-- 08_fix_etl_vehicle_key.sql
-- Fixes two distinct bugs in dwh_gold.refresh_daily_metrics():
--
-- BUG-01a (type crash): the original function inserted t.imei (TEXT) into
-- fact_daily_fleet_metrics.vehicle_key (INTEGER REFERENCES dim_vehicles),
-- so every nightly call raised "invalid input syntax for type integer".
--
-- BUG-01b (cartesian explosion): the original function joined
-- trips × alarms in a single SELECT. For every trip row it produced one
-- output row per matching alarm, multiplying every SUM/COUNT over trip
-- columns by the per-IMEI alarm count. Spot-checking the broken output
-- showed total_trips identical to alarm_count and drive_hours > 1000/day.
--
-- The fix has three parts:
--   1. Seed dwh_gold.dim_vehicles from tracksolid.devices so every IMEI
--      has a serial vehicle_key to point at.
--   2. Rewrite refresh_daily_metrics() so trip aggregates and alarm
--      aggregates are computed in separate CTEs and then joined on imei.
--   3. Map IMEI → vehicle_key via dim_vehicles inside the same statement.

BEGIN;

-- ── 1. Backfill dim_vehicles ─────────────────────────────────────────────────
-- One row per device. is_active mirrors enabled_flag; vehicle_number tracks
-- the plate so dashboards can label charts without joining back to devices.
INSERT INTO dwh_gold.dim_vehicles (imei, vehicle_number, is_active)
SELECT
  d.imei,
  d.vehicle_number,
  COALESCE(d.enabled_flag, 1) = 1
FROM tracksolid.devices d
ON CONFLICT (imei) DO UPDATE SET
  vehicle_number = EXCLUDED.vehicle_number,
  is_active      = EXCLUDED.is_active;

-- ── 2. Rewrite ETL function ──────────────────────────────────────────────────
CREATE OR REPLACE FUNCTION dwh_gold.refresh_daily_metrics(target_date DATE)
RETURNS void LANGUAGE plpgsql AS $$
BEGIN
  -- Sync dim_vehicles first so any IMEI seen in trips has a vehicle_key.
  -- Without this, a brand-new device would have trip rows but no
  -- dim_vehicles entry, and the JOIN below would drop its metrics.
  INSERT INTO dwh_gold.dim_vehicles (imei, vehicle_number, is_active)
  SELECT
    d.imei,
    d.vehicle_number,
    COALESCE(d.enabled_flag, 1) = 1
  FROM tracksolid.devices d
  ON CONFLICT (imei) DO UPDATE SET
    vehicle_number = EXCLUDED.vehicle_number,
    is_active      = EXCLUDED.is_active;

  -- Aggregate trips and alarms in separate CTEs to avoid the cartesian
  -- multiplication that the original single-SELECT version produced.
  WITH trip_agg AS (
    SELECT
      t.imei,
      SUM(t.distance_km)                                       AS total_distance_km,
      COUNT(*)                                                 AS total_trips,
      SUM(t.driving_time_s)                                    AS total_drive_seconds,
      SUM(t.idle_time_s)                                       AS total_idle_seconds,
      SUM(t.fuel_consumed_l)                                   AS fuel_consumed_l,
      MIN(t.start_time AT TIME ZONE 'Africa/Nairobi')::TIME    AS day_start_time,
      MAX(t.end_time   AT TIME ZONE 'Africa/Nairobi')::TIME    AS day_end_time,
      AVG(t.avg_speed_kmh)                                     AS avg_speed_kmh,
      MAX(t.max_speed_kmh)                                     AS peak_speed_kmh
    FROM tracksolid.trips t
    WHERE DATE(t.start_time AT TIME ZONE 'Africa/Nairobi') = target_date
      AND t.end_time IS NOT NULL
    GROUP BY t.imei
  ),
  alarm_agg AS (
    SELECT
      a.imei,
      COUNT(*)                                                AS alarm_count,
      COUNT(*) FILTER (WHERE a.alarm_type ILIKE '%speed%')    AS overspeed_count
    FROM tracksolid.alarms a
    WHERE DATE(a.alarm_time AT TIME ZONE 'Africa/Nairobi') = target_date
    GROUP BY a.imei
  )
  INSERT INTO dwh_gold.fact_daily_fleet_metrics (
    day,
    vehicle_key,
    total_distance_km,
    total_trips,
    total_drive_hours,
    total_idle_hours,
    fuel_consumed_l,
    alarm_count,
    overspeed_count,
    day_start_time,
    day_end_time,
    avg_speed_kmh,
    peak_speed_kmh
  )
  SELECT
    target_date                                                 AS day,
    dv.vehicle_key                                              AS vehicle_key,
    ROUND(tr.total_distance_km::numeric, 3)                     AS total_distance_km,
    tr.total_trips                                              AS total_trips,
    ROUND((tr.total_drive_seconds / 3600.0)::numeric, 2)        AS total_drive_hours,
    ROUND((tr.total_idle_seconds  / 3600.0)::numeric, 2)        AS total_idle_hours,
    ROUND(tr.fuel_consumed_l::numeric, 3)                       AS fuel_consumed_l,
    COALESCE(al.alarm_count, 0)                                 AS alarm_count,
    COALESCE(al.overspeed_count, 0)                             AS overspeed_count,
    tr.day_start_time                                           AS day_start_time,
    tr.day_end_time                                             AS day_end_time,
    ROUND(tr.avg_speed_kmh::numeric, 2)                         AS avg_speed_kmh,
    tr.peak_speed_kmh                                           AS peak_speed_kmh
  FROM trip_agg tr
  JOIN dwh_gold.dim_vehicles dv ON dv.imei = tr.imei
  LEFT JOIN alarm_agg al       ON al.imei = tr.imei
  ON CONFLICT (day, vehicle_key) DO UPDATE SET
    total_distance_km = EXCLUDED.total_distance_km,
    total_trips       = EXCLUDED.total_trips,
    total_drive_hours = EXCLUDED.total_drive_hours,
    total_idle_hours  = EXCLUDED.total_idle_hours,
    fuel_consumed_l   = EXCLUDED.fuel_consumed_l,
    alarm_count       = EXCLUDED.alarm_count,
    overspeed_count   = EXCLUDED.overspeed_count,
    day_start_time    = EXCLUDED.day_start_time,
    day_end_time      = EXCLUDED.day_end_time,
    avg_speed_kmh     = EXCLUDED.avg_speed_kmh,
    peak_speed_kmh    = EXCLUDED.peak_speed_kmh;
END;
$$;

COMMENT ON FUNCTION dwh_gold.refresh_daily_metrics(DATE)
  IS 'Populates or refreshes fact_daily_fleet_metrics for the given date. '
     'Trips and alarms are aggregated in separate CTEs to avoid cartesian '
     'multiplication. Maps IMEI → vehicle_key via dwh_gold.dim_vehicles. '
     'Call nightly: SELECT dwh_gold.refresh_daily_metrics(CURRENT_DATE - 1);';

COMMIT;