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package de.prob.prolog.match;

import de.prob.prolog.term.CompoundPrologTerm;
import de.prob.prolog.term.PrologTerm;

import java.util.Arrays;
import java.util.Map;

/**
 * Matches on compound Prolog terms. The found compound term can be directly
 * accessed.
 *
 * @see CompoundPrologTerm
 */
public final class PrologTermMatch extends PrologMatch {

	private final String functor;
	private final int arity;
	private final PrologMatch[] args;

	/**
	 * Matches on a term with given functor and arguments
	 *
	 * @param functor the functor, null if it should not be checked
	 * @param arity the arity, <0 if it should not be checked
	 * @param args the arguments. If null, they remain unchecked.
	 *     If an element of args is null, it remains unchecked.
	 */
	private PrologTermMatch(String name, String functor, int arity, PrologMatch[] args) {
		super(name);
		if (args != null && args.length != arity) {
			throw new IllegalArgumentException("wanted arity is inconsistent with wanted args");
		}

		this.functor = functor;
		this.arity = arity;
		this.args = args != null ? Arrays.copyOf(args, args.length) : null;
	}

	public static PrologTermMatch anonTerm() {
		return namedTerm(null);
	}

	public static PrologTermMatch anonTerm(String functor) {
		return namedTerm(null, functor);
	}

	public static PrologTermMatch anonTerm(String functor, PrologMatch... args) {
		return namedTerm(null, functor, args);
	}

	public static PrologTermMatch anonTerm(String functor, int arity) {
		return namedTerm(null, functor, arity);
	}

	public static PrologTermMatch anonAtom(String functor) {
		return namedAtom(null, functor);
	}

	public static PrologTermMatch namedTerm(String name) {
		return namedTerm(name, null);
	}

	public static PrologTermMatch namedTerm(String name, String functor) {
		return namedTerm(name, functor, -1);
	}

	public static PrologTermMatch namedTerm(String name, String functor, PrologMatch... args) {
		return new PrologTermMatch(name, functor, args != null ? args.length : -1, args);
	}

	public static PrologTermMatch namedTerm(String name, String functor, int arity) {
		return new PrologTermMatch(name, functor, arity, null);
	}

	public static PrologTermMatch namedAtom(String name, String functor) {
		return namedTerm(name, functor, 0);
	}

	@Override
	protected boolean isMatch(PrologTerm term, Map hits) {
		if (term instanceof CompoundPrologTerm) {
			CompoundPrologTerm compound = (CompoundPrologTerm) term;
			return (arity < 0 || compound.getArity() == arity)
				&& (functor == null || functor.equals(compound.getFunctor()))
				&& args == null || allArgsMatch(compound, hits);
		}
		return false;
	}

	private boolean allArgsMatch(CompoundPrologTerm term, Map hits) {
		for (int i = 0; i < arity; i++) {
			PrologMatch argMatch = args[i];
			if (argMatch != null && !argMatch.matches(term.getArgument(i + 1), hits)) {
				return false;
			}
		}
		return true;
	}
}