using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using Npgsql;
using NpgsqlTypes;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb;

/// <summary>
///     OPC UA HistoryUpdate against the QuestDB sample table (spec §2.3). Every operation is an <c>INSERT</c>: the
///     table's <c>DEDUP UPSERT KEYS(ts, tag)</c> performs the replace, and a delete writes a tombstone
///     (<c>deleted = true</c>, NULL values, <c>BadNoData</c>). QuestDB <c>UPDATE</c>/<c>DELETE</c> are never issued.
///     <para>Every status comes from <see cref="HistoryUpdatePlanner"/>, so codes equal the SQL Server backend's.
///     "Exists" means present and not deleted, so Insert over a tombstone succeeds (<c>GoodEntryInserted</c>) while
///     Replace and DeleteAtTime treat a tombstone as no entry. Existence is read with one range query and filtered
///     client-side (never an IN list).</para>
///     <para><b>Concurrency:</b> calls are serialized per tag inside this instance (64 striped async locks held from
///     the existence read through the visibility wait), so concurrent Insert/Replace/Delete on one tag cannot
///     both act on a stale read. This does NOT cover the live writer racing on the same key, nor a second node;
///     that residual is accepted.</para>
///     <para><b>Pre-1970 (RC1):</b> QuestDB cannot store such a designated timestamp. Insert/Replace/Update of such an
///     item reports <c>BadOutOfRange</c> and sends nothing (a null/<c>MinValue</c> timestamp is still
///     <c>BadInvalidTimestamp</c>); DeleteAtTime reports <c>BadNoEntryExists</c>; a DeleteRaw window may start before
///     1970 (read bounds are not clamped).</para>
///     <para><b>Read-your-writes:</b> after writing, <see cref="QuestDbWalVisibility"/> waits for the rows to become
///     visible, bounded by <c>VisibilityTimeout</c>; a timeout only logs a Warning, never changes a code.</para>
///     <para><b>Modified-value history (Part 11, #668).</b> Every sample this updater inserts, replaces or tombstones first
///     gets a row in <c>{prefix}sample_modified</c> carrying its PRIOR live value (the existence read already fetches it;
///     none for an insert — a tombstone is "absent", so an insert over one records no prior value), the caller's
///     <see cref="HistoryUpdateContext"/>, the <see cref="HistoryModificationType"/> and the modification time. QuestDB has
///     no multi-table transaction, so the trail row is written <b>BEFORE</b> the change: a crash (or a failed sample INSERT)
///     between the two leaves an orphan trail row describing a change that never landed — never a change without its
///     trail row. This is the documented deviation from SQL Server, whose trail commits atomically with the change.</para>
/// </summary>
internal sealed class QuestDbHistorianDataUpdater : IHistorianDataUpdater
{
    /// <summary>Rows per INSERT and per DeleteRaw page (T0 Q2: 9,000 parameters, far under the 32,767 limit).</summary>
    internal const int BatchSize = 1000;

    private const long ResolutionTicks = 10;
    private const int LockStripes = 64;
    private readonly SemaphoreSlim[] _locks = Enumerable.Range(0, LockStripes).Select(_ => new SemaphoreSlim(1, 1)).ToArray();
    private long _liveRowsRead;
    private static long _lastModifiedId;
    private readonly QuestDbConnection _conn;
    private readonly QuestDbTagCatalog _tags;
    private readonly QuestDbWalVisibility _wal;
    private readonly ILogger _log;

    /// <summary>Creates the updater.</summary>
    /// <param name="conn">Connection helper.</param>
    /// <param name="tags">Tag catalog (R7: the only known-tag authority).</param>
    /// <param name="wal">WAL visibility wait (R5).</param>
    /// <param name="log">Optional logger.</param>
    public QuestDbHistorianDataUpdater(QuestDbConnection conn, QuestDbTagCatalog tags, QuestDbWalVisibility wal,
        ILogger? log = null)
    {
        _conn = conn;
        _tags = tags;
        _wal = wal;
        _log = log ?? NullLogger.Instance;
    }

    /// <summary>Rows returned by existence reads so far (test/diagnostic counter).</summary>
    internal long LiveRowsRead => Interlocked.Read(ref _liveRowsRead);

    private async Task<IDisposable> LockAsync(string tag, CancellationToken ct)
    {
        var sem = _locks[(int)((uint)StringComparer.Ordinal.GetHashCode(tag) % LockStripes)];
        await sem.WaitAsync(ct).ConfigureAwait(false);
        return new Releaser(sem);
    }

    private sealed class Releaser(SemaphoreSlim sem) : IDisposable
    {
        public void Dispose() => sem.Release();
    }

    /// <inheritdoc/>
    public async Task<IReadOnlyList<uint>> UpdateDataAsync(string tag, HistoryUpdateMode mode,
        IReadOnlyList<HistorizationValue> values, HistoryUpdateContext context, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(tag);
        ArgumentNullException.ThrowIfNull(values);
        ArgumentNullException.ThrowIfNull(context);

        // RC1: a valid-timestamp item before 1970 can never be stored; refuse it and plan the rest.
        var final = new uint[values.Count];
        var kept = new List<int>(values.Count);
        for (var i = 0; i < values.Count; i++)
        {
            if (values[i].TimestampUtc is { } ts && ts != DateTime.MinValue && !QuestDbConnection.IsStorable(ts))
                final[i] = HistorianStatusCodes.BadOutOfRange;
            else
                kept.Add(i);
        }

        var plan = HistoryUpdatePlanner.Plan(tag, mode, kept.Select(i => values[i]).ToList(), ResolutionTicks);
        IReadOnlyList<uint> planned;
        if (plan.Winners.Count == 0)
        {
            planned = HistoryUpdatePlanner.Complete(plan, mode, new Dictionary<long, UpsertOutcome>());
        }
        else
        {
            using var _ = await LockAsync(tag, ct).ConfigureAwait(false);
            var known = mode == HistoryUpdateMode.Replace
                ? await _tags.ExistsAsync(tag, ct).ConfigureAwait(false)
                : await EnsureAsync(tag, plan.Winners[0].Row.Value.Kind, ct).ConfigureAwait(false);
            var outcome = known
                ? await ApplyAsync(tag, mode, plan.Winners.Select(w => w.Row).ToList(), context, ct).ConfigureAwait(false)
                : new Dictionary<long, UpsertOutcome>();
            planned = HistoryUpdatePlanner.Complete(plan, mode, outcome);
        }
        for (var k = 0; k < kept.Count; k++) final[kept[k]] = planned[k];
        return final;
    }

    /// <inheritdoc/>
    public async Task<uint> DeleteRawAsync(string tag, DateTime startUtc, DateTime endUtc, HistoryUpdateContext context,
        CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(tag);
        ArgumentNullException.ThrowIfNull(context);
        if (!HistorianTagNames.IsValid(tag)) return HistorianStatusCodes.BadInvalidArgument;
        if (!await _tags.ExistsAsync(tag, ct).ConfigureAwait(false))
            return HistoryUpdatePlanner.DeleteRawResult(tagKnown: false, 0);

        using var _ = await LockAsync(tag, ct).ConfigureAwait(false);
        var cursor = QuestDbConnection.Round(startUtc);
        var end = QuestDbConnection.Round(endUtc);
        long total = 0;
        while (cursor < end)
        {
            var page = new List<DateTime>(BatchSize);
            var priors = new List<LiveRow>(BatchSize);
            await using (var conn = await _conn.OpenAsync(ct).ConfigureAwait(false))
            await using (var cmd = _conn.CreateCommand(conn,
                             $"SELECT {LiveColumns} FROM {_conn.SampleTable} WHERE tag = $1 AND ts >= $2 AND ts < $3 AND NOT deleted ORDER BY ts LIMIT {BatchSize}"))
            {
                QuestDbConnection.BindText(cmd, tag);
                QuestDbConnection.BindTimestamp(cmd, cursor);
                QuestDbConnection.BindTimestamp(cmd, end);
                await using var rd = await cmd.ExecuteReaderAsync(ct).ConfigureAwait(false);
                while (await rd.ReadAsync(ct).ConfigureAwait(false))
                {
                    var row = ReadLiveRow(rd);
                    page.Add(row.TimeUtc);
                    priors.Add(row);
                }
            }
            if (page.Count == 0) break;
            // Trail BEFORE the change (no multi-table transaction): a crash here leaves an orphan trail row, never a
            // tombstone without its trail row.
            await WriteTrailAsync(tag, HistoryModificationType.Delete,
                priors.Select(r => (r.TimeUtc, (LiveRow?)r)).ToList(), context, ct).ConfigureAwait(false);
            await WriteTombstonesAsync(tag, page, ct).ConfigureAwait(false);
            // The wait between pages is required: without it the next page could re-read rows just tombstoned.
            await _wal.WaitAsync(_conn.SampleTable, ct).ConfigureAwait(false);
            total += page.Count;
            if (page.Count < BatchSize) break;
            cursor = page[^1].AddTicks(ResolutionTicks);
        }
        return HistoryUpdatePlanner.DeleteRawResult(tagKnown: true, total);
    }

    /// <inheritdoc/>
    public async Task<IReadOnlyList<uint>> DeleteAtTimeAsync(string tag, IReadOnlyList<DateTime> timesUtc,
        HistoryUpdateContext context, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(tag);
        ArgumentNullException.ThrowIfNull(timesUtc);
        ArgumentNullException.ThrowIfNull(context);
        if (!HistorianTagNames.IsValid(tag))
        {
            var refused = new uint[timesUtc.Count];
            Array.Fill(refused, HistorianStatusCodes.BadInvalidArgument);
            return refused;
        }

        // M-2: round BEFORE both the delete and the comparison, so a sub-µs request time matches the row it deleted.
        // MinValue stays as is: the planner turns it into BadInvalidTimestamp.
        var rounded = timesUtc.Select(t => t == DateTime.MinValue ? t : QuestDbConnection.Round(t)).ToList();
        var candidates = new HashSet<long>();
        foreach (var t in rounded)
            if (t != DateTime.MinValue && t >= DateTime.UnixEpoch) candidates.Add(t.Ticks);   // pre-1970 can hold no row
        var deleted = new HashSet<long>();
        if (candidates.Count == 0 || !await _tags.ExistsAsync(tag, ct).ConfigureAwait(false))
            return HistoryUpdatePlanner.DeleteAtTimeResults(rounded, deleted, tagKnown: false);

        using var _ = await LockAsync(tag, ct).ConfigureAwait(false);
        var live = await ReadLiveAsync(tag, candidates.Select(t => new DateTime(t, DateTimeKind.Utc)).ToList(), ct).ConfigureAwait(false);
        var toDelete = candidates.Where(live.ContainsKey).OrderBy(x => x).ToList();
        foreach (var chunk in toDelete.Chunk(BatchSize))
        {
            // Trail BEFORE the change (see the class remarks).
            await WriteTrailAsync(tag, HistoryModificationType.Delete,
                chunk.Select(t => (live[t].TimeUtc, (LiveRow?)live[t])).ToList(), context, ct).ConfigureAwait(false);
            await WriteTombstonesAsync(tag, chunk.Select(t => new DateTime(t, DateTimeKind.Utc)).ToList(), ct).ConfigureAwait(false);
        }
        if (toDelete.Count > 0) await _wal.WaitAsync(_conn.SampleTable, ct).ConfigureAwait(false);
        deleted.UnionWith(toDelete);
        return HistoryUpdatePlanner.DeleteAtTimeResults(rounded, deleted, tagKnown: true);
    }

    private async Task<bool> EnsureAsync(string tag, HistorianValueKind kind, CancellationToken ct)
    {
        await _tags.EnsureAsync(tag, HistorianDataTypes.FromKind(kind), ct).ConfigureAwait(false);
        return true;
    }

    private async Task<Dictionary<long, UpsertOutcome>> ApplyAsync(string tag, HistoryUpdateMode mode,
        List<HistorianSampleRow> rows, HistoryUpdateContext context, CancellationToken ct)
    {
        // Key = the planner's tick (what Complete looks up); the stored time is Round(of the same row).
        var live = await ReadLiveAsync(tag, rows.Select(r => QuestDbConnection.Round(r.TimeUtc)).ToList(), ct).ConfigureAwait(false);
        var outcome = new Dictionary<long, UpsertOutcome>();
        var toWrite = new List<HistorianSampleRow>();
        var trail = new List<(DateTime, LiveRow?)>();
        foreach (var r in rows)
        {
            var stored = QuestDbConnection.Round(r.TimeUtc);
            var present = live.TryGetValue(stored.Ticks, out var prior);
            if (mode == HistoryUpdateMode.Insert && present) continue;
            if (mode == HistoryUpdateMode.Replace && !present) continue;
            outcome[r.TimeUtc.Ticks] = present ? UpsertOutcome.Replaced : UpsertOutcome.Inserted;
            toWrite.Add(r);
            trail.Add((stored, present ? prior : null));
        }
        // Trail BEFORE the change (see the class remarks).
        await WriteTrailAsync(tag, ToModificationType(mode), trail, context, ct).ConfigureAwait(false);
        foreach (var chunk in toWrite.Chunk(BatchSize))
            await WriteRowsAsync(tag, chunk, ct).ConfigureAwait(false);
        if (toWrite.Count > 0) await _wal.WaitAsync(_conn.SampleTable, ct).ConfigureAwait(false);
        return outcome;
    }

    /// <summary>The live (present, not deleted) rows near the given times, keyed by stored ticks: one range query per cluster (I-2).</summary>
    private async Task<Dictionary<long, LiveRow>> ReadLiveAsync(string tag, IReadOnlyList<DateTime> times, CancellationToken ct)
    {
        var live = new Dictionary<long, LiveRow>();
        await using var conn = await _conn.OpenAsync(ct).ConfigureAwait(false);
        foreach (var (lo, hi) in QuestDbTimeClusters.Cluster(times, QuestDbTimeClusters.ExistenceGap))
        {
            await using var cmd = _conn.CreateCommand(conn,
                $"SELECT {LiveColumns} FROM {_conn.SampleTable} WHERE tag = $1 AND ts >= $2 AND ts <= $3 AND NOT deleted");
            QuestDbConnection.BindText(cmd, tag);
            QuestDbConnection.BindTimestamp(cmd, lo);
            QuestDbConnection.BindTimestamp(cmd, hi);
            await using var rd = await cmd.ExecuteReaderAsync(ct).ConfigureAwait(false);
            while (await rd.ReadAsync(ct).ConfigureAwait(false))
            {
                var row = ReadLiveRow(rd);
                live[row.TimeUtc.Ticks] = row;
                Interlocked.Increment(ref _liveRowsRead);
            }
        }
        return live;
    }

    /// <summary>The columns of a live sample the trail needs (prior value + status + server time).</summary>
    private const string LiveColumns = "ts, kind, num_value, int_value, str_value, status, server_ts";

    /// <summary>A live sample as it was before a modification.</summary>
    private readonly record struct LiveRow(DateTime TimeUtc, HistorianValue Value, uint Status, DateTime? ServerTimeUtc);

    private static LiveRow ReadLiveRow(NpgsqlDataReader rd)
    {
        var value = QuestDbHistorianDataSource.ToValue(
            QuestDbConnection.ReadKind(rd, 1),
            rd.IsDBNull(2) ? null : rd.GetDouble(2),
            rd.IsDBNull(3) ? null : rd.GetInt64(3),
            rd.IsDBNull(4) ? null : rd.GetString(4));
        var status = rd.IsDBNull(5) ? HistorianStatusCodes.BadNoData : SampleColumnMapper.FromLongStatus(rd.GetInt64(5));
        return new LiveRow(QuestDbConnection.ReadUtc(rd, 0), value, status,
            rd.IsDBNull(6) ? null : QuestDbConnection.ReadUtc(rd, 6));
    }

    /// <summary>The Part 11 modification type recorded for an update mode.</summary>
    private static HistoryModificationType ToModificationType(HistoryUpdateMode mode) => mode switch
    {
        HistoryUpdateMode.Insert => HistoryModificationType.Insert,
        HistoryUpdateMode.Replace => HistoryModificationType.Replace,
        _ => HistoryModificationType.Update,
    };

    /// <summary>
    ///     A process-wide, strictly increasing modification id (≈ UTC ticks, bumped past the last issued value). It orders a
    ///     tag's trail within one source time; ids from two nodes interleave by wall clock, which is the modification order.
    /// </summary>
    internal static long NextModifiedId()
    {
        while (true)
        {
            var last = Interlocked.Read(ref _lastModifiedId);
            var next = Math.Max(DateTime.UtcNow.Ticks, last + 1);
            if (Interlocked.CompareExchange(ref _lastModifiedId, next, last) == last) return next;
        }
    }

    /// <summary>
    ///     Appends one modification-trail row per entry (<c>prior = null</c> ⇒ an insert: kind Empty, NULL value and
    ///     status), then waits for the trail's WAL visibility so a modified read right after the update sees it.
    /// </summary>
    private async Task WriteTrailAsync(string tag, HistoryModificationType type, IReadOnlyList<(DateTime TimeUtc, LiveRow? Prior)> entries,
        HistoryUpdateContext context, CancellationToken ct)
    {
        if (entries.Count == 0) return;
        var now = DateTime.UtcNow;
        foreach (var chunk in entries.Chunk(BatchSize))
        {
            await using var conn = await _conn.OpenAsync(ct).ConfigureAwait(false);
            await using var cmd = _conn.CreateCommand(conn, "");
            var sb = new System.Text.StringBuilder(
                $"INSERT INTO {_conn.SampleModifiedTable} (ts, tag, modified_id, modification_ts, update_type, principal, " +
                "api_key_id, kind, num_value, int_value, str_value, status, server_ts) VALUES ");
            for (var i = 0; i < chunk.Length; i++)
            {
                var (time, prior) = chunk[i];
                QuestDbConnection.BindTimestamp(cmd, time, clampToEpoch: true);
                QuestDbConnection.BindText(cmd, tag);
                QuestDbConnection.BindLong(cmd, NextModifiedId());
                QuestDbConnection.BindTimestamp(cmd, now);
                QuestDbConnection.BindByte(cmd, (byte)type);
                QuestDbConnection.BindText(cmd, context.StoredPrincipal);
                QuestDbConnection.BindText(cmd, context.StoredApiKeyId);
                if (prior is { } p)
                {
                    var c = SampleColumnMapper.ToColumns(p.Value);
                    QuestDbConnection.BindByte(cmd, c.ValueKind);
                    Typed(cmd, NpgsqlDbType.Double, c.NumValue);
                    Typed(cmd, NpgsqlDbType.Bigint, c.IntValue);
                    Typed(cmd, NpgsqlDbType.Varchar, c.StrValue);
                    QuestDbConnection.BindLong(cmd, SampleColumnMapper.ToLongStatus(p.Status));
                    Typed(cmd, NpgsqlDbType.TimestampTz, p.ServerTimeUtc);
                }
                else
                {
                    // No prior value: QuestDB BYTE has no NULL, so kind is Empty (0) and the NULL status marks "none".
                    QuestDbConnection.BindByte(cmd, (byte)HistorianValueKind.Empty);
                    Typed(cmd, NpgsqlDbType.Double, null);
                    Typed(cmd, NpgsqlDbType.Bigint, null);
                    Typed(cmd, NpgsqlDbType.Varchar, null);
                    Typed(cmd, NpgsqlDbType.Bigint, null);
                    Typed(cmd, NpgsqlDbType.TimestampTz, null);
                }

                var b = i * 13;
                if (i > 0) sb.Append(',');
                sb.Append('(');
                for (var q = 1; q <= 13; q++) sb.Append(q > 1 ? "," : "").Append('$').Append(b + q);
                sb.Append(')');
            }
            cmd.CommandText = sb.ToString();
            try
            {
                await cmd.ExecuteNonQueryAsync(ct).ConfigureAwait(false);
            }
            catch (Exception ex) when (ex is not OperationCanceledException)
            {
                _log.LogWarning(ex, "QuestDB modification-trail INSERT of {Count} rows into {Table} failed; the update was not applied.",
                    chunk.Length, _conn.SampleModifiedTable);
                throw;
            }
        }
        await _wal.WaitAsync(_conn.SampleModifiedTable, ct).ConfigureAwait(false);
    }

    private Task WriteRowsAsync(string tag, IReadOnlyList<HistorianSampleRow> rows, CancellationToken ct) =>
        InsertAsync(rows.Count, ct, (cmd, i) =>
        {
            var row = rows[i];
            var c = SampleColumnMapper.ToColumns(row.Value);
            QuestDbConnection.BindTimestamp(cmd, row.TimeUtc, clampToEpoch: true);
            QuestDbConnection.BindText(cmd, tag);
            QuestDbConnection.BindByte(cmd, c.ValueKind);
            Typed(cmd, NpgsqlDbType.Double, c.NumValue);
            Typed(cmd, NpgsqlDbType.Bigint, c.IntValue);
            Typed(cmd, NpgsqlDbType.Varchar, c.StrValue);
            QuestDbConnection.BindLong(cmd, SampleColumnMapper.ToLongStatus(row.StatusCode));
            Typed(cmd, NpgsqlDbType.Boolean, false);
        });

    private Task WriteTombstonesAsync(string tag, IReadOnlyList<DateTime> times, CancellationToken ct) =>
        InsertAsync(times.Count, ct, (cmd, i) =>
        {
            QuestDbConnection.BindTimestamp(cmd, times[i], clampToEpoch: true);
            QuestDbConnection.BindText(cmd, tag);
            QuestDbConnection.BindByte(cmd, (byte)HistorianValueKind.Empty);
            Typed(cmd, NpgsqlDbType.Double, null);
            Typed(cmd, NpgsqlDbType.Bigint, null);
            Typed(cmd, NpgsqlDbType.Varchar, null);
            QuestDbConnection.BindLong(cmd, SampleColumnMapper.ToLongStatus(HistorianStatusCodes.BadNoData));
            Typed(cmd, NpgsqlDbType.Boolean, true);
        });

    /// <summary>Multi-row INSERT; <paramref name="bindRow"/> adds the first eight parameters of a row, this adds server_ts.</summary>
    private async Task InsertAsync(int count, CancellationToken ct, Action<NpgsqlCommand, int> bindRow)
    {
        if (count == 0) return;
        await using var conn = await _conn.OpenAsync(ct).ConfigureAwait(false);
        await using var cmd = _conn.CreateCommand(conn, "");
        var now = DateTime.UtcNow;
        var sb = new System.Text.StringBuilder(
            $"INSERT INTO {_conn.SampleTable} (ts, tag, kind, num_value, int_value, str_value, status, deleted, server_ts) VALUES ");
        for (var i = 0; i < count; i++)
        {
            bindRow(cmd, i);
            QuestDbConnection.BindTimestamp(cmd, now);
            var b = i * 9;
            if (i > 0) sb.Append(',');
            sb.Append('(');
            for (var p = 1; p <= 9; p++) sb.Append(p > 1 ? "," : "").Append('$').Append(b + p);
            sb.Append(')');
        }
        cmd.CommandText = sb.ToString();
        try
        {
            await cmd.ExecuteNonQueryAsync(ct).ConfigureAwait(false);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            _log.LogWarning(ex, "QuestDB HistoryUpdate INSERT of {Count} rows into {Table} failed.", count, _conn.SampleTable);
            throw;
        }
    }

    private static void Typed(NpgsqlCommand cmd, NpgsqlDbType type, object? value) =>
        cmd.Parameters.Add(new NpgsqlParameter { NpgsqlDbType = type, Value = value ?? DBNull.Value });
}