmInstant starts from the higher value with negative
+        // nanoseconds, while Instant starts from the lower value with positive nanoseconds
+        // TODO This probably breaks at edge cases like MIN/MAX
+        RealmInstant.from(sec + 1, -1_000_000 + nano)
+    }
+}

backend/src/main/java/net/buzzert/kordophone/backend/db/model/Message.kt

@@ -0,0 +1,49 @@
+package net.buzzert.kordophone.backend.db.model
+
+import android.view.Display.Mode
+import io.realm.kotlin.Realm
+import io.realm.kotlin.types.RealmInstant
+import io.realm.kotlin.types.RealmObject
+import io.realm.kotlin.types.annotations.PrimaryKey
+import net.buzzert.kordophone.backend.model.GUID
+import org.mongodb.kbson.ObjectId
+import net.buzzert.kordophone.backend.model.Message as ModelMessage
+import java.util.Date
+
+open class Message (
+    @PrimaryKey
+    var _id: String,
+
+    var text: String,
+    var guid: GUID,
+    var sender: String?,
+    var date: RealmInstant,
+): RealmObject
+{
+    constructor(): this(
+        _id = ObjectId().toString(),
+        text = "",
+        guid = "",
+        sender = null,
+        date = RealmInstant.now(),
+    )
+
+    fun toMessage(): ModelMessage {
+        return ModelMessage(
+            text = text,
+            guid = guid,
+            sender = sender,
+            date = Date.from(date.toInstant()),
+        )
+    }
+}
+
+fun ModelMessage.toDatabaseMessage(): Message {
+    val from = this
+    return Message().apply {
+        text = from.text
+        guid = from.guid
+        sender = from.sender
+        date = from.date.toInstant().toRealmInstant()
+    }
+}

backend/src/main/java/net/buzzert/kordophone/backend/model/Conversation.kt

@@ -10,7 +10,7 @@ data class Conversation(
     val date: Date,
 
     @SerializedName("participantDisplayNames")
-    val participants: List<String>?,
+    val participants: List<String>,
 
     @SerializedName("displayName")
     val displayName: String?,

backend/src/test/java/net/buzzert/kordophone/backend/DatabaseTests.kt

@@ -0,0 +1,31 @@
+package net.buzzert.kordophone.backend
+
+import net.buzzert.kordophone.backend.db.CachedChatDatabase
+import net.buzzert.kordophone.backend.model.Conversation
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.util.Date
+
+class DatabaseTests {
+    @Test
+    fun testCreateRetrieve() {
+        val db = CachedChatDatabase.testDatabase()
+
+        val conversation = Conversation(
+            date = Date(),
+            participants = listOf("james@magahern.com"),
+            displayName = "Test",
+            unreadCount = 1,
+            lastMessagePreview = "Hello!",
+            guid = "1234",
+        )
+
+        db.writeConversations(listOf(conversation))
+
+        val readBackConversations = db.fetchConversations()
+        assertEquals(readBackConversations.count(), 1)
+
+        val readConversation = readBackConversations[0]
+        assertEquals(readConversation, conversation)
+    }
+}

build.gradle

@@ -8,4 +8,5 @@ plugins {
     id 'com.android.application' version '8.0.2' apply false
     id 'com.android.library' version '8.0.2' apply false
     id 'org.jetbrains.kotlin.android' version '1.9.0' apply false
+    id 'io.realm.kotlin' version '1.10.0' apply false
 }