package org.simantics.scl.commands.internal;

import java.util.concurrent.ConcurrentHashMap;

import org.simantics.db.Resource;
import org.simantics.scl.compiler.environment.specification.EnvironmentSpecification;
import org.simantics.scl.compiler.module.repository.ImportFailureException;
import org.simantics.scl.compiler.runtime.RuntimeEnvironment;
import org.simantics.scl.compiler.top.ExpressionEvaluator;
import org.simantics.scl.compiler.top.SCLExpressionCompilationException;
import org.simantics.scl.compiler.top.ValueNotFound;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;
import org.simantics.scl.osgi.SCLOsgi;
import org.simantics.scl.runtime.function.Function2;

@SuppressWarnings({"rawtypes", "unchecked"})
public class StringConverterFactory {
    private static final ConcurrentHashMap<Type, Function2> CONVERTER_CACHE = 
            new ConcurrentHashMap<Type, Function2>();
    private static RuntimeEnvironment environment;
    
    private static final Type ALLOWED_EFFECT = Types.union(new Type[] {Types.READ_GRAPH, Types.PROC});
    
    /**
     * Creates a string converter for given type.
     * @throws ValueNotFound 
     */
    public static Function2<Resource,Object,String> stringConverterFor(Type type) throws SCLExpressionCompilationException, ImportFailureException {
        Function2 converter = CONVERTER_CACHE.get(type);
        if(converter == null) {
            if(environment == null) {
                // no need to synchronize access to environment
                environment = SCLOsgi.MODULE_REPOSITORY.createRuntimeEnvironment(
                        EnvironmentSpecification.of(
                                "Simantics/GShow", "",
                                "Simantics/RouteGraph", "",
                                "Prelude", ""
                                ), StringConverterFactory.class.getClassLoader()
                        );
            }
            converter = (Function2)new ExpressionEvaluator(environment, "\\ctx r -> gshow ctx (Par 0 r)")
            .expectedType(Types.function(Types.RESOURCE, Types.functionE(type, ALLOWED_EFFECT, Types.STRING)))
            .eval();
            CONVERTER_CACHE.put(type, converter);
        }
        return converter;
    }
}