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), "REG-REF-1");

    private static StubHandler Created(out RequestCapture capture)
    {
        var c = new RequestCapture();
        capture = c;
        return new StubHandler(async req =>
        {
            c.Seen = req;
            // Capture the length BEFORE reading the body: ReadAsStringAsync buffers the
            // content and would set ContentLength as a side effect, masking the gateway's
            // own buffering. Read here to assert the gateway sent a length (not chunked).
            c.ContentLength = req.Content?.Headers.ContentLength;
            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;
        public long? ContentLength;
    }

    [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);
        // The registration reference is set as the zaak identificatie (#78).
        Assert.Contains("\"identificatie\":\"REG-REF-1\"", 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 Sends_the_body_with_a_content_length_so_it_is_not_chunked()
    {
        // OpenZaak's uwsgi rejects a chunked request body (400). The gateway buffers
        // the body so a Content-Length is sent. JsonContent has no length until
        // buffered, so this guards the fix the real-OpenZaak integration test found.
        var handler = Created(out var capture);

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

        Assert.NotNull(capture.ContentLength);
        Assert.True(capture.ContentLength > 0);
    }

    [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"),
            }));

        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
        Assert.Contains("empty zaak response", ex.Message);
    }

    [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!));
    }

    // --- SetZaakToEindstatusAsync (approval / S-09b) ---

    private const string ZaakUrl = "http://openzaak/zaken/api/v1/zaken/xyz";
    private static readonly Uri Zaaktype = new("http://openzaak/catalogi/api/v1/zaaktypen/big");

    private sealed class Recorder
    {
        public List<HttpRequestMessage> Requests { get; } = [];
        public List<string?> Bodies { get; } = [];
        public List<long?> ContentLengths { get; } = [];

        public int IndexOf(string pathContains) =>
            Requests.FindIndex(r => r.RequestUri!.ToString().Contains(pathContains));

        // The (body, content-length, request) of the single request whose URL contains the segment.
        public (string? Body, long? Length, HttpRequestMessage Request) Sent(string pathContains)
        {
            var i = IndexOf(pathContains);
            return (Bodies[i], ContentLengths[i], Requests[i]);
        }
    }

    // Per-route response config for the four calls the approval makes.
    private sealed class OzRoutes
    {
        public string StatustypenJson { get; init; } = StatustypenPage(withEindstatusFlag: true);
        public string ResultaattypenJson { get; init; } = """{"results":[{"url":"http://openzaak/catalogi/api/v1/resultaattypen/1"}]}""";
        public HttpStatusCode StatustypenStatus { get; init; } = HttpStatusCode.OK;
        public HttpStatusCode ResultaattypenStatus { get; init; } = HttpStatusCode.OK;
        public HttpStatusCode ResultaatPostStatus { get; init; } = HttpStatusCode.Created;
        public HttpStatusCode StatusPostStatus { get; init; } = HttpStatusCode.Created;
    }

    // Routes the approval's four calls by URL: GET /statustypen, GET /resultaattypen (catalogus),
    // then POST /resultaten and POST /statussen (zaken).
    private static StubHandler ApprovalStub(Recorder rec, OzRoutes routes) => new(async req =>
    {
        rec.Requests.Add(req);
        // Capture the length BEFORE reading the body (ReadAsStringAsync buffers as a side effect).
        rec.ContentLengths.Add(req.Content?.Headers.ContentLength);
        rec.Bodies.Add(req.Content is null ? null : await req.Content.ReadAsStringAsync());

        var url = req.RequestUri!.ToString();
        if (req.Method == HttpMethod.Get && url.Contains("/statustypen"))
            return Json(routes.StatustypenStatus, routes.StatustypenJson);
        if (req.Method == HttpMethod.Get && url.Contains("/resultaattypen"))
            return Json(routes.ResultaattypenStatus, routes.ResultaattypenJson);
        if (url.Contains("/resultaten"))
            return Json(routes.ResultaatPostStatus, """{"url":"http://openzaak/zaken/api/v1/resultaten/new"}""");
        return Json(routes.StatusPostStatus, """{"url":"http://openzaak/zaken/api/v1/statussen/new"}""");
    });

    private static HttpResponseMessage Json(HttpStatusCode status, string body) =>
        new(status) { Content = new StringContent(body, Encoding.UTF8, "application/json") };

    // Two statustypen; the eindstatus is flagged on the *lower* volgnummer so the tests prove the
    // isEindstatus flag is preferred over "highest volgnummer", not coincidentally equal to it.
    private static string StatustypenPage(bool withEindstatusFlag) => JsonSerializer.Serialize(new
    {
        results = new object[]
        {
            new { url = "http://openzaak/catalogi/api/v1/statustypen/1", volgnummer = 1, isEindstatus = withEindstatusFlag },
            new { url = "http://openzaak/catalogi/api/v1/statustypen/2", volgnummer = 2, isEindstatus = false },
        },
    });

    [Fact]
    public async Task Approving_sets_a_resultaat_then_posts_the_flagged_eindstatus_against_the_zaak()
    {
        var rec = new Recorder();

        await Gateway(ApprovalStub(rec, new OzRoutes()))
            .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4));

        Assert.Equal(4, rec.Requests.Count);

        // Both catalogus queries filter by the zaaktype and carry the bearer.
        var statustypenGet = rec.Sent("/statustypen").Request;
        Assert.Equal(HttpMethod.Get, statustypenGet.Method);
        Assert.Contains(Uri.EscapeDataString(Zaaktype.ToString()), statustypenGet.RequestUri!.ToString());
        Assert.Equal("Bearer", statustypenGet.Headers.Authorization!.Scheme);
        Assert.Contains(Uri.EscapeDataString(Zaaktype.ToString()), rec.Sent("/resultaattypen").Request.RequestUri!.ToString());

        // OpenZaak requires a resultaat before the eindstatus, so /resultaten precedes /statussen.
        Assert.True(rec.IndexOf("/resultaten") < rec.IndexOf("/statussen"));

        var resultaat = rec.Sent("/resultaten");
        Assert.Equal("http://openzaak/zaken/api/v1/resultaten", resultaat.Request.RequestUri!.ToString());
        Assert.Equal("Bearer", resultaat.Request.Headers.Authorization!.Scheme);
        Assert.Contains("\"zaak\":\"" + ZaakUrl + "\"", resultaat.Body);
        Assert.Contains("\"resultaattype\":\"http://openzaak/catalogi/api/v1/resultaattypen/1\"", resultaat.Body);
        Assert.True(resultaat.Length > 0);

        var status = rec.Sent("/statussen");
        Assert.Equal("http://openzaak/zaken/api/v1/statussen", status.Request.RequestUri!.ToString());
        Assert.Equal("Bearer", status.Request.Headers.Authorization!.Scheme);
        Assert.Contains("\"zaak\":\"" + ZaakUrl + "\"", status.Body);
        // The isEindstatus-flagged statustype (/1) is chosen — even though /2 has a higher volgnummer.
        Assert.Contains("\"statustype\":\"http://openzaak/catalogi/api/v1/statustypen/1\"", status.Body);
        Assert.Contains("\"datumStatusGezet\":\"2026-06-04T00:00:00Z\"", status.Body);
        // Bodies are buffered (Content-Length set), so uwsgi doesn't get a chunked body.
        Assert.True(status.Length > 0);
    }

    [Fact]
    public async Task Approving_falls_back_to_the_highest_volgnummer_when_no_eindstatus_is_flagged()
    {
        var rec = new Recorder();

        await Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = StatustypenPage(withEindstatusFlag: false) }))
            .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4));

        // No isEindstatus flag → the highest volgnummer (/2) is chosen.
        Assert.Contains("\"statustype\":\"http://openzaak/catalogi/api/v1/statustypen/2\"", rec.Sent("/statussen").Body);
    }

    [Fact]
    public async Task Approving_throws_when_the_zaaktype_has_no_statustypen()
    {
        var rec = new Recorder();

        // A page with no `results` property (Results is null) — the eindstatus cannot be resolved.
        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = "{}" }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("No statustypen found", ex.Message);
        // It never posts anything when it cannot resolve the eindstatus.
        Assert.Single(rec.Requests);
    }

    [Fact]
    public async Task Approving_throws_when_the_statustypen_response_is_empty()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = "null" }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("empty statustypen", ex.Message);
        Assert.Single(rec.Requests);
    }

    [Fact]
    public async Task Approving_throws_when_the_statustypen_query_fails()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenStatus = HttpStatusCode.InternalServerError }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("Querying statustypen", ex.Message);
    }

    [Fact]
    public async Task Approving_throws_when_the_resultaattypen_query_fails()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { ResultaattypenStatus = HttpStatusCode.InternalServerError }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("Querying resultaattypen", ex.Message);
        Assert.Equal(-1, rec.IndexOf("/resultaten"));
    }

    [Fact]
    public async Task Approving_throws_when_the_zaaktype_has_no_resultaattype()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { ResultaattypenJson = "{}" }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("No resultaattypen found", ex.Message);
        // Resolved the eindstatus + queried resultaattypen, but posted nothing.
        Assert.Equal(-1, rec.IndexOf("/resultaten"));
        Assert.Equal(-1, rec.IndexOf("/statussen"));
    }

    [Fact]
    public async Task Approving_throws_when_posting_the_resultaat_fails()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { ResultaatPostStatus = HttpStatusCode.BadRequest }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("Setting the zaak resultaat", ex.Message);
        // The status is never posted if the resultaat could not be recorded.
        Assert.Equal(-1, rec.IndexOf("/statussen"));
    }

    [Fact]
    public async Task Approving_throws_when_posting_the_status_fails()
    {
        var rec = new Recorder();

        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
            Gateway(ApprovalStub(rec, new OzRoutes { StatusPostStatus = HttpStatusCode.BadRequest }))
                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));

        Assert.Contains("Setting the zaak status", ex.Message);
        // It got as far as the resultaat + the status POST (4 calls) before failing.
        Assert.Equal(4, rec.Requests.Count);
    }

    [Fact]
    public async Task Reading_a_zaak_returns_its_identificatie_with_bearer_and_crs()
    {
        RequestCapture? capture = null;
        var handler = new StubHandler(req =>
        {
            capture = new RequestCapture { Seen = req };
            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = JsonContent.Create(new { identificatie = "REG-XYZ", url = ZaakUrl }),
            });
        });

        var reference = await Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl));

        Assert.Equal("REG-XYZ", reference);
        Assert.Equal(HttpMethod.Get, capture!.Seen!.Method);
        Assert.Equal(ZaakUrl, capture.Seen.RequestUri!.ToString());
        Assert.Equal("Bearer", capture.Seen.Headers.Authorization!.Scheme);
        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen.Headers.GetValues("Accept-Crs")));
    }

    [Fact]
    public async Task Reading_a_zaak_throws_when_openzaak_rejects_it()
    {
        var handler = new StubHandler(_ =>
            Task.FromResult(new HttpResponseMessage(HttpStatusCode.NotFound) { Content = new StringContent("nope") }));

        var ex = await Assert.ThrowsAsync<HttpRequestException>(
            () => Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl)));
        Assert.Contains("Reading the zaak", ex.Message);
    }

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

        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
            () => Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl)));
        Assert.Contains("empty zaak response", ex.Message);
    }

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

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

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

        await Assert.ThrowsAsync<ArgumentNullException>(() =>
            Gateway(handler).SetZaakToEindstatusAsync(null!, Zaaktype, new DateOnly(2026, 6, 4)));
        await Assert.ThrowsAsync<ArgumentNullException>(() =>
            Gateway(handler).SetZaakToEindstatusAsync(new Uri(ZaakUrl), null!, new DateOnly(2026, 6, 4)));
    }

    // 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));
    }
}