-- Add zone fields to bms_product_country (nullable when no zone)
-- Idempotent: safe to re-run (skip if column/index already exists)
-- charset: utf8mb4

SET NAMES utf8mb4;
SET @db := DATABASE();

-- zone_id
SET @has := (
  SELECT COUNT(*) FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND COLUMN_NAME = 'zone_id'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD COLUMN zone_id BIGINT(20) DEFAULT NULL COMMENT ''prc_zone.zone_id'' AFTER country_code',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

-- zone_code
SET @has := (
  SELECT COUNT(*) FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND COLUMN_NAME = 'zone_code'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD COLUMN zone_code VARCHAR(50) DEFAULT NULL COMMENT ''zone code e.g. Z1'' AFTER zone_id',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

-- zone_name
SET @has := (
  SELECT COUNT(*) FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND COLUMN_NAME = 'zone_name'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD COLUMN zone_name VARCHAR(100) DEFAULT NULL COMMENT ''zone display name'' AFTER zone_code',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

-- indexes
SET @has := (
  SELECT COUNT(*) FROM information_schema.STATISTICS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND INDEX_NAME = 'idx_product_country_zone'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD INDEX idx_product_country_zone (zone_id)',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

SET @has := (
  SELECT COUNT(*) FROM information_schema.STATISTICS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND INDEX_NAME = 'idx_product_country_zone_code'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD INDEX idx_product_country_zone_code (country_code, zone_code)',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

-- unique key: drop old, add new
SET @has := (
  SELECT COUNT(*) FROM information_schema.STATISTICS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND INDEX_NAME = 'uk_product_country_weight_eff'
);
SET @sql := IF(@has > 0,
  'ALTER TABLE bms_product_country DROP INDEX uk_product_country_weight_eff',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;

SET @has := (
  SELECT COUNT(*) FROM information_schema.STATISTICS
  WHERE TABLE_SCHEMA = @db AND TABLE_NAME = 'bms_product_country' AND INDEX_NAME = 'uk_product_country_zone_weight_eff'
);
SET @sql := IF(@has = 0,
  'ALTER TABLE bms_product_country ADD UNIQUE KEY uk_product_country_zone_weight_eff (product_code, country_name, zone_code, weight_min, weight_max, effective_date)',
  'SELECT 1');
PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;