lmxopcua/src/Core/ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian/AlarmConditionStateSchema.cs

using System.Globalization;
using System.Text.Json;
using Microsoft.Data.Sqlite;

namespace ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;

/// <summary>
///     DDL for the Part 9 scripted-alarm condition state: one fixed-size row per alarm identity
///     holding the operator-supplied state (Enabled / Acked / Confirmed / Shelving) plus the
///     ack/confirm audit fields, and a separate append-only table holding each alarm's comment trail.
/// </summary>
/// <remarks>
///     <para>
///         Replaces the central config DB's <c>ScriptedAlarmState</c> table as the node-local home
///         for this state (per-cluster mesh Phase 4, which cuts the ConfigDb from driver-only
///         nodes). Living in the consolidated LocalDb file is what lets the state replicate to the
///         redundant pair peer, exactly like the alarm store-and-forward buffer — see
///         <see cref="AlarmSfSchema"/>, which this mirrors.
///     </para>
///     <para>
///         Deliberately depends on nothing but <see cref="SqliteConnection"/> so it can be applied
///         to any connection — the host's <c>LocalDbSetup.OnReady</c> in production, and a bare
///         connection in a test — without dragging the DI graph along.
///     </para>
///     <para>
///         <b>The primary key is the alarm identity, and Save is an unconditional upsert onto it.</b>
///         Convergence across the pair is last-writer-wins over the primary key, handled by the
///         LocalDb replication HLC — so the store stacks no application-level last-write-wins on top,
///         the same discipline the alarm-sf sink and the deployment pointer follow.
///     </para>
///     <para>
///         <b>ActiveState has no column</b> — it is re-derived from the live predicate on startup,
///         so persisting it would only risk operators seeing a stale Active on restart. Likewise
///         <c>LastActiveUtc</c> / <c>LastClearedUtc</c> re-derive alongside it and get no columns.
///         <c>LastTransitionUtc</c> is carried by <c>updated_at_utc</c> — the row-write timestamp is
///         the last transition. Timestamps are round-trip ("O") TEXT so lexicographic order is
///         chronological; nullable timestamps and audit fields are stored as NULL.
///     </para>
///     <para>
///         <b>The comment trail is NOT on the condition row.</b> It used to be serialized whole into
///         <c>comments_json</c>, so every transition rewrote — and replicated — the alarm's entire
///         history: O(n) per transition, O(n²) over the alarm's life (review R05:4). It now lives in
///         <see cref="CommentsTable"/>, one row per entry keyed by <c>(scripted_alarm_id, seq)</c>,
///         where <c>seq</c> is the entry's ordinal in the alarm's trail. A transition inserts only the
///         entries it appended, so the condition row stays a fixed size and a transition's write is
///         O(1) however long the history is. <c>comments_json</c> is kept, always written as
///         <c>"[]"</c>, so the condition table's shape — and with it the pair's replication digest
///         for that table — does not change and an old-shape row stays readable;
///         <see cref="MigrateInlineComments"/> moves any inline trail across.
///     </para>
///     <para>
///         <b>Why the ordinal, and not a content hash, is the key.</b> Both halves of a redundant pair
///         run the engine and both apply every operator command, each stamping the entry with its own
///         clock. A content-derived id would keep TWO rows for every logical entry once the pair
///         converged. Keyed by ordinal, the two nodes' copies of entry <i>n</i> share one primary key
///         and LWW collapses them to one row — the convergence the whole-row LWW gave before, now per
///         entry. Entries go in with <c>INSERT OR IGNORE</c> (<see cref="InsertCommentSql"/>), so an
///         entry already held — written locally, or arrived from the peer — is never rewritten.
///     </para>
/// </remarks>
public static class AlarmConditionStateSchema
{
    /// <summary>Table holding one condition-state row per scripted-alarm identity.</summary>
    public const string StateTable = "alarm_condition_state";

    /// <summary>Append-only table holding one row per comment-trail entry, keyed by alarm id + ordinal.</summary>
    public const string CommentsTable = "alarm_condition_comment";

    /// <summary>What <c>comments_json</c> holds once the trail lives in <see cref="CommentsTable"/>.</summary>
    public const string EmptyInlineComments = "[]";

    /// <summary>
    ///     The one append statement for <see cref="CommentsTable"/>, shared by the migration and the
    ///     store. <c>OR IGNORE</c> is what makes the trail append-only: an ordinal already held is
    ///     never rewritten. Parameters: <c>@Id @Seq @Ts @User @Kind @Text</c>.
    /// </summary>
    public const string InsertCommentSql =
        """
        INSERT OR IGNORE INTO alarm_condition_comment
            (scripted_alarm_id, seq, timestamp_utc, user_name, kind, text)
        VALUES (@Id, @Seq, @Ts, @User, @Kind, @Text)
        """;

    private static readonly JsonSerializerOptions InlineJsonOptions = new(JsonSerializerDefaults.Web);

    /// <summary>
    ///     Creates the state table and the comment table if they do not already exist. Idempotent.
    /// </summary>
    /// <param name="connection">
    ///     An already-open connection. <c>ILocalDb.CreateConnection()</c> hands out open,
    ///     pragma-configured connections — do not call <c>Open()</c> on one.
    /// </param>
    public static void Apply(SqliteConnection connection)
    {
        ArgumentNullException.ThrowIfNull(connection);

        using var cmd = connection.CreateCommand();

        // The four *_state columns are always written to a mapped, non-null string (Enabled/Disabled,
        // Acknowledged/Unacknowledged, Confirmed/Unconfirmed, Unshelved/OneShotShelved/TimedShelved),
        // so they are NOT NULL. comments_json is never null either — it is the literal "[]" since the
        // trail moved to alarm_condition_comment (an old-shape row may still carry an inline trail
        // until MigrateInlineComments or the next save moves it). The audit user/comment/utc columns
        // and shelving_expires_utc are NULL when the alarm has no such history yet. updated_at_utc
        // carries LastTransitionUtc (there is no dedicated transition column).
        cmd.CommandText = """
            CREATE TABLE IF NOT EXISTS alarm_condition_state (
                scripted_alarm_id    TEXT NOT NULL PRIMARY KEY,
                enabled_state        TEXT NOT NULL,
                acked_state          TEXT NOT NULL,
                confirmed_state      TEXT NOT NULL,
                shelving_state       TEXT NOT NULL,
                shelving_expires_utc TEXT NULL,
                last_ack_user        TEXT NULL,
                last_ack_comment     TEXT NULL,
                last_ack_utc         TEXT NULL,
                last_confirm_user    TEXT NULL,
                last_confirm_comment TEXT NULL,
                last_confirm_utc     TEXT NULL,
                comments_json        TEXT NOT NULL,
                updated_at_utc       TEXT NOT NULL
            );

            CREATE TABLE IF NOT EXISTS alarm_condition_comment (
                scripted_alarm_id TEXT    NOT NULL,
                seq               INTEGER NOT NULL,
                timestamp_utc     TEXT    NOT NULL,
                user_name         TEXT    NOT NULL,
                kind              TEXT    NOT NULL,
                text              TEXT    NOT NULL,
                PRIMARY KEY (scripted_alarm_id, seq)
            );
            """;
        cmd.ExecuteNonQuery();
    }

    /// <summary>
    ///     Moves every condition row's inline <c>comments_json</c> trail into
    ///     <see cref="CommentsTable"/> and resets the column to <c>"[]"</c>. Idempotent.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         <b>Run it AFTER the tables are registered for replication</b> — it writes rows, and a
    ///         row written before the capture triggers exist never reaches the peer (the same
    ///         DDL → register → writes rule <c>AlarmSfLegacyMigrator</c> follows).
    ///     </para>
    ///     <para>
    ///         Each entry lands at its ordinal in the inline array via <see cref="InsertCommentSql"/>,
    ///         so a re-run — or a row whose trail was already (partly) moved — neither duplicates nor
    ///         reorders anything, and a second run finds no non-empty inline column and writes
    ///         nothing. Each row moves in its own transaction together with its column reset, so a
    ///         crash leaves every row either fully moved or untouched. A row whose inline JSON does
    ///         not parse is left exactly as it is (the pre-split store could not load it either)
    ///         rather than failing host start.
    ///     </para>
    /// </remarks>
    /// <param name="connection">An already-open connection from <c>ILocalDb.CreateConnection()</c>.</param>
    /// <returns>The number of condition rows whose inline trail was moved.</returns>
    public static int MigrateInlineComments(SqliteConnection connection)
    {
        ArgumentNullException.ThrowIfNull(connection);

        var pending = new List<(string AlarmId, string Json)>();
        using (var select = connection.CreateCommand())
        {
            select.CommandText =
                "SELECT scripted_alarm_id, comments_json FROM alarm_condition_state WHERE comments_json <> @Empty";
            select.Parameters.AddWithValue("@Empty", EmptyInlineComments);
            using var reader = select.ExecuteReader();
            while (reader.Read())
                pending.Add((reader.GetString(0), reader.GetString(1)));
        }

        var migrated = 0;
        foreach (var (alarmId, json) in pending)
        {
            IReadOnlyList<InlineComment> entries;
            try
            {
                entries = ParseInlineComments(json);
            }
            catch (JsonException)
            {
                continue;
            }

            using var tx = connection.BeginTransaction();
            for (var seq = 0; seq < entries.Count; seq++)
            {
                using var insert = connection.CreateCommand();
                insert.Transaction = tx;
                insert.CommandText = InsertCommentSql;
                insert.Parameters.AddWithValue("@Id", alarmId);
                insert.Parameters.AddWithValue("@Seq", seq);
                insert.Parameters.AddWithValue("@Ts", FormatTimestamp(entries[seq].TimestampUtc));
                insert.Parameters.AddWithValue("@User", entries[seq].User);
                insert.Parameters.AddWithValue("@Kind", entries[seq].Kind);
                insert.Parameters.AddWithValue("@Text", entries[seq].Text);
                insert.ExecuteNonQuery();
            }

            using (var clear = connection.CreateCommand())
            {
                clear.Transaction = tx;
                clear.CommandText =
                    "UPDATE alarm_condition_state SET comments_json = @Empty WHERE scripted_alarm_id = @Id";
                clear.Parameters.AddWithValue("@Empty", EmptyInlineComments);
                clear.Parameters.AddWithValue("@Id", alarmId);
                clear.ExecuteNonQuery();
            }

            tx.Commit();
            migrated++;
        }

        return migrated;
    }

    /// <summary>Formats a comment timestamp for <see cref="CommentsTable"/> (round-trip "O" text).</summary>
    /// <param name="value">The timestamp.</param>
    /// <returns>The round-trip text form.</returns>
    public static string FormatTimestamp(DateTime value) => value.ToString("O", CultureInfo.InvariantCulture);

    /// <summary>Parses a <see cref="CommentsTable"/> timestamp, preserving its <see cref="DateTimeKind"/>.</summary>
    /// <param name="value">The round-trip text form.</param>
    /// <returns>The timestamp.</returns>
    public static DateTime ParseTimestamp(string value) =>
        DateTime.Parse(value, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind);

    /// <summary>
    ///     Parses a legacy inline <c>comments_json</c> trail exactly as the pre-split store did
    ///     (<see cref="JsonSerializerDefaults.Web"/>; null strings become empty).
    /// </summary>
    /// <param name="json">The column value.</param>
    /// <returns>The entries in trail order; empty for a blank or <c>"[]"</c> column.</returns>
    /// <exception cref="JsonException">The column is not a valid trail.</exception>
    public static IReadOnlyList<InlineComment> ParseInlineComments(string? json)
    {
        if (string.IsNullOrWhiteSpace(json)) return [];
        var dtos = JsonSerializer.Deserialize<List<InlineCommentDto>>(json, InlineJsonOptions);
        if (dtos is null || dtos.Count == 0) return [];
        return dtos
            .Select(d => new InlineComment(
                d.TimestampUtc, d.User ?? string.Empty, d.Kind ?? string.Empty, d.Text ?? string.Empty))
            .ToList();
    }

    /// <summary>One comment-trail entry as stored — the persistence-side mirror of the engine's <c>AlarmComment</c>.</summary>
    /// <param name="TimestampUtc">When the action happened.</param>
    /// <param name="User">Identity of the actor.</param>
    /// <param name="Kind">Classification (Acknowledge, Confirm, AddComment, …).</param>
    /// <param name="Text">Operator-supplied or engine-generated text.</param>
    public sealed record InlineComment(DateTime TimestampUtc, string User, string Kind, string Text);

    /// <summary>The pre-split on-disk shape of one entry in <c>comments_json</c>.</summary>
    private sealed class InlineCommentDto
    {
        /// <summary>When the comment was recorded.</summary>
        public DateTime TimestampUtc { get; set; }

        /// <summary>Identity of the actor.</summary>
        public string? User { get; set; }

        /// <summary>Classification of the entry.</summary>
        public string? Kind { get; set; }

        /// <summary>Entry text.</summary>
        public string? Text { get; set; }
    }
}