sql-utilities/tests/Strata.SqlTools.LinqToSql.Tests/QueryValidatorTests.cs

using NUnit.Framework;
using Strata.SqlTools.Builders.LinqToSql;
using Strata.SqlTools.Validators.LinqToSql;

namespace Strata.SqlTools.LinqToSql.Tests;

[TestFixture]
public class QueryValidatorTests
{
    #region Basic Validation Tests

    [Test]
    public void Validate_WithValidQuery_HasNoErrors()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns("Id", "Name")
            .FromTable("Users")
            .Where("IsActive = true")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator.HasErrors, Is.False);
    }

    [Test]
    public void Validate_WithNull_ThrowsArgumentNullException()
    {
        // Arrange
        var validator = QueryValidator.Create();

        // Act & Assert
#pragma warning disable CS8625 // Cannot convert null literal to non-nullable reference type.
        Assert.Throws<ArgumentNullException>(() => validator.Validate(null));
#pragma warning restore CS8625 // Cannot convert null literal to non-nullable reference type.
    }

    [Test]
    public void Validate_CanBeCalledMultipleTimes()
    {
        // Arrange
        var validator = QueryValidator.Create();
        var breakdown1 = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();
        var breakdown2 = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Orders")
            .Build();

        // Act
        validator.Validate(breakdown1);
        var count1 = validator.Issues.Count;
        validator.Clear();
        validator.Validate(breakdown2);
        var count2 = validator.Issues.Count;

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(count1, Is.GreaterThan(0));
            Assert.That(count2, Is.GreaterThan(0));
        });
    }

    #endregion

    #region SELECT Clause Validation Tests

    [Test]
    public void Validate_SelectStarQuery_HasSelectAllColumnsWarning()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "SELECT_ALL_COLUMNS");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Warning));
    }

    [Test]
    public void Validate_SelectManyColumns_HasSelectTooManyWarning()
    {
        // Arrange
        var columns = Enumerable.Range(1, 25).Select(i => $"Column{i}").ToArray();
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns(columns)
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "SELECT_TOO_MANY");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Warning));
    }

    [Test]
    public void Validate_MissingSelectClause_HasSelectMissingError()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();
        breakdown.SelectClause.Clause = string.Empty;

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator.HasErrors, Is.True);
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "SELECT_MISSING");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Error));
    }

    #endregion

    #region FROM Clause Validation Tests

    [Test]
    public void Validate_MissingFromClause_HasFromMissingError()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();
        breakdown.FromClause.Clause = string.Empty;

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator.HasErrors, Is.True);
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "FROM_MISSING");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Error));
    }

    #endregion

    #region GROUP BY + HAVING Validation Tests

    [Test]
    public void Validate_HavingWithoutGroupBy_HasHavingWithoutGroupByError()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Having("COUNT(*) > 5")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator.HasErrors, Is.True);
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "HAVING_WITHOUT_GROUPBY");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Error));
    }

    [Test]
    public void Validate_GroupByWithHaving_HasNoGroupByError()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns("Department", "COUNT(*)")
            .FromTable("Employees")
            .GroupBy("Department")
            .Having("COUNT(*) > 5")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "HAVING_WITHOUT_GROUPBY");
        Assert.That(issue, Is.Null);
    }

    #endregion

    #region WHERE Clause Validation Tests

    [Test]
    public void Validate_NoWhereClause_HasNoWhereClauseInfo()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "NO_WHERE_CLAUSE");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Warning));
    }

    [Test]
    public void Validate_WithWhereClause_NoWhereWarning()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Where("IsActive = true")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "NO_WHERE_CLAUSE");
        Assert.That(issue, Is.Null);
    }

    #endregion

    #region ORDER BY Validation Tests

    [Test]
    public void Validate_NoOrderByOrGroupBy_HasNoOrderByInfo()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "NO_ORDER_BY");
        Assert.That(issue, Is.Not.Null);
        Assert.That(issue!.Severity, Is.EqualTo(ValidationSeverity.Info));
    }

    [Test]
    public void Validate_WithOrderBy_NoOrderByInfo()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .OrderByAscending("Name")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "NO_ORDER_BY");
        Assert.That(issue, Is.Null);
    }

    [Test]
    public void Validate_WithGroupBy_NoOrderByInfo()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns("Department", "COUNT(*)")
            .FromTable("Employees")
            .GroupBy("Department")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        var issue = validator.Issues.FirstOrDefault(i => i.Code == "NO_ORDER_BY");
        Assert.That(issue, Is.Null);
    }

    #endregion

    #region Issue Filtering Tests

    [Test]
    public void GetIssuesBySeverity_FiltersCorrectly()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);
        var warnings = validator.GetIssuesBySeverity(ValidationSeverity.Warning);
        var infos = validator.GetIssuesBySeverity(ValidationSeverity.Info);
        var errors = validator.GetIssuesBySeverity(ValidationSeverity.Error);

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(warnings, Is.Not.Empty);
            Assert.That(infos, Is.Not.Empty);
            Assert.That(errors, Is.Empty);
        });
    }

    #endregion

    #region Custom Issue Tests

    [Test]
    public void AddIssue_AddsCustomIssue()
    {
        // Arrange
        var validator = QueryValidator.Create();

        // Act
        validator.AddIssue(
            ValidationSeverity.Error,
            "CUSTOM_001",
            "Custom validation error",
            "This is a custom issue");

        // Assert
        Assert.That(validator.Issues, Has.Count.EqualTo(1));
        Assert.Multiple(() =>
        {
            Assert.That(validator.Issues[0].Code, Is.EqualTo("CUSTOM_001"));
            Assert.That(validator.HasErrors, Is.True);
        });
    }

    [Test]
    public void AddIssue_SupportsMethodChaining()
    {
        // Arrange
        var validator = QueryValidator.Create();

        // Act
        var result = validator
            .AddIssue(ValidationSeverity.Error, "ERR_001", "Error 1")
            .AddIssue(ValidationSeverity.Warning, "WARN_001", "Warning 1")
            .AddIssue(ValidationSeverity.Info, "INFO_001", "Info 1");

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(result, Is.SameAs(validator));
            Assert.That(validator.Issues, Has.Count.EqualTo(3));
        });
    }

    #endregion

    #region Clear Tests

    [Test]
    public void Clear_RemovesAllIssues()
    {
        // Arrange
        var validator = QueryValidator.Create();
        validator.AddIssue(ValidationSeverity.Error, "ERR", "Error");
        validator.AddIssue(ValidationSeverity.Warning, "WARN", "Warning");

        // Act
        validator.Clear();

        // Assert
        Assert.That(validator.Issues, Is.Empty);
    }

    [Test]
    public void Clear_ReturnsSelf()
    {
        // Arrange
        var validator = QueryValidator.Create();

        // Act
        var result = validator.Clear();

        // Assert
        Assert.That(result, Is.SameAs(validator));
    }

    #endregion

    #region Report Generation Tests

    [Test]
    public void GetReport_WithNoIssues_ShowsSuccess()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns("Id", "Name")
            .FromTable("Users")
            .Where("IsActive = true")
            .OrderByAscending("Name")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);
        var report = validator.GetReport();

        // Assert
        Assert.That(report, Contains.Substring("No validation issues"));
    }

    [Test]
    public void GetReport_WithIssues_ListsEachIssue()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);
        var report = validator.GetReport();

        // Assert
        Assert.That(report, Contains.Substring("WARNINGS").IgnoreCase);
        Assert.That(report, Contains.Substring("Validation Report").IgnoreCase);
    }

    [Test]
    public void GetReport_IncludesIssueDetails()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);
        var report = validator.GetReport();

        // Assert
        Assert.That(report, Contains.Substring("SELECT_ALL_COLUMNS"));
    }

    #endregion

    #region Complex Anti-Pattern Tests

    [Test]
    public void Validate_ComplexProblematicQuery_FindsMultipleIssues()
    {
        // Arrange - Query with SELECT *, no WHERE, no ORDER BY
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("LargeTable")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(validator.Issues, Has.Count.GreaterThan(1));
            Assert.That(validator.HasWarnings, Is.True);
        });
    }

    [Test]
    public void Validate_WellFormedAggregationQuery_HasMinimalIssues()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectColumns("Category", "COUNT(*) as ProductCount", "SUM(Price) as TotalValue")
            .FromTable("Products")
            .Where("IsActive = true")
            .GroupBy("Category")
            .OrderByDescending("TotalValue")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator.HasErrors, Is.False);
    }

    #endregion

    #region Static Factory Tests

    [Test]
    public void Create_ReturnsNewValidator()
    {
        // Act
        var validator = QueryValidator.Create();

        // Assert
        Assert.That(validator, Is.Not.Null);
        Assert.That(validator, Is.TypeOf<QueryValidator>());
    }

    [Test]
    public void ValidateQuery_ReturnsValidatorWithResults()
    {
        // Arrange
        var breakdown = LinqQueryBreakdownBuilder
            .Create()
            .SelectAll()
            .FromTable("Users")
            .Build();

        // Act
        var validator = QueryValidator.ValidateQuery(breakdown);

        // Assert
        Assert.That(validator, Is.Not.Null);
        Assert.That(validator.Issues, Is.Not.Empty);
    }

    #endregion

    #region String Representation Tests

    [Test]
    public void QueryValidationIssue_ToString_FormatsCorrectly()
    {
        // Arrange
        var issue = new QueryValidationIssue(
            ValidationSeverity.Error,
            "TEST_001",
            "Test error message",
            "Additional details");

        // Act
        var str = issue.ToString();

        // Assert
        Assert.That(str, Contains.Substring("Error"));
        Assert.That(str, Contains.Substring("TEST_001"));
        Assert.That(str, Contains.Substring("Test error message"));
        Assert.That(str, Contains.Substring("Additional details"));
    }

    [Test]
    public void QueryValidationIssue_ToStringWithoutDetails_FormatsCorrectly()
    {
        // Arrange
        var issue = new QueryValidationIssue(
            ValidationSeverity.Warning,
            "WARN_001",
            "Warning message");

        // Act
        var str = issue.ToString();

        // Assert
        Assert.That(str, Contains.Substring("Warning"));
        Assert.That(str, Contains.Substring("WARN_001"));
        Assert.That(str, Contains.Substring("Warning message"));
    }

    #endregion
}