1 files changed, 265 insertions, 0 deletions
diff --git a/base/src/main/java/bjc/utils/ioutils/RuleBasedConfigReader.java b/base/src/main/java/bjc/utils/ioutils/RuleBasedConfigReader.java
new file mode 100644
index 0000000..7c5205b
--- /dev/null
+++ b/base/src/main/java/bjc/utils/ioutils/RuleBasedConfigReader.java
@@ -0,0 +1,265 @@
+package bjc.utils.ioutils;
+
+import java.io.InputStream;
+import java.util.InputMismatchException;
+import java.util.Scanner;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+
+import bjc.utils.data.IHolder;
+import bjc.utils.data.IPair;
+import bjc.utils.data.Identity;
+import bjc.utils.data.Pair;
+import bjc.utils.exceptions.UnknownPragmaException;
+import bjc.utils.funcdata.FunctionalMap;
+import bjc.utils.funcdata.FunctionalStringTokenizer;
+import bjc.utils.funcdata.IMap;
+
+/**
+ * This class parses a rules based config file, and uses it to drive a provided
+ * set of actions
+ *
+ * @author ben
+ *
+ * @param <E>
+ *                The type of the state object to use
+ *
+ */
+public class RuleBasedConfigReader<E> {
+	/* Function to execute when starting a rule.
+	 * Takes the tokenizer, and a pair of the read token and application state
+	 */
+	private BiConsumer<FunctionalStringTokenizer, IPair<String, E>> start;
+
+	/*
+	 * Function to use when continuing a rule
+	 * Takes a tokenizer and application state
+	 */
+	private BiConsumer<FunctionalStringTokenizer, E> continueRule;
+
+	/*
+	 * Function to use when ending a rule
+	 * Takes an application state
+	 */
+	private Consumer<E> end;
+
+	/*
+	 * Map of pragma names to pragma actions
+	 * Pragma actions are functions taking a tokenizer and application state
+	 */
+	private final IMap<String, BiConsumer<FunctionalStringTokenizer, E>> pragmas;
+
+	/**
+	 * Create a new rule-based config reader
+	 *
+	 * @param start
+	 *                The action to fire when starting a rule
+	 * @param continueRule
+	 *                The action to fire when continuing a rule
+	 * @param end
+	 *                The action to fire when ending a rule
+	 */
+	public RuleBasedConfigReader(final BiConsumer<FunctionalStringTokenizer, IPair<String, E>> start,
+			final BiConsumer<FunctionalStringTokenizer, E> continueRule, final Consumer<E> end) {
+		this.start = start;
+		this.continueRule = continueRule;
+		this.end = end;
+
+		this.pragmas = new FunctionalMap<>();
+	}
+
+	/**
+	 * Add a pragma to this reader
+	 *
+	 * @param name
+	 *                The name of the pragma to add
+	 * @param action
+	 *                The function to execute when this pragma is read
+	 */
+	public void addPragma(final String name, final BiConsumer<FunctionalStringTokenizer, E> action) {
+		if (name == null)        throw new NullPointerException("Pragma name must not be null");
+		else if (action == null) throw new NullPointerException("Pragma action must not be null");
+
+		pragmas.put(name, action);
+	}
+
+	private void continueRule(final E state, final boolean isRuleOpen, final String line) {
+		// Make sure our input is correct
+		if (isRuleOpen == false)
+			throw new InputMismatchException("Cannot continue rule with no rule open");
+		else if (continueRule == null)
+			throw new InputMismatchException("Rule continuation not supported for current grammar");
+
+		/*
+		 * Accept the rule
+		 */
+		continueRule.accept(new FunctionalStringTokenizer(line.substring(1), " "), state);
+	}
+
+	private boolean endRule(final E state, final boolean isRuleOpen) {
+		/*
+		 * Ignore blank line without an open rule
+		 */
+		if (isRuleOpen == false)
+			/*
+			 * Do nothing
+			 */
+			return false;
+		else {
+			/*
+			 * Nothing happens on rule end
+			 */
+			if (end != null) {
+				/*
+				 * Process the rule ending
+				 */
+				end.accept(state);
+			}
+
+			/*
+			 * Return a closed rule
+			 */
+			return false;
+		}
+	}
+
+	/**
+	 * Run a stream through this reader
+	 *
+	 * @param input
+	 *                The stream to get input
+	 * @param initialState
+	 *                The initial state of the reader
+	 * @return The final state of the reader
+	 */
+	public E fromStream(final InputStream input, final E initialState) {
+		if (input == null) throw new NullPointerException("Input stream must not be null");
+
+		/*
+		 * Application state: We're giving this back later
+		 */
+		final E state = initialState;
+
+		/*
+		 * Prepare our input source
+		 */
+		try (Scanner source = new Scanner(input)) {
+			source.useDelimiter("\n");
+			/*
+			 * This is true when a rule's open
+			 */
+			final IHolder<Boolean> isRuleOpen = new Identity<>(false);
+
+			/*
+			 * Do something for every line of the file
+			 */
+			source.forEachRemaining((line) -> {
+				/*
+				 * Skip comment lines
+				 */
+				if (line.startsWith("#") || line.startsWith("//"))
+					/*
+					 * It's a comment
+					 */
+					return;
+				else if (line.equals("")) {
+					/*
+					 * End the rule
+					 */
+					isRuleOpen.replace(endRule(state, isRuleOpen.getValue()));
+				} else if (line.startsWith("\t")) {
+					/*
+					 * Continue the rule
+					 */
+					continueRule(state, isRuleOpen.getValue(), line);
+				} else {
+					/*
+					 * Open a rule
+					 */
+					isRuleOpen.replace(startRule(state, isRuleOpen.getValue(), line));
+				}
+			});
+		}
+
+		/*
+		 * Return the state that the user has created
+		 */
+		return state;
+	}
+
+	/**
+	 * Set the action to execute when continuing a rule
+	 *
+	 * @param continueRule
+	 *                The action to execute on continuation of a rule
+	 */
+	public void setContinueRule(final BiConsumer<FunctionalStringTokenizer, E> continueRule) {
+		this.continueRule = continueRule;
+	}
+
+	/**
+	 * Set the action to execute when ending a rule
+	 *
+	 * @param end
+	 *                The action to execute on ending of a rule
+	 */
+	public void setEndRule(final Consumer<E> end) {
+		this.end = end;
+	}
+
+	/**
+	 * Set the action to execute when starting a rule
+	 *
+	 * @param start
+	 *                The action to execute on starting of a rule
+	 */
+	public void setStartRule(final BiConsumer<FunctionalStringTokenizer, IPair<String, E>> start) {
+		if (start == null) throw new NullPointerException("Action on rule start must be non-null");
+
+		this.start = start;
+	}
+
+	private boolean startRule(final E state, boolean isRuleOpen, final String line) {
+		/*
+		 * Create the line tokenizer
+		 */
+		final FunctionalStringTokenizer tokenizer = new FunctionalStringTokenizer(line, " ");
+
+		/*
+		 * Get the initial token
+		 */
+		final String nextToken = tokenizer.nextToken();
+
+		/*
+		 * Handle pragmas
+		 */
+		if (nextToken.equals("pragma")) {
+			/*
+			 * Get the pragma name
+			 */
+			final String token = tokenizer.nextToken();
+
+			/*
+			 * Handle pragmas
+			 */
+			pragmas.getOrDefault(token, (tokenzer, stat) -> {
+				throw new UnknownPragmaException("Unknown pragma " + token);
+			}).accept(tokenizer, state);
+		} else {
+			/*
+			 * Make sure input is correct
+			 */
+			if (isRuleOpen == true)
+				throw new InputMismatchException("Nested rules are currently not supported");
+
+			/*
+			 * Start a rule
+			 */
+			start.accept(tokenizer, new Pair<>(nextToken, state));
+
+			isRuleOpen = true;
+		}
+
+		return isRuleOpen;
+	}
+}