Tab complete block properties

src/api/java/baritone/api/command/datatypes/BlockById.java

@@ -19,15 +19,28 @@ package baritone.api.command.datatypes;
 
 import baritone.api.command.exception.CommandException;
 import baritone.api.command.helpers.TabCompleteHelper;
+
 import net.minecraft.block.Block;
+import net.minecraft.block.properties.IProperty;
 import net.minecraft.init.Blocks;
 import net.minecraft.util.ResourceLocation;
 
+import java.util.Set;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 public enum BlockById implements IDatatypeFor<Block> {
     INSTANCE;
 
+    /**
+     * Matches (domain:)?name([(property=value)*])? but the input can be truncated at any position.
+     * domain and name are [a-z0-9_.-]+ and [a-z0-9/_.-]+ because that's what mc 1.13+ accepts.
+     * property and value use the same format as domain.
+     */
+    // Good luck reading this.
+    private static Pattern PATTERN = Pattern.compile("(?:[a-z0-9_.-]+:)?(?:[a-z0-9/_.-]+(?:\\[(?:(?:[a-z0-9_.-]+=[a-z0-9_.-]+,)*(?:[a-z0-9_.-]+(?:=(?:[a-z0-9_.-]+(?:\\])?)?)?)?|\\])?)?)?");
+
     @Override
     public Block get(IDatatypeContext ctx) throws CommandException {
         ResourceLocation id = new ResourceLocation(ctx.getConsumer().getString());
@@ -40,14 +53,111 @@ public enum BlockById implements IDatatypeFor<Block> {
 
     @Override
     public Stream<String> tabComplete(IDatatypeContext ctx) throws CommandException {
+        String arg = ctx.getConsumer().getString();
+
+        if (!PATTERN.matcher(arg).matches()) {
+            // Invalid format; we can't complete this.
+            return Stream.empty();
+        }
+
+        if (arg.endsWith("]")) {
+            // We are already done.
+            return Stream.empty();
+        }
+
+        if (!arg.contains("[")) {
+            // no properties so we are completing the block id
+            return new TabCompleteHelper()
+                    .append(
+                            Block.REGISTRY.getKeys()
+                                    .stream()
+                                    .map(Object::toString)
+                    )
+                    .filterPrefixNamespaced(arg)
+                    .sortAlphabetically()
+                    .stream();
+        }
+
+        // destructuring assignment? Please?
+        String blockId, properties;
+        {
+            String[] parts = splitLast(arg, '[');
+            blockId = parts[0];
+            properties = parts[1];
+        }
+
+        Block block = Block.REGISTRY.getObject(new ResourceLocation(blockId));
+        if (block == null) {
+            // This block doesn't exist so there's no properties to complete.
+            return Stream.empty();
+        }
+
+        String leadingProperties, lastProperty;
+        {
+            String[] parts = splitLast(properties, ',');
+            leadingProperties = parts[0];
+            lastProperty = parts[1];
+        }
+
+        if (!lastProperty.contains("=")) {
+            // The last property-value pair doesn't have a value yet so we are completing its name
+            Set<String> usedProps = Stream.of(leadingProperties.split(","))
+                    .map(pair -> pair.split("=")[0])
+                    .collect(Collectors.toSet());
+
+            String prefix = arg.substring(0, arg.length() - lastProperty.length());
+            return new TabCompleteHelper()
+                    .append(
+                            block.getBlockState()
+                                    .getProperties()
+                                    .stream()
+                                    .map(IProperty::getName)
+                    )
+                    .filter(prop -> !usedProps.contains(prop))
+                    .filterPrefix(lastProperty)
+                    .sortAlphabetically()
+                    .map(prop -> prefix + prop)
+                    .stream();
+        }
+
+        String lastName, lastValue;
+        {
+            String[] parts = splitLast(lastProperty, '=');
+            lastName = parts[0];
+            lastValue = parts[1];
+        }
+
+        // We are completing the value of a property
+        String prefix = arg.substring(0, arg.length() - lastValue.length());
+
+        IProperty<?> property = block.getBlockState().getProperty(lastName);
+        if (property == null) {
+            // The property does not exist so there's no values to complete
+            return Stream.empty();
+        }
+
         return new TabCompleteHelper()
-                .append(
-                        Block.REGISTRY.getKeys()
-                                .stream()
-                                .map(Object::toString)
-                )
-                .filterPrefixNamespaced(ctx.getConsumer().getString())
+                .append(getValues(property))
+                .filterPrefix(lastValue)
                 .sortAlphabetically()
+                .map(val -> prefix + val)
                 .stream();
     }
+
+    /**
+     * Always returns exactly two strings.
+     * If the separator is not found the FIRST returned string is empty.
+     */
+    private static String[] splitLast(String string, char chr) {
+        int idx = string.lastIndexOf(chr);
+        if (idx == -1) {
+            return new String[]{"", string};
+        }
+        return new String[]{string.substring(0, idx), string.substring(idx + 1)};
+    }
+
+    // this shouldn't need to be a separate method?
+    private static <T extends Comparable<T>> Stream<String> getValues(IProperty<T> property) {
+        return property.getAllowedValues().stream().map(property::getName);
+    }
 }