package bjc.dicelang.dice;

import java.util.Random;
import java.util.function.Predicate;
import java.util.regex.Pattern;

/**
 * Contains static methods for producing dice from strings.
 *
 * @author Ben Culkin
 */
public class DiceBox {
	static final Random rng = new Random();

	/**
	 * Parse a die expression from a string.
	 *
	 * @param expString
	 *                The string to parse.
	 *
	 * @return The die expression from the string, or null if it wasn't one
	 */
	public static DieExpression parseExpression(final String expString) {
		try {
			return doParseExpression(expString);
		} catch (Exception ex) {
			/*
			 * @TODO 10/08/17 Ben Culkin :DieErrors :ErrorRefactor
			 * 	Use different types of exceptions to provide
			 * 	better error messages. 
			 */
			String exMessage = ex.getMessage();

			System.out.printf("ERROR: Could not parse die expression (Cause: %s)\n", exMessage);
			ex.printStackTrace();

			return null;
		}
	}

	private static DieExpression doParseExpression(final String expString) {
		/* Only bother with valid expressions. */
		if (!isValidExpression(expString)) {
			return null;
		}

		if (scalarDiePattern.matcher(expString).matches()) {
			/* Parse scalar die. */
			/* @TODO 10/08/17 Ben Culkin :SubstringIndexOf
			 * 	This substring/index of call should be
			 * 	abstracted into its own method so as to make the
			 * 	code more explanatory and ensure that things
			 * 	like the return code of indexOf are correctly
			 * 	checked.
			 */
			final String dieString = expString.substring(0, expString.indexOf('s'));

			final long lar = Long.parseLong(dieString);

			final Die scal = new ScalarDie(lar);

			return new DieExpression(scal);
		} else if (simpleDiePattern.matcher(expString).matches()) {
			/* Parse simple die groups. */
			final String[] dieParts = expString.split("d");

			final long right = Long.parseLong(dieParts[1]);
			final long left;

			if (dieParts[0].equals("")) {
				/* Handle short-form expressions. */
				left = 1;
			} else {
				left = Long.parseLong(dieParts[0]);
			}

			final Die scal = new SimpleDie(left, right);

			return new DieExpression(scal);
		} else if (fudgeDiePattern.matcher(expString).matches()) {
			/* Parse fudge dice. */
			/* :SubstringIndexOf */
			final String nDice = expString.substring(0, expString.indexOf('d'));
			final Die fudge    = new FudgeDie(Long.parseLong(nDice));

			return new DieExpression(fudge);
		} else if (compoundDiePattern.matcher(expString).matches()) {
			/* Parse compound die expressions. */
			final String[] dieParts = expString.split("c");

			/* @TODO 10/08/17 :SplitParse
			 * 	Should this split string/parse split parts be
			 * 	abstracted into something else that handles
			 * 	doing the splitting correctly, as well as
			 * 	making sure that the resulting DieExpressions
			 * 	are of the right type?
			 */
			final DieExpression left  = parseExpression(dieParts[0]);
			final DieExpression right = parseExpression(dieParts[1]);

			/* :ErrorRefactor */
			if (left.isList) {
				System.out.printf("ERROR: Expected a scalar die expression for lhs of compound die, got a list expression instead (%s)\n",
				                  left);
			} else if (right.isList) {
				System.out.printf("ERROR: Expected a scalar die expression for rhs of compound die, got a list expression instead (%s)\n",
				                  right);
			}

			final Die compound = new CompoundDie(left.scalar, right.scalar);

			return new DieExpression(new CompoundDie(left.scalar, right.scalar));
		} else if (compoundingDiePattern.matcher(expString).matches()) {
			/* Parse compounding die expressions. */
			final String[] dieParts = expString.split("!!");

			final DieExpression left    = parseExpression(dieParts[0]);
			final Predicate<Long> right = deriveCond(dieParts[1]);

			final Die scal = new CompoundingDie(left.scalar, right, dieParts[1]);

			return new DieExpression(scal);
		} else if (explodingDiePattern.matcher(expString).matches()) {
			/* Parse exploding die expressions. */
			final String[] dieParts = expString.split("!");

			final DieExpression left    = parseExpression(dieParts[0]);
			final Predicate<Long> right = deriveCond(dieParts[1]);

			final DieList lst = new ExplodingDice(left.scalar, right, dieParts[1], false);

			return new DieExpression(lst);
		} else if (penetratingDiePattern.matcher(expString).matches()) {
			/* Parse penetrating die expressions. */
			final String[] dieParts = expString.split("p!");

			final DieExpression left    = parseExpression(dieParts[0]);
			final Predicate<Long> right = deriveCond(dieParts[1]);

			final DieList lst = new ExplodingDice(left.scalar, right, dieParts[1], true);

			return new DieExpression(lst);
		} else if (diceListPattern.matcher(expString).matches()) {
			/* Parse simple die lists. */
			final String[] dieParts = expString.split("dl");

			final DieExpression left  = parseExpression(dieParts[0]);
			final DieExpression right = parseExpression(dieParts[1]);

			final DieList lst = new SimpleDieList(left.scalar, right.scalar);
			return new DieExpression(lst);
		}

		/* Unhandled type of die expression. */
		System.out.printf("INTERNAL ERROR: Valid die expression '%s' not parsed\n", expString);
		return null;
	}

	/* The strings and patterns used for matching. */
	/* @TODO 10/08/17 Ben Culkin :RegexResource
	 * 	These regexes and patterns should be moved to something
	 * 	external, probably using the SimpleProperties-based system that
	 * 	BJC-Utils2 uses.
	 */
	/* Defines a comparison predicate. */
	private static final String comparePoint = "[<>=]\\d+";

	/*
	 * Defines a scalar die.
	 *
	 * This is just a number.
	 */
	private static final String     scalarDie        = "[\\+\\-]?\\d+sd";
	private static final Pattern    scalarDiePattern = Pattern.compile(
	                        String.format("\\A%s\\Z", scalarDie));

	/*
	 * Defines a simple die.
	 *
	 * This is a group of one or more dice of the same size.
	 */
	private static final String     simpleDie               = "(?:\\d+)?d\\d+";
	private static final Pattern    simpleDiePattern        = Pattern.compile("\\A" +
	                simpleDie + "\\Z");

	/*
	 * Defines a fudge die.
	 *
	 * This is like a simple die, but all the die give -1, 0, or 1 as
	 * results.
	 */
	private static final String     fudgeDie        = "(?:\\d+)?dF";
	private static final Pattern    fudgeDiePattern = Pattern.compile("\\A" + fudgeDie +
	                "\\Z");

	/*
	 * Defines a compound die.
	 *
	 * This is like using two d10's to simulate a d100
	 */
	private static final String     compoundDie             = simpleDie + "c(?:(?:" +
	                simpleDie + ")|(?:\\d+))";
	private static final Pattern    compoundDiePattern      = Pattern.compile("\\A" +
	                compoundDie + "\\Z");

	/*
	 * Defines a compound group.
	 *
	 * This is used for forming die list type expressions.
	 */
	private static final String compoundGroup = "(?:(?:" + scalarDie + ")|(?:" + simpleDie +
	                ")|(?:" + compoundDie
	                + ")|(?:" + fudgeDie + "))";

	/*
	 * Defines a compounding die.
	 *
	 * This is like an exploding die, but is a single die, not a group of
	 * them.
	 */
	private static final String     compoundingDie          = compoundGroup + "!!" +
	                comparePoint;
	private static final Pattern    compoundingDiePattern   = Pattern.compile("\\A" +
	                compoundingDie + "\\Z");

	/*
	 * Defines an exploding die.
	 *
	 * This is a die that you reroll the component of if it meets a certain
	 * condition.
	 */
	private static final String     explodingDie            = compoundGroup + "!" +
	                comparePoint;
	private static final Pattern    explodingDiePattern     = Pattern.compile("\\A" +
	                explodingDie + "\\Z");

	/*
	 * Defines a penetrating die.
	 *
	 * This is like an exploding die, but the exploded result gets a -1
	 * penalty.
	 */
	private static final String     penetratingDie          = compoundGroup + "!" +
	                comparePoint;
	private static final Pattern    penetratingDiePattern   = Pattern.compile("\\A" +
	                penetratingDie + "\\Z");

	/*
	 * Defines a die list.
	 *
	 * This is an array of dice of the specified size.
	 */
	private static final String     diceList        = compoundGroup + "dl" + compoundGroup;
	private static final Pattern    diceListPattern = Pattern.compile("\\A" + diceList +
	                "\\Z");

	/**
	 * Check if a given string is a valid die expression.
	 *
	 * @param exp
	 *                The string to check validity of.
	 *
	 * @return Whether or not the string is a valid command.
	 */
	public static boolean isValidExpression(final String exp) {
		/* @NOTE
		 * 	Should this matcher/matches expression be abstracted in
		 * 	some way?
		 */
		if (scalarDiePattern.matcher(exp).matches()) {
			return true;
		} else if (simpleDiePattern.matcher(exp).matches()) {
			return true;
		} else if (fudgeDiePattern.matcher(exp).matches()) {
			return true;
		} else if (compoundDiePattern.matcher(exp).matches()) {
			return true;
		} else if (compoundingDiePattern.matcher(exp).matches()) {
			return true;
		} else if (explodingDiePattern.matcher(exp).matches()) {
			return true;
		} else if (penetratingDiePattern.matcher(exp).matches()) {
			return true;
		} else if (diceListPattern.matcher(exp).matches()) {
			return true;
		} else {
			return false;
		}
	}

	/* Derive a predicate from a compare point */
	private static Predicate<Long> deriveCond(final String patt) {
		final long num = Long.parseLong(patt.substring(1));

		/* @NOTE
		 * 	Should this be extended in some way, to provide other
		 * 	operators?
		 */
		switch (patt.charAt(0)) {
		case '<':
			return (roll) -> (roll < num);
		case '=':
			return (roll) -> (roll == num);
		case '>':
			return (roll) -> (roll > num);
		default:
			return (roll) -> (false);
		}
	}
}