Implement autoplace (#6)

src/main/java/com/gtnewhorizon/structurelib/util/ItemStackPredicate.java

@@ -0,0 +1,112 @@
+package com.gtnewhorizon.structurelib.util;
+
+import java.util.Objects;
+import java.util.function.BiPredicate;
+import java.util.function.Predicate;
+import net.minecraft.block.Block;
+import net.minecraft.init.Items;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.NBTBase;
+import net.minecraft.nbt.NBTTagCompound;
+
+public final class ItemStackPredicate implements Predicate<ItemStack> {
+    public static ItemStackPredicate from(Item item) {
+        return new ItemStackPredicate(item);
+    }
+
+    public static ItemStackPredicate from(ItemStack itemStack) {
+        return new ItemStackPredicate(itemStack.getItem()).setMeta(Items.feather.getDamage(itemStack));
+    }
+
+    public static ItemStackPredicate from(ItemStack itemStack, NBTMode mode) {
+        return new ItemStackPredicate(itemStack.getItem())
+                .setMeta(Items.feather.getDamage(itemStack))
+                .setTag(mode, itemStack.stackTagCompound);
+    }
+
+    public static ItemStackPredicate from(Block block) {
+        return new ItemStackPredicate(Item.getItemFromBlock(block));
+    }
+
+    private final Item item;
+    private int meta = -1;
+
+    private NBTTagCompound tag;
+    private NBTMode mode = NBTMode.IGNORE;
+
+    private ItemStackPredicate(Item item) {
+        this.item = item;
+    }
+
+    public ItemStackPredicate ignoreMeta() {
+        this.meta = -1;
+        return this;
+    }
+
+    public ItemStackPredicate setMeta(int meta) {
+        this.meta = meta;
+        return this;
+    }
+
+    public ItemStackPredicate setTag(NBTMode mode, NBTTagCompound tag) {
+        this.mode = mode;
+        this.tag = tag;
+        return this;
+    }
+
+    @Override
+    public boolean test(ItemStack itemStack) {
+        if (item != null) if (itemStack.getItem() != item) return false;
+        if (meta != -1) if (Items.feather.getDamage(itemStack) != meta) return false;
+        return mode.test(tag, itemStack.stackTagCompound);
+    }
+
+    public enum NBTMode implements BiPredicate<NBTTagCompound, NBTTagCompound> {
+        IGNORE {
+            @Override
+            public boolean test(NBTTagCompound lhs, NBTTagCompound rhs) {
+                return true;
+            }
+        },
+        IN {
+            @Override
+            public boolean test(NBTTagCompound lhs, NBTTagCompound rhs) {
+                if (lhs == null || lhs.hasNoTags()) return true;
+                if (rhs == null || rhs.hasNoTags()) return false;
+                for (String key : MiscUtils.getTagKeys(lhs)) {
+                    if (!rhs.hasKey(key, lhs.func_150299_b(key))) return false;
+                    NBTBase tag = lhs.getTag(key);
+                    if (tag instanceof NBTTagCompound) {
+                        if (!test((NBTTagCompound) tag, rhs.getCompoundTag(key))) return false;
+                    } else {
+                        if (!tag.equals(rhs.getTag(key))) return false;
+                    }
+                }
+                return true;
+            }
+        },
+        EXACT {
+            @Override
+            public boolean test(NBTTagCompound lhs, NBTTagCompound rhs) {
+                if (lhs != null && lhs.hasNoTags()) lhs = null;
+                if (rhs != null && rhs.hasNoTags()) rhs = null;
+                return Objects.equals(lhs, rhs);
+            }
+        },
+        IGNORE_KNOWN_INSIGNIFICANT_TAGS {
+            @Override
+            public boolean test(NBTTagCompound lhs, NBTTagCompound rhs) {
+                // fast path for empty tags
+                if (rhs == null || rhs.hasNoTags()) return lhs == null || lhs.hasNoTags();
+                // TODO make an implementation without copying a potentially huge tag
+                rhs = (NBTTagCompound) rhs.copy();
+                for (String s : KNOWN_INSIGNIFICANT_TAGS) rhs.removeTag(s);
+                return EXACT.test(lhs, rhs);
+            }
+        };
+        private static final String[] KNOWN_INSIGNIFICANT_TAGS = {
+            "display", // TODO expand/refine this
+        };
+    }
+}