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package com.oracle.truffle.regex;

import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.regex.tregex.TRegexOptions;
import com.oracle.truffle.regex.tregex.parser.Counter;

This profile is used for tracking statistics about a compiled regular expression, such as the
amount of times the expression was executed and the amount of matches that were found. The
profiling information is used by TRegex for deciding whether a regular expression should match
capture groups in a lazy or eager way.
See Also:
TRegexExecRootNode
TRegexLazyCaptureGroupsRootNode/**
 * This profile is used for tracking statistics about a compiled regular expression, such as the
 * amount of times the expression was executed and the amount of matches that were found. The
 * profiling information is used by TRegex for deciding whether a regular expression should match
 * capture groups in a lazy or eager way.
 *
 * @see com.oracle.truffle.regex.tregex.nodes.TRegexExecRootNode
 * @see com.oracle.truffle.regex.tregex.nodes.dfa.TRegexLazyCaptureGroupsRootNode
 */
public final class RegexProfile {

    private static final int EVALUATION_TRIP_POINT = 800;

    private final Counter.ThreadSafeCounter calls = new Counter.ThreadSafeCounter();
    private final Counter.ThreadSafeCounter matches = new Counter.ThreadSafeCounter();
    private final Counter.ThreadSafeCounter captureGroupAccesses = new Counter.ThreadSafeCounter();
    private double avgMatchLength = 0;
    private double avgMatchedPortionOfSearchSpace = 0;

    
Increase the number of times the regular expression was executed by one.
/**
     * Increase the number of times the regular expression was executed by one.
     */
    public void incCalls() {
        calls.inc();
    }

    public void resetCalls() {
        calls.reset();
    }

    
Increase the number of times a match for the regular expression was found by one.
/**
     * Increase the number of times a match for the regular expression was found by one.
     */
    public void incMatches() {
        matches.inc();
    }

    
Update profile after the execution of a lazy capture groups search DFA.
Params:
matchLength – the length of capture group 0 of the match.
numberOfCharsTraversed – the number of characters that were traversed between the
           initial index (fromIndex) and the end of the match.
See Also:
TRegexLazyCaptureGroupsRootNode/**
     * Update profile after the execution of a lazy capture groups search DFA.
     *
     * @param matchLength the length of capture group 0 of the match.
     * @param numberOfCharsTraversed the number of characters that were traversed between the
     *            initial index (fromIndex) and the end of the match.
     * @see com.oracle.truffle.regex.tregex.nodes.dfa.TRegexLazyCaptureGroupsRootNode
     */
    public void profileCaptureGroupAccess(int matchLength, int numberOfCharsTraversed) {
        captureGroupAccesses.inc();
        avgMatchLength += (matchLength - avgMatchLength) / captureGroupAccesses.getCount();
        double matchedPortion = ((double) matchLength) / numberOfCharsTraversed;
        avgMatchedPortionOfSearchSpace += (matchedPortion - avgMatchedPortionOfSearchSpace) / captureGroupAccesses.getCount();
    }

    
Check if the profiling information gathered so far is sufficient for making a decision.
Returns:
true if the number of times the regular expression was called is divisible by 800./**
     * Check if the profiling information gathered so far is sufficient for making a decision.
     *
     * @return {@code true} if the number of times the regular expression was called is divisible by
     *         {@value #EVALUATION_TRIP_POINT}.
     */
    public boolean atEvaluationTripPoint() {
        return calls.getCount() > 0 && (calls.getCount() % EVALUATION_TRIP_POINT) == 0;
    }

    private double matchRatio() {
        assert calls.getCount() > 0;
        return (double) matches.getCount() / calls.getCount();
    }

    private double cgAccessRatio() {
        assert matches.getCount() > 0;
        return (double) captureGroupAccesses.getCount() / matches.getCount();
    }

    
Decides whether the regular expression was executed often enough to warrant the costly
generation of a fully expanded DFA.
/**
     * Decides whether the regular expression was executed often enough to warrant the costly
     * generation of a fully expanded DFA.
     */
    public boolean shouldGenerateDFA() {
        return calls.getCount() >= TRegexOptions.TRegexGenerateDFAThreshold;
    }

    
Decides whether the capture groups of the regular expression should be matched in an eager
manner.
Returns:
true if: 

        
most searches led to a match
        
the capture groups of most search results were queried
        
the match often covered a big part of the part of the input string that had to be
        traversed in order to find it.
        /**
     * Decides whether the capture groups of the regular expression should be matched in an eager
     * manner.
     *
     * @return {@code true} if:
     *         <ul>
     *         <li>most searches led to a match</li>
     *         <li>the capture groups of most search results were queried</li>
     *         <li>the match often covered a big part of the part of the input string that had to be
     *         traversed in order to find it.</li>
     *         </ul>
     */
    public boolean shouldUseEagerMatching() {
        return matchRatio() > 0.5 && cgAccessRatio() > 0.5 && avgMatchedPortionOfSearchSpace > 0.4;
    }

    @TruffleBoundary
    @Override
    public String toString() {
        return String.format("calls: %d, matches: %d (%.2f%%), cg accesses: %d (%.2f%%), avg matched portion of search space: %.2f%%",
                        calls.getCount(), matches.getCount(), matchRatio() * 100, captureGroupAccesses.getCount(), cgAccessRatio() * 100, avgMatchedPortionOfSearchSpace * 100);
    }

    public interface TracksRegexProfile {
        RegexProfile getRegexProfile();
    }
}