sql-utilities/tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/StatementReaderTests.cs

using Strata.SqlTools.SqlBreakdown.Enums.SQL;
using Strata.SqlTools.SqlBreakdown.Exceptions;
using StatementReader = Strata.SqlTools.Statements.PostgreSql.StatementReader;

namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;

[TestFixture]
public class StatementReaderTests
{
    [Test]
    public void StatementReader_ParsesCalculationString()
    {
        // Arrange
        var calculationString = "(1 + 2) / SUM(column_id) + SUM(other_column) - SUM(another_column) * 2.3";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Is.Not.Empty);
        Assert.Multiple(() =>
        {
            Assert.That(tokens[0].Type, Is.EqualTo(TokenType.LeftParenthesis));
            Assert.That(tokens[1].Type, Is.EqualTo(TokenType.Number));
            Assert.That(tokens[1].Value, Is.EqualTo("1"));
        });
    }

    [Test]
    public void StatementReader_ParsesDoubleQuotedIdentifiers()
    {
        // Arrange - PostgreSQL-specific double-quoted identifiers (case-sensitive)
        var calculationString = "\"COLUMN_1\" + \"COLUMN_2\" * 2";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Has.Count.EqualTo(5)); // "COLUMN_1" + "COLUMN_2" * 2
        Assert.Multiple(() =>
        {
            Assert.That(tokens[0].Type, Is.EqualTo(TokenType.ColumnIdentifier));
            Assert.That(tokens[0].Value, Is.EqualTo("COLUMN_1"));
            Assert.That(tokens[1].Type, Is.EqualTo(TokenType.Plus));
            Assert.That(tokens[2].Type, Is.EqualTo(TokenType.ColumnIdentifier));
        });
    }

    [Test]
    public void StatementReader_ParsesDoubleQuotedIdentifiersWithCase()
    {
        // Arrange - PostgreSQL preserves case in double-quoted identifiers
        var calculationString = "\"MyColumn\" + \"AnotherColumn\"";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        Assert.Multiple(() =>
        {
            // Assert
            Assert.That(tokens[0].Type, Is.EqualTo(TokenType.ColumnIdentifier));
            Assert.That(tokens[0].Value, Is.EqualTo("MyColumn"));
            Assert.That(tokens[2].Type, Is.EqualTo(TokenType.ColumnIdentifier));
            Assert.That(tokens[2].Value, Is.EqualTo("AnotherColumn"));
        });
    }

    [Test]
    public void StatementReader_ParsesPositionalParameters()
    {
        // Arrange - PostgreSQL positional parameters ($1, $2, etc.)
        var calculationString = "column_id = $1 AND status = $2";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Is.Not.Empty);
        var paramTokens = tokens.Where(t => t.Type == TokenType.Parameter).ToList();
        Assert.That(paramTokens, Has.Count.EqualTo(2));
        Assert.Multiple(() =>
        {
            Assert.That(paramTokens[0].Value, Is.EqualTo("$1"));
            Assert.That(paramTokens[1].Value, Is.EqualTo("$2"));
        });
    }

    [Test]
    public void StatementReader_ParsesUnderscorePrefixedIdentifiers()
    {
        // Arrange - PostgreSQL allows underscores to start identifiers
        var calculationString = "_internal_column + _private_field";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        var identifierTokens = tokens.Where(t => t.Type == TokenType.ColumnIdentifier).ToList();
        Assert.That(identifierTokens, Has.Count.GreaterThanOrEqualTo(2));
    }

    [Test]
    public void StatementReader_ParsesComplexExpression()
    {
        // Arrange - Complex PostgreSQL expression
        var calculationString = "(\"Price\" * quantity) - discount WHERE user_id = $1";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Is.Not.Empty);
        var identifierCount = tokens.Count(t => t.Type == TokenType.ColumnIdentifier);
        Assert.That(identifierCount, Is.GreaterThan(0));
    }

    [Test]
    public void StatementReader_ThrowsOnUnclosedDoubleQuote()
    {
        // Arrange
        var calculationString = "\"UNCLOSED_IDENTIFIER + 1";
        var sqlReader = new StatementReader(calculationString);

        // Act & Assert
        Assert.Throws<InvalidSyntaxException>(() =>
        {
            while (sqlReader.Read()) { }
        });
    }

    [Test]
    public void StatementReader_ParsesWhitespace()
    {
        // Arrange
        var calculationString = "  column_1   +   column_2  ";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Is.Not.Empty);
    }

    [Test]
    public void StatementReader_ParsesOperators()
    {
        // Arrange
        var calculationString = "a = b";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        Assert.That(tokens, Is.Not.Empty);
    }

    [Test]
    public void StatementReader_ParsesStrings()
    {
        // Arrange
        var calculationString = "column = 'string value' AND other = 'another string'";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        var stringTokens = tokens.Where(t => t.Type == TokenType.String).ToList();
        Assert.That(stringTokens, Has.Count.GreaterThanOrEqualTo(2));
    }

    [Test]
    public void StatementReader_ParsesNumbers()
    {
        // Arrange
        var calculationString = "42 + 3.14 - 100";
        var sqlReader = new StatementReader(calculationString);
        var tokens = new List<(TokenType Type, string Value)>();

        // Act
        while (sqlReader.Read())
        {
            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
        }

        // Assert
        var numberTokens = tokens.Where(t => t.Type == TokenType.Number).ToList();
        Assert.That(numberTokens, Is.Not.Empty);
    }
}