package bjc.utils.gen;

import java.util.Random;
import java.util.function.Function;

import bjc.utils.data.IPair;
import bjc.utils.data.Pair;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.FunctionalMap;
import bjc.utils.funcdata.IList;
import bjc.utils.funcdata.IMap;

/**
 * A random grammar, where certain rules will come up more often than
 * others.
 * 
 * @author ben
 *
 * @param <E>
 *            The values that make up sentances of this grammar.
 */
public class WeightedGrammar<E> {
	/**
	 * The initial rule of the grammar
	 */
	protected String initialRule;

	/**
	 * The rules currently in this grammar
	 */
	protected IMap<E, WeightedRandom<IList<E>>>	rules;

	/**
	 * The random number generator used for random numbers
	 */
	private Random rng;

	/**
	 * All of the subgrammars of this grammar
	 */
	protected IMap<E, WeightedGrammar<E>> subgrammars;

	/**
	 * Create a new weighted grammar.
	 */
	public WeightedGrammar() {
		rules = new FunctionalMap<>();
		subgrammars = new FunctionalMap<>();
	}

	/**
	 * Create a new weighted grammar that uses the specified source of
	 * randomness.
	 * 
	 * @param source
	 *            The source of randomness to use
	 */
	public WeightedGrammar(Random source) {
		this();

		if (source == null) {
			throw new NullPointerException("Source of randomness must be non-null");
		}

		rng = source;
	}

	/**
	 * Add a case to an already existing rule.
	 * 
	 * @param ruleName
	 *            The rule to add a case to.
	 * @param probability
	 *            The probability for this rule to be chosen.
	 * @param cse
	 *            The case being added.
	 */
	public void addCase(E ruleName, int probability, IList<E> cse) {
		if (ruleName == null) {
			throw new NullPointerException("Rule name must be not null");
		} else if (cse == null) {
			throw new NullPointerException("Case body must not be null");
		}

		rules.get(ruleName).addProbability(probability, cse);
	}

	/**
	 * Add a alias for an existing subgrammar
	 * 
	 * @param name
	 *            The name of the subgrammar to alias
	 * @param alias
	 *            The alias of the subgrammar
	 * @return Whether the alias was succesfully created
	 */
	public boolean addGrammarAlias(E name, E alias) {
		if (name == null) {
			throw new NullPointerException("Subgrammar name must not be null");
		} else if (alias == null) {
			throw new NullPointerException("Subgrammar alias must not be null");
		}

		if (subgrammars.containsKey(alias)) {
			return false;
		}

		if (subgrammars.containsKey(name)) {
			subgrammars.put(alias, subgrammars.get(name));
			return true;
		}

		return false;
	}

	/**
	 * Add a new rule with no cases.
	 * 
	 * @param name
	 *            The name of the rule to add.
	 * @return Whether or not the rule was succesfully added.
	 */
	public boolean addRule(E name) {
		if (rng == null) {
			rng = new Random();
		}

		if (name == null) {
			throw new NullPointerException("Rule name must not be null");
		}

		return addRule(name, new WeightedRandom<>(rng));
	}

	/**
	 * Add a new rule with a set of cases.
	 * 
	 * @param name
	 *            The name of the rule to add.
	 * @param cases
	 *            The set of cases for the rule.
	 * @return Whether or not the rule was succesfully added.
	 */
	public boolean addRule(E name, WeightedRandom<IList<E>> cases) {
		if (name == null) {
			throw new NullPointerException("Name must not be null");
		} else if (cases == null) {
			throw new NullPointerException("Cases must not be null");
		}

		if (rules.containsKey(name)) {
			return false;
		}

		rules.put(name, cases);
		return true;
	}

	/**
	 * Add a subgrammar.
	 * 
	 * @param name
	 *            The name of the subgrammar.
	 * @param subgrammar
	 *            The subgrammar to add.
	 * @return Whether or not the subgrammar was succesfully added.
	 */
	public boolean addSubgrammar(E name, WeightedGrammar<E> subgrammar) {
		if (name == null) {
			throw new NullPointerException("Subgrammar name must not be null");
		} else if (subgrammar == null) {
			throw new NullPointerException("Subgrammar must not be null");
		}

		if (subgrammars.containsKey(name)) {
			return false;
		}

		subgrammars.put(name, subgrammar);
		return true;
	}

	/**
	 * Remove a rule with the specified name.
	 * 
	 * @param name
	 *            The name of the rule to remove.
	 */
	public void deleteRule(E name) {
		if (name == null) {
			throw new NullPointerException("Rule name must not be null");
		}

		rules.remove(name);
	}

	/**
	 * Remove a subgrammar with the specified name.
	 * 
	 * @param name
	 *            The name of the subgrammar to remove.
	 */
	public void deleteSubgrammar(E name) {
		if (name == null) {
			throw new NullPointerException("Rule name must not be null");
		}

		subgrammars.remove(name);
	}

	/**
	 * Generate a set of debug sentences for the specified rule.
	 *
	 * Only generates sentances one layer deep.
	 * 
	 * @param ruleName
	 *            The rule to test.
	 * @return A set of sentances generated by the specified rule.
	 */
	public IList<IList<E>> generateDebugValues(E ruleName) {
		if (ruleName == null) {
			throw new NullPointerException("Rule name must not be null");
		}

		IList<IList<E>> returnedList = new FunctionalList<>();

		WeightedRandom<IList<E>> ruleGenerator = rules.get(ruleName);

		for (int i = 0; i < 10; i++) {
			returnedList.add(ruleGenerator.generateValue());
		}

		return returnedList;
	}

	/**
	 * Generate a generic sentance from a initial rule.
	 * 
	 * @param <T>
	 *            The type of the transformed output
	 * 
	 * @param initRule
	 *            The initial rule to start with.
	 * @param tokenTransformer
	 *            The function to transform grammar output into something.
	 * @param spacer
	 *            The spacer element to add in between output tokens.
	 * @return A randomly generated sentance from the specified initial
	 *         rule.
	 */
	public <T> IList<T> generateGenericValues(E initRule, Function<E, T> tokenTransformer, T spacer) {
		if (initRule == null) {
			throw new NullPointerException("Initial rule must not be null");
		} else if (tokenTransformer == null) {
			throw new NullPointerException("Transformer must not be null");
		} else if (spacer == null) {
			throw new NullPointerException("Spacer must not be null");
		}

		IList<T> returnedList = new FunctionalList<>();

		if (subgrammars.containsKey(initRule)) {
			subgrammars.get(initRule)
				.generateGenericValues(initRule, tokenTransformer, spacer)
				.forEach(rulePart -> {
						returnedList.add(rulePart);
						returnedList.add(spacer);
					});
		} else if (rules.containsKey(initRule)) {
			rules.get(initRule)
				 .generateValue().forEach(rulePart -> {
					 if(rulePart.matches("\\[\\S+\\]") {
						 generateGenericValues(rulePart, tokenTransformer, spacer)
							 .forEach(generatedRulePart -> {
										returnedList.add(generatedRulePart);
										returnedList.add(spacer);
								});
					 } else {
						 T transformedToken = tokenTransformer.apply(initRule);

						 if (transformedToken == null) {
							 throw new NullPointerException("Transformer created null token");
						 }

						 returnedList.add(transformedToken);
						 returnedList.add(spacer);
					 }
				});
		} else {
			T transformedToken = tokenTransformer.apply(initRule);

			if (transformedToken == null) {
				throw new NullPointerException("Transformer created null token");
			}

			returnedList.add(transformedToken);
			returnedList.add(spacer);
		}

		return returnedList;
	}

	/**
	 * Generate a random list of grammar elements from a given initial
	 * rule.
	 * 
	 * @param initRule
	 *            The initial rule to start with.
	 * @param spacer
	 *            The item to use to space the list.
	 * @return A list of random grammar elements generated by the specified
	 *         rule.
	 */
	public IList<E> generateListValues(E initRule, E spacer) {
		return generateGenericValues(initRule, strang -> strang, spacer);
	}

	/**
	 * Get the initial rule of this grammar
	 * 
	 * @return The initial rule of this grammar
	 */
	public String getInitialRule() {
		return initialRule;
	}

	/**
	 * Returns the number of rules in this grammar
	 * 
	 * @return The number of rules in this grammar
	 */
	public int getRuleCount() {
		return rules.getSize();
	}

	/**
	 * Returns a set containing all of the rules in this grammar
	 * 
	 * @return The set of all rule names in this grammar
	 */
	public IList<E> getRuleNames() {
		return rules.keyList();
	}

	/**
	 * Get the subgrammar with the specified name.
	 * 
	 * @param name
	 *            The name of the subgrammar to get.
	 * @return The subgrammar with the specified name.
	 */
	public WeightedGrammar<E> getSubgrammar(E name) {
		if (name == null) {
			throw new NullPointerException("Subgrammar name must not be null");
		}

		return subgrammars.get(name);
	}

	/**
	 * Check if this grammar has an initial rule
	 * 
	 * @return Whether or not this grammar has an initial rule
	 */
	public boolean hasInitialRule() {
		return initialRule != null && !initialRule.equalsIgnoreCase("");
	}

	/**
	 * Prefix a given rule with a token multiple times
	 * 
	 * @param ruleName
	 *            The name of the rule to prefix
	 * @param prefixToken
	 *            The token to prefix to the rules
	 * @param additionalProbability
	 *            The additional probability of the tokens
	 * @param numberOfTimes
	 *            The number of times to prefix the token
	 */
	public void multiPrefixRule(E ruleName, E prefixToken,
			int additionalProbability, int numberOfTimes) {
		if (ruleName == null) {
			throw new NullPointerException("Rule name must not be null");
		} else if (prefixToken == null) {
			throw new NullPointerException("Prefix token must not be null");
		} else if (numberOfTimes < 1) {
			throw new IllegalArgumentException("Number of times to prefix must be positive.");
		}

		WeightedRandom<IList<E>> rule = rules.get(ruleName);

		IList<IPair<Integer, IList<E>>> newResults = new FunctionalList<>();

		rule.getValues().forEach((pair) -> {
			IList<IList<E>> newRule = new FunctionalList<>();

			for (int i = 1; i <= numberOfTimes; i++) {
				IList<E> newCase = pair.merge((left, right) -> {
					IList<E> returnVal = new FunctionalList<>();

					for (E val : right.toIterable()) {
						returnVal.add(val);
					}

					return returnVal;
				});

				for (int j = 1; j <= i; j++) {
					newCase.prepend(prefixToken);
				}

				newRule.add(newCase);
			}

			newRule.forEach((list) -> {
				Integer currentProb = pair.merge((left, right) -> left);

				newResults.add(new Pair<>(currentProb + additionalProbability, list));
			});
		});

		newResults.forEach((pair) -> {
			pair.doWith((left, right) -> {
				addCase(ruleName, left, right);
			});
		});
	}

	/**
	 * Create a series of alternatives for a rule by prefixing them with a
	 * given token
	 * 
	 * @param additionalProbability
	 *            The amount to adjust the probability by
	 * @param ruleName
	 *            The name of the rule to prefix
	 * @param prefixToken
	 *            The token to prefix to the rule
	 */
	public void prefixRule(E ruleName, E prefixToken, int additionalProbability) {
		if (ruleName == null) {
			throw new NullPointerException("Rule name must not be null");
		} else if (prefixToken == null) {
			throw new NullPointerException("Prefix token must not be null");
		}

		WeightedRandom<IList<E>> rule = rules.get(ruleName);

		IList<IPair<Integer, IList<E>>> newResults = new FunctionalList<>();

		rule.getValues().forEach((pair) -> {
			IList<E> newCase = pair.merge((left, right) -> {
				IList<E> returnVal = new FunctionalList<>();

				for (E val : right.toIterable()) {
					returnVal.add(val);
				}

				return returnVal;
			});

			newCase.prepend(prefixToken);

			newResults.add(new Pair<>(pair.merge((left, right) -> left) + additionalProbability, newCase));
		});

		newResults.forEach((pair) -> 
				pair.doWith((left, right) ->
					addCase(ruleName, left, right)));
	}

	/**
	 * Set the initial rule of the graphic
	 * 
	 * @param initRule
	 *            The initial rule of this grammar
	 */
	public void setInitialRule(String initRule) {
		this.initialRule = initRule;
	}

	/**
	 * Suffix a token to a rule
	 * 
	 * @param ruleName
	 *            The rule to suffix
	 * @param suffixToken
	 *            The token to prefix to the rule
	 * @param additionalProbability
	 *            Additional probability of the prefixed rule
	 */
	public void suffixRule(E ruleName, E suffixToken, int additionalProbability) {
		if (ruleName == null) {
			throw new NullPointerException("Rule name must not be null");
		} else if (suffixToken == null) {
			throw new NullPointerException("Prefix token must not be null");
		}

		WeightedRandom<IList<E>> rule = rules.get(ruleName);

		IList<IPair<Integer, IList<E>>> newResults = new FunctionalList<>();

		rule.getValues().forEach((par) -> {
			IList<E> newCase = par.merge((left, right) -> {
				IList<E> returnVal = new FunctionalList<>();

				for (E val : right.toIterable()) {
					returnVal.add(val);
				}

				return returnVal;
			});

			newCase.add(suffixToken);

			newResults.add(new Pair<>(par.merge((left, right) -> left) + additionalProbability, newCase));
		});

		newResults.forEach((pair) -> 
				pair.doWith((left, right) ->
					addCase(ruleName, left, right)));
	}
}