using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json.Serialization;
using Acl.Application;

namespace Acl.Infrastructure;

/// <summary>The only code that talks to OpenZaak's Zaken API (ADR-0001).</summary>
public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) : IZaakGateway
{
    public async Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(request);

        using var message = new HttpRequestMessage(
            HttpMethod.Post, new Uri(options.BaseUrl, "/zaken/api/v1/zaken"))
        {
            Content = JsonContent.Create(new ZaakDto(
                request.Bronorganisatie,
                request.Zaaktype.ToString(),
                request.VerantwoordelijkeOrganisatie,
                request.Startdatum.ToString("yyyy-MM-dd"),
                request.Vertrouwelijkheidaanduiding)),
        };
        message.Headers.Authorization =
            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
        // ZRC is a geo API; it requires the CRS headers.
        message.Headers.Add("Accept-Crs", "EPSG:4326");
        message.Content.Headers.Add("Content-Crs", "EPSG:4326");
        // OpenZaak runs behind uwsgi, which rejects a chunked request body with 400.
        // JsonContent streams without a known length (→ Transfer-Encoding: chunked),
        // so buffer it first to send a Content-Length instead. Only a real OpenZaak
        // surfaces this — a stubbed HttpMessageHandler accepts either framing.
        await message.Content.LoadIntoBufferAsync(ct);

        using var response = await http.SendAsync(message, ct);
        response.EnsureSuccessStatusCode();

        var created = await response.Content.ReadFromJsonAsync<ZaakCreatedDto>(ct)
            ?? throw new InvalidOperationException("OpenZaak returned an empty zaak response");
        return new Uri(created.Url);
    }

    public async Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(zaakUrl);
        ArgumentNullException.ThrowIfNull(zaaktypeUrl);

        var eindstatus = await ResolveEindstatusAsync(zaaktypeUrl, ct);

        using var message = new HttpRequestMessage(
            HttpMethod.Post, new Uri(options.BaseUrl, "/zaken/api/v1/statussen"))
        {
            Content = JsonContent.Create(new StatusDto(
                zaakUrl.ToString(),
                eindstatus.ToString(),
                // datumStatusGezet is a ZGW date-time; set it at the start of the given day (UTC).
                datumStatusGezet.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc).ToString("yyyy-MM-ddTHH:mm:ssZ"))),
        };
        message.Headers.Authorization =
            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
        // The status resource carries no geometry, so no CRS headers. As with zaak-create, buffer the
        // body so uwsgi gets a Content-Length instead of a chunked body.
        await message.Content.LoadIntoBufferAsync(ct);

        using var response = await http.SendAsync(message, ct);
        response.EnsureSuccessStatusCode();
    }

    /// <summary>Resolve the zaaktype's eindstatus (the terminal statustype) from the catalogus.</summary>
    private async Task<Uri> ResolveEindstatusAsync(Uri zaaktypeUrl, CancellationToken ct)
    {
        var query = new Uri(options.BaseUrl,
            "/catalogi/api/v1/statustypen?status=alles&zaaktype=" + Uri.EscapeDataString(zaaktypeUrl.ToString()));
        using var message = new HttpRequestMessage(HttpMethod.Get, query);
        message.Headers.Authorization =
            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));

        using var response = await http.SendAsync(message, ct);
        response.EnsureSuccessStatusCode();

        var page = await response.Content.ReadFromJsonAsync<StatustypePage>(ct)
            ?? throw new InvalidOperationException("OpenZaak returned an empty statustypen response");
        var results = page.Results ?? [];

        // OpenZaak flags the terminal statustype (highest volgnummer) as isEindstatus; fall back to the
        // highest volgnummer if the flag is absent.
        var eindstatus = results.FirstOrDefault(s => s.IsEindstatus)
            ?? results.OrderByDescending(s => s.Volgnummer).FirstOrDefault()
            ?? throw new InvalidOperationException($"No statustypen found for zaaktype {zaaktypeUrl}");
        return new Uri(eindstatus.Url);
    }

    private sealed record ZaakDto(
        [property: JsonPropertyName("bronorganisatie")] string Bronorganisatie,
        [property: JsonPropertyName("zaaktype")] string Zaaktype,
        [property: JsonPropertyName("verantwoordelijkeOrganisatie")] string VerantwoordelijkeOrganisatie,
        [property: JsonPropertyName("startdatum")] string Startdatum,
        [property: JsonPropertyName("vertrouwelijkheidaanduiding")] string Vertrouwelijkheidaanduiding);

    private sealed record ZaakCreatedDto(
        [property: JsonPropertyName("url")] string Url);

    private sealed record StatusDto(
        [property: JsonPropertyName("zaak")] string Zaak,
        [property: JsonPropertyName("statustype")] string Statustype,
        [property: JsonPropertyName("datumStatusGezet")] string DatumStatusGezet);

    private sealed record StatustypePage(
        [property: JsonPropertyName("results")] IReadOnlyList<StatustypeDto>? Results);

    private sealed record StatustypeDto(
        [property: JsonPropertyName("url")] string Url,
        [property: JsonPropertyName("volgnummer")] int Volgnummer,
        [property: JsonPropertyName("isEindstatus")] bool IsEindstatus);
}