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package cdc.perfs.runtime;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArrayList;

import cdc.perfs.EnvironmentKind;
import cdc.perfs.api.MeasureLevel;
import cdc.perfs.api.RuntimeManager;
import cdc.perfs.api.RuntimeProbe;
import cdc.perfs.api.Source;
import cdc.perfs.core.AbstractContext;
import cdc.perfs.core.AbstractEnvironment;
import cdc.perfs.core.SourceImpl;
import cdc.util.time.RefTime;

/**
 * Implementation of Environment for runtime measures.
 *
 * @author Damien Carbonne
 *
 */
public final class RuntimeEnvironment extends AbstractEnvironment implements RuntimeManager.RuntimeService {
    static final RuntimeEnvironment INSTANCE = new RuntimeEnvironment();

    /**
     * Map of Threads to associated contexts.
     */
    private final Map contexts = new HashMap<>();

    /**
     * Map of source names to dumb probes.
     * When present, a source is associated to an array of dumb probes, one for
     * each level.
     */
    private final Map dumbs = new HashMap<>();

    /**
     * Collection of Contexts that can be safely used in a multi-threaded
     * environment
     */
    private final List safeContexts = new CopyOnWriteArrayList<>();

    private RuntimeEnvironment() {
        super(RefTime.REF_NANOS, RefTime.REF_INSTANT);
    }

    public static RuntimeEnvironment getInstance() {
        return INSTANCE;
    }

    @Override
    public EnvironmentKind getKind() {
        return EnvironmentKind.RUNTIME;
    }

    @Override
    public List getContexts() {
        return safeContexts;
    }

    @Override
    public void removeDeadContexts() {
        final ArrayList deads = new ArrayList<>();
        for (final RuntimeContext context : safeContexts) {
            if (!context.isAlive()) {
                deads.add(context);
            }
        }
        safeContexts.removeAll(deads);
    }

    @Override
    public long getCurrentNanos() {
        return System.nanoTime();
    }

    @Override
    public long getElapsedNanos() {
        return System.nanoTime() - refNanos;
    }

    /**
     * Returns the RuntimeContext associated to calling thread.
     * 
     * If necessary, a new context is created.

     * If current thread was already associated to a context, this context is returned.
     *
     * @return The RuntimeContext associated to calling thread.
     */
    public synchronized RuntimeContext getCurrentContext() {
        final Thread thread = Thread.currentThread();
        RuntimeContext context = contexts.get(thread);
        if (context == null) {
            context = new RuntimeContext(this, contexts.size() + 1, thread);
            contexts.put(context.getThread(), context);
            safeContexts.add(context);
            fireContextCreation(context);
        }
        return context;
    }

    /**
     * Creates a probe that can be used to create measures at a given level and
     * associated to a source.
     *
     * @param source The source for which a probe must be created.
     * @param level The level of generated measures.
     * @return An appropriate probe (matching source and level).
     */
    @Override
    public RuntimeProbe createProbe(Source source,
                                    MeasureLevel level) {
        if (source.isEnabled(level)) {
            return new RuntimeSmartProbe((SourceImpl) source, level);
        } else {
            return getDumbProbe((SourceImpl) source, level);
        }
    }

    /**
     * Creates a probe at the DEBUG level.
     *
     * @param source The source for which a probe must be created.
     * @return An appropriate probe (matching source and DEBUG level).
     */
    @Override
    public RuntimeProbe createProbe(Source source) {
        return createProbe(source, MeasureLevel.DEBUG);
    }

    private RuntimeDumbProbe getDumbProbe(SourceImpl source,
                                          MeasureLevel level) {
        RuntimeDumbProbe[] probes = dumbs.get(source.getName());
        if (probes == null) {
            probes = new RuntimeDumbProbe[MeasureLevel.values().length];
            dumbs.put(source.getName(), probes);
        }
        if (probes[level.ordinal()] == null) {
            probes[level.ordinal()] = new RuntimeDumbProbe(source, level);
        }
        return probes[level.ordinal()];
    }
}