SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci;
SET time_zone = '+00:00';

-- 工资政策是小型配置表；迁移只回填政策行并创建周期索引，不扫描用户、工资进度或钱包流水。
SET @ddl := IF(
  (SELECT COUNT(*) FROM information_schema.COLUMNS
   WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'admin_host_agency_salary_policies' AND COLUMN_NAME = 'cycle_key') = 0,
  'ALTER TABLE admin_host_agency_salary_policies ADD COLUMN cycle_key VARCHAR(7) NOT NULL DEFAULT '''' COMMENT ''政策归属工资周期，UTC yyyy-MM'' AFTER region_id, ALGORITHM=INPLACE, LOCK=NONE',
  'SELECT 1'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @ddl := IF(
  (SELECT COUNT(*) FROM information_schema.COLUMNS
   WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'admin_host_agency_salary_policies' AND COLUMN_NAME = 'policy_version') = 0,
  'ALTER TABLE admin_host_agency_salary_policies ADD COLUMN policy_version BIGINT UNSIGNED NOT NULL DEFAULT 0 COMMENT ''不可变政策版本，等于政策 ID'' AFTER cycle_key, ALGORITHM=INPLACE, LOCK=NONE',
  'SELECT 1'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

-- 老记录优先按原有效期起点归档；没有起点时依次使用发布时间、创建时间，全部按 UTC 计算。
UPDATE admin_host_agency_salary_policies
SET cycle_key = DATE_FORMAT(FROM_UNIXTIME(
      COALESCE(NULLIF(effective_from_ms, 0), NULLIF(published_at_ms, 0), created_at_ms) / 1000
    ), '%Y-%m'),
    policy_version = id
WHERE cycle_key = '' OR policy_version = 0;

SET @ddl := IF(
  (SELECT COUNT(*) FROM information_schema.STATISTICS
   WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'admin_host_agency_salary_policies'
     AND INDEX_NAME = 'uk_admin_host_agency_salary_policy_version') = 0,
  'ALTER TABLE admin_host_agency_salary_policies ADD UNIQUE INDEX uk_admin_host_agency_salary_policy_version (app_code, region_id, cycle_key, policy_version), ALGORITHM=INPLACE, LOCK=NONE',
  'SELECT 1'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @ddl := IF(
  (SELECT COUNT(*) FROM information_schema.STATISTICS
   WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'admin_host_agency_salary_policies'
     AND INDEX_NAME = 'idx_admin_host_agency_salary_policy_cycle') = 0,
  'ALTER TABLE admin_host_agency_salary_policies ADD INDEX idx_admin_host_agency_salary_policy_cycle (app_code, region_id, cycle_key, status), ALGORITHM=INPLACE, LOCK=NONE',
  'SELECT 1'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;