Cache implementation

README.md

@@ -2,6 +2,6 @@
 An API designed to provide real-time access to a user's Discord data.
 
 ## TODO
-- [ ] Caching
+- [x] Caching
 - [ ] WebSockets
 - [ ] User account for extra data? (about me, connections, etc)

src/main/java/me/braydon/tether/model/CachedDiscordUser.java

@@ -0,0 +1,30 @@
+package me.braydon.tether.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.Setter;
+import net.dv8tion.jda.api.entities.User;
+
+/**
+ * A model representing a cached Discord user.
+ *
+ * @author Braydon
+ */
+@AllArgsConstructor @Setter @Getter
+public final class CachedDiscordUser {
+    /**
+     * The cached user.
+     */
+    @NonNull private final User user;
+
+    /**
+     * The cached user profile.
+     */
+    @NonNull private final User.Profile profile;
+
+    /**
+     * The unix time of when this user was cached.
+     */
+    private long cached;
+}

src/main/java/me/braydon/tether/service/DiscordService.java

@@ -1,5 +1,7 @@
 package me.braydon.tether.service;
 
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
 import jakarta.annotation.PostConstruct;
 import lombok.NonNull;
 import lombok.SneakyThrows;
@@ -7,6 +9,7 @@ import lombok.extern.log4j.Log4j2;
 import me.braydon.tether.exception.impl.BadRequestException;
 import me.braydon.tether.exception.impl.ResourceNotFoundException;
 import me.braydon.tether.exception.impl.ServiceUnavailableException;
+import me.braydon.tether.model.CachedDiscordUser;
 import me.braydon.tether.model.DiscordUser;
 import me.braydon.tether.model.response.DiscordUserResponse;
 import net.dv8tion.jda.api.JDA;
@@ -18,6 +21,8 @@ import net.dv8tion.jda.api.utils.cache.CacheFlag;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;
 
+import java.util.concurrent.TimeUnit;
+
 /**
  * This service is responsible for
  * interacting with the Discord API.
@@ -35,6 +40,13 @@ public final class DiscordService {
      */
     private JDA jda;
 
+    /**
+     * A cache of users retrieved from Discord.
+     */
+    private final Cache<Long, CachedDiscordUser> cachedUsers = Caffeine.newBuilder()
+            .expireAfterAccess(3L, TimeUnit.MINUTES)
+            .build();
+
     @PostConstruct
     public void onInitialize() {
         connectBot();
@@ -67,9 +79,21 @@ public final class DiscordService {
                     break;
                 }
             }
-            User user = jda.retrieveUserById(snowflake).complete();
-            User.Profile profile = user.retrieveProfile().complete();
-            return new DiscordUserResponse(DiscordUser.buildFromEntity(user, profile, member), -1L);
+            // Then retrieve the user
+            CachedDiscordUser cachedUser = cachedUsers.getIfPresent(snowflake);
+            boolean fromCache = cachedUser != null;
+            if (cachedUser == null) { // No cache, retrieve fresh data
+                User user = jda.retrieveUserById(snowflake).complete();
+                cachedUser = new CachedDiscordUser(
+                        user, user.retrieveProfile().complete(), System.currentTimeMillis()
+                );
+                cachedUsers.put(snowflake, cachedUser);
+            }
+            // Finally build the response and respond with it
+            return new DiscordUserResponse(
+                    DiscordUser.buildFromEntity(cachedUser.getUser(), cachedUser.getProfile(), member),
+                    fromCache ? cachedUser.getCached() : -1L
+            );
         } catch (ErrorResponseException ex) {
             // Failed to lookup the user, handle appropriately
             if (ex.getErrorCode() == 10013) {