sql-utilities/tests/Strata.SqlTools.Tests/ExpressionTests/ConditionalExpressionTests.cs

using Strata.SqlTools.SqlBreakdown.Classes;
using Strata.SqlTools.SqlBreakdown.Expressions;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions.Aggregate;
using Strata.SqlTools.SqlBreakdown.Expressions.Functions.Conditional;

namespace Strata.SqlTools.SqlBreakdown.Tests.ExpressionTests;

[TestFixture]
public class ConditionalExpressionTests : ExpressionTestsBase
{
    private static IEnumerable<TestCaseData> ConditionalExpressionTestCases()
    {
        var testCases = new[]
        {
            new ExpressionTestCase
            {
                Name = "CaseExpression_{m}",
                Arrange = new Dictionary<string, Expression>(),
                Act = (columns, visitor) =>
                {
                    var table = new RegisteredTableSource(101, "CLIENT_DSS", "DEPT", "PES");
                    var nameCol = new RegisteredTableColumnExpression(1, "DEPARTMENT_NAME", table);
                    var revenueCol = new RegisteredTableColumnExpression(2, "NET_REVENUE", table);
                    var caseExp = new CaseExpression(nameCol == "department 1", revenueCol, 0);
                    return caseExp.Accept(visitor);
                },
                Assertions = result =>
                {
                    var sql = (string)result;
                    Assert.That(sql, Does.Contain("CASE"));
                    Assert.That(sql, Does.Contain("WHEN"));
                    Assert.That(sql, Does.Contain("THEN"));
                    Assert.That(sql, Does.Contain("ELSE"));
                    Assert.That(sql, Does.Contain("END"));
                    return true;
                }
            },
            new ExpressionTestCase
            {
                Name = "CaseExpressionWithSum_{m}",
                Arrange = new Dictionary<string, Expression>(),
                Act = (columns, visitor) =>
                {
                    var table = new RegisteredTableSource(101, "CLIENT_DSS", "DEPT", "PES");
                    var nameCol = new RegisteredTableColumnExpression(1, "DEPARTMENT_NAME", table);
                    var revenueCol = new RegisteredTableColumnExpression(2, "NET_REVENUE", table);
                    var caseExp = new CaseExpression(nameCol == "department 1", revenueCol, 0);
                    var sumCaseExp = new SumFunction(caseExp);
                    return sumCaseExp.Accept(visitor);
                },
                Assertions = result =>
                {
                    var sql = (string)result;
                    Assert.That(sql, Does.Contain("SUM"));
                    Assert.That(sql, Does.Contain("CASE"));
                    Assert.That(sql, Does.Contain("WHEN"));
                    Assert.That(sql, Is.EqualTo("SUM(CASE\n  WHEN PES.DEPARTMENT_NAME = 'department 1' THEN PES.NET_REVENUE\n  ELSE 0\nEND)"));
                    return true;
                }
            },
            new ExpressionTestCase
            {
                Name = "CaseExpressionWithSumInSelectColumn_{m}",
                Arrange = new Dictionary<string, Expression>(),
                Act = (columns, visitor) =>
                {
                    var table = new RegisteredTableSource(101, "CLIENT_DSS", "DEPT", "PES");
                    var nameCol = new RegisteredTableColumnExpression(1, "DEPARTMENT_NAME", table);
                    var revenueCol = new RegisteredTableColumnExpression(2, "NET_REVENUE", table);
                    var caseExp = new CaseExpression(nameCol == "department 1", revenueCol, 0);
                    var sumCaseExp = new SumFunction(caseExp);
                    var column = new SelectClauseColumn(sumCaseExp, "mySumCaseCol");
                    return column.Accept(visitor);
                },
                Assertions = result =>
                {
                    var sql = (string)result;
                    Assert.That(sql, Does.Contain("SUM"));
                    Assert.That(sql, Does.Contain("CASE"));
                    Assert.That(sql, Does.Contain("mySumCaseCol"));
                    Assert.That(sql, Is.EqualTo("SUM(CASE\n  WHEN PES.DEPARTMENT_NAME = 'department 1' THEN PES.NET_REVENUE\n  ELSE 0\nEND) AS mySumCaseCol"));
                    return true;
                }
            },
            new ExpressionTestCase
            {
                Name = "IfThenElseExpression_{m}",
                Arrange = new Dictionary<string, Expression>(),
                Act = (columns, visitor) =>
                {
                    var table = new RegisteredTableSource(101, "CLIENT_DSS", "DEPT", "PES");
                    var nameCol = new RegisteredTableColumnExpression(1, "DEPARTMENT_NAME", table);
                    var revenueCol = new RegisteredTableColumnExpression(2, "NET_REVENUE", table);
                    var costCol = new RegisteredTableColumnExpression(3, "COST", table);
                    var ifElseExp = new IfThenElseExpression(nameCol == "myDeptName", revenueCol, costCol);
                    return ifElseExp.Accept(visitor);
                },
                Assertions = result =>
                {
                    var sql = (string)result;
                    Assert.That(sql, Does.Contain("IFF"));
                    Assert.That(sql, Is.EqualTo("IFF(PES.DEPARTMENT_NAME = 'myDeptName', PES.NET_REVENUE, PES.COST)"));
                    return true;
                }
            }
        };

        foreach (var testCase in testCases)
        {
            yield return new TestCaseData(testCase).SetName(testCase.Name);
        }
    }

    [TestCaseSource(nameof(ConditionalExpressionTestCases))]
    public void ConditionalExpression_GeneratesCorrectSql(ExpressionTestCase testCase)
        => ExecuteExpressionTest(testCase);
}