/**
 * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
 */

package net.sourceforge.pmd.lang.rule;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import net.sourceforge.pmd.Rule;
import net.sourceforge.pmd.RuleContext;
import net.sourceforge.pmd.RuleSet;
import net.sourceforge.pmd.benchmark.Benchmark;
import net.sourceforge.pmd.benchmark.Benchmarker;
import net.sourceforge.pmd.lang.ast.Node;

/**
 * This is a base class for RuleChainVisitor implementations which extracts
 * interesting nodes from an AST, and lets each Rule visit the nodes it has
 * expressed interest in.
 */
public abstract class AbstractRuleChainVisitor implements RuleChainVisitor {
    /**
     * These are all the rules participating in the RuleChain, grouped by
     * RuleSet.
     */
    protected Map<RuleSet, List<Rule>> ruleSetRules = new LinkedHashMap<>();

    /**
     * This is a mapping from node names to nodes instances for the current AST.
     */
    protected Map<String, List<Node>> nodeNameToNodes;

    /**
     * @see RuleChainVisitor#add(RuleSet, Rule)
     */
    @Override
    public void add(RuleSet ruleSet, Rule rule) {

        if (!ruleSetRules.containsKey(ruleSet)) {
            ruleSetRules.put(ruleSet, new ArrayList<Rule>());
        }
        ruleSetRules.get(ruleSet).add(rule);
    }

    /**
     * @see RuleChainVisitor#visitAll(List, RuleContext)
     */
    @Override
    public void visitAll(List<Node> nodes, RuleContext ctx) {
        initialize();
        clear();

        // Perform a visitation of the AST to index nodes which need visiting by
        // type
        long start = System.nanoTime();
        indexNodes(nodes, ctx);
        long end = System.nanoTime();
        Benchmarker.mark(Benchmark.RuleChainVisit, end - start, 1);

        // For each RuleSet, only if this source file applies
        for (Map.Entry<RuleSet, List<Rule>> entry : ruleSetRules.entrySet()) {
            RuleSet ruleSet = entry.getKey();
            if (!ruleSet.applies(ctx.getSourceCodeFile())) {
                continue;
            }

            // For each rule, allow it to visit the nodes it desires
            start = System.nanoTime();
            for (Rule rule : entry.getValue()) {
                int visits = 0;
                if (!RuleSet.applies(rule, ctx.getLanguageVersion())) {
                    continue;
                }
                final List<String> nodeNames = rule.getRuleChainVisits();
                for (int j = 0; j < nodeNames.size(); j++) {
                    List<Node> ns = nodeNameToNodes.get(nodeNames.get(j));
                    for (Node node : ns) {
                        // Visit with underlying Rule, not the RuleReference
                        Rule actualRule = rule;
                        while (actualRule instanceof RuleReference) {
                            actualRule = ((RuleReference) actualRule).getRule();
                        }
                        visit(actualRule, node, ctx);
                    }
                    visits += ns.size();
                }
                end = System.nanoTime();
                Benchmarker.mark(Benchmark.RuleChainRule, rule.getName(), end - start, visits);
                start = end;
            }
        }
    }

    /**
     * Visit the given rule to the given node.
     */
    protected abstract void visit(Rule rule, Node node, RuleContext ctx);

    /**
     * Index all nodes for visitation by rules.
     */
    protected abstract void indexNodes(List<Node> nodes, RuleContext ctx);

    /**
     * Index a single node for visitation by rules.
     */
    protected void indexNode(Node node) {
        List<Node> nodes = nodeNameToNodes.get(node.toString());
        if (nodes != null) {
            nodes.add(node);
        }
    }

    /**
     * Initialize the RuleChainVisitor to be ready to perform visitations. This
     * method should not be called until it is known that all Rules
     * participating in the RuleChain are ready to be initialized themselves.
     * Some rules may require full initialization to determine if they will
     * participate in the RuleChain, so this has been delayed as long as
     * possible to ensure that manipulation of the Rules is no longer occurring.
     */
    protected void initialize() {
        if (nodeNameToNodes != null) {
            return;
        }

        // Determine all node types that need visiting
        Set<String> visitedNodes = new HashSet<>();
        for (Iterator<Map.Entry<RuleSet, List<Rule>>> entryIterator = ruleSetRules.entrySet().iterator(); entryIterator
                .hasNext();) {
            Map.Entry<RuleSet, List<Rule>> entry = entryIterator.next();
            for (Iterator<Rule> ruleIterator = entry.getValue().iterator(); ruleIterator.hasNext();) {
                Rule rule = ruleIterator.next();
                if (rule.usesRuleChain()) {
                    visitedNodes.addAll(rule.getRuleChainVisits());
                } else {
                    // Drop rules which do not participate in the rule chain.
                    ruleIterator.remove();
                }
            }
            // Drop RuleSets in which all Rules have been dropped.
            if (entry.getValue().isEmpty()) {
                entryIterator.remove();
            }
        }

        // Setup the data structure to manage mapping node names to node
        // instances. We intend to reuse this data structure between
        // visits to different ASTs.
        nodeNameToNodes = new HashMap<>();
        for (String s : visitedNodes) {
            List<Node> nodes = new ArrayList<>(100);
            nodeNameToNodes.put(s, nodes);
        }
    }

    /**
     * Clears the internal data structure used to manage the nodes visited
     * between visiting different ASTs.
     */
    protected void clear() {
        for (List<Node> l : nodeNameToNodes.values()) {
            l.clear();
        }
    }
}