SqliteExpression.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

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

namespace Microsoft.EntityFrameworkCore.Sqlite.Query.Internal
{
    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public static class SqliteExpression
    {
        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public static SqlFunctionExpression Strftime(
            ISqlExpressionFactory sqlExpressionFactory,
            Type returnType,
            string format,
            SqlExpression timestring,
            IEnumerable<SqlExpression>? modifiers = null,
            RelationalTypeMapping? typeMapping = null)
        {
            modifiers ??= Enumerable.Empty<SqlExpression>();

            // If the inner call is another strftime then shortcut a double call
            if (timestring is SqlFunctionExpression rtrimFunction
                && rtrimFunction.Name == "rtrim"
                && rtrimFunction.Arguments!.Count == 2
                && rtrimFunction.Arguments[0] is SqlFunctionExpression rtrimFunction2
                && rtrimFunction2.Name == "rtrim"
                && rtrimFunction2.Arguments!.Count == 2
                && rtrimFunction2.Arguments[0] is SqlFunctionExpression strftimeFunction
                && strftimeFunction.Name == "strftime"
                && strftimeFunction.Arguments!.Count > 1)
            {
                // Use its timestring parameter directly in place of ours
                timestring = strftimeFunction.Arguments[1];

                // Prepend its modifier arguments (if any) to the current call
                modifiers = strftimeFunction.Arguments.Skip(2).Concat(modifiers);
            }

            var finalArguments = new[] { sqlExpressionFactory.Constant(format), timestring }.Concat(modifiers);

            return sqlExpressionFactory.Function(
                "strftime",
                finalArguments,
                nullable: true,
                argumentsPropagateNullability: finalArguments.Select(a => true),
                returnType,
                typeMapping);
        }
    }
}