using System.Net;
using System.Net.Http.Json;
using System.Text.Json;
using Xunit;

namespace Azaion.Missions.E2E.Helpers;

/// <summary>
/// Reusable HTTP-shape assertions: PascalCase JSON keys, the
/// <c>{ error, traceId }</c> error envelope, paginated-response shape, and
/// expected-status helpers.
/// </summary>
public static class HttpAssertions
{
    public static async Task AssertStatusAsync(HttpResponseMessage response, HttpStatusCode expected)
    {
        if (response.StatusCode != expected)
        {
            var body = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
            Assert.Fail($"Expected HTTP {(int)expected}; got {(int)response.StatusCode}. Body:\n{body}");
        }
    }

    public static async Task AssertErrorEnvelopeAsync(HttpResponseMessage response)
    {
        var body = await response.Content.ReadFromJsonAsync<JsonElement>().ConfigureAwait(false);
        Assert.True(body.TryGetProperty("error", out _), "error-envelope missing 'error' property");
        Assert.True(body.TryGetProperty("traceId", out _), "error-envelope missing 'traceId' property");
        AssertNoStackLeak(body);
    }

    /// <summary>
    /// Asserts the {statusCode, message} envelope produced by
    /// <c>ErrorHandlingMiddleware</c>. The envelope uses camelCase keys
    /// because the middleware emits an anonymous object literal — see
    /// _docs/02_document/components/06_http_conventions/description.md.
    /// </summary>
    public static async Task<ProblemDto> AssertProblemEnvelopeAsync(
        HttpResponseMessage response,
        HttpStatusCode expectedStatus)
    {
        await AssertStatusAsync(response, expectedStatus).ConfigureAwait(false);
        var body = await response.Content.ReadFromJsonAsync<JsonElement>().ConfigureAwait(false);

        Assert.True(body.TryGetProperty("statusCode", out var statusEl),
            "problem envelope missing 'statusCode' property");
        Assert.True(body.TryGetProperty("message", out var messageEl),
            "problem envelope missing 'message' property");
        Assert.Equal((int)expectedStatus, statusEl.GetInt32());
        var message = messageEl.GetString();
        Assert.False(string.IsNullOrEmpty(message),
            "problem envelope 'message' must be non-empty");

        AssertNoStackLeak(body);

        // Reject any extra keys to pin the envelope contract — the spec says
        // EXACTLY these two keys (results_report.md row 1.8 + AC-8.6).
        var extraKeys = body.EnumerateObject()
            .Select(p => p.Name)
            .Where(n => n is not ("statusCode" or "message"))
            .ToArray();
        Assert.True(extraKeys.Length == 0,
            $"problem envelope has unexpected extra keys: {string.Join(",", extraKeys)}");

        return new ProblemDto(statusEl.GetInt32(), message!);
    }

    public static void AssertNoStackLeak(JsonElement body)
    {
        // Walk the JSON DOM and fail if any key looks like it leaks server internals.
        var leakKeys = new[] { "stack", "stackTrace", "exception", "inner", "trace", "innerException", "type", "details" };
        WalkAndAssert(body, leakKeys);
    }

    private static void WalkAndAssert(JsonElement element, string[] leakKeys)
    {
        switch (element.ValueKind)
        {
            case JsonValueKind.Object:
                foreach (var prop in element.EnumerateObject())
                {
                    foreach (var leak in leakKeys)
                    {
                        if (string.Equals(prop.Name, leak, StringComparison.OrdinalIgnoreCase))
                            Assert.Fail($"error envelope leaks server internals via key '{prop.Name}'");
                    }
                    WalkAndAssert(prop.Value, leakKeys);
                }
                break;
            case JsonValueKind.Array:
                foreach (var item in element.EnumerateArray())
                    WalkAndAssert(item, leakKeys);
                break;
        }
    }

    public static AuthenticationHeaderValueLike Bearer(string jwt) => new(jwt);

    public sealed record AuthenticationHeaderValueLike(string Jwt)
    {
        public override string ToString() => $"Bearer {Jwt}";
    }
}