Init

.gitignore

@@ -0,0 +1,45 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Kotlin ###
+.kotlin
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

@@ -0,0 +1,3 @@
+# Default ignored files
+/shelf/
+/workspace.xml

.idea/gradle.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="GradleMigrationSettings" migrationVersion="1" />
+  <component name="GradleSettings">
+    <option name="linkedExternalProjectsSettings">
+      <GradleProjectSettings>
+        <option name="externalProjectPath" value="$PROJECT_DIR$" />
+        <option name="gradleHome" value="" />
+        <option name="modules">
+          <set>
+            <option value="$PROJECT_DIR$" />
+          </set>
+        </option>
+      </GradleProjectSettings>
+    </option>
+  </component>
+</project>

.idea/kotlinc.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="KotlinJpsPluginSettings">
+    <option name="version" value="2.2.10" />
+  </component>
+</project>

.idea/misc.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="azul-21" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

build.gradle.kts

@@ -0,0 +1,45 @@
+plugins {
+    kotlin("jvm") version "2.2.10"
+}
+
+group = "no.iktdev"
+version = "1.0-SNAPSHOT"
+
+repositories {
+    mavenCentral()
+}
+
+val exposedVersion = "0.61.0"
+
+dependencies {
+
+    implementation ("mysql:mysql-connector-java:8.0.29")
+    implementation("org.jetbrains.exposed:exposed-core:${exposedVersion}")
+    implementation("org.jetbrains.exposed:exposed-dao:${exposedVersion}")
+    implementation("org.jetbrains.exposed:exposed-jdbc:${exposedVersion}")
+    implementation("org.jetbrains.exposed:exposed-java-time:${exposedVersion}")
+
+    implementation("com.google.code.gson:gson:2.8.9")
+
+
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.10.2")
+
+    //testImplementation(kotlin("test"))
+    testImplementation("org.assertj:assertj-core:3.4.1")
+
+    testImplementation("org.junit.jupiter:junit-jupiter-api:5.7.2")
+    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:5.7.2")
+    testImplementation(platform("org.junit:junit-bom:5.9.1"))
+    testImplementation("org.junit.jupiter:junit-jupiter")
+    testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.10.2")
+
+
+    testImplementation("com.h2database:h2:2.2.220")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+kotlin {
+    jvmToolchain(21)
+}

gradle.properties

@@ -0,0 +1 @@
+kotlin.code.style=official

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Sat Oct 04 23:50:48 CEST 2025
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

@@ -0,0 +1,4 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
+}
+rootProject.name = "Eventi"

src/main/kotlin/no/iktdev/eventi/ZDS.kt

@@ -0,0 +1,67 @@
+package no.iktdev.eventi
+
+import com.google.gson.GsonBuilder
+import com.google.gson.JsonDeserializationContext
+import com.google.gson.JsonDeserializer
+import com.google.gson.JsonElement
+import com.google.gson.JsonPrimitive
+import com.google.gson.JsonSerializationContext
+import com.google.gson.JsonSerializer
+import no.iktdev.eventi.events.EventTypeRegistry
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.models.store.PersistedEvent
+import java.lang.reflect.Type
+import java.time.LocalDateTime
+import java.time.format.DateTimeFormatter
+
+object ZDS {
+    val gson = WGson.gson
+
+    fun Event.toPersisted(id: Long, persistedAt: LocalDateTime): PersistedEvent {
+        val payloadJson = gson.toJson(this)
+        val eventName = this::class.simpleName ?: error("Missing class name")
+        return PersistedEvent(
+            id = id,
+            referenceId = referenceId,
+            eventId = eventId,
+            event = eventName,
+            data = payloadJson,
+            persistedAt = persistedAt
+        )
+    }
+
+    /**
+     * Convert a PersistedEvent back to its original Event type using the event type registry and Gson for deserialization.
+     */
+    fun PersistedEvent.toEvent(): Event {
+        val clazz = EventTypeRegistry.resolve(event)
+            ?: error("Unknown event type: $event")
+        return gson.fromJson(data, clazz)
+    }
+
+
+    object WGson {
+        val gson = GsonBuilder()
+            .registerTypeAdapter(LocalDateTime::class.java, LocalDateTimeAdapter())
+            .create()
+        fun toJson(data: Any?): String {
+            return gson.toJson(data)
+        }
+
+        class LocalDateTimeAdapter : JsonSerializer<LocalDateTime>, JsonDeserializer<LocalDateTime> {
+            private val formatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME
+
+            override fun serialize(
+                src: LocalDateTime, typeOfSrc: Type, context: JsonSerializationContext
+            ): JsonElement {
+                return JsonPrimitive(src.format(formatter))
+            }
+
+            override fun deserialize(
+                json: JsonElement, typeOfT: Type, context: JsonDeserializationContext
+            ): LocalDateTime {
+                return LocalDateTime.parse(json.asString, formatter)
+            }
+        }
+    }
+}

src/main/kotlin/no/iktdev/eventi/events/AbstractEventPoller.kt

@@ -0,0 +1,52 @@
+package no.iktdev.eventi.events
+
+import kotlinx.coroutines.delay
+import no.iktdev.eventi.ZDS.toEvent
+import no.iktdev.eventi.stores.EventStore
+import java.time.Duration
+import java.time.LocalDateTime
+import java.util.UUID
+import kotlin.collections.iterator
+
+abstract class AbstractEventPoller(
+    private val eventStore: EventStore,
+    private val dispatchQueue: SequenceDispatchQueue,
+    private val dispatcher: EventDispatcher
+) {
+    var lastSeenTime: LocalDateTime = LocalDateTime.MIN
+    var backoff = Duration.ofSeconds(2)
+        private set
+    private val maxBackoff = Duration.ofMinutes(1)
+
+
+    suspend fun start() {
+        while (true) {
+            pollOnce()
+        }
+    }
+
+    suspend fun pollOnce() {
+        val newPersisted = eventStore.getPersistedEventsAfter(lastSeenTime)
+
+        if (newPersisted.isEmpty()) {
+            delay(backoff.toMillis())
+            backoff = backoff.multipliedBy(2).coerceAtMost(maxBackoff)
+            return
+        }
+
+        backoff = Duration.ofSeconds(2)
+
+        val grouped = newPersisted.groupBy { it.referenceId }
+
+        for ((referenceId, _) in grouped) {
+            if (dispatchQueue.isProcessing(referenceId)) continue
+
+            val fullLog = eventStore.getPersistedEventsFor(referenceId)
+            val events = fullLog.map { it.toEvent() }
+
+            dispatchQueue.dispatch(referenceId, events, dispatcher)
+            lastSeenTime = fullLog.maxOf { it.persistedAt }
+        }
+    }
+
+}

src/main/kotlin/no/iktdev/eventi/events/EventDispatcher.kt

@@ -0,0 +1,28 @@
+package no.iktdev.eventi.events
+
+import no.iktdev.eventi.models.DeleteEvent
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.stores.EventStore
+import java.util.UUID
+
+class EventDispatcher(val eventStore: EventStore) {
+
+    fun dispatch(referenceId: UUID, events: List<Event>) {
+        val derivedFromIds = events.mapNotNull { it.metadata.derivedFromId }.toSet()
+        val deletedEventIds = events.filterIsInstance<DeleteEvent>().map { it.deletedEventId }
+        val candidates = events
+            .filter { it.eventId !in derivedFromIds }
+            .filter { it.eventId !in deletedEventIds }
+
+        EventListenerRegistry.getListeners().forEach { listener ->
+            for (candidate in candidates) {
+                val result = listener.onEvent(candidate, events)
+                if (result != null) {
+
+                    eventStore.save(result)
+                    return
+                }
+            }
+        }
+    }
+}

src/main/kotlin/no/iktdev/eventi/events/EventListener.kt

@@ -0,0 +1,14 @@
+package no.iktdev.eventi.events
+
+import no.iktdev.eventi.models.Event
+
+abstract class EventListener: EventListenerImplementation {
+    init {
+        EventListenerRegistry.registerListener(this)
+    }
+
+}
+
+interface EventListenerImplementation {
+    fun onEvent(event: Event, history: List<Event>): Event?
+}

src/main/kotlin/no/iktdev/eventi/events/EventListenerRegistry.kt

@@ -0,0 +1,11 @@
+package no.iktdev.eventi.events
+
+object EventListenerRegistry {
+    private val listeners = mutableListOf<EventListener>()
+
+    fun registerListener(listener: EventListener) {
+        listeners.add(listener)
+    }
+
+    fun getListeners(): List<EventListener> = listeners.toList()
+}

src/main/kotlin/no/iktdev/eventi/events/EventTypeRegistry.kt

@@ -0,0 +1,31 @@
+package no.iktdev.eventi.events
+
+import no.iktdev.eventi.models.Event
+
+object EventTypeRegistry {
+    private val types = mutableMapOf<String, Class<out Event>>()
+
+    fun register(clazz: Class<out Event>) {
+        types[clazz.simpleName] = clazz
+    }
+    fun register(clazzes: List<Class<out Event>>) {
+        clazzes.forEach { clazz ->
+            types[clazz.simpleName] = clazz
+        }
+    }
+
+    fun resolve(name: String): Class<out Event>? = types[name]
+
+    fun all(): Map<String, Class<out Event>> = types.toMap()
+}
+
+
+abstract class EventTypeRegistration {
+    init {
+        definedTypes().forEach { clazz ->
+            EventTypeRegistry.register(clazz)
+        }
+    }
+
+    protected abstract fun definedTypes(): List<Class<out Event>>
+}

src/main/kotlin/no/iktdev/eventi/events/SequenceDispatchQueue.kt

@@ -0,0 +1,40 @@
+package no.iktdev.eventi.events
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Semaphore
+import no.iktdev.eventi.models.Event
+import java.util.UUID
+import java.util.concurrent.ConcurrentHashMap
+
+class SequenceDispatchQueue(
+    private val maxConcurrency: Int = 8,
+    private val scope: CoroutineScope = CoroutineScope(Dispatchers.Default + SupervisorJob())
+) {
+    private val semaphore = Semaphore(maxConcurrency)
+    private val active = ConcurrentHashMap.newKeySet<UUID>()
+
+    fun isProcessing(referenceId: UUID): Boolean = referenceId in active
+
+    fun dispatch(referenceId: UUID, events: List<Event>, dispatcher: EventDispatcher): Job? {
+        if (!active.add(referenceId)) return null // already processing
+
+        return scope.launch {
+            try {
+                semaphore.acquire()
+                try {
+                    dispatcher.dispatch(referenceId, events)
+                } catch (e: Exception) {
+                    println("Dispatch failed for $referenceId: ${e.message}")
+                } finally {
+                    semaphore.release()
+                }
+            } finally {
+                active.remove(referenceId)
+            }
+        }
+    }
+}

src/main/kotlin/no/iktdev/eventi/models/Event.kt

@@ -0,0 +1,33 @@
+package no.iktdev.eventi.models
+
+import java.time.LocalDateTime
+import java.util.UUID
+
+abstract class Event {
+    var referenceId: UUID = UUID.randomUUID()
+        protected set
+    var eventId: UUID = UUID.randomUUID()
+        private set
+    var metadata: Metadata = Metadata()
+        protected set
+
+    @Transient
+    open val data: Any? = null
+
+    fun derivedOf(event: Event) = apply {
+        this.referenceId = event.referenceId
+        this.metadata = Metadata(derivedFromId = event.eventId)
+    }
+
+}
+
+abstract class DeleteEvent: Event() {
+    open lateinit var deletedEventId: UUID
+}
+
+
+open class Metadata(
+    val created: LocalDateTime = LocalDateTime.now(), val derivedFromId: UUID? = null
+) {}
+
+

src/main/kotlin/no/iktdev/eventi/models/Task.kt

@@ -0,0 +1,3 @@
+package no.iktdev.eventi.models
+
+class Task()

src/main/kotlin/no/iktdev/eventi/models/store/PersistedEvent.kt

@@ -0,0 +1,13 @@
+package no.iktdev.eventi.models.store
+
+import java.time.LocalDateTime
+import java.util.UUID
+
+data class PersistedEvent(
+    val id: Long,
+    val referenceId: UUID,
+    val eventId: UUID,
+    val event: String,
+    val data: String,
+    val persistedAt: LocalDateTime
+)

src/main/kotlin/no/iktdev/eventi/stores/EventStore.kt

@@ -0,0 +1,13 @@
+package no.iktdev.eventi.stores
+
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.models.store.PersistedEvent
+import java.time.LocalDateTime
+import java.util.UUID
+
+interface EventStore {
+    fun getPersistedEventsAfter(timestamp: LocalDateTime): List<PersistedEvent>
+    fun getPersistedEventsFor(referenceId: UUID): List<PersistedEvent>
+    fun save(event: Event)
+}
+

src/test/kotlin/no/iktdev/eventi/EventDispatcherTest.kt

@@ -0,0 +1,165 @@
+package no.iktdev.eventi
+
+import no.iktdev.eventi.ZDS.toEvent
+import no.iktdev.eventi.ZDS.toPersisted
+import no.iktdev.eventi.events.EventDispatcher
+import no.iktdev.eventi.events.EventListener
+import no.iktdev.eventi.events.EventListenerRegistry
+import no.iktdev.eventi.events.EventTypeRegistry
+import no.iktdev.eventi.models.DeleteEvent
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.testUtil.wipe
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertNotNull
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.time.LocalDateTime
+import java.util.UUID
+
+class EventDispatcherTest: TestBase() {
+    val dispatcher = EventDispatcher(store)
+
+    class DerivedEvent(): Event()
+    class TriggerEvent(): Event() {
+        fun usingReferenceId(id: UUID) = apply { referenceId = id }
+    }
+    class OtherEvent(): Event()
+
+
+    @BeforeEach
+    fun setup() {
+        EventTypeRegistry.wipe()
+        EventListenerRegistry.wipe()
+        // Verifiser at det er tomt
+
+        EventTypeRegistry.register(listOf(
+            DerivedEvent::class.java,
+            TriggerEvent::class.java,
+            OtherEvent::class.java
+        ))
+    }
+
+
+    @Test
+    fun `should produce one event and stop`() {
+        val listener = ProducingListener()
+
+        val trigger = TriggerEvent()
+        dispatcher.dispatch(trigger.referenceId, listOf(trigger))
+
+        val produced = store.all().firstOrNull()
+        assertNotNull(produced)
+
+        val event = produced!!.toEvent()
+        assertEquals(trigger.eventId, event.metadata.derivedFromId)
+        assertTrue(event is DerivedEvent)
+    }
+
+    @Test
+    fun `should skip already derived events`() {
+        val listener = ProducingListener()
+
+        val trigger = TriggerEvent()
+        val derived = DerivedEvent().derivedOf(trigger).toPersisted(1L, LocalDateTime.now())
+        store.save(derived.toEvent()) // simulate prior production
+
+        dispatcher.dispatch(trigger.referenceId, listOf(trigger, derived.toEvent()))
+
+        assertEquals(1, store.all().size) // no new event produced
+    }
+
+    @Test
+    fun `should pass full context to listener`() {
+        val listener = ContextCapturingListener()
+
+        val e1 = TriggerEvent()
+        val e2 = OtherEvent()
+        dispatcher.dispatch(e1.referenceId, listOf(e1, e2))
+
+        assertEquals(2, listener.context.size)
+    }
+
+    @Test
+    fun `should behave deterministically across replays`() {
+        val listener = ProducingListener()
+
+        val trigger = TriggerEvent()
+        dispatcher.dispatch(trigger.referenceId, listOf(trigger))
+        val replayContext = listOf(trigger) + store.all().map { it.toEvent() }
+
+        dispatcher.dispatch(trigger.referenceId, replayContext)
+
+        assertEquals(1, store.all().size) // no duplicate
+    }
+
+    @Test
+    fun `should not deliver deleted events as candidates`() {
+        val dispatcher = EventDispatcher(store)
+        val received = mutableListOf<Event>()
+        object : EventListener() {
+            override fun onEvent(event: Event, history: List<Event>): Event? {
+                received += event
+                return null
+            }
+        }
+        // Original hendelse
+        val original = TriggerEvent()
+
+        // Slettehendelse som peker på original
+        val deleted = object : DeleteEvent() {
+            override var deletedEventId = original.eventId
+        }
+
+        // Dispatch med begge hendelser
+        dispatcher.dispatch(original.referenceId, listOf(original, deleted))
+
+        // Verifiser at original ikke ble levert som kandidat
+        assertFalse(received.contains(original)) {
+            "Original hendelse ble levert til lytteren selv om den var slettet"
+        }
+
+        // Verifiser at slett-hendelsen finnes i konteksten
+        assertTrue(received.any() { it is DeleteEvent }) {
+            "DeleteEvent skal leveres som kandidat"
+        }
+    }
+
+    @Test
+    fun `should deliver DeleteEvent to listeners that react to it`() {
+        val received = mutableListOf<Event>()
+        val listener = object : EventListener() {
+            override fun onEvent(event: Event, context: List<Event>): Event? {
+                if (event is DeleteEvent) received += event
+                return null
+            }
+        }
+
+        val deleted = object : DeleteEvent() {
+            override var deletedEventId = UUID.randomUUID()
+        }
+        dispatcher.dispatch(deleted.referenceId, listOf(deleted))
+
+        assertTrue(received.contains(deleted))
+    }
+
+
+
+    // --- Test helpers ---
+
+    class ProducingListener : EventListener() {
+        override fun onEvent(event: Event, context: List<Event>): Event? {
+            return if (event is TriggerEvent) DerivedEvent().derivedOf(event) else null
+        }
+    }
+
+    class ContextCapturingListener : EventListener() {
+        var context: List<Event> = emptyList()
+        override fun onEvent(event: Event, context: List<Event>): Event? {
+            this.context = context
+            return null
+        }
+    }
+
+}

src/test/kotlin/no/iktdev/eventi/EventTypeRegistryTest.kt

@@ -0,0 +1,31 @@
+package no.iktdev.eventi
+
+import no.iktdev.eventi.events.EchoEvent
+import no.iktdev.eventi.events.EventTypeRegistry
+import no.iktdev.eventi.events.StartEvent
+import no.iktdev.eventi.testUtil.wipe
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+
+class EventTypeRegistryTest: TestBase() {
+
+    @BeforeEach
+    fun setup() {
+        EventTypeRegistry.wipe()
+        // Verifiser at det er tomt
+        assertNull(EventTypeRegistry.resolve("SomeEvent"))
+    }
+
+
+    @Test
+    @DisplayName("Test EventTypeRegistry registration")
+    fun scenario1() {
+        DefaultTestEvents()
+        assertThat(EventTypeRegistry.resolve("EchoEvent")).isEqualTo(EchoEvent::class.java)
+        assertThat(EventTypeRegistry.resolve("StartEvent")).isEqualTo(StartEvent::class.java)
+    }
+
+}

src/test/kotlin/no/iktdev/eventi/InMemoryEventStore.kt

@@ -0,0 +1,27 @@
+package no.iktdev.eventi
+
+import no.iktdev.eventi.ZDS.toPersisted
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.models.store.PersistedEvent
+import no.iktdev.eventi.stores.EventStore
+import java.time.LocalDateTime
+import java.util.UUID
+
+class InMemoryEventStore : EventStore {
+    private val persisted = mutableListOf<PersistedEvent>()
+    private var nextId = 1L
+
+    override fun getPersistedEventsAfter(timestamp: LocalDateTime): List<PersistedEvent> =
+        persisted.filter { it.persistedAt > timestamp }
+
+    override fun getPersistedEventsFor(referenceId: UUID): List<PersistedEvent> =
+        persisted.filter { it.referenceId == referenceId }
+
+    override fun save(event: Event) {
+        val persistedEvent = event.toPersisted(nextId++, LocalDateTime.now())
+        persisted += persistedEvent
+    }
+
+    fun all(): List<PersistedEvent> = persisted
+    fun clear() { persisted.clear(); nextId = 1L }
+}

src/test/kotlin/no/iktdev/eventi/TestBase.kt

@@ -0,0 +1,25 @@
+package no.iktdev.eventi
+
+import no.iktdev.eventi.events.EchoEvent
+import no.iktdev.eventi.events.EventTypeRegistration
+import no.iktdev.eventi.events.StartEvent
+import no.iktdev.eventi.models.Event
+
+open class TestBase {
+
+    val store = InMemoryEventStore()
+
+    class DefaultTestEvents() : EventTypeRegistration() {
+        override fun definedTypes(): List<Class<out Event>> {
+            return listOf(
+                EchoEvent::class.java,
+                StartEvent::class.java
+            )
+        }
+    }
+
+    init {
+        DefaultTestEvents()
+    }
+
+}

src/test/kotlin/no/iktdev/eventi/ZDSTest.kt

@@ -0,0 +1,37 @@
+package no.iktdev.eventi
+
+import no.iktdev.eventi.ZDS.toEvent
+import no.iktdev.eventi.ZDS.toPersisted
+import no.iktdev.eventi.events.EchoEvent
+import no.iktdev.eventi.events.EventTypeRegistry
+import no.iktdev.eventi.testUtil.wipe
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+import java.time.LocalDateTime
+
+class ZDSTest {
+
+    @BeforeEach
+    fun setup() {
+        EventTypeRegistry.wipe()
+        // Verifiser at det er tomt
+        assertNull(EventTypeRegistry.resolve("SomeEvent"))
+    }
+
+    @Test
+    @DisplayName("Test ZDS")
+    fun scenario1() {
+        EventTypeRegistry.register(EchoEvent::class.java)
+
+        val echo = EchoEvent("hello")
+        val persisted = echo.toPersisted(id = 1L, persistedAt = LocalDateTime.now())
+
+        val restored = persisted.toEvent()
+        assert(restored is EchoEvent)
+        assert((restored as EchoEvent).data == "hello")
+
+    }
+
+}

src/test/kotlin/no/iktdev/eventi/events/AbstractEventPollerTest.kt

@@ -0,0 +1,152 @@
+package no.iktdev.eventi.events
+
+import kotlinx.coroutines.CompletableDeferred
+import kotlinx.coroutines.awaitAll
+import kotlinx.coroutines.test.runTest
+import no.iktdev.eventi.EventDispatcherTest
+import no.iktdev.eventi.EventDispatcherTest.DerivedEvent
+import no.iktdev.eventi.EventDispatcherTest.OtherEvent
+import no.iktdev.eventi.EventDispatcherTest.TriggerEvent
+import no.iktdev.eventi.TestBase
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.testUtil.wipe
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.time.Duration
+import java.time.LocalDateTime
+import java.util.UUID
+import java.util.concurrent.ConcurrentHashMap
+
+class AbstractEventPollerTest : TestBase() {
+    val dispatcher = EventDispatcher(store)
+    val queue = SequenceDispatchQueue(maxConcurrency = 8)
+
+    val poller = object : AbstractEventPoller(store, queue, dispatcher) {}
+
+    @BeforeEach
+    fun setup() {
+        EventTypeRegistry.wipe()
+        EventListenerRegistry.wipe()
+        store.clear()
+        // Verifiser at det er tomt
+
+        EventTypeRegistry.register(listOf(
+            DerivedEvent::class.java,
+            TriggerEvent::class.java,
+            OtherEvent::class.java
+        ))
+    }
+
+    @Test
+    fun `pollOnce should dispatch all new referenceIds and update lastSeenTime`() = runTest {
+        val dispatched = ConcurrentHashMap.newKeySet<UUID>()
+        val completionMap = mutableMapOf<UUID, CompletableDeferred<Unit>>()
+
+        EventListenerRegistry.registerListener(object : EventListener() {
+            override fun onEvent(event: Event, context: List<Event>): Event? {
+                dispatched += event.referenceId
+                completionMap[event.referenceId]?.complete(Unit)
+                return null
+            }
+        })
+
+        val referenceIds = (1..10).map { UUID.randomUUID() }
+
+        referenceIds.forEach { refId ->
+            val e = EventDispatcherTest.TriggerEvent().usingReferenceId(refId)
+            store.save(e) // persistedAt settes automatisk her
+            completionMap[refId] = CompletableDeferred()
+        }
+
+        poller.pollOnce()
+
+        completionMap.values.awaitAll()
+
+        assertEquals(referenceIds.toSet(), dispatched)
+    }
+
+    @Test
+    fun `pollOnce should increase backoff when no events and reset when events arrive`() = runTest {
+        val testPoller = object : AbstractEventPoller(store, queue, dispatcher) {
+            fun currentBackoff(): Duration = backoff
+        }
+
+        testPoller.pollOnce()
+        val afterFirst = testPoller.currentBackoff()
+
+        testPoller.pollOnce()
+        val afterSecond = testPoller.currentBackoff()
+
+        assertTrue(afterSecond > afterFirst)
+
+        val e = TriggerEvent().usingReferenceId(UUID.randomUUID())
+        store.save(e)
+
+        testPoller.pollOnce()
+        val afterReset = testPoller.currentBackoff()
+
+        assertEquals(Duration.ofSeconds(2), afterReset)
+    }
+
+    @Test
+    fun `pollOnce should group and dispatch exactly 3 events for one referenceId`() = runTest {
+        val refId = UUID.randomUUID()
+        val received = mutableListOf<Event>()
+        val done = CompletableDeferred<Unit>()
+
+        // Wipe alt før test
+        EventTypeRegistry.wipe()
+        EventListenerRegistry.wipe()
+        store.clear() // sørg for at InMemoryEventStore støtter dette
+
+        EventTypeRegistry.register(listOf(TriggerEvent::class.java))
+
+        object : EventListener() {
+            override fun onEvent(event: Event, context: List<Event>): Event? {
+                received += event
+                if (received.size == 3) done.complete(Unit)
+                return null
+            }
+        }
+
+        repeat(3) {
+            store.save(TriggerEvent().usingReferenceId(refId))
+        }
+
+        poller.pollOnce()
+
+        done.await()
+
+        assertEquals(3, received.size)
+        assertTrue(received.all { it.referenceId == refId })
+    }
+
+
+
+    @Test
+    fun `pollOnce should ignore events before lastSeenTime`() = runTest {
+        val refId = UUID.randomUUID()
+        val ignored = TriggerEvent().usingReferenceId(refId)
+
+        val testPoller = object : AbstractEventPoller(store, queue, dispatcher) {
+            init {
+                lastSeenTime = LocalDateTime.now().plusSeconds(1)
+            }
+        }
+
+        store.save(ignored)
+
+        testPoller.pollOnce()
+
+        assertFalse(queue.isProcessing(refId))
+    }
+
+
+
+
+
+
+}

src/test/kotlin/no/iktdev/eventi/events/SequenceDispatchQueueTest.kt

@@ -0,0 +1,65 @@
+package no.iktdev.eventi.events
+
+import kotlinx.coroutines.joinAll
+import kotlinx.coroutines.test.runTest
+import no.iktdev.eventi.EventDispatcherTest
+import no.iktdev.eventi.EventDispatcherTest.DerivedEvent
+import no.iktdev.eventi.EventDispatcherTest.OtherEvent
+import no.iktdev.eventi.EventDispatcherTest.TriggerEvent
+import no.iktdev.eventi.TestBase
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.testUtil.wipe
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.UUID
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+
+class SequenceDispatchQueueTest: TestBase() {
+
+    @BeforeEach
+    fun setup() {
+        EventTypeRegistry.wipe()
+        EventListenerRegistry.wipe()
+        // Verifiser at det er tomt
+
+        EventTypeRegistry.register(listOf(
+            DerivedEvent::class.java,
+            TriggerEvent::class.java,
+            OtherEvent::class.java
+        ))
+    }
+
+
+    @Test
+    fun `should dispatch all referenceIds with limited concurrency`() = runTest {
+        val dispatcher = EventDispatcher(store)
+        val queue = SequenceDispatchQueue(maxConcurrency = 8)
+
+        val dispatched = ConcurrentHashMap.newKeySet<UUID>()
+
+        EventListenerRegistry.registerListener(object : EventListener() {
+            override fun onEvent(event: Event, context: List<Event>): Event? {
+                dispatched += event.referenceId
+                Thread.sleep(50) // simuler tung prosessering
+                return null
+            }
+        })
+
+        val referenceIds = (1..100).map { UUID.randomUUID() }
+
+        val jobs = referenceIds.mapNotNull { refId ->
+            val e = TriggerEvent().usingReferenceId(refId)
+            store.save(e)
+            queue.dispatch(refId, listOf(e), dispatcher)
+        }
+
+        jobs.joinAll()
+
+        assertEquals(100, dispatched.size)
+    }
+
+
+}

src/test/kotlin/no/iktdev/eventi/events/TestEvents.kt

@@ -0,0 +1,11 @@
+package no.iktdev.eventi.events
+
+import no.iktdev.eventi.models.Event
+import no.iktdev.eventi.models.Metadata
+import java.util.UUID
+
+class StartEvent(): Event() {
+}
+
+class EchoEvent(override var data: String): Event() {
+}

src/test/kotlin/no/iktdev/eventi/testUtil/EventListenerRegistryUtil.kt

@@ -0,0 +1,18 @@
+package no.iktdev.eventi.testUtil
+
+import no.iktdev.eventi.events.EventListener
+import no.iktdev.eventi.events.EventListenerRegistry
+import org.assertj.core.api.Assertions.assertThat
+import java.lang.reflect.Field
+
+fun EventListenerRegistry.wipe() {
+    val field: Field = EventListenerRegistry::class.java.getDeclaredField("listeners")
+    field.isAccessible = true
+
+    // Tøm map’en
+    val mutableList = field.get(EventListenerRegistry) as MutableList<*>
+    (mutableList as MutableList<Class<out EventListener>>).clear()
+
+    // Verifiser at det er tomt
+    assertThat(EventListenerRegistry.getListeners().isEmpty())
+}

src/test/kotlin/no/iktdev/eventi/testUtil/EventTypeRegistryUtil.kt

@@ -0,0 +1,18 @@
+package no.iktdev.eventi.testUtil
+
+import no.iktdev.eventi.events.EventTypeRegistry
+import no.iktdev.eventi.models.Event
+import org.junit.jupiter.api.Assertions.assertNull
+import java.lang.reflect.Field
+
+fun EventTypeRegistry.wipe() {
+    val field: Field = EventTypeRegistry::class.java.getDeclaredField("types")
+    field.isAccessible = true
+
+    // Tøm map’en
+    val typesMap = field.get(EventTypeRegistry) as MutableMap<*, *>
+    (typesMap as MutableMap<String, Class<out Event>>).clear()
+
+    // Verifiser at det er tomt
+    assertNull(EventTypeRegistry.resolve("ANnonExistingEvent"))
+}