make the skin renderer less bad (thanks bray)

src/main/java/cc/fascinated/service/MojangService.java

@@ -0,0 +1,165 @@
+package cc.fascinated.service;
+
+import cc.fascinated.common.ExpiringSet;
+import cc.fascinated.common.WebRequest;
+import cc.fascinated.model.mojang.MojangProfile;
+import cc.fascinated.model.mojang.MojangUsernameToUuid;
+import com.google.common.base.Joiner;
+import com.google.common.base.Splitter;
+import com.google.common.collect.Lists;
+import com.google.common.hash.Hashing;
+import io.micrometer.common.lang.NonNull;
+import lombok.SneakyThrows;
+import lombok.extern.log4j.Log4j2;
+import net.jodah.expiringmap.ExpirationPolicy;
+import org.springframework.stereotype.Service;
+
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.concurrent.TimeUnit;
+
+@Service @Log4j2
+public class MojangService {
+
+    private static final String SESSION_SERVER_ENDPOINT = "https://sessionserver.mojang.com";
+    private static final String API_ENDPOINT = "https://api.mojang.com";
+    private static final String FETCH_BLOCKED_SERVERS = SESSION_SERVER_ENDPOINT + "/blockedservers";
+    private static final Splitter DOT_SPLITTER = Splitter.on('.');
+    private static final Joiner DOT_JOINER = Joiner.on('.');
+
+    /**
+     * A list of banned server hashes provided by Mojang.
+     * <p>
+     * This is periodically fetched from Mojang, see
+     * {@link #fetchBlockedServers()} for more info.
+     * </p>
+     *
+     * @see <a href="https://wiki.vg/Mojang_API#Blocked_Servers">Mojang API</a>
+     */
+    private List<String> bannedServerHashes;
+
+    /**
+     * A cache of blocked server hostnames.
+     *
+     * @see #isServerHostnameBlocked(String) for more
+     */
+    private final ExpiringSet<String> blockedServersCache = new ExpiringSet<>(ExpirationPolicy.CREATED, 10L, TimeUnit.MINUTES);
+
+    public MojangService() {
+        new Timer().scheduleAtFixedRate(new TimerTask() {
+            @Override
+            public void run() {
+                fetchBlockedServers();
+            }
+        }, 0L, 60L * 15L * 1000L);
+    }
+
+    /**
+     * Fetch a list of blocked servers from Mojang.
+     */
+    @SneakyThrows
+    private void fetchBlockedServers() {
+        try (
+                InputStream inputStream = new URL(FETCH_BLOCKED_SERVERS).openStream();
+                Scanner scanner = new Scanner(inputStream, StandardCharsets.UTF_8).useDelimiter("\n");
+        ) {
+            List<String> hashes = new ArrayList<>();
+            while (scanner.hasNext()) {
+                hashes.add(scanner.next());
+            }
+            bannedServerHashes = Collections.synchronizedList(hashes);
+            log.info("Fetched {} banned server hashes", bannedServerHashes.size());
+        }
+    }
+
+    /**
+     * Check if the server with the
+     * given hostname is blocked by Mojang.
+     *
+     * @param hostname the server hostname to check
+     * @return whether the hostname is blocked
+     */
+    public boolean isServerBlocked(@NonNull String hostname) {
+        // Remove trailing dots
+        while (hostname.charAt(hostname.length() - 1) == '.') {
+            hostname = hostname.substring(0, hostname.length() - 1);
+        }
+        // Is the hostname banned?
+        if (isServerHostnameBlocked(hostname)) {
+            return true;
+        }
+        List<String> splitDots = Lists.newArrayList(DOT_SPLITTER.split(hostname)); // Split the hostname by dots
+        boolean isIp = splitDots.size() == 4; // Is it an IP address?
+        if (isIp) {
+            for (String element : splitDots) {
+                try {
+                    int part = Integer.parseInt(element);
+                    if (part >= 0 && part <= 255) { // Ensure the part is within the valid range
+                        continue;
+                    }
+                } catch (NumberFormatException ignored) {
+                    // Safely ignore, not a number
+                }
+                isIp = false;
+                break;
+            }
+        }
+        // Check if the hostname is blocked
+        if (!isIp && isServerHostnameBlocked("*." + hostname)) {
+            return true;
+        }
+        // Additional checks for the hostname
+        while (splitDots.size() > 1) {
+            splitDots.remove(isIp ? splitDots.size() - 1 : 0);
+            String starredPart = isIp ? DOT_JOINER.join(splitDots) + ".*" : "*." + DOT_JOINER.join(splitDots);
+            if (isServerHostnameBlocked(starredPart)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Check if the hash for the given
+     * hostname is in the blocked server list.
+     *
+     * @param hostname the hostname to check
+     * @return whether the hostname is blocked
+     */
+    private boolean isServerHostnameBlocked(@NonNull String hostname) {
+        // Check the cache first for the hostname
+        if (blockedServersCache.contains(hostname)) {
+            return true;
+        }
+        String hashed = Hashing.sha1().hashBytes(hostname.toLowerCase().getBytes(StandardCharsets.ISO_8859_1)).toString();
+        boolean blocked = bannedServerHashes.contains(hashed); // Is the hostname blocked?
+        if (blocked) { // Cache the blocked hostname
+            blockedServersCache.add(hostname);
+        }
+        return blocked;
+    }
+
+    /**
+     * Gets the Session Server profile of the
+     * player with the given UUID.
+     *
+     * @param id the uuid or name of the player
+     * @return the profile
+     */
+    public MojangProfile getProfile(String id) {
+        return WebRequest.getAsEntity(SESSION_SERVER_ENDPOINT + "/session/minecraft/profile/" + id, MojangProfile.class);
+    }
+
+    /**
+     * Gets the UUID of the player using
+     * the name of the player.
+     *
+     * @param id the name of the player
+     * @return the profile
+     */
+    public MojangUsernameToUuid getUuidFromUsername(String id) {
+        return WebRequest.getAsEntity(API_ENDPOINT + "/users/profiles/minecraft/" + id, MojangUsernameToUuid.class);
+    }
+}