sql-utilities/tests/Strata.SqlTools.Snowflake.Tests/Snowflake/StatementExpressionParserTests.cs

using Strata.SqlTools.SqlBreakdown.Expressions;
using Strata.SqlTools.SqlBreakdown.Expressions.Arithmetic;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions.Aggregate;
using Strata.SqlTools.SqlBreakdown.Expressions.Literals;

namespace Strata.SqlTools.SqlBreakdown.Tests.Snowflake;

/// <summary>
/// Tests for Snowflake SQL statement expression parser.
/// Note: The parser currently only supports identifiers enclosed in double quotes ("ID")
/// or brackets ([ID]). Unquoted identifiers and spaces in identifiers are not supported yet.
/// </summary>
[TestFixture]
public class StatementExpressionParserTests
{
    private Strata.SqlTools.Statements.Snowflake.StatementExpressionParser _parser = null!;

    [SetUp]
    public void SetUp()
    {
        _parser = new Strata.SqlTools.Statements.Snowflake.StatementExpressionParser();
    }

    #region Basic Tests

    [Test]
    public void Parse_Number_ReturnsNumberExpression()
    {
        // Arrange
        var sql = "42";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<NumberLiteralExpression>());
            Assert.That(((NumberLiteralExpression)result).Value, Is.EqualTo(42));
        });
    }

    [Test]
    public void Parse_DecimalNumber_ReturnsNumberExpression()
    {
        // Arrange
        var sql = "3.14";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<NumberLiteralExpression>());
            Assert.That(((NumberLiteralExpression)result).Value, Is.EqualTo(3.14m));
        });
    }

    [Test]
    public void Parse_DoubleQuotedIdentifier_ReturnsColumnExpression()
    {
        // Arrange - Snowflake convention: double-quoted identifiers
        var sql = "\"CUSTOMER_ID\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<ColumnExpression>());
            Assert.That(((ColumnExpression)result).ColumnName, Is.EqualTo("CUSTOMER_ID"));
        });
    }

    [Test]
    public void Parse_BracketedIdentifier_ReturnsColumnExpression()
    {
        // Arrange - Also supports SQL Server bracket style
        var sql = "[CUSTOMER_ID]";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<ColumnExpression>());
            Assert.That(((ColumnExpression)result).ColumnName, Is.EqualTo("CUSTOMER_ID"));
        });
    }

    #endregion

    #region Arithmetic Tests

    [Test]
    public void Parse_Addition_ReturnsAdditionExpression()
    {
        // Arrange
        var sql = "\"REVENUE\" + \"COST\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<AdditionExpression>());
    }

    [Test]
    public void Parse_Subtraction_ReturnsSubtractionExpression()
    {
        // Arrange
        var sql = "\"REVENUE\" - \"COST\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<SubtractionExpression>());
    }

    [Test]
    public void Parse_Multiplication_ReturnsMultiplicationExpression()
    {
        // Arrange
        var sql = "\"PRICE\" * \"QUANTITY\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<MultiplicationExpression>());
    }

    [Test]
    public void Parse_Division_ReturnsDivisionExpression()
    {
        // Arrange
        var sql = "\"TOTAL\" / \"COUNT\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<DivisionExpression>());
    }

    [Test]
    public void Parse_ColumnWithNumber_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "\"NET_REVENUE\" * 1.15";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<MultiplicationExpression>());
    }

    [Test]
    public void Parse_ComplexArithmetic_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "(\"BASE_PRICE\" + \"TAX_AMOUNT\") * \"QUANTITY\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<MultiplicationExpression>());
    }

    #endregion

    #region Function Tests

    [Test]
    public void Parse_SumFunction_ReturnsSumFunctionExpression()
    {
        // Arrange
        var sql = "SUM(\"REVENUE\")";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<SumFunction>());
    }

    [Test]
    public void Parse_AvgFunction_ReturnsAverageFunctionExpression()
    {
        // Arrange
        var sql = "AVG(\"REVENUE\")";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<AverageFunction>());
    }

    [Test]
    public void Parse_FunctionWithExpression_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "SUM(\"NET_REVENUE\" * 1.1)";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<SumFunction>());
    }

    #endregion

    #region Snowflake-Specific Syntax Tests

    [Test]
    public void Parse_UppercaseIdentifier_ReturnsColumnExpression()
    {
        // Arrange - Snowflake convention: identifiers typically uppercase
        var sql = "\"ORDER_TOTAL\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<ColumnExpression>());
            Assert.That(((ColumnExpression)result).ColumnName, Is.EqualTo("ORDER_TOTAL"));
        });
    }

    [Test]
    public void Parse_IdentifierWithUnderscores_ReturnsColumnExpression()
    {
        // Arrange - Snowflake naming: underscores common
        var sql = "\"NET_REVENUE_USD_2024\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.Multiple(() =>
        {
            Assert.That(result, Is.InstanceOf<ColumnExpression>());
            Assert.That(((ColumnExpression)result).ColumnName, Is.EqualTo("NET_REVENUE_USD_2024"));
        });
    }

    [Test]
    public void Parse_MixedQuotingStyles_ReturnsCorrectExpression()
    {
        // Arrange - Mix of double-quoted and bracketed identifiers
        var sql = "SUM(\"GROSS_REVENUE\") - [COST]";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<SubtractionExpression>());
    }

    [Test]
    public void Parse_MultipleDoubleQuotedIdentifiers_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "\"A\" + \"B\" * \"C\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<AdditionExpression>());
    }

    #endregion

    #region Parentheses and Precedence Tests

    [Test]
    public void Parse_SimpleParentheses_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "(\"A\" + \"B\")";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<AdditionExpression>());
    }

    [Test]
    public void Parse_ParenthesesWithMultiplication_ReturnsCorrectPrecedence()
    {
        // Arrange
        var sql = "(1 + 2) * 3";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<MultiplicationExpression>());
    }

    [Test]
    public void Parse_NestedParentheses_ReturnsCorrectExpression()
    {
        // Arrange
        var sql = "((\"A\" + \"B\") * \"C\") - \"D\"";

        // Act
        var result = _parser.Parse(sql);

        // Assert
        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.InstanceOf<SubtractionExpression>());
    }

    #endregion

    #region Error Handling Tests

    [Test]
    public void Parse_NullInput_ThrowsArgumentNullException()
    {
        // Arrange
        string? sql = null;

        // Act & Assert
        Assert.Throws<ArgumentNullException>(() => _parser.Parse(sql!));
    }

    [Test]
    public void Parse_EmptyString_ThrowsArgumentNullException()
    {
        // Arrange
        var sql = "";

        // Act & Assert
        Assert.Throws<ArgumentNullException>(() => _parser.Parse(sql));
    }

    [Test]
    public void Parse_Whitespace_ThrowsArgumentNullException()
    {
        // Arrange
        var sql = "   ";

        // Act & Assert
        Assert.Throws<ArgumentNullException>(() => _parser.Parse(sql));
    }

    [Test]
    public void TryParse_InvalidSyntax_ReturnsFalse()
    {
        // Arrange
        var sql = "\"A\" +"; // Incomplete expression

        // Act
        var success = _parser.TryParse(sql, out var result);

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(success, Is.False);
            Assert.That(result, Is.Null);
        });
    }

    #endregion
}