Connected.Framework/Connected.Expressions/Languages/Linguist.cs

using Connected.Expressions.Formatters;
using Connected.Expressions.Translation;
using Connected.Expressions.Translation.Optimization;
using Connected.Expressions.Translation.Rewriters;
using System.Linq.Expressions;

namespace Connected.Expressions.Languages;

public class Linguist
{
    /// <summary>
    /// Construct a <see cref="Linguist"/>
    /// </summary>
    public Linguist(ExpressionCompilationContext context, QueryLanguage language, Translator translator)
    {
        Context = context;
        Language = language;
        Translator = translator;
    }

    protected ExpressionCompilationContext Context { get; }
    public QueryLanguage Language { get; }
    public Translator Translator { get; }
    /// <summary>
    /// Provides language specific query translation.  Use this to apply language specific rewrites or
    /// to make assertions/validations about the query.
    /// </summary>
    public virtual Expression Translate(Expression expression)
    {
        /*
		 * remove redundant layers again before cross apply rewrite
		 */
        expression = UnusedColumns.Remove(expression);
        expression = RedundantColumns.Remove(expression);
        expression = RedundantSubqueries.Remove(expression);
        /*
		 * convert cross-apply and outer-apply joins into inner & left-outer-joins if possible
		 */
        var rewritten = CrossApplyRewriter.Rewrite(this.Language, expression);
        /*
		 * convert cross joins into inner joins
		 */
        rewritten = CrossJoinRewriter.Rewrite(rewritten);

        if (rewritten != expression)
        {
            expression = rewritten;
            /*
			 * do final reduction
			 */
            expression = UnusedColumns.Remove(expression);
            expression = RedundantSubqueries.Remove(expression);
            expression = RedundantJoins.Remove(expression);
            expression = RedundantColumns.Remove(expression);
        }

        return expression;
    }
    /// <summary>
    /// Converts the query expression into text of this query language
    /// </summary>
    public virtual string Format(Expression expression)
    {
        /*
		 * use common SQL formatter by default
		 */
        return SqlFormatter.Format(expression);
    }
    /// <summary>
    /// Determine which sub-expressions must be parameters
    /// </summary>
    public virtual Expression Parameterize(Expression expression)
    {
        return Parameterizer.Parameterize(Language, expression);
    }
}