using System.Data;
using Microsoft.Data.SqlClient;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests;

/// <summary>
///     #683: <see cref="SqlAggregateQueries.StartEnd"/> aggregates the pick times, then fetches each pick by a key join.
///     The joins must be bounded to the window: keyed on the pick time alone, a hash/merge/adaptive join reads the tag's
///     whole history (review of 910befc8: 43,657 logical reads vs 361 on a tag with 3M rows outside a 1 d window). The
///     plan choice depends on estimates, so the test FORCES the worst shape (<c>OPTION (HASH JOIN)</c>) on a tag with long
///     history either side of the window and asserts the statement reads only window-sized pages — and returns exactly
///     what the unhinted plan and the data source return.
/// </summary>
[Collection(SqlHistorianCollection.Name)]
public sealed class StartEndJoinBackTests(SqlHistorianFixture fx)
{
    private static readonly CancellationToken Ct = CancellationToken.None;
    private static DateTime At(double s) => ReadTestDb.At(s);
    private const int HistoryRowsEachSide = 150_000;

    /// <summary>
    ///     Tag <c>H</c>: one sample a minute over the hour [+0, +3600) of mixed quality (Good, Uncertain, Bad, an outage
    ///     marker, a string), plus <see cref="HistoryRowsEachSide"/> rows a second before +0 and after +3600.
    /// </summary>
    private static async Task<(ReadTestDb Db, int Id, List<(DateTime T, HistorianValue V, uint S)> Window)> SeedAsync(SqlHistorianFixture fx)
    {
        var db = await ReadTestDb.CreateAsync(fx);
        var window = new List<(DateTime T, HistorianValue V, uint S)>();
        for (var i = 0; i < 60; i++)
        {
            var (v, s) = (i % 7) switch
            {
                3 => (HistorianValue.FromDouble(i), ReadTestDb.Bad),
                4 => (HistorianValue.FromDouble(i), ReadTestDb.Uncertain),
                5 => (HistorianValue.Empty, ReadTestDb.BadNoCommunication),
                6 => (HistorianValue.FromString("s" + i), ReadTestDb.Good),
                _ => (HistorianValue.FromDouble(i), ReadTestDb.Good),
            };
            window.Add((At(i * 60 + 7), v, s));
        }
        var id = await db.SeedAsync("H", window.ToArray());
        // The history: inserted set-based (a per-row INSERT of 300k rows would dominate the test).
        await db.ScalarAsync(
            $"WITH n AS (SELECT TOP ({HistoryRowsEachSide}) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS x " +
            "FROM sys.all_objects a CROSS JOIN sys.all_objects b) " +
            $"INSERT {db.Conn.Q("Sample")} (TagId, SourceTimeUtc, ValueKind, NumValue, IntValue, StrValue, StatusCode, ServerTimeUtc) " +
            $"SELECT {id}, DATEADD(second, -x, CAST('{At(0):yyyy-MM-dd HH:mm:ss.fffffff}' AS datetime2(7))), 3, x, NULL, NULL, 0, SYSUTCDATETIME() FROM n " +
            $"UNION ALL SELECT {id}, DATEADD(second, x, CAST('{At(3600):yyyy-MM-dd HH:mm:ss.fffffff}' AS datetime2(7))), 3, x, NULL, NULL, 0, SYSUTCDATETIME() FROM n; " +
            "SELECT 0");
        await db.ScalarAsync($"UPDATE STATISTICS {db.Conn.Q("Sample")}; SELECT 0");
        return (db, id, window);
    }

    /// <summary>
    ///     Runs the StartEnd SQL (optionally with a query hint) and returns its rows as strings plus the session's logical
    ///     reads during the statement (<c>sys.dm_exec_sessions.logical_reads</c> before/after — STATISTICS IO messages do
    ///     not reach SqlClient's InfoMessage here). The two probes add a few reads of their own; the bound is far apart.
    /// </summary>
    private static async Task<(List<string> Rows, long LogicalReads)> RunAsync(ReadTestDb db, int id, BucketPlan plan, string? hint)
    {
        var sql = SqlAggregateQueries.StartEnd(db.Conn.Q("Sample"), plan.Reversed);
        if (hint is not null) sql = sql.TrimEnd().TrimEnd(';') + $" OPTION ({hint});";
        await using var c = await db.Conn.OpenAsync(Ct);
        async Task<long> SessionReadsAsync()
        {
            await using var probe = db.Conn.CreateCommand(c, "SELECT logical_reads FROM sys.dm_exec_sessions WHERE session_id = @@SPID");
            return Convert.ToInt64(await probe.ExecuteScalarAsync(Ct));
        }
        var before = await SessionReadsAsync();
        await using var cmd = db.Conn.CreateCommand(c, sql);
        cmd.Parameters.Add(new SqlParameter("@id", SqlDbType.Int) { Value = id });
        SqlHistorianConnection.AddDateTime2(cmd, "@start", plan.StartUtc);
        SqlHistorianConnection.AddDateTime2(cmd, "@end", plan.EndUtc);
        cmd.Parameters.Add(new SqlParameter("@intervalTicks", SqlDbType.BigInt) { Value = plan.IntervalTicks });
        cmd.Parameters.Add(new SqlParameter("@bucketAdjustTicks", SqlDbType.BigInt) { Value = plan.BucketIndexAdjustTicks });
        var rows = new List<string>();
        await using (var r = await cmd.ExecuteReaderAsync(Ct))
            while (await r.ReadAsync(Ct))
                rows.Add(string.Join("|", Enumerable.Range(0, r.FieldCount).Select(i => r.IsDBNull(i) ? "NULL" : Convert.ToString(r.GetValue(i), System.Globalization.CultureInfo.InvariantCulture))));
        return (rows, await SessionReadsAsync() - before);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task The_pick_joins_read_only_the_window_even_under_a_forced_hash_join(bool reverse)
    {
        fx.SkipIfUnavailable();
        var (db, id, window) = await SeedAsync(fx);
        var plan = reverse
            ? BucketPlan.Create(At(3600), At(0), TimeSpan.FromMinutes(10))
            : BucketPlan.Create(At(0), At(3600), TimeSpan.FromMinutes(10));

        var (plain, _) = await RunAsync(db, id, plan, hint: null);
        var (hashed, hashReads) = await RunAsync(db, id, plan, hint: "HASH JOIN");
        var (merged, mergeReads) = await RunAsync(db, id, plan, hint: "MERGE JOIN");

        plain.Count.ShouldBe(6);
        hashed.ShouldBe(plain);
        merged.ShouldBe(plain);
        // Measured: 183 session logical reads bounded vs 8,055 with the window bound removed from the joins (300k history
        // rows either side; the threshold sits ~5x above the one and ~8x below the other). Every join
        // bounded ⇒ each input is a window-range seek, whatever the join algorithm.
        hashReads.ShouldBeGreaterThan(0L, "the session read counter must move (positive control)");
        hashReads.ShouldBeLessThan(1000, "a hash join's inner input must be bounded to the window");
        mergeReads.ShouldBeLessThan(1000, "a merge join's inner input must be bounded to the window");

        // And the picks are right: Start / End are each bucket's first / last sample of any quality.
        var src = db.Source();
        var start = await src.ReadProcessedAsync("H", reverse ? At(3600) : At(0), reverse ? At(0) : At(3600),
            TimeSpan.FromMinutes(10), HistoryAggregateType.Start, Ct);
        var end = await src.ReadProcessedAsync("H", reverse ? At(3600) : At(0), reverse ? At(0) : At(3600),
            TimeSpan.FromMinutes(10), HistoryAggregateType.End, Ct);
        var buckets = Enumerable.Range(0, 6).Select(b => window.Skip(b * 10).Take(10).ToList()).ToList();
        if (reverse) buckets.Reverse();
        start.Samples.Select(s => s.SourceTimestampUtc).ShouldBe(buckets.Select(b => (DateTime?)b[0].T));
        end.Samples.Select(s => s.SourceTimestampUtc).ShouldBe(buckets.Select(b => (DateTime?)b[^1].T));
    }
}