From 33eaeaaa3cd19ee8c63d5e72034aa565b49a4d6c Mon Sep 17 00:00:00 2001
From: Tobias Eidelpes <tobias@eidelpes.info>
Date: Wed, 7 Apr 2021 16:45:06 +0200
Subject: [PATCH] Implement Key-Value part (1.5)

---
 .../java/dst/ass1/kv/impl/SessionManager.java | 86 +++++++++++++++++++
 .../ass1/kv/impl/SessionManagerFactory.java   |  7 +-
 2 files changed, 90 insertions(+), 3 deletions(-)
 create mode 100644 ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManager.java

diff --git a/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManager.java b/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManager.java
new file mode 100644
index 0000000..5118495
--- /dev/null
+++ b/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManager.java
@@ -0,0 +1,86 @@
+package dst.ass1.kv.impl;
+
+import dst.ass1.kv.ISessionManager;
+import dst.ass1.kv.SessionCreationFailedException;
+import dst.ass1.kv.SessionNotFoundException;
+import redis.clients.jedis.Jedis;
+import redis.clients.jedis.Transaction;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+
+public class SessionManager implements ISessionManager {
+    private final Jedis jedis;
+
+    public SessionManager(Jedis jedis) {
+        this.jedis = jedis;
+    }
+
+    @Override
+    public String createSession(Long userId, int timeToLive) throws SessionCreationFailedException {
+        UUID sessionToken = UUID.randomUUID();
+
+        // Watch keys to avoid interference with other operations
+        jedis.watch(sessionToken.toString(), userId.toString());
+
+        Transaction t = jedis.multi();
+        Map<String, String> sessionMap = new HashMap<>();
+        sessionMap.put("userId", userId.toString());
+        t.hset(sessionToken.toString(), sessionMap);
+        t.expire(sessionToken.toString(), timeToLive);
+
+        t.set(userId.toString(), sessionToken.toString());
+        t.expire(userId.toString(), timeToLive);
+
+        if (t.exec() == null)
+            throw new SessionCreationFailedException("Could not create session for userId " + userId);
+
+        return sessionToken.toString();
+    }
+
+    @Override
+    public void setSessionVariable(String sessionId, String key, String value) throws SessionNotFoundException {
+        if (!jedis.exists(sessionId))
+            throw new SessionNotFoundException("Session for session id " + sessionId + " could not be found");
+
+        jedis.watch(sessionId);
+        Transaction t = jedis.multi();
+        t.hset(sessionId, key, value);
+        t.exec();
+    }
+
+    @Override
+    public String getSessionVariable(String sessionId, String key) throws SessionNotFoundException {
+        if (!jedis.exists(sessionId))
+            throw new SessionNotFoundException("Session for session id " + sessionId + " could not be found");
+
+        return jedis.hget(sessionId, key);
+    }
+
+    @Override
+    public Long getUserId(String sessionId) throws SessionNotFoundException {
+        return Long.valueOf(getSessionVariable(sessionId, "userId"));
+    }
+
+    @Override
+    public int getTimeToLive(String sessionId) throws SessionNotFoundException {
+        if (!jedis.exists(sessionId))
+            throw new SessionNotFoundException("Session for session id " + sessionId + " could not be found");
+
+        return Math.toIntExact(jedis.ttl(sessionId));
+    }
+
+    @Override
+    public String requireSession(Long userId, int timeToLive) throws SessionCreationFailedException {
+        if (!jedis.exists(userId.toString()))
+            return createSession(userId, timeToLive);
+        else
+            return jedis.get(userId.toString());
+    }
+
+    @Override
+    public void close() {
+        jedis.close();
+    }
+}
diff --git a/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManagerFactory.java b/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManagerFactory.java
index 06b84d7..879c9de 100644
--- a/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManagerFactory.java
+++ b/ass1-kv/src/main/java/dst/ass1/kv/impl/SessionManagerFactory.java
@@ -2,6 +2,7 @@ package dst.ass1.kv.impl;
 
 import dst.ass1.kv.ISessionManager;
 import dst.ass1.kv.ISessionManagerFactory;
+import redis.clients.jedis.Jedis;
 
 import java.util.Properties;
 
@@ -9,9 +10,9 @@ public class SessionManagerFactory implements ISessionManagerFactory {
 
     @Override
     public ISessionManager createSessionManager(Properties properties) {
-        // TODO
-        // read "redis.host" and "redis.port" from the properties
+        Jedis jedis = new Jedis(properties.getProperty("redis.host"),
+                Integer.parseInt(properties.getProperty("redis.port")));
 
-        return null;
+        return new SessionManager(jedis);
     }
 }