From fec96d77272c8abe5008062affdfbf9bbabc6069 Mon Sep 17 00:00:00 2001
From: Martin <martin@svrcina.eu>
Date: Fri, 20 Mar 2026 00:45:59 +0100
Subject: [PATCH] feat: implement CSV import service with tests (TDD)

---
 .../CsvImportServiceTests.cs                  | 123 ++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 src/AccountTracking.Api.Tests/CsvImportServiceTests.cs

diff --git a/src/AccountTracking.Api.Tests/CsvImportServiceTests.cs b/src/AccountTracking.Api.Tests/CsvImportServiceTests.cs
new file mode 100644
index 0000000..55afd6c
--- /dev/null
+++ b/src/AccountTracking.Api.Tests/CsvImportServiceTests.cs
@@ -0,0 +1,123 @@
+using AccountTracking.Api.Data;
+using AccountTracking.Api.Services;
+using Microsoft.EntityFrameworkCore;
+
+namespace AccountTracking.Api.Tests;
+
+public class CsvImportServiceTests
+{
+    private static AppDbContext CreateDb()
+    {
+        var opts = new DbContextOptionsBuilder<AppDbContext>()
+            .UseInMemoryDatabase(Guid.NewGuid().ToString())
+            .Options;
+        return new AppDbContext(opts);
+    }
+
+    private static CsvImportService CreateService(AppDbContext db)
+        => new(db);
+
+    // Minimal valid CSV with two data rows
+    private const string ValidCsv = """
+        Pohyby na účtu 216868554/0300 dne 19.03.2026
+
+        číslo účtu;datum zaúčtování;částka;měna;zůstatek;číslo protiúčtu;kód banky protiúčtu;jméno protistrany;adresa protistrany;konstantní symbol;variabilní symbol;specifický symbol;označení operace;název trálého příkazu;vlastní poznámka;zpráva;kategorie;původní transakce;kurz;E2E identifikace;reference plátce;původní plátce;konečný příjemce;ID transakce
+        216868554/0300;15.03.2026;-1 740,80;CZK;93 346,57;;;;;;205000001;;Transakce platební kartou;;;Zpráva 1;Potraviny;;;;;;;tx-001
+        216868554/0300;14.03.2026;-800,00;CZK;95 087,37;;;;;;205000002;;Transakce platební kartou;;;Zpráva 2;Restaurace;;;;;;;tx-002
+        """;
+
+    private const string CsvMissingHeader = """
+        Pohyby na účtu
+        Nějaky obsah bez správné hlavičky
+        datum;částka
+        """;
+
+    private const string CsvMissingRequiredColumn = """
+        číslo účtu;datum zaúčtování;měna;zůstatek;ID transakce
+        216868554/0300;15.03.2026;CZK;93346,57;tx-001
+        """;
+
+    [Fact]
+    public async Task Import_ParsesRowsCorrectly()
+    {
+        using var db = CreateDb();
+        var svc = CreateService(db);
+
+        var result = await svc.ImportAsync(ValidCsv, "test.csv");
+
+        Assert.True(result.IsSuccess);
+        Assert.Equal(2, result.Value!.RecordsImported);
+        Assert.Equal(0, result.Value.RecordsSkipped);
+
+        var transactions = await db.Transactions.ToListAsync();
+        Assert.Equal(2, transactions.Count);
+
+        var tx = transactions.First(t => t.TransactionId == "tx-001");
+        Assert.Equal(-1740.80m, tx.Amount);
+        Assert.Equal(93346.57m, tx.Balance);
+        Assert.Equal("Potraviny", tx.Category);
+        Assert.Equal(new DateOnly(2026, 3, 15), tx.BookingDate);
+    }
+
+    [Fact]
+    public async Task Import_SkipsDuplicateTransactionIds()
+    {
+        using var db = CreateDb();
+        var svc = CreateService(db);
+
+        await svc.ImportAsync(ValidCsv, "first.csv");
+        var result = await svc.ImportAsync(ValidCsv, "second.csv");
+
+        Assert.True(result.IsSuccess);
+        Assert.Equal(0, result.Value!.RecordsImported);
+        Assert.Equal(2, result.Value.RecordsSkipped);
+        Assert.Equal(2, await db.Transactions.CountAsync());
+    }
+
+    [Fact]
+    public async Task Import_FindsHeaderByScanning_NotByLineNumber()
+    {
+        // Header is on line 3 in ValidCsv — but we scan, not hardcode
+        using var db = CreateDb();
+        var svc = CreateService(db);
+
+        var result = await svc.ImportAsync(ValidCsv, "test.csv");
+
+        Assert.True(result.IsSuccess);
+    }
+
+    [Fact]
+    public async Task Import_ReturnsError_WhenHeaderNotFound()
+    {
+        using var db = CreateDb();
+        var svc = CreateService(db);
+
+        var result = await svc.ImportAsync(CsvMissingHeader, "bad.csv");
+
+        Assert.False(result.IsSuccess);
+        Assert.Contains("hlavičku", result.Error, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task Import_ReturnsError_WhenRequiredColumnMissing()
+    {
+        using var db = CreateDb();
+        var svc = CreateService(db);
+
+        var result = await svc.ImportAsync(CsvMissingRequiredColumn, "bad.csv");
+
+        Assert.False(result.IsSuccess);
+        Assert.Contains("částka", result.Error, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Theory]
+    [InlineData("1 740,80", 1740.80)]
+    [InlineData("-4 263,15", -4263.15)]
+    [InlineData("-800,00", -800.00)]
+    [InlineData("93 346,57", 93346.57)]
+    public void ParseAmount_HandlesChechLocaleFormat(string input, decimal expected)
+    {
+        var result = CsvImportService.ParseCzechDecimal(input);
+        Assert.Equal(expected, result);
+    }
+}