using Connected.Expressions.Formatters;
using Connected.Expressions.Serialization;
using System.Linq.Expressions;

namespace Connected.Expressions;

public sealed class ProjectionExpression : DatabaseExpression
{
    public ProjectionExpression(SelectExpression source, Expression projector)
        : this(source, projector, null)
    {
    }

    public ProjectionExpression(SelectExpression source, Expression projector, LambdaExpression? aggregator)
        : base(DatabaseExpressionType.Projection, aggregator is not null ? aggregator.Body.Type : typeof(IEnumerable<>).MakeGenericType(projector.Type))
    {
        Select = source;
        Projector = projector;
        Aggregator = aggregator;
    }

    public SelectExpression Select { get; }
    public Expression Projector { get; }
    public LambdaExpression? Aggregator { get; }
    public bool IsSingleton => Aggregator?.Body.Type == Projector.Type;
    public string QueryText => SqlFormatter.Format(Select);

    public override string ToString()
    {
        return DatabaseSerializer.Serialize(this);
    }
}