-- Migration: repair foreign key between horaires_gares_desservies.horaire_id and horaires.id
-- This script will:
-- 1) check the column types of horaires.id and horaires_gares_desservies.horaire_id
-- 2) if types match and FK doesn't exist, create the FK constraint
-- 3) otherwise, print a NOTICE explaining the mismatch for manual resolution

DO $$
DECLARE
  t_horaire TEXT;
  t_horaire_fk TEXT;
  cnt INT;
BEGIN
  -- ensure target tables exist
  IF NOT EXISTS (SELECT 1 FROM pg_class WHERE relname = 'horaires' AND relkind = 'r') THEN
    RAISE NOTICE 'Table public.horaires does not exist in this database/schema.';
    RETURN;
  END IF;
  IF NOT EXISTS (SELECT 1 FROM pg_class WHERE relname = 'horaires_gares_desservies' AND relkind = 'r') THEN
    RAISE NOTICE 'Table public.horaires_gares_desservies does not exist in this database/schema.';
    RETURN;
  END IF;

  -- get formatted types
  SELECT pg_catalog.format_type(a.atttypid, a.atttypmod)
    INTO t_horaire
    FROM pg_attribute a
    WHERE a.attrelid = 'public.horaires'::regclass AND a.attname = 'id';

  SELECT pg_catalog.format_type(a.atttypid, a.atttypmod)
    INTO t_horaire_fk
    FROM pg_attribute a
    WHERE a.attrelid = 'public.horaires_gares_desservies'::regclass AND a.attname = 'horaire_id';

  RAISE NOTICE 'Detected types -> horaires.id: %, horaires_gares_desservies.horaire_id: %', t_horaire, t_horaire_fk;

  -- check existing FK from horaires_gares_desservies to horaires
  SELECT count(*) INTO cnt
    FROM pg_constraint c
    WHERE c.conrelid = 'public.horaires_gares_desservies'::regclass
      AND c.confrelid = 'public.horaires'::regclass
      AND c.contype = 'f';

  IF cnt > 0 THEN
    RAISE NOTICE 'A foreign-key constraint from horaires_gares_desservies to horaires already exists (count=%). No action taken.', cnt;
    RETURN;
  END IF;

  -- If types match, create the FK
  IF t_horaire IS NOT NULL AND t_horaire_fk IS NOT NULL AND t_horaire = t_horaire_fk THEN
    EXECUTE 'ALTER TABLE public.horaires_gares_desservies
             ADD CONSTRAINT fk_horaires_gares_horaire_id
             FOREIGN KEY (horaire_id)
             REFERENCES public.horaires(id)
             ON DELETE CASCADE';
    RAISE NOTICE 'Foreign key constraint fk_horaires_gares_horaire_id created successfully.';
  ELSE
    RAISE NOTICE 'Column types do not match or could not be determined. Manual intervention required.';
    RAISE NOTICE 'Detected types -> horaires.id: %, horaires_gares_desservies.horaire_id: %', t_horaire, t_horaire_fk;
    RAISE NOTICE 'If both should be UUID, consider converting [or recreating] the columns and then re-run this script.';
    RAISE NOTICE 'If both should be BIGINT, consider altering types to bigint. Do not run automatic conversion without backup.';
  END IF;
END $$;