using System.Net;
using System.Net.Http.Headers;
using Azaion.Missions.E2E.Fixtures;
using Azaion.Missions.E2E.Helpers;
using Npgsql;
using Xunit;

namespace Azaion.Missions.E2E.Tests.Missions;

/// <summary>
/// FT-N-06 — DELETE /missions/{missing_uuid} must short-circuit on the
/// initial existence check (Step 1 of the cascade walk) and emit ZERO
/// DELETE statements against any dependency table. The contract protects
/// downstream consumers from typo'd UUIDs silently corrupting unrelated
/// missions' data (results_report.md row 3.2 / AC-3.2).
/// </summary>
/// <remarks>
/// The strict assertion uses two independent signals: (1) per-table row
/// counts before and after must match, AND (2) when
/// <c>pg_stat_statements</c> is available, the post-request query stats
/// must contain ZERO <c>DELETE FROM map_objects/waypoints/media/...</c>
/// rows attributable to this request window.
/// Without pg_stat_statements (e.g. extension not preloaded in the
/// postgres image), the test still asserts the row-count invariant and
/// records a warning trait — silent passing is rejected by the
/// row-count check.
/// </remarks>
[Collection("CascadeShortCircuit")]
[Trait("Category", "Blackbox")]
[Trait("db_access", "seed-or-assert-only")]
public sealed class CascadeShortCircuitTests : TestBase
{
    [Fact]
    [Trait("Traces", "AC-3.2")]
    [Trait("max_ms", "5000")]
    public async Task FT_N_06_delete_missing_mission_emits_zero_dependency_table_deletes()
    {
        // Arrange — clean DB, F3 fixture for a populated cascade chain.
        DbResetFixture.ResetDatabase(TestEnvironment.DbSideChannel);
        StubSchema.EnsureCreated();
        Seeds.Apply(FixtureSql.Load("fixture_cascade_F3"));

        // Try to attach pg_stat_statements; fall back gracefully if the
        // extension isn't preloaded.
        var pgssAvailable = TryEnablePgStatStatements();
        if (pgssAvailable) ResetPgStatStatements();

        var token = await Tokens.MintDefaultAsync();
        var notInDb = Guid.NewGuid();

        // Pre-state row counts — these must equal post-state counts iff the
        // cascade short-circuited correctly.
        var pre = SnapshotCounts();

        // Act
        using var http = new HttpRequestMessage(HttpMethod.Delete, $"/missions/{notInDb}");
        http.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token.Jwt);
        using var response = await Missions.SendAsync(http);

        // Assert
        await HttpAssertions.AssertProblemEnvelopeAsync(response, HttpStatusCode.NotFound)
;

        var post = SnapshotCounts();
        foreach (var table in pre.Keys)
        {
            Assert.True(pre[table] == post[table],
                $"row count for '{table}' changed after a 404 cascade: " +
                $"pre={pre[table]} post={post[table]} — short-circuit failed");
        }

        if (pgssAvailable)
        {
            var deleteCount = ScalarCountSql("""
                SELECT COUNT(*) FROM pg_stat_statements
                WHERE query ILIKE '%DELETE FROM map_objects%'
                   OR query ILIKE '%DELETE FROM waypoints%'
                   OR query ILIKE '%DELETE FROM media%'
                   OR query ILIKE '%DELETE FROM annotations%'
                   OR query ILIKE '%DELETE FROM detection%'
                   OR query ILIKE '%DELETE FROM missions%'
                """);
            Assert.True(deleteCount == 0,
                $"pg_stat_statements shows {deleteCount} DELETE statements against " +
                "cascade tables after a 404 — short-circuit failed at the SQL layer");
        }
    }

    private static Dictionary<string, long> SnapshotCounts()
    {
        var tables = new[] { "missions", "waypoints", "map_objects",
                             "media", "annotations", "detection" };
        return tables.ToDictionary(t => t, DbAssertions.TableRowCount);
    }

    private static bool TryEnablePgStatStatements()
    {
        try
        {
            using var conn = new NpgsqlConnection(TestEnvironment.DbSideChannel);
            conn.Open();
            using var cmd = conn.CreateCommand();
            cmd.CommandText = "CREATE EXTENSION IF NOT EXISTS pg_stat_statements;";
            cmd.ExecuteNonQuery();
            return true;
        }
        catch (PostgresException ex)
        {
            // Most common cause: the extension is not in
            // shared_preload_libraries. Surface the reason — skipping
            // silently would defeat the purpose of this test.
            Console.WriteLine(
                $"[FT-N-06] pg_stat_statements unavailable ({ex.SqlState}: {ex.MessageText}); " +
                "falling back to row-count short-circuit assertion only.");
            return false;
        }
    }

    private static void ResetPgStatStatements()
    {
        using var conn = new NpgsqlConnection(TestEnvironment.DbSideChannel);
        conn.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT pg_stat_statements_reset();";
        cmd.ExecuteScalar();
    }

    private static long ScalarCountSql(string sql)
    {
        using var conn = new NpgsqlConnection(TestEnvironment.DbSideChannel);
        conn.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText = sql;
        var result = cmd.ExecuteScalar();
        if (result is null || result is DBNull)
            throw new InvalidOperationException($"scalar query returned NULL: {sql}");
        return Convert.ToInt64(result, System.Globalization.CultureInfo.InvariantCulture);
    }
}