/*
 *    The contents of this file are subject to the Initial
 *    Developer's Public License Version 1.0 (the "License");
 *    you may not use this file except in compliance with the
 *    License. You may obtain a copy of the License at
 *    https://github.com/FirebirdSQL/NETProvider/raw/master/license.txt.
 *
 *    Software distributed under the License is distributed on
 *    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either
 *    express or implied. See the License for the specific
 *    language governing rights and limitations under the License.
 *
 *    All Rights Reserved.
 */

//$Authors = Jiri Cincura (jiri@cincura.net)

using System.Collections.Generic;
using System.Reflection;
using FirebirdSql.EntityFrameworkCore.Firebird.Query.Internal;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Diagnostics;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;

namespace FirebirdSql.EntityFrameworkCore.Firebird.Query.ExpressionTranslators.Internal;

public class FbStringStartsWithTranslator : IMethodCallTranslator
{
	static readonly MethodInfo StartsWithMethod = typeof(string).GetRuntimeMethod(nameof(string.StartsWith), new[] { typeof(string) });

	readonly FbSqlExpressionFactory _fbSqlExpressionFactory;

	public FbStringStartsWithTranslator(FbSqlExpressionFactory fbSqlExpressionFactory)
	{
		_fbSqlExpressionFactory = fbSqlExpressionFactory;
	}

	public SqlExpression Translate(SqlExpression instance, MethodInfo method, IReadOnlyList<SqlExpression> arguments, IDiagnosticsLogger<DbLoggerCategory.Query> logger)
	{
		if (!method.Equals(StartsWithMethod))
			return null;

		var patternExpression = _fbSqlExpressionFactory.ApplyDefaultTypeMapping(arguments[0]);
		var patternConstantExpression = patternExpression as SqlConstantExpression;
		var likePatternExpression = patternConstantExpression != null
			? (SqlExpression)_fbSqlExpressionFactory.Constant(((string)patternConstantExpression.Value) + "%")
			: (SqlExpression)_fbSqlExpressionFactory.Add(patternExpression, _fbSqlExpressionFactory.Constant("%"));
		var startsWithExpression = _fbSqlExpressionFactory.AndAlso(
			_fbSqlExpressionFactory.Like(
				instance,
				likePatternExpression),
			_fbSqlExpressionFactory.Equal(
				_fbSqlExpressionFactory.ApplyDefaultTypeMapping(_fbSqlExpressionFactory.Function(
					"LEFT",
					new[] {
							instance,
							_fbSqlExpressionFactory.Function(
								"CHAR_LENGTH",
								new[] { patternExpression },
								true,
								new[] { true },
								typeof(int)) },
					true,
					new[] { true, true },
					instance.Type)),
				patternExpression));
		var matchingExpression = patternConstantExpression != null
			? (SqlExpression)((string)patternConstantExpression.Value == string.Empty ? _fbSqlExpressionFactory.Constant(true) : startsWithExpression)
			: (SqlExpression)_fbSqlExpressionFactory.OrElse(
				startsWithExpression,
				_fbSqlExpressionFactory.Equal(
					_fbSqlExpressionFactory.Function("CHAR_LENGTH", new[] { patternExpression }, true, new[] { true }, typeof(int)),
					_fbSqlExpressionFactory.Constant(0)));
		return _fbSqlExpressionFactory.AndAlso(matchingExpression, _fbSqlExpressionFactory.AndAlso(_fbSqlExpressionFactory.IsNotNull(instance), _fbSqlExpressionFactory.IsNotNull(patternExpression)));
	}
}
