From cea3e47938322b97c318dea38dc0d649e196dc1b Mon Sep 17 00:00:00 2001
From: Ben Culkin <scorpress@gmail.com>
Date: Tue, 16 Aug 2022 23:03:27 -0400
Subject: Refactor to add backtracking support

This probably doesn't help w/ error messages, but it enables some cool
ideas where syntax can be reused in cases where it would otherwise be
invalid
---
 .../java/bjc/pratt/commands/CommandResult.java     | 97 ++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 JPratt/src/main/java/bjc/pratt/commands/CommandResult.java

(limited to 'JPratt/src/main/java/bjc/pratt/commands/CommandResult.java')

diff --git a/JPratt/src/main/java/bjc/pratt/commands/CommandResult.java b/JPratt/src/main/java/bjc/pratt/commands/CommandResult.java
new file mode 100644
index 0000000..d27400f
--- /dev/null
+++ b/JPratt/src/main/java/bjc/pratt/commands/CommandResult.java
@@ -0,0 +1,97 @@
+package bjc.pratt.commands;
+
+import bjc.data.Tree;
+import bjc.pratt.tokens.Token;
+
+/**
+ * Represents the result of executing a command.
+ * 
+ * @author bjcul
+ *
+ * @param <K> The key type of the tokens
+ * @param <V> The value type of the tokens
+ */
+public class CommandResult<K, V> {
+	/**
+	 * Represents the status of a command execution
+	 * 
+	 * @author bjcul
+	 *
+	 */
+	public static enum Status {
+		/**
+		 * The command successfully parsed.
+		 */
+		SUCCESS,
+		/**
+		 * The command failed, in a non-recoverable way
+		 */
+		FAIL,
+		/**
+		 * The command failed. Attempt recovery via backtracking
+		 */
+		BACKTRACK
+	}
+
+	/**
+	 * The status of this command.
+	 */
+	public final Status status;
+	
+	private Tree<Token<K, V>> success;
+	
+	private CommandResult(Status status) {
+		this.status = status;
+	}
+
+	/**
+	 * Get the success value of this command, or null if it failed.
+	 * 
+	 * @return The success value of the command
+	 */
+	public Tree<Token<K, V>> success() {
+		return success;
+	}
+
+	/**
+	 * Create a success result
+	 * 
+	 * @param <K2> The key type of the token
+	 * @param <V2> The value type of the token
+	 * 
+	 * @param succ The tree produced by the command
+	 * 
+	 * @return A command result representing a success
+	 */
+	public static <K2, V2> CommandResult<K2, V2> success(Tree<Token<K2, V2>> succ) {
+		CommandResult<K2, V2> result = new CommandResult<>(Status.SUCCESS);
+		result.success = succ;
+		return result;
+	}
+
+	/**
+	 * Create a non-backtracking failure result.
+	 * 
+	 * @param <K2> The key type of the token
+	 * @param <V2> The value type of the token
+	 * 
+	 * @return A command result representing a non-backtracking fail
+	 */
+	public static <K2, V2> CommandResult<K2, V2> fail() {
+		CommandResult<K2, V2> result = new CommandResult<>(Status.FAIL);
+		return result;
+	}
+
+	/**
+	 * Create a backtracking failure result.
+	 * 
+	 * @param <K2> The key type of the token
+	 * @param <V2> The value type of the token
+	 * 
+	 * @return A command result representing a backtracking fail
+	 */
+	public static <K2, V2> CommandResult<K2, V2> backtrack() {
+		CommandResult<K2, V2> result = new CommandResult<>(Status.BACKTRACK);
+		return result;
+	}
+}
-- 
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