first working version

Markov/src/directory/passive/markov/Data.java

+package directory.passive.markov;
+
+import java.util.HashMap;
+import java.util.Map;
+
+// FIXME rename
+public class Data {
+
+	private final Map<Prefix, Lookup> data = new HashMap<>();
+
+	public void add(Prefix p, Token t) {
+		Lookup l = data.getOrDefault(p, new Lookup());
+		l.add(t);
+		data.put(p, l);
+	}
+	
+	public Lookup fetch(Prefix p) {
+		return data.getOrDefault(p, Lookup.empty);
+	}
+
+	@Override
+	public String toString() {
+		return "Data [data=" + data + "]";
+	}
+
+}

Markov/src/directory/passive/markov/Lookup.java

+package directory.passive.markov;
+
+import java.util.LinkedHashMap;
+import java.util.Map.Entry;
+
+// FIXME rename
+public class Lookup {
+
+	public static final Lookup empty = new Lookup() {
+		public Token forRandom(double random) {
+			return Token.EMPTY;
+		}
+	};
+
+	public Lookup() {
+	}
+
+	private final LinkedHashMap<Token, Integer> tokens = new LinkedHashMap<Token, Integer>();
+
+	private int getTotalCounts() {
+		return tokens.values().stream().mapToInt(i -> i.intValue()).sum();
+	}
+
+	public void add(Token t) {
+		Integer i = tokens.getOrDefault(t, 0);
+		tokens.put(t, i + 1);
+	}
+
+	public Token forRandom(double random) {
+		int id = (int) Math.floor(random * getTotalCounts());
+		int i = 0;
+		for (Entry<Token, Integer> entry : tokens.entrySet()) {
+			i += entry.getValue();
+			if (id < i) {
+				return entry.getKey();
+			}
+		}
+		throw new IllegalStateException(String.format(
+				"failed to find a random token with seed %d within %s", id,
+				this));
+
+	}
+
+	@Override
+	public String toString() {
+		return "Lookup [tokens=" + tokens + "]";
+	}
+
+}

Markov/src/directory/passive/markov/Prefix.java

+package directory.passive.markov;
+
+import java.util.Arrays;
+
+// FIXME rename
+public class Prefix {
+	private final Token[] tokens;
+
+	public Prefix(Token[] tokens) {
+		this.tokens = tokens;
+	}
+
+	@Override
+	public String toString() {
+		return "Prefix [tokens=" + Arrays.toString(tokens) + "]";
+	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + Arrays.hashCode(tokens);
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		Prefix other = (Prefix) obj;
+		if (!Arrays.equals(tokens, other.tokens))
+			return false;
+		return true;
+	}
+	
+	
+}

Markov/src/directory/passive/markov/Token.java

+package directory.passive.markov;
+
+public class Token {
+
+	public static final Token START = new SpecialToken();
+	public static final Token END = new SpecialToken();
+	protected static final Token EMPTY = new SpecialToken();
+
+	public Token(String content) {
+		super();
+		this.content = content;
+	}
+
+	String content;
+
+	@Override
+	public String toString() {
+		if (this == END) {
+			return "Token <END>";
+		}
+		if (this == START) {
+			return "TOKEN <START>";
+		}
+		if (this == EMPTY)
+			return "TOKEN <empty>";
+		return "Token [content=" + content + "]";
+	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + ((content == null) ? 0 : content.hashCode());
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) {
+			return true;
+		}
+		if (obj == null)
+			return false;
+		if (this == START)
+			return false;
+		if (this == END)
+			return false;
+		if (this == EMPTY)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		Token other = (Token) obj;
+		if (content == null) {
+			if (other.content != null)
+				return false;
+		} else if (!content.equals(other.content))
+			return false;
+		return true;
+	}
+
+	public String render(String prefix) {
+		return prefix + content;
+	}
+
+	private static class SpecialToken extends Token {
+
+		public SpecialToken() {
+			super("");
+		}
+
+		@Override
+		public String render(String prefix) {
+			return "";
+		}
+
+	}
+
+}