CREATE OR REPLACE FUNCTION ems.fn_fill_forecast_accuracy(
    p_site_id INT,
    p_lookback_hours INT DEFAULT 48
)
RETURNS INT
LANGUAGE plpgsql
AS $$
DECLARE
    v_count INT := 0;
BEGIN
    INSERT INTO ems.forecast_accuracy (
        site_id, pv_array_id, interval_start, run_id,
        forecast_power_w, forecast_created_at, lead_time_hours,
        actual_power_w, actual_filled_at,
        error_w, error_pct
    )
    SELECT
        fpr.site_id,
        fpr.pv_array_id,
        fpi.interval_start,
        fpi.run_id,
        fpi.power_w                                          AS forecast_power_w,
        fpr.created_at                                       AS forecast_created_at,
        ROUND(
            EXTRACT(EPOCH FROM (fpi.interval_start - fpr.created_at))
            / 3600.0, 2
        )                                                    AS lead_time_hours,
        slot.avg_actual_w::INT                               AS actual_power_w,
        now()                                                AS actual_filled_at,
        fpi.power_w - COALESCE(slot.avg_actual_w::INT, 0)    AS error_w,
        CASE
            WHEN slot.avg_actual_w IS NOT NULL
                 AND slot.avg_actual_w > 0
            THEN ROUND(
                (fpi.power_w::NUMERIC - slot.avg_actual_w::NUMERIC)
                / slot.avg_actual_w::NUMERIC * 100,
                4
            )
            ELSE NULL
        END                                                  AS error_pct
    FROM ems.forecast_pv_interval fpi
    JOIN ems.forecast_pv_run fpr ON fpr.id = fpi.run_id
    JOIN ems.asset_pv_array pa   ON pa.id  = fpr.pv_array_id
    LEFT JOIN LATERAL (
        SELECT AVG(
            CASE
                WHEN pa.controllable = false THEN ti.gen_port_power_w::NUMERIC
                ELSE (COALESCE(ti.pv1_power_w, 0) + COALESCE(ti.pv2_power_w, 0))::NUMERIC
            END
        ) AS avg_actual_w
        FROM ems.telemetry_inverter ti
        WHERE ti.site_id = fpr.site_id
          AND ti.measured_at >= fpi.interval_start
          AND ti.measured_at < fpi.interval_start + INTERVAL '15 minutes'
    ) slot ON true
    WHERE fpr.site_id = p_site_id
      AND fpr.status  = 'ok'
      AND fpi.interval_start < now() - INTERVAL '15 minutes'
      AND fpi.interval_start >= now() - make_interval(hours => p_lookback_hours)
    ON CONFLICT (run_id, interval_start) DO UPDATE SET
        actual_power_w   = EXCLUDED.actual_power_w,
        actual_filled_at = EXCLUDED.actual_filled_at,
        error_w          = EXCLUDED.error_w,
        error_pct        = EXCLUDED.error_pct;

    GET DIAGNOSTICS v_count = ROW_COUNT;
    RETURN v_count;
END;
$$;

COMMENT ON FUNCTION ems.fn_fill_forecast_accuracy(INT, INT) IS
'Doplní skutečné hodnoty výroby do forecast_accuracy z telemetrie.
Volat každých 15 minut (spolu s audit_filler) pro inkrementální plnění.
p_lookback_hours: kolik hodin zpět zpracovat (default 48h pro catch-up).
Pro první backfill: SELECT ems.fn_fill_forecast_accuracy(2, 8760) -- 1 rok';