feat: integrate Redis for screen time caching with fallback to PostgreSQL

build.gradle.kts

@@ -31,4 +31,8 @@ dependencies {
     implementation("org.jetbrains.exposed:exposed-jdbc:0.50.0")
     testImplementation(kotlin("test"))
     testImplementation(ktorLibs.server.testHost)
+
+    //redis
+    implementation("redis.clients:jedis:5.1.2")
+
 }

src/main/kotlin/com/oliver/kidio/backend/data/database/RedisFactory.kt

@@ -0,0 +1,28 @@
+package com.oliver.kidio.backend.data.database
+import io.ktor.server.config.*
+import redis.clients.jedis.JedisPool
+import redis.clients.jedis.JedisPoolConfig
+
+object RedisFactory {
+    private var jedisPool: JedisPool? = null
+
+    fun init(config: ApplicationConfig) {
+        val host = System.getenv("REDIS_HOST")
+            ?: config.propertyOrNull("storage.redisHost")?.getString()
+            ?: "localhost"
+
+        val port = (System.getenv("REDIS_PORT")
+            ?: config.propertyOrNull("storage.redisPort")?.getString()
+            ?: "6379").toInt()
+
+        val poolConfig = JedisPoolConfig().apply {
+            maxTotal = 32
+            maxIdle = 8
+            minIdle = 2
+        }
+        jedisPool = JedisPool(poolConfig, host, port)
+    }
+
+    fun getResource() = jedisPool?.resource
+        ?: throw IllegalStateException("Redis Verbindungspool ist nicht initzialisiert")
+}

src/main/kotlin/com/oliver/kidio/backend/domain/repository/KidioRepository.kt

@@ -2,6 +2,7 @@ package com.oliver.kidio.backend.domain.repository
 
 import com.oliver.kidio.backend.Task
 import com.oliver.kidio.backend.data.database.DatabaseFactory
+import com.oliver.kidio.backend.data.database.RedisFactory
 import com.oliver.kidio.backend.data.database.ScreentimeTable
 import com.oliver.kidio.backend.data.database.TasksTable
 import org.jetbrains.exposed.sql.*
@@ -32,12 +33,36 @@ class ExposedKidioRepository : KidioRepository {
             .singleOrNull()
     }
 
-    override suspend fun getScreentime(userId: String): Int = DatabaseFactory.dbQuery {
+    override suspend fun getScreentime(userId: String): Int {
+        var redisKey = "screentime:$userId"
+
+        try {
+            RedisFactory.getResource().use { jedis ->
+                val cachedSeconds = jedis.get(redisKey)
+                if (cachedSeconds != null) {
+                    println("DEBUG: Bildschirmzeit für $userId aus REDIS geladen: $cachedSeconds Sek")
+                    return cachedSeconds.toInt()
+                }
+            }
+        } catch (e: Exception) {
+            println("WARNUNG: Konnte nicht aus Redis lesen (Postgres-Fallback genutzt): ${e.message}")
+        }
+        val dbSeconds = DatabaseFactory.dbQuery {
             ScreentimeTable.selectAll()
                 .where { ScreentimeTable.userId eq userId }
                 .map { it[ScreentimeTable.remainingSeconds] }
                 .singleOrNull() ?: 1800
         }
+        try {
+            RedisFactory.getResource().use { jedis ->
+                jedis.setex(redisKey, 3600, dbSeconds.toString())
+                println("DEBUG: Bildschirmzeit für $userId in REDIS gecacht.")
+            }
+        } catch (e: Exception) {
+            println("WARNUNG: Konnte Wert nicht in Redis speichern: ${e.message}")
+        }
+        return dbSeconds
+    }
 
     override suspend fun updateScreentime(userId: String, seconds: Int): Unit = DatabaseFactory.dbQuery {
         val rowsUpdated = ScreentimeTable.update({ ScreentimeTable.userId eq userId }) {

src/main/kotlin/main.kt

@@ -1,5 +1,6 @@
 import com.oliver.kidio.backend.plugins.configureRouting
 import com.oliver.kidio.backend.data.database.DatabaseFactory
+import com.oliver.kidio.backend.data.database.RedisFactory
 import com.oliver.kidio.backend.domain.repository.ExposedKidioRepository
 import io.ktor.serialization.kotlinx.json.*
 import io.ktor.server.application.*
@@ -8,6 +9,7 @@ import io.ktor.server.plugins.contentnegotiation.*
 fun Application.module() {
     // Datenbank initialisieren
     DatabaseFactory.init(environment.config)
+    RedisFactory.init(environment.config)
 
     // JSON aktivieren
     install(ContentNegotiation) {