using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

namespace MeterVault.Infrastructure.Persistence.Migrations
{
    /// <inheritdoc />
    public partial class BindUnboundMqttSourcesToSoleBroker : Migration
    {
        /// <inheritdoc />
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            // MQTT routing now honours meter_source.endpoint_id (SDD §6.1): a source is served only
            // by the broker it is bound to. Previously an unbound source was subscribed on every
            // broker and matched on topic alone, so unbound sources that work today would silently
            // go quiet after this deploy.
            //
            // Backfill them onto the single broker only when exactly one exists — then the old
            // "any broker" behaviour and the new "its broker" behaviour are the same thing, so the
            // rewrite is provably lossless. With zero brokers there is nothing to bind to; with two
            // or more the old behaviour was already ambiguous and a guess could route a meter's
            // data to the wrong broker, so those are left for the operator to resolve in the UI.
            //
            // Enums persist as their C# names (HasConversion<string>), hence 'Mqtt'/'MqttBroker'.
            // HomeAssistant sources are deliberately excluded: the HA workers have always required
            // endpoint_id, so an unbound HA source is already inert and binding it here would
            // activate ingestion the operator never had running.
            migrationBuilder.Sql("""
                UPDATE meter_source AS s
                SET endpoint_id = sole.id
                FROM (SELECT id FROM ingestion_endpoint WHERE type = 'MqttBroker') AS sole
                WHERE s.endpoint_id IS NULL
                  AND s.source_type IN ('Mqtt', 'Tasmota')
                  AND (SELECT count(*) FROM ingestion_endpoint WHERE type = 'MqttBroker') = 1;
                """);
        }

        /// <inheritdoc />
        protected override void Down(MigrationBuilder migrationBuilder)
        {
            // Intentionally empty. The rows this bound are indistinguishable from ones the operator
            // bound by hand, so clearing endpoint_id on the way down would discard real
            // configuration. Leaving the binding in place is harmless under the old routing, which
            // ignored endpoint_id entirely.
        }
    }
}