-- Migration: Enforce unique economic customer number on customers
-- Prevents ambiguous mapping during e-conomic sync

-- Normalize values before uniqueness check
UPDATE customers
SET economic_customer_number = NULL
WHERE economic_customer_number IS NOT NULL
  AND btrim(economic_customer_number) = '';

UPDATE customers
SET economic_customer_number = btrim(economic_customer_number)
WHERE economic_customer_number IS NOT NULL;

-- Abort migration if duplicates exist (must be manually resolved first)
DO $$
DECLARE
    duplicate_value TEXT;
    duplicate_count INTEGER;
BEGIN
    SELECT economic_customer_number, COUNT(*)::INTEGER
    INTO duplicate_value, duplicate_count
    FROM customers
    WHERE economic_customer_number IS NOT NULL
    GROUP BY economic_customer_number
    HAVING COUNT(*) > 1
    ORDER BY COUNT(*) DESC, economic_customer_number
    LIMIT 1;

    IF duplicate_value IS NOT NULL THEN
        RAISE EXCEPTION 'Cannot create unique index on customers.economic_customer_number. Duplicate value: % (count=%). Resolve duplicates and rerun migration.', duplicate_value, duplicate_count;
    END IF;
END $$;

-- Enforce uniqueness for non-null values
CREATE UNIQUE INDEX IF NOT EXISTS customers_economic_customer_number_unique_idx
ON customers (economic_customer_number)
WHERE economic_customer_number IS NOT NULL;

COMMENT ON INDEX customers_economic_customer_number_unique_idx IS
'Ensures e-conomic customer numbers are unique to prevent sync mismatch.';