Initial commitHEADmain

9 files changed, 779 insertions, 0 deletions

diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionController.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionController.java
new file mode 100644
index 0000000..9a0d898
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionController.java
@@ -0,0 +1,129 @@
+package org.psesquared.server.episode.actions.api.controller;
+
+import java.util.List;
+import lombok.RequiredArgsConstructor;
+import org.psesquared.server.episode.actions.api.service.EpisodeActionService;
+import org.psesquared.server.util.UpdateUrlsWrapper;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * This is a controller class for the Episode Action API that
+ * handles the requests from the client concerning the synchronization
+ * of episodes between clients.
+ * In the end an appropriate response is sent back to the user.
+ */
+@RequestMapping("/api/2/episodes/{username}.json")
+@RestController
+@RequiredArgsConstructor
+public class EpisodeActionController {
+
+  /**
+   * The service class that this controller calls to further process requests.
+   */
+  private final EpisodeActionService episodeActionService;
+
+  /**
+   * Takes a list of EpisodeActionPosts of a user and adds them to the database.
+   *
+   * @param username           The username of the user uploading the
+   *                           EpisodeActions
+   * @param episodeActionPosts The list of EpisodeActionPosts to be uploaded
+   * @return The exit status of the function
+   */
+  @PostMapping
+  public ResponseEntity<UpdateUrlsWrapper> addEpisodeActions(
+      @PathVariable final String username,
+      @RequestBody final List<EpisodeActionPost> episodeActionPosts) {
+    episodeActionService.addEpisodeActions(username, episodeActionPosts);
+    return ResponseEntity.ok(new UpdateUrlsWrapper());
+  }
+
+  /**
+   * Returns a list of all EpisodeActions a user has uploaded so far in the form
+   * of an EpisodeActionGetResponse.
+   *
+   * @param username The username of the user whose EpisodeActions are requested
+   * @return The exit status with a response body containing all requested
+   *        EpisodeActions
+   */
+  @GetMapping
+  public ResponseEntity<EpisodeActionGetResponse> getEpisodeActions(
+      @PathVariable final String username) {
+    EpisodeActionGetResponse responseBody
+        = new EpisodeActionGetResponse(episodeActionService
+        .getEpisodeActions(username));
+    return ResponseEntity.ok(responseBody);
+  }
+
+  /**
+   * Returns a list of EpisodeActions of a user for a given podcast in the form
+   * of an EpisodeActionGetResponse.
+   *
+   * @param username   The username of the user whose EpisodeActions are
+   *                   requested
+   * @param podcastUrl The RSS-Feed URL of the podcast in question
+   * @return The exit status with a response body containing all requested
+   *        EpisodeActions
+   */
+  @GetMapping(params = {"podcast"})
+  public ResponseEntity<EpisodeActionGetResponse> getEpisodeActionsOfPodcast(
+      @PathVariable final String username,
+      @RequestParam("podcastUrl") final String podcastUrl) {
+    EpisodeActionGetResponse responseBody
+        = new EpisodeActionGetResponse(episodeActionService
+        .getEpisodeActionsOfPodcast(username, podcastUrl));
+    return ResponseEntity.ok(responseBody);
+  }
+
+  /**
+   * Returns a list of EpisodeActions of a user since a given timestamp in the
+   * form of an EpisodeActionGetResponse.
+   *
+   * @param username The username of the user whose EpisodeActions are requested
+   * @param since    The timestamp signifying how old the EpisodeActions are
+   *                 allowed to be
+   * @return The exit status with a response body containing all requested
+   *        EpisodeActions
+   */
+  @GetMapping(params = {"since"})
+  public ResponseEntity<EpisodeActionGetResponse> getEpisodeActionsSince(
+      @PathVariable final String username,
+      @RequestParam("since") final long since) {
+    EpisodeActionGetResponse responseBody
+        = new EpisodeActionGetResponse(episodeActionService
+        .getEpisodeActionsSince(username, since));
+    return ResponseEntity.ok(responseBody);
+  }
+
+  /**
+   * Returns a list of EpisodeActions of a user for a given podcast, since a
+   * given time in the form of an EpisodeActionGetResponse.
+   *
+   * @param username   The username of the user whose EpisodeActions are
+   *                   requested
+   * @param podcastUrl The RSS-Feed URL of the podcast in question
+   * @param since      The timestamp signifying how old the EpisodeActions are
+   *                   allowed to be
+   * @return The exit status with a response body containing all requested
+   *        EpisodeActions
+   */
+  @GetMapping(params = {"podcast", "since"})
+  public ResponseEntity<EpisodeActionGetResponse>
+      getEpisodeActionsOfPodcastSince(
+          @PathVariable final String username,
+          @RequestParam("podcastUrl") final String podcastUrl,
+          @RequestParam("since") final long since) {
+    EpisodeActionGetResponse responseBody
+        = new EpisodeActionGetResponse(episodeActionService
+        .getEpisodeActionsOfPodcastSince(username, podcastUrl, since));
+    return ResponseEntity.ok(responseBody);
+  }
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionGetResponse.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionGetResponse.java
new file mode 100644
index 0000000..d1facac
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionGetResponse.java
@@ -0,0 +1,37 @@
+package org.psesquared.server.episode.actions.api.controller;
+
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.util.List;
+import lombok.Data;
+
+/**
+ * The Response Object for a GET-Request concerning an EpisodeAction.
+ * <br>
+ * May contain multiple EpisodeActions.
+ */
+@Data
+public class EpisodeActionGetResponse {
+
+  /**
+   * The list of EpisodeActionPosts.
+   */
+  private final List<EpisodeActionPost> actions;
+
+  /**
+   * The timestamp of the response.
+   */
+  private final long timestamp;
+
+  /**
+   * Instantiates a new EpisodeActionGetResponse with the current timestamp.
+   *
+   * @param episodeActionPosts A list of EpisodeActionPosts
+   */
+  public EpisodeActionGetResponse(
+      final List<EpisodeActionPost> episodeActionPosts) {
+    this.actions = episodeActionPosts;
+    this.timestamp = LocalDateTime.now().toEpochSecond(ZoneOffset.UTC);
+  }
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionPost.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionPost.java
new file mode 100644
index 0000000..28613f2
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/EpisodeActionPost.java
@@ -0,0 +1,61 @@
+package org.psesquared.server.episode.actions.api.controller;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonUnwrapped;
+import jakarta.validation.constraints.NotBlank;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.psesquared.server.model.EpisodeAction;
+
+/**
+ * An Episode Action that is being sent to the server via a POST Request.
+ * <br>
+ * If the user listened to an episode or did another action, an
+ * EpisodeActionPOST is uploaded.
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class EpisodeActionPost {
+
+  /**
+   * The URL of the podcast the posted episode action belongs to.
+   */
+  @JsonProperty(value = "podcast", required = true)
+  @NotBlank
+  private String podcastUrl;
+
+  /**
+   * The URL of the corresponding episode.
+   */
+  @JsonProperty(value = "episode", required = true)
+  @NotBlank
+  private String episodeUrl;
+
+  /**
+   * The title of the corresponding episode.
+   */
+  private String title;
+
+  /**
+   * The GUID of the corresponding episode.
+   */
+  private String guid;
+
+  /**
+   * The total length of the corresponding episode in milliseconds.
+   */
+  private int total;
+
+  /**
+   * The actual episode action whose attributes are presented unwrapped.
+   *
+   * @see JsonUnwrapped
+   */
+  @JsonUnwrapped
+  private EpisodeAction episodeAction;
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/package-info.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/package-info.java
new file mode 100644
index 0000000..3115012
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/controller/package-info.java
@@ -0,0 +1,13 @@
+/**
+ * This package represents the highest logical layer of the episode action API
+ * ({@link org.psesquared.server.episode.actions.api}) - the controller layer.
+ * <br>
+ * It contains the
+ * {@link
+ * org.psesquared.server.episode.actions.api.controller.EpisodeActionController}
+ * along with some wrapper classes for JSON request and response bodies.
+ *
+ * @author PSE-Squared Team
+ * @version 1.0
+ */
+package org.psesquared.server.episode.actions.api.controller;
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeActionDao.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeActionDao.java
new file mode 100644
index 0000000..7f23312
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeActionDao.java
@@ -0,0 +1,107 @@
+package org.psesquared.server.episode.actions.api.data.access;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.Optional;
+import org.psesquared.server.model.Action;
+import org.psesquared.server.model.EpisodeAction;
+import org.psesquared.server.model.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+/**
+ * A DAO interface responsible for transactions involving EpisodeActions.
+ */
+@Repository
+public interface EpisodeActionDao extends JpaRepository<EpisodeAction, Long> {
+
+  /**
+   * Find all EpisodeActions a user has uploaded.
+   *
+   * @param username The username of the user who uploaded the EpisodeActions
+   * @return The list of EpisodeActions regarding the user
+   */
+  List<EpisodeAction> findByUserUsername(String username);
+
+  /**
+   * Find all EpisodeActions of a user that concern a certain podcast identified
+   * by its RSS-Feed URL.
+   *
+   * @param username The username of the user who uploaded the EpisodeActions
+   * @param url      The RSS-Feed URL of the podcast in question
+   * @return The list of EpisodeActions regarding the user and the given podcast
+   */
+  List<EpisodeAction> findByUserUsernameAndEpisodeSubscriptionUrl(
+      String username,
+      String url);
+
+  /**
+   * Deletes all EpisodeActions of a podcast for a user.
+   *
+   * @param username The username of the user
+   * @param url The podcast URL
+   */
+  void deleteByUserUsernameAndEpisodeSubscriptionUrl(
+      String username,
+      String url);
+
+  /**
+   * Checks if an EpisodeAction of the specified action type for a given user
+   * and episode already exists.
+   *
+   * @param user The user
+   * @param url The episode URL
+   * @param action The type of action
+   * @return {@code true} if such an EpisodeAction exists,
+   *        <br>
+   *        {@code false} otherwise
+   */
+  boolean existsByUserAndEpisodeUrlAndAction(User user,
+                                             String url,
+                                             Action action);
+
+  /**
+   * Finds the EpisodeAction of the specified action type and of an Episode
+   * for a User.
+   *
+   * @param user The user
+   * @param url The episode URL
+   * @param action The type of action
+   * @return An {@link Optional} containing the EpisodeAction if present
+   */
+  Optional<EpisodeAction> findByUserAndEpisodeUrlAndAction(User user,
+                                                           String url,
+                                                           Action action);
+
+  /**
+   * Find all EpisodeActions of a user since a given timestamp.
+   *
+   * @param username  The username of the user
+   * @param timestamp The timestamp signifying how old an EpisodeAction is
+   *                  allowed
+   *                  to be
+   * @return A list containing all EpisodeActions not older than the timestamp
+   */
+  List<EpisodeAction> findByUserUsernameAndTimestampGreaterThanEqual(
+      String username,
+      LocalDateTime timestamp);
+
+  /**
+   * Find all EpisodeActions of a user since a given timestamp of a given
+   * podcast.
+   *
+   * @param username  The username of the user
+   * @param timestamp The timestamp signifying how old an EpisodeAction is
+   *                  allowed to be
+   * @param url       The RSS-Feed URL of the podcast whose EpisodeActions are
+   *                  requested
+   * @return A list containing all EpisodeActions of the given podcast not older
+   *        than the timestamp
+   */
+  List<EpisodeAction>
+      findByUserUsernameAndTimestampGreaterThanEqualAndEpisodeSubscriptionUrl(
+          String username,
+          LocalDateTime timestamp,
+          String url);
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeDao.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeDao.java
new file mode 100644
index 0000000..16c647f
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/EpisodeDao.java
@@ -0,0 +1,46 @@
+package org.psesquared.server.episode.actions.api.data.access;
+
+import java.util.Optional;
+import org.psesquared.server.model.Episode;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+/**
+ * A DAO interface responsible for transactions involving Episodes.
+ */
+@Repository
+public interface EpisodeDao extends JpaRepository<Episode, Long> {
+
+  /**
+   * Find an episode by its URL.
+   *
+   * @param url The URL of the episode
+   * @return The matching episode / NULL, if there was no match.
+   */
+  Optional<Episode> findByUrl(String url);
+
+  /**
+   * Returns true if there is an episode that matches a given URL.
+   *
+   * @param url The URL of the episode
+   * @return A boolean value signifying whether the episode exists
+   */
+  boolean existsByUrl(String url);
+
+  /**
+   * Returns true if there is an episode that matches a given GUID.
+   *
+   * @param guid The GUID of the episode
+   * @return A boolean value signifying whether the episode exists
+   */
+  boolean existsByGuid(String guid);
+
+  /**
+   * Find an episode by its GUID.
+   *
+   * @param guid The GUID of the episode
+   * @return The matching episode / NULL, if there was no match.
+   */
+  Optional<Episode> findByGuid(String guid);
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/package-info.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/package-info.java
new file mode 100644
index 0000000..b32f249
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/data/access/package-info.java
@@ -0,0 +1,13 @@
+/**
+ * This package represents the lowest logical layer of the episode action API
+ * ({@link org.psesquared.server.episode.actions.api}) - the data-access layer.
+ * <br>
+ * It features the interfaces {@link
+ * org.psesquared.server.episode.actions.api.data.access.EpisodeActionDao}
+ * and {@link
+ * org.psesquared.server.episode.actions.api.data.access.EpisodeDao}.
+ *
+ * @author PSE-Squared Team
+ * @version 1.0
+ */
+package org.psesquared.server.episode.actions.api.data.access;
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/EpisodeActionService.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/EpisodeActionService.java
new file mode 100644
index 0000000..8c4f93a
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/EpisodeActionService.java
@@ -0,0 +1,360 @@
+package org.psesquared.server.episode.actions.api.service;
+
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import lombok.RequiredArgsConstructor;
+import org.psesquared.server.authentication.api.data.access.AuthenticationDao;
+import org.psesquared.server.episode.actions.api.controller.EpisodeActionPost;
+import org.psesquared.server.episode.actions.api.data.access.EpisodeActionDao;
+import org.psesquared.server.episode.actions.api.data.access.EpisodeDao;
+import org.psesquared.server.model.Action;
+import org.psesquared.server.model.Episode;
+import org.psesquared.server.model.EpisodeAction;
+import org.psesquared.server.model.Subscription;
+import org.psesquared.server.model.SubscriptionAction;
+import org.psesquared.server.model.User;
+import org.psesquared.server.subscriptions.api.data.access.SubscriptionActionDao;
+import org.psesquared.server.subscriptions.api.data.access.SubscriptionDao;
+import org.psesquared.server.util.RssParser;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+/**
+ * This service class manages all business logic associated with the
+ * episode action API.
+ * <br>
+ * It is called from the
+ * {@link
+ * org.psesquared.server.episode.actions.api.controller.EpisodeActionController}
+ * and passes on requests concerning data access mainly to the
+ * {@link EpisodeDao} and {@link EpisodeActionDao}.
+ */
+@Service
+@Transactional
+@RequiredArgsConstructor
+public class EpisodeActionService {
+
+  /**
+   * The nano of second default value for
+   * {@link LocalDateTime#ofEpochSecond(long, int, ZoneOffset)}.
+   */
+  private static final int NANO_OF_SECOND_DEFAULT = 0;
+
+  /**
+   * The JPA repository that handles all episode action related database
+   * requests.
+   */
+  private final EpisodeActionDao episodeActionDao;
+
+  /**
+   * The JPA repository that handles all episode related database requests.
+   */
+  private final EpisodeDao episodeDao;
+
+  /**
+   * The JPA repository that handles all user related database requests.
+   */
+  private final AuthenticationDao authenticationDao;
+
+  /**
+   * The JPA repository that handles all subscription related database requests.
+   */
+  private final SubscriptionDao subscriptionDao;
+
+  /**
+   * The JPA repository that handles all subscription action related database
+   * requests.
+   */
+  private final SubscriptionActionDao subscriptionActionDao;
+
+  /**
+   * The class for asynchronously fetching data from RSS feeds.
+   */
+  private final RssParser rssParser;
+
+  /**
+   * A map of subscription that need to be fetched with the {@link RssParser}.
+   */
+  private final Map<String, Subscription> subscriptionsToFetch
+      = new HashMap<>();
+
+  /**
+   * Takes a list of EpisodeActionPosts, converts them to EpisodeActions and
+   * saves them to the database.
+   *
+   * @param username           The username of the user who uploads these
+   *                           EpisodeActions
+   * @param episodeActionPosts List of EpisodeActionPosts that were sent via the
+   *                           POST request
+   */
+  public void addEpisodeActions(
+      final String username,
+      final List<EpisodeActionPost> episodeActionPosts) {
+    User user = authenticationDao.findByUsername(username).orElseThrow();
+    List<EpisodeActionPost> filteredEpisodeActionPosts
+        = new ArrayList<>(filterNewestAction(episodeActionPosts));
+    List<EpisodeAction> episodeActions
+        = episodeActionPostsToEpisodeActions(user, filteredEpisodeActionPosts);
+    addEpisodeActionsToDatabase(user, episodeActions);
+    validateDummyEpisodes();
+  }
+
+  private Collection<EpisodeActionPost> filterNewestAction(
+      final List<EpisodeActionPost> episodeActionPosts) {
+    Map<String, EpisodeActionPost> relevantEpisodeActionPosts = new HashMap<>();
+    for (EpisodeActionPost episodeActionPost : episodeActionPosts) {
+      if (episodeActionPost.getEpisodeAction().getAction() != Action.PLAY) {
+        continue;
+      }
+      String url = episodeActionPost.getEpisodeUrl();
+      if (relevantEpisodeActionPosts.containsKey(url)) {
+        EpisodeActionPost currentEpisodeActionPost
+            = relevantEpisodeActionPosts.get(url);
+        if (episodeActionPost.getEpisodeAction().getTimestamp()
+            .isAfter(
+                currentEpisodeActionPost.getEpisodeAction().getTimestamp())) {
+          relevantEpisodeActionPosts.put(url, episodeActionPost);
+        }
+      } else {
+        relevantEpisodeActionPosts.put(url, episodeActionPost);
+      }
+    }
+    return relevantEpisodeActionPosts.values();
+  }
+
+  private List<EpisodeAction> episodeActionPostsToEpisodeActions(
+      final User user,
+      final List<EpisodeActionPost> episodeActionPosts) {
+    List<EpisodeAction> episodeActions = new ArrayList<>();
+    for (EpisodeActionPost episodeActionPost : episodeActionPosts) {
+      if (episodeActionPost.getEpisodeAction().getAction() == Action.PLAY) {
+        episodeActions.add(episodeActionPostToEpisodeAction(
+            user,
+            episodeActionPost));
+      }
+    }
+    return episodeActions;
+  }
+
+  private EpisodeAction episodeActionPostToEpisodeAction(
+      final User user,
+      final EpisodeActionPost episodeActionPost) {
+    EpisodeAction episodeAction = episodeActionPost.getEpisodeAction();
+    episodeAction.setUser(user);
+    // If Subscription does not exist, create dummy Subscription
+    Subscription subscription = null;
+    if (!subscriptionDao.existsByUrl(episodeActionPost.getPodcastUrl())) {
+      subscription = new Subscription();
+      subscription.setTimestamp(
+          LocalDateTime.now().toEpochSecond(ZoneOffset.UTC));
+      subscription.setUrl(episodeActionPost.getPodcastUrl());
+      subscription = subscriptionDao.save(subscription);
+      // create Subscription Action
+      SubscriptionAction subscriptionAction = SubscriptionAction.builder()
+          .user(user)
+          .added(true)
+          .subscription(
+              subscriptionDao.findByUrl(
+                  episodeActionPost.getPodcastUrl()).orElseThrow())
+          .timestamp(LocalDateTime.now().toEpochSecond(ZoneOffset.UTC))
+          .build();
+      subscriptionActionDao.save(subscriptionAction);
+    } else {
+      subscription = subscriptionDao
+          .findByUrl(episodeActionPost.getPodcastUrl()).orElseThrow();
+    }
+    Episode episode = getEpisodeFromDatabase(episodeActionPost);
+    episodeAction.setEpisode(episode);
+    subscription.addEpisode(episode);
+    return episodeAction;
+  }
+
+  private Episode getEpisodeFromDatabase(
+      final EpisodeActionPost episodeActionPost) {
+    Episode episode;
+    String episodeUrl = episodeActionPost.getEpisodeUrl();
+    String episodeGuid = episodeActionPost.getGuid();
+    // If guid is passed and a matching episode exists get it
+    if (episodeGuid != null && episodeDao.existsByGuid(episodeGuid)) {
+      episode = episodeDao.findByGuid(episodeGuid).orElseThrow();
+    } else if (episodeDao.existsByUrl(episodeUrl)) {
+      // No episode with matching guid found -> search by url
+      episode = episodeDao.findByUrl(episodeUrl).orElseThrow();
+      // If guid was passed, pass it along to the database
+      if (episodeGuid != null) {
+        episode.setGuid(episodeGuid);
+        episodeDao.save(episode);
+      }
+    } else {
+      // Episode does not exist, so construct a new one
+      episode = createEpisode(episodeActionPost);
+    }
+    return episode;
+  }
+
+  private Episode createEpisode(final EpisodeActionPost episodeActionPost) {
+    Episode episode = Episode.builder()
+        .title(episodeActionPost.getTitle())
+        .url(episodeActionPost.getEpisodeUrl())
+        .total(episodeActionPost.getTotal())
+        .subscription(subscriptionDao
+            .findByUrl(episodeActionPost.getPodcastUrl()).orElseThrow())
+        .build();
+    if (episodeActionPost.getGuid() != null) {
+      episode.setGuid(episodeActionPost.getGuid());
+    }
+    episodeDao.save(episode);
+    Subscription subscription = episode.getSubscription();
+    subscriptionsToFetch.put(subscription.getUrl(), subscription);
+    return episode;
+  }
+
+  private void addEpisodeActionsToDatabase(
+      final User user,
+      final List<EpisodeAction> episodeActions) {
+    for (EpisodeAction episodeAction : episodeActions) {
+      addEpisodeActionToDatabase(user, episodeAction);
+    }
+  }
+
+  private void addEpisodeActionToDatabase(
+      final User user,
+      final EpisodeAction episodeAction) {
+    if (episodeActionDao.existsByUserAndEpisodeUrlAndAction(
+        user,
+        episodeAction.getEpisode().getUrl(),
+        episodeAction.getAction())) {
+      addNewestEpisodeActionToDatabase(user, episodeAction);
+    } else {
+      episodeActionDao.save(episodeAction);
+    }
+  }
+
+  private void addNewestEpisodeActionToDatabase(
+      final User user,
+      final EpisodeAction episodeAction) {
+    EpisodeAction oldEpisodeAction
+        = episodeActionDao.findByUserAndEpisodeUrlAndAction(
+        user,
+        episodeAction.getEpisode().getUrl(),
+        episodeAction.getAction()).orElseThrow();
+    if (episodeAction.getTimestamp().isAfter(oldEpisodeAction.getTimestamp())) {
+      episodeActionDao.delete(oldEpisodeAction);
+      episodeActionDao.save(episodeAction);
+    }
+  }
+
+  private void validateDummyEpisodes() {
+    Collection<Subscription> subscriptions = subscriptionsToFetch.values();
+    for (Subscription subscription : subscriptions) {
+      rssParser.validate(subscription);
+    }
+    subscriptionsToFetch.clear();
+  }
+
+  /**
+   * Gets all EpisodeActions of a user and converts them to EpisodeActionPosts
+   * before returning them.
+   *
+   * @param username The username of the user whose EpisodeActions are requested
+   * @return A list containing the requested EpisodeActions as
+   *        EpisodeActionPosts
+   */
+  public List<EpisodeActionPost> getEpisodeActions(final String username) {
+    List<EpisodeAction> episodeActions
+        = episodeActionDao.findByUserUsername(username);
+    return episodeActionsToEpisodeActionPosts(episodeActions);
+  }
+
+  /**
+   * Gets all EpisodeActions of a user that correspond to a given podcast.
+   * Returns the EpisodeActions after converting them to EpisodeActionPosts.
+   *
+   * @param username   The username of the user whose EpisodeActions are
+   *                   requested
+   * @param podcastUrl The RSS-Feed URL of the podcast
+   * @return A list containing the requested EpisodeActions as
+   *        EpisodeActionPosts
+   */
+  public List<EpisodeActionPost> getEpisodeActionsOfPodcast(
+      final String username,
+      final String podcastUrl) {
+    List<EpisodeAction> episodeActions
+        = episodeActionDao.findByUserUsernameAndEpisodeSubscriptionUrl(
+            username,
+            podcastUrl);
+    return episodeActionsToEpisodeActionPosts(episodeActions);
+  }
+
+  /**
+   * Gets all EpisodeActions of a user since a given timestamp and converts them
+   * to EpisodeActionPosts before returning them.
+   *
+   * @param username The username of the user whose EpisodeActions are requested
+   * @param since    the timestamp signifying how old the EpisodeActions are
+   *                 allowed to be
+   * @return A list containing the requested EpisodeActions as
+   *        EpisodeActionPosts
+   */
+  public List<EpisodeActionPost> getEpisodeActionsSince(
+      final String username,
+      final long since) {
+    LocalDateTime sinceTimestamp
+        = LocalDateTime.ofEpochSecond(
+            since,
+            NANO_OF_SECOND_DEFAULT,
+            ZoneOffset.UTC);
+    List<EpisodeAction> episodeActions
+        = episodeActionDao.findByUserUsernameAndTimestampGreaterThanEqual(
+            username,
+            sinceTimestamp);
+    return episodeActionsToEpisodeActionPosts(episodeActions);
+  }
+
+  /**
+   * Gets all EpisodeActions of a user concerning a certain podcast since a
+   * given timestamp and converts them to EpisodeActionPosts before returning
+   * them.
+   *
+   * @param username   The username of the user whose EpisodeActions are
+   *                   requested
+   * @param podcastUrl The RSS-Feed URL of the podcast
+   * @param since      The timestamp signifying how old the EpisodeActions are
+   *                   allowed to be
+   * @return A list containing the requested EpisodeActions as
+   *        EpisodeActionPosts
+   */
+  public List<EpisodeActionPost> getEpisodeActionsOfPodcastSince(
+      final String username,
+      final String podcastUrl,
+      final long since) {
+    LocalDateTime sinceTimestamp
+        = LocalDateTime.ofEpochSecond(
+            since,
+            NANO_OF_SECOND_DEFAULT,
+            ZoneOffset.UTC);
+    List<EpisodeAction> episodeActions = episodeActionDao
+      .findByUserUsernameAndTimestampGreaterThanEqualAndEpisodeSubscriptionUrl(
+            username,
+            sinceTimestamp,
+            podcastUrl);
+    return episodeActionsToEpisodeActionPosts(episodeActions);
+  }
+
+  private List<EpisodeActionPost> episodeActionsToEpisodeActionPosts(
+      final List<EpisodeAction> episodeActions) {
+    List<EpisodeActionPost> episodeActionPosts = new ArrayList<>();
+
+    for (EpisodeAction episodeAction : episodeActions) {
+      episodeActionPosts.add(episodeAction.toEpisodeActionPost());
+    }
+
+    return episodeActionPosts;
+  }
+
+}
diff --git a/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/package-info.java b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/package-info.java
new file mode 100644
index 0000000..c431539
--- /dev/null
+++ b/pse-server/src/main/java/org/psesquared/server/episode/actions/api/service/package-info.java
@@ -0,0 +1,13 @@
+/**
+ * This package represents the logical middle layer of the episode action API
+ * ({@link org.psesquared.server.episode.actions.api}) - the service layer.
+ * <br>
+ * All business logic is handled here with the
+ * {@link
+ * org.psesquared.server.episode.actions.api.service.EpisodeActionService}
+ * class.
+ *
+ * @author PSE-Squared Team
+ * @version 1.0
+ */
+package org.psesquared.server.episode.actions.api.service;