-- =============================================================
-- DWH OBSERVABILITY VIEWS
-- Target Database: tracksolid_dwh
-- Purpose: Surface pipeline health for Grafana dashboards. Three views,
--          one concern each:
--            v_table_freshness  — how long since each table was last loaded
--            v_recent_failures  — failed runs in the last 24h
--            v_watermark_lag    — per-table watermark vs. now
-- Applies after: 261001_dwh_control.sql
-- Readability: owned by dwh_owner → grafana_ro inherits SELECT via the
--              ALTER DEFAULT PRIVILEGES set in 261001. Explicit GRANT below
--              covers the case where defaults were set AFTER this file runs.
-- =============================================================

BEGIN;

SET ROLE dwh_owner;

-- 1. FRESHNESS
-- One row per table that has ever loaded successfully. `lag` drives the
-- freshness panel; `loads_last_24h` sanity-checks the cron cadence.
CREATE OR REPLACE VIEW dwh_control.v_table_freshness AS
SELECT
    table_name,
    MAX(run_finished_at)                                                   AS last_loaded_at,
    NOW() - MAX(run_finished_at)                                           AS lag,
    COUNT(*) FILTER (WHERE run_started_at > NOW() - INTERVAL '24 hours')   AS loads_last_24h
FROM dwh_control.extract_runs
WHERE status = 'loaded'
GROUP BY table_name;

COMMENT ON VIEW dwh_control.v_table_freshness IS
  'Per-table load lag. Alert when lag > 4h during active hours (05:00–23:00 EAT).';

-- 2. RECENT FAILURES
-- Failures retain error_message; the CSV stays in dwh/exports/ for the next
-- scheduled run to retry. Panel should show run_id so operators can grep logs.
CREATE OR REPLACE VIEW dwh_control.v_recent_failures AS
SELECT
    run_id,
    table_name,
    run_started_at,
    run_finished_at,
    csv_path,
    error_message
FROM dwh_control.extract_runs
WHERE status = 'failed'
  AND run_started_at > NOW() - INTERVAL '24 hours'
ORDER BY run_started_at DESC;

COMMENT ON VIEW dwh_control.v_recent_failures IS
  'Failed extract/load runs in the last 24h. Alert on any row.';

-- 3. WATERMARK LAG
-- Distinguishes "pipeline ran but found nothing" (load_lag small, extract_lag
-- growing) from "pipeline is stuck" (both lags growing). Snapshot tables are
-- not in extract_watermarks so they do not appear here — that is intentional.
CREATE OR REPLACE VIEW dwh_control.v_watermark_lag AS
SELECT
    table_name,
    last_extracted_at,
    last_loaded_at,
    rows_loaded_last_run,
    NOW() - last_loaded_at    AS load_lag,
    NOW() - last_extracted_at AS extract_lag
FROM dwh_control.extract_watermarks;

COMMENT ON VIEW dwh_control.v_watermark_lag IS
  'Per-table watermark position vs. now. Incremental tables only (6 rows).';

RESET ROLE;

-- Explicit grants: defensive in case ALTER DEFAULT PRIVILEGES from 261001
-- was not in effect when these views were created.
GRANT SELECT ON dwh_control.v_table_freshness TO grafana_ro;
GRANT SELECT ON dwh_control.v_recent_failures TO grafana_ro;
GRANT SELECT ON dwh_control.v_watermark_lag   TO grafana_ro;

COMMIT;