package lambda2sql;

import com.trigersoft.jaque.expression.*;

import java.util.ArrayList;

import java.util.List;

import static com.trigersoft.jaque.expression.ExpressionType.*;

public class ToSqlVisitor implements ExpressionVisitor<StringBuilder> {

private StringBuilder sb = new StringBuilder();

private Expression body;

private List<ConstantExpression> parameters = new ArrayList<>();

private static String toSqlOp(int expressionType) {

switch (expressionType) {

case Equal:

return "=";

case LogicalAnd:

return "AND";

case LogicalOr:

return "OR";

case Convert:

return "";

}

return ExpressionType.toString(expressionType);

}

@Override

public StringBuilder visit(BinaryExpression e) {

boolean quote = e != body && e.getExpressionType() == LogicalOr;

if (quote) sb.append('(');

e.getFirst().accept(this);

sb.append(' ').append(toSqlOp(e.getExpressionType())).append(' ');

e.getSecond().accept(this);

if (quote) sb.append(')');

return sb;

}

@Override

public StringBuilder visit(ConstantExpression e) {

if (e.getValue() instanceof String) {

return sb.append("'").append(e.getValue().toString()).append("'");

}

return sb.append(e.getValue().toString());

}

@Override

public StringBuilder visit(InvocationExpression e) {

e.getArguments().stream().filter(x -> x instanceof ConstantExpression).forEach(x -> parameters.add((ConstantExpression) x));

return e.getTarget().accept(this);

}

@Override

public StringBuilder visit(LambdaExpression<?> e) {

this.body = e.getBody();

return body.accept(this);

}

@Override

public StringBuilder visit(MemberExpression e) {

String name = e.getMember().getName();

name = name.replaceAll("^(get)", "");

name = name.substring(0, 1).toLowerCase() + name.substring(1);

return sb.append(name);

}

@Override

public StringBuilder visit(ParameterExpression e) {

parameters.get(e.getIndex()).accept(this);

return sb;

}

@Override

public StringBuilder visit(UnaryExpression e) {

sb.append(toSqlOp(e.getExpressionType()));

return e.getFirst().accept(this);

}

}