package org.simantics.scl.compiler.top;

import java.util.ArrayList;

import org.simantics.scl.compiler.common.names.Name;
import org.simantics.scl.compiler.common.names.Names;
import org.simantics.scl.compiler.elaboration.expressions.Case;
import org.simantics.scl.compiler.elaboration.expressions.EApply;
import org.simantics.scl.compiler.elaboration.expressions.ECHRRuleset;
import org.simantics.scl.compiler.elaboration.expressions.EConstant;
import org.simantics.scl.compiler.elaboration.expressions.EEnforce;
import org.simantics.scl.compiler.elaboration.expressions.EFieldAccess;
import org.simantics.scl.compiler.elaboration.expressions.ELambda;
import org.simantics.scl.compiler.elaboration.expressions.ERuleset;
import org.simantics.scl.compiler.elaboration.expressions.ESelect;
import org.simantics.scl.compiler.elaboration.expressions.ESimpleLambda;
import org.simantics.scl.compiler.elaboration.expressions.EWhen;
import org.simantics.scl.compiler.elaboration.expressions.Expression;
import org.simantics.scl.compiler.elaboration.expressions.StandardExpressionTransformer;
import org.simantics.scl.compiler.elaboration.expressions.Variable;
import org.simantics.scl.compiler.elaboration.modules.SCLValue;
import org.simantics.scl.compiler.environment.Environment;
import org.simantics.scl.compiler.errors.ErrorLog;
import org.simantics.scl.compiler.errors.Locations;
import org.simantics.scl.compiler.types.TCon;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;

import gnu.trove.map.hash.THashMap;

public class ToplevelEffectDecorator extends StandardExpressionTransformer {

    ErrorLog errorLog;
    Environment environment;

    public ToplevelEffectDecorator(ErrorLog errorLog, Environment environment) {
        this.errorLog = errorLog;
        this.environment = environment;
    }

    @Override
    public Expression transform(EEnforce expression) {
        return decorateByEffect(expression, expression.getEffect());
    }
    
    @Override
    public Expression transform(EWhen expression) {
        return decorateByEffect(expression, expression.getEffect());
    }
    
    @Override
    public Expression transform(ERuleset expression) {
        return decorateByEffect(expression, expression.getEffect());
    }
    
    @Override
    public Expression transform(ECHRRuleset expression) {
        return decorateByEffect(expression, expression.getEffect());
    }
    
    @Override
    public Expression transform(EFieldAccess expression) {
        // Can we encounter EFieldAccess in this transformer?
        return decorateByEffect(expression, expression.getEffect());
    }
    
    @Override
    public Expression transform(ESelect expression) {
        return decorateByEffect(expression, expression.getEffect());
    }

    @Override
    public Expression transform(EApply expression) {
        return decorateByEffect(super.transform(expression), expression.getLocalEffect());
    }

    @Override
    public Expression transform(ESimpleLambda expression) {
        // Never has side effects
        return expression;
    }

    @Override
    public Expression transform(ELambda expression) {
        // Never has side effects
        return expression;
    }

    @Override
    protected void transformCases(Case[] cases) {
        for(Case case_ : cases)
            case_.value = case_.value.accept(this);
    }
    
    private static final THashMap<TCon, Name> DECORATION_MAP = new THashMap<TCon, Name>();

    static {
        DECORATION_MAP.put(Types.WRITE_GRAPH,     Names.Simantics_DB_syncWrite);
        DECORATION_MAP.put(Types.READ_GRAPH,      Names.Simantics_DB_syncRead);
        DECORATION_MAP.put(Types.con("R/R", "R"), Names.R_R_runR);
        DECORATION_MAP.put(Types.RANDOM,          Names.Random_runRandom);
    }

    private Expression decorateByEffect(Expression expression, Type effect) {
        if(effect == Types.NO_EFFECTS) 
            return expression;

        ArrayList<TCon> concreteEffects = new ArrayList<TCon>();
        effect.collectConcreteEffects(concreteEffects);
        for(TCon ce : concreteEffects) {
            Name transactionFunctionName = DECORATION_MAP.get(ce);
            if(transactionFunctionName == null)
                continue;
            SCLValue transactionFunction = environment.getValue(transactionFunctionName);
            if(transactionFunction == null) {
                errorLog.log(expression.location, "Cannot locate " + transactionFunctionName);
                continue;
            }
            expression = decorate(transactionFunction, ce, expression);
        }

        return expression;
    }

    private static Expression decorate(SCLValue transactionFunction, Type effect, Expression expression) {
        Variable var = new Variable("_");
        var.setType(effect == Types.RANDOM ? Types.PUNIT : Types.UNIT);
        Expression trans = new EApply(expression.getLocation(), Types.PROC,
                effect == Types.RANDOM ? new EConstant(transactionFunction, Types.PROC, expression.getType()) : new EConstant(transactionFunction, expression.getType()),
                new ESimpleLambda(Locations.NO_LOCATION, var, effect, expression)
                );
        if(expression instanceof EApply) {
            EApply apply = (EApply)expression;
            trans = apply.toANormalForm(trans);
        }
        return trans;
    }
}