Convert to a multi-module Maven setup

This is much more user-friendly - users can either compile a specific module or create a profile to compile for the specific Minecraft versions they're looking to support. It means that it's much easier for people to continue assisting with the development of OpenInv in the future without access to every version of CB since 1.4.5.

This commit restores and updates most of the old system.

plugin/src/main/java/com/lishid/openinv/util/Cache.java

@@ -0,0 +1,160 @@
+package com.lishid.openinv.util;
+
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+import com.google.common.collect.Multimap;
+import com.google.common.collect.TreeMultimap;
+
+/**
+ * A minimal time-based cache implementation backed by a HashMap and TreeMultimap.
+ * 
+ * @author Jikoo
+ */
+public class Cache<K, V> {
+
+    private final Map<K, V> internal;
+    private final Multimap<Long, K> expiry;
+    private final long retention;
+    private final Function<V> inUseCheck, postRemoval;
+
+    /**
+     * Constructs a Cache with the specified retention duration, in use function, and post-removal function.
+     * 
+     * @param retention duration after which keys are automatically invalidated if not in use
+     * @param inUseCheck Function used to check if a key is considered in use
+     * @param postRemoval Function used to perform any operations required when a key is invalidated
+     */
+    public Cache(long retention, Function<V> inUseCheck, Function<V> postRemoval) {
+        this.internal = new HashMap<K, V>();
+
+        this.expiry = TreeMultimap.create(new Comparator<Long>() {
+                    @Override
+                    public int compare(Long long1, Long long2) {
+                        return long1.compareTo(long2);
+                    }
+                },
+                new Comparator<K>() {
+                    @Override
+                    public int compare(K k1, K k2) {
+                        return 0;
+                    }
+                });
+
+        this.retention = retention;
+        this.inUseCheck = inUseCheck;
+        this.postRemoval = postRemoval;
+    }
+
+    /**
+     * Set a key and value pair. Keys are unique. Using an existing key will cause the old value to
+     * be overwritten and the expiration timer to be reset.
+     * 
+     * @param key key with which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     */
+    public void put(K key, V value) {
+        // Invalidate key - runs lazy check and ensures value won't be cleaned up early
+        invalidate(key);
+
+        internal.put(key, value);
+        expiry.put(System.currentTimeMillis() + retention, key);
+    }
+
+    /**
+     * Returns the value to which the specified key is mapped, or null if no value is mapped for the key.
+     * 
+     * @param key the key whose associated value is to be returned
+     * @return the value to which the specified key is mapped, or null if no value is mapped for the key
+     */
+    public V get(K key) {
+        // Run lazy check to clean cache
+        lazyCheck();
+
+        return internal.get(key);
+    }
+
+    /**
+     * Returns true if the specified key is mapped to a value.
+     * 
+     * @param key key to check if a mapping exists for
+     * @return true if a mapping exists for the specified key
+     */
+    public boolean containsKey(K key) {
+        // Run lazy check to clean cache
+        lazyCheck();
+
+        return internal.containsKey(key);
+    }
+
+    /**
+     * Forcibly invalidates a key, even if it is considered to be in use.
+     * 
+     * @param key key to invalidate
+     */
+    public void invalidate(K key) {
+        // Run lazy check to clean cache
+        lazyCheck();
+
+        if (!internal.containsKey(key)) {
+            // Value either not present or cleaned by lazy check. Either way, we're good
+            return;
+        }
+
+        // Remove stored object
+        internal.remove(key);
+
+        // Remove expiration entry - prevents more work later, plus prevents issues with values invalidating early
+        for (Iterator<Map.Entry<Long, K>> iterator = expiry.entries().iterator(); iterator.hasNext();) {
+            if (key.equals(iterator.next().getValue())) {
+                iterator.remove();
+                break;
+            }
+        }
+    }
+
+    /**
+     * Forcibly invalidates all keys, even if they are considered to be in use.
+     */
+    public void invalidateAll() {
+        for (V value : internal.values()) {
+            postRemoval.run(value);
+        }
+        expiry.clear();
+        internal.clear();
+    }
+
+    /**
+     * Invalidate all expired keys that are not considered in use. If a key is expired but is
+     * considered in use by the provided Function, its expiration time is reset.
+     */
+    private void lazyCheck() {
+        long now = System.currentTimeMillis();
+        long nextExpiry = now + retention;
+        for (Iterator<Map.Entry<Long, K>> iterator = expiry.entries().iterator(); iterator.hasNext();) {
+            Map.Entry<Long, K> entry = iterator.next();
+
+            if (entry.getKey() > now) {
+                break;
+            }
+
+            iterator.remove();
+
+            if (inUseCheck.run(internal.get(entry.getValue()))) {
+                expiry.put(nextExpiry, entry.getValue());
+                continue;
+            }
+
+            V value = internal.remove(entry.getValue());
+
+            if (value == null) {
+                continue;
+            }
+
+            postRemoval.run(value);
+        }
+    }
+
+}

plugin/src/main/java/com/lishid/openinv/util/Function.java

@@ -0,0 +1,12 @@
+package com.lishid.openinv.util;
+
+/**
+ * Abstraction for some simple cache calls.
+ * 
+ * @author Jikoo
+ */
+public abstract class Function<V> {
+
+    public abstract boolean run(V value);
+
+}