add support for the filter tag

src/main/java/com/ecwid/consul/v1/Filter.java

@@ -0,0 +1,262 @@
+package com.ecwid.consul.v1;
+
+import com.ecwid.consul.UrlParameters;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+/**
+ * Implements a query filter parameter.
+ * See https://www.consul.io/api-docs/features/filtering
+ */
+public class Filter implements UrlParameters {
+	public enum MatchingOperator {
+		EQUAL("=", false),
+		NOT_EQUAL("!=", false),
+		IS_EMPTY("is empty", true),
+		IS_NOT_EMPTY("is not empty", true),
+		IN("in", false),
+		NOT_IN("not in", false),
+		CONTAINS("contains", false),
+		NOT_CONTAINS("not contains", false),
+		MATCHES("matches", false),
+		NOT_MATCHES("not matches", false);
+
+		private final String representation;
+		private final boolean unary;
+
+		MatchingOperator(final String representation, final boolean unary) {
+			this.representation = representation;
+			this.unary = unary;
+		}
+
+		@Override
+		public String toString() {
+			return representation;
+		}
+	}
+
+	public static class Selector {
+		private final String s;
+
+		private Selector(String s) {
+			this.s = s;
+		}
+
+		public static Selector of(final String s) {
+			return new Selector(s);
+		}
+	}
+
+	/**
+	 * Creates a filter with a unary operator (e.g {@link MatchingOperator#IN} or {@link MatchingOperator#NOT_IN})
+	 * @throws IllegalArgumentException if used with a binary matching operator
+	 */
+	public static Filter of(final MatchingOperator matchingOperator, final Selector selector) {
+		if (!matchingOperator.unary) {
+			throw new IllegalArgumentException("operator " + matchingOperator.name() + " requires a value");
+		}
+		return new Filter(Collections.emptyList(), BoolOp.AND, new Leaf(matchingOperator, selector.s, null), true);
+	}
+
+	/**
+	 * Creates a filter with a binary operator
+	 * @throws IllegalArgumentException if used with a unary matching operator ({@link MatchingOperator#IN} or
+	 * {@link MatchingOperator#NOT_IN}) specifying a value, or if used with a binary matching operator w/o specifying
+	 * a value.
+	 */
+	public static Filter of(final MatchingOperator matchingOperator, final Selector selector, final String value) {
+		if (matchingOperator.unary && (value != null)) {
+			throw new IllegalArgumentException("operator " + matchingOperator.name() + " does not accept a value");
+		}
+		if (!matchingOperator.unary && (value == null)) {
+			throw new IllegalArgumentException("operator " + matchingOperator.name() + " requires a value");
+		}
+		if (matchingOperator == MatchingOperator.IN) {
+			return in(value, selector);
+		}
+		if (matchingOperator == MatchingOperator.NOT_IN) {
+			return notIn(value, selector);
+		}
+		return new Filter(Collections.emptyList(), BoolOp.AND, new Leaf(matchingOperator, selector.s, value), true);
+	}
+
+	/**
+	 * Creates a {@code "<Value>" in <Selector>} query
+	 */
+	public static Filter in(final String value, final Selector selector) {
+		return new Filter(Collections.emptyList(), BoolOp.AND, new Leaf(MatchingOperator.IN, selector.s, value), true);
+	}
+
+	/**
+	 * Creates a {@code "<Value>" not in <Selector>} query
+	 */
+	public static Filter notIn(final String value, final Selector selector) {
+		return new Filter(Collections.emptyList(), BoolOp.AND, new Leaf(MatchingOperator.NOT_IN, selector.s, value), true);
+	}
+
+	/**
+	 * Returns a new filter, with the specified filters added, all joined with 'and'.
+	 */
+	public Filter and(final Filter ...filters) {
+		return add(BoolOp.AND, filters);
+	}
+
+	/**
+	 * Creates a new filter with the specified filters, all joined with 'and'.
+	 */
+	public static Filter andAll(final List<Filter> filters) {
+		return new Filter(filters, BoolOp.AND, true);
+	}
+
+	/**
+	 * Returns a new filter, with the specified filters added, all joined with 'or'.
+	 */
+	public Filter or(final Filter ...filters) {
+		return add(BoolOp.OR, filters);
+	}
+
+	/**
+	 * Creates a new filter with the specified filters, all joined with 'and'.
+	 */
+	public static Filter orAll(final List<Filter> filters) {
+		return new Filter(filters, BoolOp.OR, true);
+	}
+
+	/**
+	 * Returns a negated copy of this filter.
+	 * Calling this method on a negative filter will turn it into a positive filter,
+	 * i.e {@code filter.not().not().equals(filter)} is true
+	 */
+	public Filter not() {
+		return new Filter(children, boolOp, leaf, !positive);
+	}
+
+	@Override
+	public List<String> toUrlParameters() {
+		return Collections.singletonList("filter=" + toString());
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (this == o) {
+			return true;
+		}
+		if ((o == null) || (getClass() != o.getClass())) {
+			return false;
+		}
+		final Filter filter = (Filter) o;
+		return (positive == filter.positive) &&
+				Objects.equals(children, filter.children) &&
+				(boolOp == filter.boolOp) &&
+				Objects.equals(leaf, filter.leaf);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(children, boolOp, leaf, positive);
+	}
+
+	@Override
+	public String toString() {
+		final String prefix = positive ? "" : "not ";
+		if (leaf != null) {
+			if (leaf.value != null) {
+				if ((leaf.matchingOperator == MatchingOperator.IN) || (leaf.matchingOperator == MatchingOperator.NOT_IN)) {
+					return String.format(prefix + "\"%s\" %s %s", leaf.value, leaf.matchingOperator, leaf.selector);
+				}
+				return String.format(prefix + "%s %s \"%s\"", leaf.selector, leaf.matchingOperator, leaf.value);
+			}
+			return String.format(prefix + "%s %s", leaf.selector, leaf.matchingOperator);
+		}
+
+		final String result = children.stream().map(Filter::toString).collect(Collectors.joining(" " + boolOp + " "));
+		if ((parent == null) && positive) {
+			return result;
+		}
+		return prefix + "(" + result + ")";
+	}
+
+	private enum BoolOp {
+		OR("or"),
+		AND("and");
+
+		private final String representation;
+
+		BoolOp(final String representation) {
+			this.representation = representation;
+		}
+
+		@Override
+		public String toString() {
+			return representation;
+		}
+
+	}
+
+	private static class Leaf {
+		private final Filter.MatchingOperator matchingOperator;
+		private final String selector;
+		private final String value;
+
+		private Leaf(final MatchingOperator matchingOperator, final String selector, final String value) {
+			this.matchingOperator = matchingOperator;
+			this.selector = selector;
+			this.value = value;
+		}
+
+		@Override
+		public boolean equals(final Object o) {
+			if (this == o) {
+				return true;
+			}
+			if ((o == null) || (getClass() != o.getClass())) {
+				return false;
+			}
+			final Leaf leaf = (Leaf) o;
+			return (matchingOperator == leaf.matchingOperator) &&
+					selector.equals(leaf.selector) &&
+					value.equals(leaf.value);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(matchingOperator, selector, value);
+		}
+
+	}
+	private final List<Filter> children;
+
+	private final BoolOp boolOp;
+	private final Leaf leaf;
+	private Filter parent;
+	private final boolean positive;
+	private Filter(final List<Filter> children, final BoolOp boolOp, final boolean positive) {
+		this.children = children;
+		this.boolOp = boolOp;
+		leaf = null;
+		this.positive = positive;
+	}
+
+	private Filter(final List<Filter> children, final BoolOp boolOp, final Leaf leaf, final boolean positive) {
+		this.children = children;
+		this.boolOp = boolOp;
+		this.leaf = leaf;
+		this.positive = positive;
+	}
+
+	private Filter add(final BoolOp op, final Filter... filters) {
+		final List<Filter> newChildren = new LinkedList<>();
+		newChildren.add(this);
+		newChildren.addAll(Arrays.asList(filters));
+		final Filter result = new Filter(newChildren, op, null, true);
+		for (final Filter child : newChildren) {
+			child.parent = result;
+		}
+		return result;
+	}
+}