using System.Net;
using System.Net.Http.Json;
using System.Text;
using System.Text.Json;
using Acl.Application;
using Acl.Infrastructure;

namespace Acl.Tests;

public class OpenZaakGatewayTests
{
    private sealed class StubHandler(Func<HttpRequestMessage, Task<HttpResponseMessage>> onSend)
        : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
            => onSend(request);
    }

    private static OpenZaakGateway Gateway(StubHandler handler) => new(
        new HttpClient(handler),
        new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });

    private static ZaakRequest SampleRequest() => new(
        "517439943", "517439943", "openbaar",
        new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));

    private static StubHandler Created(out RequestCapture capture)
    {
        var c = new RequestCapture();
        capture = c;
        return new StubHandler(async req =>
        {
            c.Seen = req;
            c.Body = req.Content is null ? null : await req.Content.ReadAsStringAsync();
            return new HttpResponseMessage(HttpStatusCode.Created)
            {
                Content = JsonContent.Create(new { url = "http://openzaak/zaken/api/v1/zaken/xyz" }),
            };
        });
    }

    private sealed class RequestCapture
    {
        public HttpRequestMessage? Seen;
        public string? Body;
    }

    [Fact]
    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
    {
        var handler = Created(out var capture);

        var url = await Gateway(handler).OpenZaakAsync(SampleRequest());

        Assert.Equal("http://openzaak/zaken/api/v1/zaken/xyz", url.ToString());
        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
        Assert.Equal("http://openzaak/zaken/api/v1/zaken", capture.Seen.RequestUri!.ToString());
        Assert.Equal("Bearer", capture.Seen.Headers.Authorization!.Scheme);
        Assert.False(string.IsNullOrWhiteSpace(capture.Seen.Headers.Authorization.Parameter));
        Assert.Contains("\"bronorganisatie\":\"517439943\"", capture.Body);
        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", capture.Body);
        Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", capture.Body);
        Assert.Contains("\"startdatum\":\"2026-06-04\"", capture.Body);
        Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", capture.Body);
    }

    [Fact]
    public async Task Sends_the_geo_crs_headers_required_by_the_zaken_api()
    {
        var handler = Created(out var capture);

        await Gateway(handler).OpenZaakAsync(SampleRequest());

        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen!.Headers.GetValues("Accept-Crs")));
        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen.Content!.Headers.GetValues("Content-Crs")));
    }

    [Fact]
    public async Task Mints_a_hs256_jwt_carrying_the_acl_identity_claims()
    {
        var handler = Created(out var capture);

        await Gateway(handler).OpenZaakAsync(SampleRequest());

        var parts = capture.Seen!.Headers.Authorization!.Parameter!.Split('.');
        Assert.Equal(3, parts.Length);
        using var header = JsonDocument.Parse(DecodeSegment(parts[0]));
        Assert.Equal("HS256", header.RootElement.GetProperty("alg").GetString());
        Assert.Equal("JWT", header.RootElement.GetProperty("typ").GetString());
        using var payload = JsonDocument.Parse(DecodeSegment(parts[1]));
        Assert.Equal("cid", payload.RootElement.GetProperty("client_id").GetString());
        Assert.Equal("acl", payload.RootElement.GetProperty("user_id").GetString());
        Assert.Equal("acl", payload.RootElement.GetProperty("user_representation").GetString());
    }

    [Fact]
    public async Task Throws_when_openzaak_rejects_the_request()
    {
        var handler = new StubHandler(_ =>
            Task.FromResult(new HttpResponseMessage(HttpStatusCode.BadRequest)));

        await Assert.ThrowsAsync<HttpRequestException>(
            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
    }

    [Fact]
    public async Task Throws_when_openzaak_returns_an_empty_body()
    {
        var handler = new StubHandler(_ =>
            Task.FromResult(new HttpResponseMessage(HttpStatusCode.Created)
            {
                Content = new StringContent("null", Encoding.UTF8, "application/json"),
            }));

        await Assert.ThrowsAsync<InvalidOperationException>(
            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
    }

    [Fact]
    public async Task Rejects_a_null_request()
    {
        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));

        await Assert.ThrowsAsync<ArgumentNullException>(
            () => Gateway(handler).OpenZaakAsync(null!));
    }

    // ZGW tokens are base64url with padding stripped (ZgwToken.B64Url); restore it to decode.
    private static string DecodeSegment(string segment)
    {
        var b64 = segment.Replace('-', '+').Replace('_', '/');
        b64 = (b64.Length % 4) switch { 2 => b64 + "==", 3 => b64 + "=", _ => b64 };
        return Encoding.UTF8.GetString(Convert.FromBase64String(b64));
    }
}