using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

namespace ScadaLink.ConfigurationDatabase.Migrations
{
    /// <summary>
    /// Adds the <c>SourceNode</c> column to the centralized <c>AuditLog</c> table (#23,
    /// SourceNode-stamping). <c>SourceNode</c> identifies the cluster node that produced the
    /// audit row (e.g. <c>node-a</c>, <c>central-a</c>) — ASCII-only, so <c>varchar(64)</c>
    /// not <c>nvarchar</c>. <c>NULL</c> is valid (reconciled rows from a retired node,
    /// central direct-write rows pre-this-feature).
    ///
    /// The change is purely additive:
    /// 1. <c>SourceNode varchar(64) NULL</c> is added with no default, so the operation
    ///    is a metadata-only <c>ALTER TABLE … ADD</c> — it does NOT rewrite the
    ///    monthly-partitioned <c>AuditLog</c> table, and historical rows stay <c>NULL</c>.
    /// 2. <c>IX_AuditLog_Node_Occurred (SourceNode, OccurredAtUtc)</c> is created via raw
    ///    SQL so it lands on the <c>ps_AuditLog_Month(OccurredAtUtc)</c> partition scheme,
    ///    matching every other <c>IX_AuditLog_*</c> index. Keeping it partition-aligned
    ///    preserves the partition-switch purge path (see
    ///    AuditLogRepository.SwitchOutPartitionAsync).
    /// </summary>
    public partial class AddAuditLogSourceNode : Migration
    {
        /// <inheritdoc />
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.AddColumn<string>(
                name: "SourceNode",
                table: "AuditLog",
                type: "varchar(64)",
                unicode: false,
                maxLength: 64,
                nullable: true);

            // Raw SQL so the index is created on the partition scheme — EF's
            // CreateIndex cannot express the ON ps_AuditLog_Month(OccurredAtUtc)
            // clause. Mirrors IX_AuditLog_ParentExecution (aligned, unfiltered here:
            // NULL SourceNode is a legitimate query target, e.g. "rows produced
            // before stamping shipped" — no HasFilter on this index).
            migrationBuilder.Sql(@"
CREATE NONCLUSTERED INDEX IX_AuditLog_Node_Occurred
ON dbo.AuditLog (SourceNode, OccurredAtUtc)
ON ps_AuditLog_Month(OccurredAtUtc);");
        }

        /// <inheritdoc />
        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.Sql(@"
IF EXISTS (SELECT 1 FROM sys.indexes WHERE name = 'IX_AuditLog_Node_Occurred' AND object_id = OBJECT_ID('dbo.AuditLog'))
    DROP INDEX IX_AuditLog_Node_Occurred ON dbo.AuditLog;");

            migrationBuilder.DropColumn(
                name: "SourceNode",
                table: "AuditLog");
        }
    }
}