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,
                request.Identificatie)),
        };
        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);
        var resultaattype = await ResolveResultaattypeAsync(zaaktypeUrl, ct);

        // OpenZaak refuses to set a zaak's eindstatus unless the zaak has a resultaat
        // ("resultaat-does-not-exist"), so record the resultaat first, then the status.
        await PostAsync("/zaken/api/v1/resultaten",
            new ResultaatDto(zaakUrl.ToString(), resultaattype.ToString()), "Setting the zaak resultaat", ct);

        await PostAsync("/zaken/api/v1/statussen",
            // datumStatusGezet is a ZGW date-time; set it at the start of the given day (UTC).
            new StatusDto(zaakUrl.ToString(), eindstatus.ToString(),
                datumStatusGezet.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc).ToString("yyyy-MM-ddTHH:mm:ssZ")),
            "Setting the zaak status", ct);
    }

    public async Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(zaakUrl);

        using var message = new HttpRequestMessage(HttpMethod.Get, zaakUrl);
        message.Headers.Authorization =
            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
        // The zaak is a geo resource; the Zaken API requires the CRS header even on GET.
        message.Headers.Add("Accept-Crs", "EPSG:4326");

        using var response = await http.SendAsync(message, ct);
        await EnsureSuccessAsync(response, "Reading the zaak", ct);

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

    // POSTs a non-geo ZGW resource (resultaat/status — no CRS headers). Buffers the body so uwsgi gets
    // a Content-Length instead of a chunked body (as with zaak-create).
    private async Task PostAsync(string path, object dto, string action, CancellationToken ct)
    {
        using var message = new HttpRequestMessage(HttpMethod.Post, new Uri(options.BaseUrl, path))
        {
            Content = JsonContent.Create(dto),
        };
        message.Headers.Authorization =
            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
        await message.Content.LoadIntoBufferAsync(ct);

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

    // EnsureSuccessStatusCode discards the response body; ZGW returns a JSON problem detail on 400 that
    // is essential for diagnosing a rejected request, so surface it in the exception.
    private static async Task EnsureSuccessAsync(HttpResponseMessage response, string action, CancellationToken ct)
    {
        if (response.IsSuccessStatusCode)
            return;

        var body = await response.Content.ReadAsStringAsync(ct);
        throw new HttpRequestException($"{action} failed: {(int)response.StatusCode} {response.ReasonPhrase}. {body}");
    }

    /// <summary>Resolve the zaaktype's eindstatus (the terminal statustype) from the catalogus.</summary>
    private async Task<Uri> ResolveEindstatusAsync(Uri zaaktypeUrl, CancellationToken ct)
    {
        var page = await GetCatalogusAsync<StatustypePage>("statustypen", zaaktypeUrl, "statustypen", ct);
        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);
    }

    /// <summary>Resolve the zaaktype's resultaattype from the catalogus (the seed defines one).</summary>
    private async Task<Uri> ResolveResultaattypeAsync(Uri zaaktypeUrl, CancellationToken ct)
    {
        var page = await GetCatalogusAsync<ResultaattypePage>("resultaattypen", zaaktypeUrl, "resultaattypen", ct);
        var resultaattype = (page.Results ?? []).FirstOrDefault()
            ?? throw new InvalidOperationException($"No resultaattypen found for zaaktype {zaaktypeUrl}");
        return new Uri(resultaattype.Url);
    }

    // GETs a catalogus collection filtered by zaaktype (status=alles includes concept + published).
    private async Task<T> GetCatalogusAsync<T>(string resource, Uri zaaktypeUrl, string label, CancellationToken ct)
    {
        var query = new Uri(options.BaseUrl,
            $"/catalogi/api/v1/{resource}?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);
        await EnsureSuccessAsync(response, $"Querying {label}", ct);

        return await response.Content.ReadFromJsonAsync<T>(ct)
            ?? throw new InvalidOperationException($"OpenZaak returned an empty {label} response");
    }

    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,
        [property: JsonPropertyName("identificatie")] string Identificatie);

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

    private sealed record ZaakReadDto(
        [property: JsonPropertyName("identificatie")] string Identificatie);

    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);

    private sealed record ResultaatDto(
        [property: JsonPropertyName("zaak")] string Zaak,
        [property: JsonPropertyName("resultaattype")] string Resultaattype);

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

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