[Feature/SessionStats] Endpoint to fetch session data

JShellAPI/src/main/java/org/togetherjava/jshellapi/dto/sessionstats/SessionStats.java

@@ -0,0 +1,17 @@
+package org.togetherjava.jshellapi.dto.sessionstats;
+
+/**
+ * Represents the stats of a session.
+ *
+ * @param id the id of this session
+ * @param timeSinceCreation the time in seconds since the creation of this session
+ * @param timeUntilExpiration the time in seconds until the expiration of this session
+ * @param totalEvalTime the time spent evaluating code
+ * @param doingOperation if the session is currently evaluating some code
+ */
+public record SessionStats(
+        String id,
+        long timeSinceCreation,
+        long timeUntilExpiration,
+        long totalEvalTime,
+        boolean doingOperation) {}

JShellAPI/src/main/java/org/togetherjava/jshellapi/rest/JShellController.java

@@ -7,6 +7,7 @@
 
 import org.togetherjava.jshellapi.dto.JShellResult;
 import org.togetherjava.jshellapi.dto.JShellResultWithId;
+import org.togetherjava.jshellapi.dto.sessionstats.SessionStats;
 import org.togetherjava.jshellapi.exceptions.DockerException;
 import org.togetherjava.jshellapi.service.JShellService;
 import org.togetherjava.jshellapi.service.JShellSessionService;
@@ -71,6 +72,11 @@ public void delete(@PathVariable String id) throws DockerException {
         service.deleteSession(id);
     }
 
+    @GetMapping("sessions")
+    public List<SessionStats> sessions() {
+        return service.fetchStats();
+    }
+
     @GetMapping("/startup_script/{id}")
     public String startupScript(@PathVariable StartupScriptId id) {
         return startupScriptsService.get(id);

JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellService.java

@@ -6,6 +6,7 @@
 import org.springframework.lang.Nullable;
 
 import org.togetherjava.jshellapi.dto.*;
+import org.togetherjava.jshellapi.dto.sessionstats.SessionStats;
 import org.togetherjava.jshellapi.exceptions.DockerException;
 
 import java.io.*;
@@ -21,6 +22,8 @@ public class JShellService implements Closeable {
     private final String id;
     private final BufferedWriter writer;
     private final BufferedReader reader;
+    private final Instant creationTime;
+    private long totalEvalTime;
 
     private Instant lastTimeoutUpdate;
     private final long timeout;
@@ -66,6 +69,7 @@ public JShellService(DockerService dockerService, JShellSessionService sessionSe
             throw new DockerException("Creation of the session failed.", e);
         }
         this.doingOperation = false;
+        this.creationTime = Instant.now();
     }
 
     public Optional<JShellResult> eval(String code) throws DockerException {
@@ -80,6 +84,7 @@ public Optional<JShellResult> eval(String code) throws DockerException {
         }
         updateLastTimeout();
         sessionService.scheduleEvalTimeoutValidation(id, evalTimeout + evalTimeoutValidationLeeway);
+        Instant start = Instant.now();
         if (!code.endsWith("\n"))
             code += '\n';
         try {
@@ -98,6 +103,7 @@ public Optional<JShellResult> eval(String code) throws DockerException {
             close();
             throw new DockerException(ex);
         } finally {
+            totalEvalTime += Duration.between(start, Instant.now()).getSeconds();
             stopOperation();
         }
     }
@@ -204,6 +210,18 @@ public String id() {
         return id;
     }
 
+    public SessionStats fetchSessionInfo() {
+        long timeSinceCreation = Duration.between(creationTime, Instant.now()).getSeconds();
+        long timeUntilExpiration =
+                Duration.between(Instant.now(), lastTimeoutUpdate.plusSeconds(timeout))
+                        .getSeconds();
+        if (timeUntilExpiration < 0) {
+            timeUntilExpiration = 0;
+        }
+        return new SessionStats(
+                id, timeSinceCreation, timeUntilExpiration, totalEvalTime, doingOperation);
+    }
+
     @Override
     public void close() {
         LOGGER.debug("Close called for session {}.", id);

JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java

@@ -9,6 +9,7 @@
 import org.springframework.web.server.ResponseStatusException;
 
 import org.togetherjava.jshellapi.Config;
+import org.togetherjava.jshellapi.dto.sessionstats.SessionStats;
 import org.togetherjava.jshellapi.exceptions.DockerException;
 
 import java.util.*;
@@ -133,6 +134,13 @@ public void scheduleEvalTimeoutValidation(String id, long timeSeconds) {
         }, timeSeconds, TimeUnit.SECONDS);
     }
 
+    public List<SessionStats> fetchStats() {
+        return jshellSessions.values().stream()
+                .map(JShellService::fetchSessionInfo)
+                .sorted(Comparator.comparingLong(SessionStats::timeSinceCreation).reversed())
+                .toList();
+    }
+
     @Autowired
     public void setConfig(Config config) {
         this.config = config;