Merge branch 'master' of https://github.com/bculkin2442/JPratt.git

1 files changed, 104 insertions, 0 deletions

diff --git a/JPratt/src/main/java/bjc/pratt/tokens/TokenStream.java b/JPratt/src/main/java/bjc/pratt/tokens/TokenStream.java
new file mode 100644
index 0000000..a5febcc
--- /dev/null
+++ b/JPratt/src/main/java/bjc/pratt/tokens/TokenStream.java
@@ -0,0 +1,104 @@
+package bjc.pratt.tokens;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+import bjc.utils.funcutils.StringUtils;
+import bjc.utils.parserutils.ParserException;
+
+/**
+ * A stream of tokens.
+ *
+ * @author EVE
+ *
+ * @param <K>
+ *                The key type of the token.
+ *
+ * @param <V>
+ *                The value type of the token.
+ */
+public abstract class TokenStream<K, V> implements Iterator<Token<K, V>> {
+	/**
+	 * The exception thrown when an expectation fails.
+	 *
+	 * @author EVE
+	 *
+	 */
+	public static class ExpectationException extends ParserException {
+		private static final long serialVersionUID = 4299299480127680805L;
+
+		/**
+		 * Create a new exception with the specified message.
+		 *
+		 * @param msg
+		 *                The message of the exception.
+		 */
+		public ExpectationException(final String msg) {
+			super(msg);
+		}
+	}
+
+	/**
+	 * Get the current token.
+	 *
+	 * @return The current token.
+	 */
+	public abstract Token<K, V> current();
+
+	@Override
+	public abstract Token<K, V> next();
+
+	@Override
+	public abstract boolean hasNext();
+
+	/**
+	 * Utility method for checking that the next token is one of a specific
+	 * set of types, and then consuming it.
+	 *
+	 * @param expectedKeys
+	 *                The expected values
+	 *
+	 * @throws ExpectationException
+	 *                 If the token is not one of the expected types.
+	 */
+	public void expect(final Set<K> expectedKeys) throws ExpectationException {
+		final K curKey = current().getKey();
+
+		if (!expectedKeys.contains(curKey)) {
+			final String expectedList = StringUtils.toEnglishList(expectedKeys.toArray(), false);
+
+			throw new ExpectationException("One of '" + expectedList + "' was expected, not " + curKey);
+		}
+
+		next();
+	}
+
+	/**
+	 * Utility method for checking that the next token is one of a specific
+	 * set of types, and then consuming it.
+	 *
+	 * @param expectedKeys
+	 *                The expected values
+	 *
+	 * @throws ExpectationException
+	 *                 If the token is not one of the expected types.
+	 */
+	@SafeVarargs
+	public final void expect(final K... expectedKeys) throws ExpectationException {
+		expect(new HashSet<>(Arrays.asList(expectedKeys)));
+	}
+
+	/**
+	 * Check whether the head token is a certain type.
+	 *
+	 * @param val
+	 *                The type to check for.
+	 *
+	 * @return Whether or not the head token is of that type.
+	 */
+	public boolean headIs(final K val) {
+		return current().getKey().equals(val);
+	}
+}