package org.simantics.scl.runtime;

import org.simantics.scl.runtime.reporting.SCLReportingHandler;

import gnu.trove.map.hash.THashMap;

public class SCLContext extends THashMap<String,Object> {
    private static ThreadLocal<SCLContext> CONTEXT = new ThreadLocal<SCLContext>();
    private static ThreadLocal<OldContextNode> OLD_CONTEXT = new ThreadLocal<OldContextNode>();
    
    private static class OldContextNode {
        final SCLContext context;
        final OldContextNode next;
        
        public OldContextNode(SCLContext context, OldContextNode next) {
            this.context = context;
            this.next = next;
        }
    }
    
    public static SCLContext getCurrent() {
        SCLContext context = CONTEXT.get();
        if(context == null) {
            context = new SCLContext();
            CONTEXT.set(context);
        }
        return context;
    }
    
    public static void push(SCLContext newContext) {
        SCLContext oldContext = CONTEXT.get();
        if(oldContext != null)
            OLD_CONTEXT.set(new OldContextNode(oldContext, OLD_CONTEXT.get()));
        CONTEXT.set(newContext);
    }
    
    /**
     * Creates a new context based on some properties of the current context.
     * The new context is safe for use in parallel threads.
     */
    public static SCLContext createDerivedContext() {
        SCLContext newContext = new SCLContext();
        
        SCLContext baseContext = CONTEXT.get();
        if(baseContext != null) {
            Object reportingHandler = baseContext.get(SCLReportingHandler.REPORTING_HANDLER);
            if(reportingHandler != null)
                newContext.put(SCLReportingHandler.REPORTING_HANDLER, reportingHandler);
        }
        return newContext;
    }
    
    public static void pop() {
        OldContextNode node = OLD_CONTEXT.get();
        if(node == null)
            CONTEXT.set(null);
        else {
            CONTEXT.set(node.context);
            OLD_CONTEXT.set(node.next);
        }
    }
    
    /*
    @Override
    public Object get(Object key) {
        Object result = super.get(key);
        System.out.println(this + ": " + key + " -> " + result);
        return result;
    }
    
    @Override
    public Object put(String key, Object value) {
        System.out.println(this + ": " + key + " <- " + value);
        return super.put(key, value);
    }*/
}