package org.simantics.scl.compiler.elaboration.expressions;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Set;

import org.simantics.scl.compiler.common.exceptions.InternalCompilerError;
import org.simantics.scl.compiler.compilation.CompilationContext;
import org.simantics.scl.compiler.elaboration.contexts.ReplaceContext;
import org.simantics.scl.compiler.elaboration.contexts.SimplificationContext;
import org.simantics.scl.compiler.elaboration.contexts.TranslationContext;
import org.simantics.scl.compiler.elaboration.contexts.TypingContext;
import org.simantics.scl.compiler.errors.Locations;
import org.simantics.scl.compiler.internal.codegen.references.IVal;
import org.simantics.scl.compiler.internal.codegen.writer.CodeWriter;
import org.simantics.scl.compiler.internal.interpreted.IExpression;
import org.simantics.scl.compiler.internal.interpreted.IVariable;
import org.simantics.scl.compiler.top.ExpressionInterpretationContext;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;
import org.simantics.scl.compiler.types.exceptions.MatchException;
import org.simantics.scl.compiler.types.kinds.Kinds;
import org.simantics.scl.compiler.types.util.TypeUnparsingContext;

public class EVariable extends Expression {
    public static final EVariable[] EMPTY_ARRAY = new EVariable[0];
    
    public Variable variable;
    
    public EVariable(Variable variable) {
        this.variable = variable;
    }

    public EVariable(long loc, Variable variable) {
        super(loc);
        this.variable = variable;
    }

    public Variable getVariable() {
        return variable;
    }
    
    public void setVariable(Variable variable) {
        this.variable = variable;
    }

    @Override
    public Set<Variable> getFreeVariables() {
        if(variable == null)
            return Collections.emptySet();
        else
            return Collections.singleton(variable);
    }

    public void toString(StringBuilder b, TypeUnparsingContext tuc) {
        b.append(variable == null ? "???" : variable.toString());
    }

    @Override
    protected void updateType() throws MatchException {
        setType(variable.getType());
    }

    @Override
    public IVal toVal(CompilationContext context, CodeWriter w) {
        return variable.getVal();
    }

    @Override
    public Expression simplify(SimplificationContext context) {
        Expression expression = context.getInlinedValue(variable);
        if(expression != null)
            return expression.copy();
        else
            return this;
    }

    @Override
    public Expression resolve(TranslationContext context) {
        return this;
    }
    
    @Override
    public void getParameters(TranslationContext translationContext,
            ArrayList<Expression> parameters) {
    }
    
    @Override
    public Expression resolveAsPattern(TranslationContext context) {
        return this;
    }

    @Override
    public Expression replace(ReplaceContext context) {
        if(context.inPattern) {
            Type type = variable.getType().replace(context.tvarMap);
            
            Variable newVariable = new Variable(variable.name);
            newVariable.setType(type);
            EVariable result = new EVariable(newVariable);
            context.varMap.put(variable, result);
            return result;
        }
        else {
            if(variable == null) {
                EVariable newVariable = new EVariable(location, null);
                newVariable.setType(getType().replace(context.tvarMap));
                if(context.typingContext == null)
                    throw new InternalCompilerError(location, "Encountered unresolved variable but not in type checking phase.");
                context.typingContext.addConstraintDemand(newVariable);
                return newVariable;
            }
            else {
                Expression expression = context.varMap.get(variable);
                if(expression != null)
                    return expression.copy(context.typingContext);
                else {
                    return new EVariable(variable);
                }
            }
        }
    }
    
    @Override
    public IExpression toIExpression(ExpressionInterpretationContext target) {
        return new IVariable(target.getVariableId(variable));
    }
    
    @Override
    public Expression inferType(TypingContext context) {
        if(context.isInPattern()) {
            variable.setType(Types.metaVar(Kinds.STAR));
            return this;
        }
        else {
            if(variable.getType() == null) {
                context.getErrorLog().log(location, "Type of the variable is not defined.");
                variable.setType(Types.metaVar(Kinds.STAR));
            }
            return applyPUnit(context);
        }
    }
    
    @Override
    public Expression checkBasicType(TypingContext context, Type requiredType) {
        if(context.isInPattern()) {
            variable.setType(requiredType);
            return this;
        }
        else {
            if(variable.getType() == null) {
                context.getErrorLog().log(location, "Type of the variable is not defined.");
                variable.setType(Types.metaVar(Kinds.STAR));
            }
            return context.subsume(this, requiredType);
        }
    }
    
    @Override
    public boolean isEffectful() {
    	return false;
    }
    
    @Override
    public void setLocationDeep(long loc) {
        if(location == Locations.NO_LOCATION)
            location = loc;
    }
    
    @Override
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }
    
    @Override
    public boolean isPattern(int arity) {
        return arity == 0;
    }
    
    @Override
    public Expression accept(ExpressionTransformer transformer) {
        return transformer.transform(this);
    }
    
    @Override
    public boolean equalsExpression(Expression expression) {
        if(expression.getClass() != getClass())
            return false;
        EVariable other = (EVariable)expression;
        return variable == other.variable;
    }

}