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package org.jruby.ext.coverage;

import java.util.Arrays;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;
import org.jruby.Ruby;
import org.jruby.runtime.EventHook;
import org.jruby.runtime.RubyEvent;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;

public class CoverageData {
    public static final String STARTED = "";        // no load/require ruby file can be "" so we
    private static final int[] SVALUE = new int[0];  // use it as a holder to know if start occurs
    private volatile Map<String, int[]> coverage;

    public boolean isCoverageEnabled() {
        return coverage != null && coverage.get(STARTED) != null;
    }

    public Map<String, int[]> getCoverage() {
      return coverage;
    }

    public synchronized void setCoverageEnabled(Ruby runtime, boolean enabled) {
        Map<String, int[]> coverage = this.coverage;

        if (coverage == null) coverage = new HashMap<String, int[]>();

        if (enabled) {
            coverage.put(STARTED, SVALUE);
            runtime.addEventHook(COVERAGE_HOOK);
        } else {
            coverage.remove(STARTED);
        }

        this.coverage = coverage;
    }

    public synchronized Map<String, int[]> resetCoverage(Ruby runtime) {
        Map<String, int[]> coverage = this.coverage;
        runtime.removeEventHook(COVERAGE_HOOK);
        coverage.remove(STARTED);


        for (Map.Entry<String, int[]> entry : coverage.entrySet()) {
            String key = entry.getKey();

            // on reset we do not reset files where no execution ever happened but we do reset
            // any files visited to be an empty array.  Why?  I don't know.  Matching MRI.
            if (hasCodeBeenPartiallyCovered(entry.getValue())) coverage.put(key, SVALUE);
        }

        this.coverage = null;

        return coverage;
    }

    private static boolean hasCodeBeenPartiallyCovered(int[] lines) {
        for (int i = 0; i < lines.length; i++) {
            if (lines[i] > 0) return true;
        }

        return false;
    }

    public synchronized Map<String, int[]> prepareCoverage(String filename, int[] lines) {
        assert lines != null;

        Map<String, int[]> coverage = this.coverage;

        if (filename == null) {
            // null filename from certain evals, Ruby.executeScript, etc (jruby/jruby#5111)
            // we opt to ignore scripts with no filename, since coverage means nothing
            return coverage;
        }

        if (coverage != null) {
            coverage.put(filename, lines);
        }

        return coverage;
    }

    private static final EnumSet<RubyEvent> COVERAGE_EVENTS = EnumSet.of(RubyEvent.COVERAGE);
    
    private final EventHook COVERAGE_HOOK = new EventHook() {
        @Override
        public void eventHandler(ThreadContext context, String eventName, String file, int line, String name, IRubyObject type) {
            synchronized (CoverageData.this) {
                Map<String, int[]> coverage = CoverageData.this.coverage;

                // Should not be needed but I predict serialization of IR might hit this.
                if (coverage == null || line <= 0) return;

                int[] lines = coverage.get(file);

                // no coverage lines for this record.  bail out (should never happen)
                if (lines == null) return;

                // coverage is dead for this record.  result() has been called once and we marked it as such as an empty list.
                if (lines.length == 0) return;

                // increment usage count by one.
                lines[line - 1] += 1;
            }
        }

        @Override
        public boolean isInterestedInEvent(RubyEvent event) {
            return event == RubyEvent.COVERAGE;
        }

        @Override
        public EnumSet<RubyEvent> eventSet() {
            return COVERAGE_EVENTS;
        }
    };
    
}