/r added: first working version

3 files changed, 173 insertions, 1 deletions

diff --git a/Readme.md b/Readme.md
index 5b458b3..7a32158 100644
--- a/Readme.md
+++ b/Readme.md
@@ -30,6 +30,14 @@ usercache.
 If `MULTIPLIER < 0` the score is modified with `1/MULTIPLIER`, since FloatArgumentType does not support exponentials
 like 1.3e-4
 
+### `/r`
+
+Calculator for simple mathematical expressions.
+Supported operators: `+-*/`
+
+The player's coordinates are available though variables `x` `y` `z`.
+
+
 ## Features
 
 ### Dispenser Behavior
diff --git a/src/main/java/re/jag/parquet/Parquet.java b/src/main/java/re/jag/parquet/Parquet.java
index 05d3c93..11bebde 100644
--- a/src/main/java/re/jag/parquet/Parquet.java
+++ b/src/main/java/re/jag/parquet/Parquet.java
@@ -13,6 +13,7 @@ import net.minecraft.item.DyeItem;
 import net.minecraft.item.Items;
 import net.minecraft.server.command.ServerCommandSource;
 import net.minecraft.util.DyeColor;
+import re.jag.parquet.commands.Calculator;
 import re.jag.parquet.commands.CameraMode;
 import re.jag.parquet.commands.Savedata;
 
@@ -27,7 +28,8 @@ public class Parquet implements ModInitializer {
 	public static void registerCommands(CommandDispatcher<ServerCommandSource> dispatcher) {
 		Savedata.register(dispatcher);
 		CameraMode.register(dispatcher);
-		
+		Calculator.register(dispatcher);
+
 		LOG.info("[PQ] Registered commands");
 	}
 	
diff --git a/src/main/java/re/jag/parquet/commands/Calculator.java b/src/main/java/re/jag/parquet/commands/Calculator.java
new file mode 100644
index 0000000..73634c6
--- /dev/null
+++ b/src/main/java/re/jag/parquet/commands/Calculator.java
@@ -0,0 +1,162 @@
+package re.jag.parquet.commands;
+
+import static net.minecraft.server.command.CommandManager.argument;
+import static net.minecraft.server.command.CommandManager.literal;
+
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+
+import net.minecraft.command.arguments.MessageArgumentType;
+import net.minecraft.entity.Entity;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.text.LiteralText;
+import net.minecraft.text.Text;
+
+import java.util.ArrayList;
+import jdk.internal.jline.internal.Nullable;
+
+public class Calculator {
+	public static void register(CommandDispatcher<ServerCommandSource> dispatcher) {
+		LiteralArgumentBuilder<ServerCommandSource> r = literal("r").executes( (c) -> help(c.getSource()) ).then(
+				argument("expression", MessageArgumentType.message()).executes((c) -> calc(c.getSource(), MessageArgumentType.getMessage(c, "expression")))
+		);
+
+		dispatcher.register(r);
+	}
+
+	private static int calc(ServerCommandSource _source, Text _expression) {
+		String expression = _expression.asString();
+		expression = expression.replace(" ", "");
+		char expression_array[] = expression.toCharArray();
+		ArrayList<String> parts = new ArrayList<String>();
+		ArrayList<String> operators = new ArrayList<String>();
+
+		int last_break=-1;
+		String element="";
+		for(int i = 0; i < expression_array.length; i++) {
+			int op_weight = get_operator_weight(expression_array[i]);
+
+			if (Math.abs(last_break - i) > 1 && op_weight > 0) {
+				parts.add(element);
+				//parts.add(String.copyValueOf(expression_array, i, 1));
+				operators.add(String.copyValueOf(expression_array, i, 1));
+
+				element = "";
+				last_break = i;
+			} else {
+				element+=expression_array[i];
+			}
+		}
+
+		if(element.length() > 0)
+			parts.add(element);
+
+		int current_level = 2;
+		while(current_level > 0) {
+			int level_count = 0;
+			for (int o = 0; o < operators.size(); o++) {
+				String operator = operators.get(o);
+				if (get_operator_weight(operator) == current_level) {
+					level_count++;
+
+					String result = execute_operation(operator, parts.get(o), parts.get(o+1), _source);
+					parts.set(o, result);
+					parts.remove(o+1);
+					operators.remove(o);
+					break;
+				}
+			}
+
+			if (level_count == 0)
+				current_level--;
+		}
+
+		_source.sendFeedback(new LiteralText(parts.get(0)), false);
+
+		return 0;
+	}
+
+	@Nullable
+	private static Integer parse_operand(String _operand, ServerCommandSource _source) {
+		Integer operand = null;
+
+		try {
+			operand = Integer.parseInt(_operand);
+		} catch (NumberFormatException e) {
+			Entity player = _source.getEntity();
+			switch (_operand) {
+				case "x":
+					if (player != null)
+						operand = (int)player.getPos().x;
+					break;
+				case "y":
+					if (player != null)
+						operand = (int)player.getPos().y;
+					break;
+				case "z":
+					if (player != null)
+						operand = (int)player.getPos().z;
+					break;
+				default:
+			}
+		}
+
+		if (operand == null) {
+			String msg = "Parsing failed for Operand \"" + _operand + "\"";
+			_source.sendError(new LiteralText(msg));
+		}
+
+		return operand;
+	}
+
+	private static int get_operator_weight(char _c) {
+		switch(_c) {
+			case '+':
+			case '-':
+				return 1;
+			case '*':
+			case '/':
+				return 2;
+		}
+		return 0;
+	}
+
+	private static int get_operator_weight(String _s) {
+		if (_s.length() != 1)
+			return 0;
+		return get_operator_weight(_s.toCharArray()[0]);
+	}
+
+	@Nullable
+	private static String execute_operation(String _operator, String _left, String _right, ServerCommandSource _source) {
+		String result = null;
+
+		Integer left = parse_operand(_left, _source);
+		Integer right = parse_operand(_right, _source);
+
+		if (left == null || right == null)
+			return null;
+
+		switch (_operator) {
+			case "+":
+				result = String.valueOf(left + right);
+				break;
+			case "-":
+				result = String.valueOf(left - right);
+				break;
+			case "*":
+				result = String.valueOf(left * right);
+				break;
+			case "/":
+				result = String.valueOf(left / right);
+				break;
+		}
+
+		return result;
+	}
+
+	private static int help(ServerCommandSource _source){
+		_source.sendFeedback(new LiteralText("RTFM"), false);
+		return 0;
+	}
+}