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

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.ILet;
import org.simantics.scl.compiler.internal.interpreted.ISeq;
import org.simantics.scl.compiler.top.ExpressionInterpretationContext;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.exceptions.MatchException;

public class ESimpleLet extends Expression {
    public Variable variable; // may be null
    public Expression value;
    public Expression in;
    
    public ESimpleLet(Variable variable, Expression value, Expression in) {
        if(value == null)
            throw new NullPointerException();
        if(in == null)
            throw new NullPointerException();
        this.variable = variable;
        this.value = value;
        this.in = in;
    }

    public ESimpleLet(long loc, Variable variable, Expression value, Expression in) {
        super(loc);
        if(value == null)
            throw new NullPointerException();
        if(in == null)
            throw new NullPointerException();
        this.variable = variable;
        this.value = value;
        this.in = in;
    }

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

    @Override
    public IVal toVal(CompilationContext context, CodeWriter w) {
        IVal valueVal = value.toVal(context, w);
        if(variable != null)
            variable.setVal(valueVal);
        return in.toVal(context, w);
    }

    @Override
    public Expression simplify(SimplificationContext context) {
        value = value.simplify(context);
        if(value instanceof EConstant || value instanceof ELiteral) {
            context.addInlinedVariable(variable, value);
            return in.simplify(context);
        }
        in = in.simplify(context);
        return this;
    }

    @Override
    public Expression resolve(TranslationContext context) {
        value = value.resolve(context);
        in = in.resolve(context);
        return this;
    }

    @Override
    public Expression replace(ReplaceContext context) {
        if(variable == null)
            return new ESimpleLet(location,
                    null, 
                    value.replace(context), 
                    in.replace(context));
        else {
            Variable newVariable = variable.copy();
            context.varMap.put(variable, new EVariable(newVariable));
            ESimpleLet result = new ESimpleLet(location, newVariable, 
                    value.replace(context), 
                    in.replace(context));
            context.varMap.remove(variable);
            return result;
        }
    }
    
    @Override
    public void setLocationDeep(long loc) {
        if(location == Locations.NO_LOCATION) {
            location = loc;
            value.setLocationDeep(loc);
            in.setLocationDeep(loc);
        }
    }

    @Override
    public IExpression toIExpression(ExpressionInterpretationContext context) {
        if(variable == null) {
            IExpression valueI = value.toIExpression(context);
            IExpression inI = in.toIExpression(context);
            return new ISeq(valueI, inI);
        }
        else {
            IExpression valueI = value.toIExpression(context);
            int variableId = context.push(variable);
            IExpression inI = in.toIExpression(context);
            context.pop(variable);
            return new ILet(variableId, valueI, inI);
        }
    }

    private void checkBinding(TypingContext context) {
        if(variable == null)
            value = value.checkIgnoredType(context);
        else if(variable.getType() == null) {
            value = value.inferType(context);
            variable.setType(value.getType());
        }
        else
            value = value.checkType(context, variable.type);
        /*else {
            if(variable.getType() == null)
                variable.setType(Types.metaVar(Kinds.STAR));
            value = value.checkType(context, variable.type);
        }*/
    }
    
    @Override
    public Expression inferType(TypingContext context) {
        checkBinding(context);
        in = in.inferType(context);
        return this;
    }
    
    @Override
    public Expression checkBasicType(TypingContext context, Type requiredType) {
        checkBinding(context);
        in = in.checkType(context, requiredType);
        return this;
    }
    
    @Override
    public Expression checkIgnoredType(TypingContext context) {
        checkBinding(context);
        in = in.checkIgnoredType(context);
        return this;
    }
    
    @Override
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }
    
    public Expression getValue() {
        return value;
    }
    
    public Variable getVariable() {
        return variable;
    }
    
    public Expression getIn() {
        return in;
    }

    @Override
    public Expression accept(ExpressionTransformer transformer) {
        return transformer.transform(this);
    }

    @Override
    public int getSyntacticFunctionArity() {
        return in.getSyntacticFunctionArity();
    }
}