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using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
using Microsoft.EntityFrameworkCore.Storage;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

namespace MySql.Data.EntityFrameworkCore.Query.Expressions.Internal
{
  internal class MySQLComplexFunctionArgumentExpression : SqlExpression
  {
    public MySQLComplexFunctionArgumentExpression(
      IEnumerable<SqlExpression> argumentParts,
      Type type,
      RelationalTypeMapping typeMapping)
    : base(type, typeMapping)
    {
      ArgumentParts = argumentParts.ToList().AsReadOnly();
    }

    /// <summary>
    ///     The arguments parts.
    /// </summary>
    public virtual IReadOnlyList<SqlExpression> ArgumentParts { get; }

    /// <summary>
    ///     Dispatches to the specific visit method for this node type.
    /// </summary>
    protected override Expression Accept(ExpressionVisitor visitor) =>
        visitor is MySQLQuerySqlGenerator mySqlQuerySqlGenerator
            ? mySqlQuerySqlGenerator.VisitMySQLComplexFunctionArgumentExpression(this)
            : base.Accept(visitor);

    protected override Expression VisitChildren(ExpressionVisitor visitor)
    {
      var changed = false;
      var newArgumentParts = new SqlExpression[ArgumentParts.Count];

      for (var i = 0; i < newArgumentParts.Length; i++)
      {
        newArgumentParts[i] = (SqlExpression)visitor.Visit(ArgumentParts[i]);
        changed |= newArgumentParts[i] != ArgumentParts[i];
      }

      return changed
          ? new MySQLComplexFunctionArgumentExpression(
              newArgumentParts,
              Type,
              TypeMapping)
          : this;
    }

    public override void Print(ExpressionPrinter expressionPrinter)
        => expressionPrinter.Append(ToString());

    public override bool Equals(object obj)
        => obj != null
        && (ReferenceEquals(this, obj)
            || obj is MySQLComplexFunctionArgumentExpression sqlFragmentExpression
                && Equals(sqlFragmentExpression));

    private bool Equals(MySQLComplexFunctionArgumentExpression other)
        => base.Equals(other)
           && Type == other.Type
           && ArgumentParts.SequenceEqual(other.ArgumentParts);

    /// <summary>
    ///     Returns a hash code for this object.
    /// </summary>
    /// <returns>
    ///     A hash code for this object.
    /// </returns>
    public override int GetHashCode()
    {
      unchecked
      {
        var hashCode = ArgumentParts.Aggregate(0, (current, argument) => current + ((current * 397) ^ argument.GetHashCode()));
        hashCode = (hashCode * 397) ^ Type.GetHashCode();
        return hashCode;
      }
    }

    /// <summary>
    ///     Creates a <see cref="string" /> representation of the Expression.
    /// </summary>
    /// <returns>A <see cref="string" /> representation of the Expression.</returns>
    public override string ToString()
        => string.Join(" ", ArgumentParts);
  }
}
