-- 034_trade_in_estimates_geom.sql
-- Purpose: schema-consistency debt — add PostGIS geom column + GIST index + trigger
--          to trade_in_estimates (table currently has lat/lon but no geom).
-- Dependencies: 001_trade_in_estimates.sql (table must exist)
-- Deploy order: any time after 001.
--
-- Why: rule `.claude/rules/sql.md` — any table with lat/lon should have geom + GIST
--      for future spatial queries. Currently estimator does not query trade_in_estimates
--      spatially, but views/audits will. Trigger keeps geom in sync with lat/lon writes.
--
-- Idempotent: ADD COLUMN/INDEX IF NOT EXISTS; CREATE OR REPLACE FUNCTION; DROP+CREATE TRIGGER.

BEGIN;

ALTER TABLE trade_in_estimates
  ADD COLUMN IF NOT EXISTS geom geometry(Point, 4326);

-- Backfill from existing lat/lon (idempotent — only rows where geom is currently NULL).
UPDATE trade_in_estimates
SET geom = ST_SetSRID(ST_MakePoint(lon, lat), 4326)
WHERE geom IS NULL
  AND lat IS NOT NULL
  AND lon IS NOT NULL;

CREATE INDEX IF NOT EXISTS trade_in_estimates_geom_idx
  ON trade_in_estimates USING GIST (geom);

CREATE OR REPLACE FUNCTION trade_in_estimates_set_geom()
RETURNS trigger AS $$
BEGIN
  IF NEW.lat IS NOT NULL AND NEW.lon IS NOT NULL THEN
    NEW.geom := ST_SetSRID(ST_MakePoint(NEW.lon, NEW.lat), 4326);
  ELSE
    NEW.geom := NULL;
  END IF;
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

DROP TRIGGER IF EXISTS trade_in_estimates_set_geom_trg ON trade_in_estimates;
CREATE TRIGGER trade_in_estimates_set_geom_trg
  BEFORE INSERT OR UPDATE OF lat, lon ON trade_in_estimates
  FOR EACH ROW EXECUTE FUNCTION trade_in_estimates_set_geom();

COMMIT;