CurlyBracketsStructureCheck.java

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package com.qulice.checkstyle;

import com.google.common.collect.Lists;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import java.util.List;

/**
 * Checks node/closing curly brackets to be the last symbols on the line.
 *
 * <p>This is how a correct curly bracket structure should look like:
 *
 * <pre>
 * String[] array = new String[] {
 *      "first",
 *      "second"
 * };
 * </pre>
 *
 * or
 *
 * <pre>
 * String[] array = new String[] {"first", "second"};
 * </pre>
 *
 * <p>The motivation for such formatting is simple - we want to see the entire
 * block as fast as possible. When you look at a block of code you should be
 * able to see where it starts and where it ends.
 *
 * @since 0.6
 */
public final class CurlyBracketsStructureCheck extends AbstractCheck {

    @Override
    public int[] getDefaultTokens() {
        return new int[] {
            TokenTypes.ARRAY_INIT,
        };
    }

    @Override
    public int[] getAcceptableTokens() {
        return this.getDefaultTokens();
    }

    @Override
    public int[] getRequiredTokens() {
        return this.getDefaultTokens();
    }

    @Override
    public void visitToken(final DetailAST ast) {
        if (ast.getType() == TokenTypes.ARRAY_INIT) {
            this.checkParams(ast);
        }
    }

    /**
     * Checks params statement to satisfy the rule.
     * @param node Tree node, containing containing array init statement.
     */
    private void checkParams(final DetailAST node) {
        final DetailAST closing = node.findFirstToken(TokenTypes.RCURLY);
        if (closing != null) {
            this.checkLines(node, node.getLineNo(), closing.getLineNo());
        }
    }

    /**
     * Checks params statement to satisfy the rule.
     * @param node Tree node, containing array init statement.
     * @param start First line
     * @param end Final line
     */
    private void checkLines(final DetailAST node, final int start,
        final int end) {
        if (start != end) {
            this.checkExpressions(
                CurlyBracketsStructureCheck.findAllChildren(
                    node,
                    TokenTypes.EXPR
                ),
                start,
                end
            );
        }
    }

    /**
     * Checks that all EXPR nodes satisfy the rule.
     * @param exprs Iterable of EXPR nodes
     * @param start First line of ARRAY_INIT node
     * @param end Final line ARRAY_INIT node (corresponds to RCURLY)
     */
    private void checkExpressions(final Iterable<DetailAST> exprs,
        final int start,
        final int end
    ) {
        for (final DetailAST expr : exprs) {
            final int pline = expr.getLineNo();
            if (pline == start) {
                this.log(pline, "Parameters should start on a new line");
            }
            final DetailAST last = expr.getLastChild();
            final int lline = last.getLineNo();
            if (lline == end) {
                this.log(lline, "Closing bracket should be on a new line");
            }
        }
    }

    /**
     * Search for all children of given type.
     * @param base Parent node to start from
     * @param type Node type
     * @return Iterable
     */
    private static Iterable<DetailAST> findAllChildren(final DetailAST base,
        final int type) {
        final List<DetailAST> children = Lists.newArrayList();
        DetailAST child = base.getFirstChild();
        while (child != null) {
            if (child.getType() == type) {
                children.add(child);
            }
            child = child.getNextSibling();
        }
        return children;
    }
}