CVR API i C#: opslag, søgning og fejlhåndtering

dotnet user-secrets set "FirmaApi:Key" "cvr_live_din_api_nøgle"

FirmaApiClient.cs

using System.Net;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;

public sealed record Virksomhed(
    [property: JsonPropertyName("cvr")] string Cvr,
    [property: JsonPropertyName("name")] string Name,
    [property: JsonPropertyName("status")] string Status,
    [property: JsonPropertyName("address")] string? Address,
    [property: JsonPropertyName("zipcode")] string? Zipcode,
    [property: JsonPropertyName("city")] string? City,
    [property: JsonPropertyName("industry_text")] string? IndustryText,
    [property: JsonPropertyName("employees")] string? Employees);

public sealed record SoegeSvar(
    [property: JsonPropertyName("results")] List<Virksomhed> Results,
    [property: JsonPropertyName("total")] int Total);

public sealed record BatchSvar(
    [property: JsonPropertyName("results")] List<Virksomhed> Results,
    [property: JsonPropertyName("errors")] List<JsonElement> Errors,
    [property: JsonPropertyName("quota_used")] int QuotaUsed);

public sealed class FirmaApiException : Exception
{
    public HttpStatusCode Status { get; }
    public string Code { get; }

    public FirmaApiException(HttpStatusCode status, string code, string message)
        : base($"{(int)status} {code}: {message}")
    {
        Status = status;
        Code = code;
    }
}

public sealed class FirmaApiClient
{
    private const int MaxRetries = 3;
    private readonly HttpClient _http;

    // HttpClient skal være sat op med BaseAddress, timeout og Authorization-header.
    public FirmaApiClient(HttpClient http) => _http = http;

    public static bool ErGyldigtCvr(string input)
    {
        var cifre = new string(input.Where(char.IsDigit).ToArray());
        if (cifre.Length != 8) return false;
        int[] vaegte = [2, 7, 6, 5, 4, 3, 2, 1];
        var sum = cifre.Select((c, i) => (c - '0') * vaegte[i]).Sum();
        return sum % 11 == 0;
    }

    public Task<Virksomhed> HentVirksomhedAsync(string cvr, string? include = null, CancellationToken ct = default)
    {
        var sti = "company/" + Uri.EscapeDataString(cvr);
        if (include is not null) sti += "?include=" + Uri.EscapeDataString(include);
        return SendAsync<Virksomhed>(HttpMethod.Get, sti, null, ct);
    }

    public Task<SoegeSvar> SoegAsync(string q, int limit = 10, CancellationToken ct = default) =>
        SendAsync<SoegeSvar>(HttpMethod.Get,
            "company/search?q=" + Uri.EscapeDataString(q) + "&limit=" + limit, null, ct);

    public Task<BatchSvar> BatchAsync(IEnumerable<string> cvrNumre, CancellationToken ct = default) =>
        SendAsync<BatchSvar>(HttpMethod.Post, "company/batch", new { cvr_numbers = cvrNumre }, ct);

    private async Task<T> SendAsync<T>(HttpMethod method, string sti, object? body, CancellationToken ct)
    {
        for (var forsoeg = 0; ; forsoeg++)
        {
            using var request = new HttpRequestMessage(method, sti);
            if (body is not null)
            {
                request.Content = new StringContent(JsonSerializer.Serialize(body), Encoding.UTF8, "application/json");
            }

            using var response = await _http.SendAsync(request, ct);
            var tekst = await response.Content.ReadAsStringAsync(ct);

            if (response.IsSuccessStatusCode)
            {
                return JsonSerializer.Deserialize<T>(tekst)!;
            }

            var (kode, besked) = LaesFejl(tekst);
            var kanProevesIgen =
                (response.StatusCode == HttpStatusCode.TooManyRequests && kode == "RATE_LIMIT_EXCEEDED")
                || response.StatusCode is HttpStatusCode.BadGateway or HttpStatusCode.ServiceUnavailable;

            if (kanProevesIgen && forsoeg < MaxRetries)
            {
                var ventetid = response.Headers.RetryAfter?.Delta ?? TimeSpan.FromSeconds(Math.Pow(2, forsoeg));
                await Task.Delay(ventetid, ct);
                continue;
            }

            throw new FirmaApiException(response.StatusCode, kode, besked);
        }
    }

    private static (string Kode, string Besked) LaesFejl(string tekst)
    {
        try
        {
            using var doc = JsonDocument.Parse(tekst);
            if (doc.RootElement.TryGetProperty("error", out var e))
            {
                var kode = e.TryGetProperty("code", out var c) ? c.GetString() ?? "UNKNOWN" : "UNKNOWN";
                var besked = e.TryGetProperty("message", out var m) ? m.GetString() ?? "" : "";
                return (kode, besked);
            }
        }
        catch (JsonException) { }
        return ("UNKNOWN", tekst.Length > 200 ? tekst[..200] : tekst);
    }
}

using System.Net.Http.Headers;

using var http = new HttpClient
{
    BaseAddress = new Uri("https://firmaapi.dk/api/v1/"),
    Timeout = TimeSpan.FromSeconds(10),
};
http.DefaultRequestHeaders.Authorization =
    new AuthenticationHeaderValue("Bearer", Environment.GetEnvironmentVariable("FIRMAAPI_KEY"));
var api = new FirmaApiClient(http);

var cvr = "24256790";
if (!FirmaApiClient.ErGyldigtCvr(cvr))
{
    Console.WriteLine("Ugyldigt CVR-nummer");
    return;
}

try
{
    var v = await api.HentVirksomhedAsync(cvr);
    Console.WriteLine($"{v.Name} ({v.Status}), {v.City}");
}
catch (FirmaApiException ex) when (ex.Code == "NOT_FOUND")
{
    Console.WriteLine("CVR-nummeret findes ikke");
}
catch (FirmaApiException ex) when (ex.Code == "MONTHLY_LIMIT_EXCEEDED")
{
    Console.WriteLine("Månedskvoten er brugt");
}

// Find CVR-nummer ud fra et navn
var svar = await api.SoegAsync("novo nordisk", limit: 5);
foreach (var hit in svar.Results)
{
    Console.WriteLine($"{hit.Cvr} {hit.Name} {hit.City}");
}

// Batch-opslag (Basis eller højere), op til 100 pr. kald på Basis
var batch = await api.BatchAsync(new[] { "24256790", "54562519", "25313763" });
Console.WriteLine($"{batch.Results.Count} fundet, {batch.Errors.Count} fejl, {batch.QuotaUsed} opslag brugt");

// Program.cs i ASP.NET Core
builder.Services.AddHttpClient<FirmaApiClient>(client =>
{
    client.BaseAddress = new Uri("https://firmaapi.dk/api/v1/");
    client.Timeout = TimeSpan.FromSeconds(10);
    client.DefaultRequestHeaders.Authorization =
        new AuthenticationHeaderValue("Bearer", builder.Configuration["FirmaApi:Key"]);
});

// Brug klienten ved at injicere FirmaApiClient i en controller eller en minimal API-rute.