using System.Diagnostics;

namespace Strata.SqlTools.Rules.Rule.Expression;

/// <summary>
/// Represents a comparison operation between two expressions.
/// </summary>
[DebuggerDisplay("{Left} {Type} {Right}")]
public abstract class Comparison : BoolExpr, IBinary
{
    /// <summary>
    /// Gets the left operand of the comparison.
    /// </summary>
    public Expression Left { get; }

    /// <summary>
    /// Gets the right operand of the comparison.
    /// </summary>
    public Expression Right { get; }

    /// <summary>
    /// Gets the type of comparison operation.
    /// </summary>
    public abstract Type Type { get; }

    /// <summary>
    /// Initializes a new instance of the <see cref="Comparison"/> class.
    /// </summary>
    /// <param name="left">The left operand.</param>
    /// <param name="right">The right operand.</param>
    protected Comparison(Expression left, Expression right)
    {
        Left = left;
        Right = right;
    }

    /// <summary>
    /// Creates a new comparison expression with updated operands.
    /// </summary>
    /// <param name="left">The new left operand.</param>
    /// <param name="right">The new right operand.</param>
    /// <returns>A new comparison expression or this instance if operands are unchanged.</returns>
    public Expression Update(Expression left, Expression right)
    {
        if (ReferenceEquals(left, Left) && ReferenceEquals(right, Right))
        {
            return this;
        }

        return Create(left, right, Type);
    }

    private static Comparison Create(Expression left, Expression right, Type Type)
    {
        return Type switch
        {
            Type.Equal => new Equal(left, right),
            Type.NotEqual => new NotEqual(left, right),
            Type.GreaterThan => new GreaterThan(left, right),

            _ => throw new NotImplementedException("not yet")
        };
    }
}