Add a lot of comments. More to come.

src/org/nwapw/abacus/lexing/pattern/AnyNode.java

@@ -1,5 +1,9 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A pattern node that matches any character.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class AnyNode<T> extends PatternNode<T> {
 
     @Override

src/org/nwapw/abacus/lexing/pattern/EndNode.java

@@ -1,13 +1,28 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A node that represents a successful match.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class EndNode<T> extends PatternNode<T> {
 
+    /**
+     * The ID of the pattenr that has been matched.
+     */
     private T patternId;
 
+    /**
+     * Creates a new end node with the given ID.
+     * @param patternId the pattern ID.
+     */
     public EndNode(T patternId){
         this.patternId = patternId;
     }
 
+    /**
+     * Gets the pattern ID.
+     * @return the pattern ID.
+     */
     public T getPatternId(){
         return patternId;
     }

src/org/nwapw/abacus/lexing/pattern/LinkNode.java

@@ -3,6 +3,10 @@ package org.nwapw.abacus.lexing.pattern;
 import java.util.ArrayList;
 import java.util.Collection;
 
+/**
+ * A node that is used as structural glue in pattern compilation.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class LinkNode<T> extends PatternNode<T> {
 
     @Override

src/org/nwapw/abacus/lexing/pattern/Match.java

@@ -1,25 +1,56 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A match that has been generated by the lexer.
+ * @param <T> the type used to represent the ID of the pattern this match belongs to.
+ */
 public class Match<T> {
 
+    /**
+     * The bottom range of the string, inclusive.
+     */
     private int from;
+    /**
+     * The top range of the string, exclusive.
+     */
     private int to;
+    /**
+     * The pattern type this match matched.
+     */
     private T type;
 
+    /**
+     * Creates a new match with the given parameters.
+     * @param from the bottom range of the string.
+     * @param to the top range of the string.
+     * @param type the type of the match.
+     */
     public Match(int from, int to, T type){
         this.from = from;
         this.to = to;
         this.type = type;
     }
 
+    /**
+     * Gets the bottom range bound of the string.
+     * @return the bottom range bound of the string.
+     */
     public int getFrom() {
         return from;
     }
 
+    /**
+     * Gets the top range bound of the string.
+     * @return the top range bound of the string.
+     */
     public int getTo() {
         return to;
     }
 
+    /**
+     * Gets the pattern type of the node.
+     * @return the ID of the pattern that this match matched.
+     */
     public T getType() {
         return type;
     }

src/org/nwapw/abacus/lexing/pattern/Pattern.java

@@ -5,13 +5,33 @@ import java.util.HashMap;
 import java.util.Stack;
 import java.util.function.Function;
 
+/**
+ * A pattern that can be compiled from a string and used in lexing.
+ * @param <T> the type that is used to identify and sort this pattern.
+ */
 public class Pattern<T> {
 
+    /**
+     * The ID of this pattern.
+     */
     private T id;
+    /**
+     * The head of this pattern.
+     */
     private PatternNode<T> head;
+    /**
+     * The source string of this pattern.
+     */
     private String source;
+    /**
+     * The index at which the compilation has stopped.
+     */
     private int index;
 
+    /**
+     * A map of regex operator to functions that modify a PatternChain
+     * with the appropriate operation.
+     */
     private HashMap<Character, Function<PatternChain<T>, PatternChain<T>>> operations =
             new HashMap<Character, Function<PatternChain<T>, PatternChain<T>>>() {{
                 put('+', Pattern.this::transformPlus);
@@ -19,11 +39,23 @@ public class Pattern<T> {
                 put('?', Pattern.this::transformQuestion);
             }};
 
+    /**
+     * A regex operator function that turns the chain
+     * into a one-or-more chain.
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
     private PatternChain<T> transformPlus(PatternChain<T> chain){
         chain.tail.outputStates.add(chain.head);
         return chain;
     }
 
+    /**
+     * A regex operator function that turns the chain
+     * into a zero-or-more chain.
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
     private PatternChain<T> transformStar(PatternChain<T> chain){
         LinkNode<T> newTail = new LinkNode<>();
         LinkNode<T> newHead = new LinkNode<>();
@@ -36,6 +68,12 @@ public class Pattern<T> {
         return chain;
     }
 
+    /**
+     * A regex operator function that turns the chain
+     * into a zero-or-one chain.
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
     private PatternChain<T> transformQuestion(PatternChain<T> chain){
         LinkNode<T> newTail = new LinkNode<>();
         LinkNode<T> newHead = new LinkNode<>();
@@ -47,6 +85,11 @@ public class Pattern<T> {
         return chain;
     }
 
+    /**
+     * Combines a collection of chains into one OR chain.
+     * @param collection the collection of chains to combine.
+     * @return the resulting OR chain.
+     */
     private PatternChain<T> combineChains(Collection<PatternChain<T>> collection){
         LinkNode<T> head = new LinkNode<>();
         LinkNode<T> tail = new LinkNode<>();
@@ -58,6 +101,10 @@ public class Pattern<T> {
         return newChain;
     }
 
+    /**
+     * Parses a single value from the input into a chain.
+     * @return the resulting chain, or null on error.
+     */
     private PatternChain<T> parseValue(){
         if(index >= source.length()) return null;
         if(source.charAt(index) == '\\'){
@@ -66,6 +113,10 @@ public class Pattern<T> {
         return new PatternChain<>(new ValueNode<>(source.charAt(index++)));
     }
 
+    /**
+     * Parses a [] range from the input into a chain.
+     * @return the resulting chain, or null on error.
+     */
     private PatternChain<T> parseOr(){
         Stack<PatternChain<T>> orStack = new Stack<>();
         index++;
@@ -88,6 +139,12 @@ public class Pattern<T> {
         return (orStack.size() == 1) ? orStack.pop() : combineChains(orStack);
     }
 
+    /**
+     * Parses a repeatable segment from the input into a chain
+     * @param isSubsegment whether the segment is a sub-expression "()", and therefore
+     *                     whether to expect a closing brace.
+     * @return the resulting chain, or null on error.
+     */
     private PatternChain<T> parseSegment(boolean isSubsegment){
         if(index >= source.length() || ((source.charAt(index) != '(') && isSubsegment)) return null;
         if(isSubsegment) index++;
@@ -152,6 +209,11 @@ public class Pattern<T> {
         return fullChain;
     }
 
+    /**
+     * Creates / compiles a new pattern with the given id from the given string.
+     * @param from the string to compile a pattern from.
+     * @param id the ID to use.
+     */
     public Pattern(String from, T id){
         this.id = id;
         index = 0;
@@ -166,6 +228,10 @@ public class Pattern<T> {
         }
     }
 
+    /**
+     * Gets the head PatternNode, for use in matching
+     * @return the pattern node.
+     */
     public PatternNode<T> getHead() {
         return head;
     }

src/org/nwapw/abacus/lexing/pattern/PatternChain.java

@@ -1,23 +1,52 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A chain of nodes that can be treated as a single unit.
+ * Used during pattern compilation.
+ * @param <T> the type used to identify which pattern has been matched.
+ */
 public class PatternChain<T> {
 
+    /**
+     * The head node of the chain.
+     */
     public PatternNode<T> head;
+    /**
+     * The tail node of the chain.
+     */
     public PatternNode<T> tail;
 
+    /**
+     * Creates a new chain with the given start and end.
+     * @param head the start of the chain.
+     * @param tail the end of the chain.
+     */
     public PatternChain(PatternNode<T> head, PatternNode<T> tail){
         this.head = head;
         this.tail = tail;
     }
 
+    /**
+     * Creates a chain that starts and ends with the same node.
+     * @param node the node to use.
+     */
     public PatternChain(PatternNode<T> node){
         this(node, node);
     }
 
+    /**
+     * Creates an empty chain.
+     */
     public PatternChain(){
         this(null);
     }
 
+    /**
+     * Appends the other chain to this one. This modifies
+     * the nodes, as well.
+     * If this chain is empty, it is set to the other.
+     * @param other the other chain to append.
+     */
     public void append(PatternChain<T> other){
         if(other.head == null || tail == null) {
             this.head = other.head;
@@ -28,6 +57,12 @@ public class PatternChain<T> {
         }
     }
 
+    /**
+     * Appends a single node to this chain. This modifies
+     * the nodes, as well.
+     * If this chain is empty, it is set to the node.
+     * @param node the node to append to this chain.
+     */
     public void append(PatternNode<T> node){
         if(tail == null){
             head = tail = node;

src/org/nwapw/abacus/lexing/pattern/PatternNode.java

@@ -4,26 +4,58 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 
+/**
+ * A base class for a pattern node. Provides all functions
+ * necessary for matching, and is constructed by a Pattern instance
+ * from a string.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class PatternNode<T> {
 
+    /**
+     * The set of states to which the lexer should continue
+     * should this node be correctly matched.
+     */
     protected HashSet<PatternNode<T>> outputStates;
 
+    /**
+     * Creates a new pattern node.
+     */
     public PatternNode(){
         outputStates = new HashSet<>();
     }
 
+    /**
+     * Determines whether the current input character can
+     * be matched by this node.
+     * @param other the character being matched.
+     * @return true if the character can be matched, false otherwise.
+     */
     public boolean matches(char other){
         return false;
     }
 
+    /**
+     * If this node can be used as part of a range, returns that value.
+     * @return a NULL terminator if this character cannot be converted
+     * into a range bound, or the appropriate range bound if it can.
+     */
     public char range(){
         return '\0';
     }
 
+    /**
+     * Adds this node in a collection of other nodes.
+     * @param into the collection to add into.
+     */
     public void addInto(Collection<PatternNode<T>> into){
         into.add(this);
     }
 
+    /**
+     * Adds the node's children into a collection of other nodes.
+     * @param into the collection to add into.
+     */
     public void addOutputsInto(Collection<PatternNode<T>> into){
         outputStates.forEach(e -> e.addInto(into));
     }

src/org/nwapw/abacus/lexing/pattern/RangeNode.java

@@ -1,10 +1,25 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A node that matches a range of characters.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class RangeNode<T> extends PatternNode<T> {
 
+    /**
+     * The bottom bound of the range, inclusive.
+     */
     private char from;
+    /**
+     * The top bound of the range, inclusive.
+     */
     private char to;
 
+    /**
+     * Creates a new range node from the given range.
+     * @param from the bottom bound of the range.
+     * @param to the top bound of hte range.
+     */
     public RangeNode(char from, char to){
         this.from = from;
         this.to = to;

src/org/nwapw/abacus/lexing/pattern/ValueNode.java

@@ -1,9 +1,20 @@
 package org.nwapw.abacus.lexing.pattern;
 
+/**
+ * A node that matches a single value.
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
 public class ValueNode<T> extends PatternNode<T> {
 
+    /**
+     * The value this node matches.
+     */
     private char value;
 
+    /**
+     * Creates a new node that matches the given character.
+     * @param value
+     */
     public ValueNode(char value){
         this.value = value;
     }