-- 在当前商户业务库增加消息加密字段。
-- 可重复执行，覆盖单聊、消息修订、群聊主表及全部现有群消息月分片。

DELIMITER $$

DROP PROCEDURE IF EXISTS add_message_crypto_column$$
CREATE PROCEDURE add_message_crypto_column(
  IN p_table VARCHAR(64),
  IN p_column VARCHAR(64),
  IN p_definition TEXT
)
BEGIN
  IF EXISTS (
    SELECT 1 FROM information_schema.TABLES
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = p_table
  ) AND NOT EXISTS (
    SELECT 1 FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = p_table AND COLUMN_NAME = p_column
  ) THEN
    SET @ddl = CONCAT('ALTER TABLE `', REPLACE(p_table, '`', '``'), '` ADD COLUMN `',
                      REPLACE(p_column, '`', '``'), '` ', p_definition);
    PREPARE stmt FROM @ddl;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
  END IF;
END$$

DROP PROCEDURE IF EXISTS drop_message_crypto_column$$
CREATE PROCEDURE drop_message_crypto_column(IN p_table VARCHAR(64), IN p_column VARCHAR(64))
BEGIN
  IF EXISTS (
    SELECT 1 FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = p_table AND COLUMN_NAME = p_column
  ) THEN
    SET @ddl = CONCAT('ALTER TABLE `', REPLACE(p_table, '`', '``'), '` DROP COLUMN `',
                      REPLACE(p_column, '`', '``'), '`');
    PREPARE stmt FROM @ddl;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
  END IF;
END$$

DROP PROCEDURE IF EXISTS migrate_message_crypto_table$$
CREATE PROCEDURE migrate_message_crypto_table(IN p_table VARCHAR(64))
BEGIN
  CALL add_message_crypto_column(p_table, 'content_nonce', 'VARBINARY(12) NULL COMMENT ''每条消息独立随机Nonce'' AFTER `content`');
  CALL add_message_crypto_column(p_table, 'key_version', 'INT NOT NULL DEFAULT 0 COMMENT ''商户消息DEK版本'' AFTER `content_nonce`');
  CALL drop_message_crypto_column(p_table, 'content_ciphertext');
  CALL drop_message_crypto_column(p_table, 'encryption_alg');
  CALL drop_message_crypto_column(p_table, 'encrypted');
END$$

DROP PROCEDURE IF EXISTS migrate_message_crypto_schema$$
CREATE PROCEDURE migrate_message_crypto_schema()
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE table_name_value VARCHAR(64);
  DECLARE shard_cursor CURSOR FOR
    SELECT TABLE_NAME
    FROM information_schema.TABLES
    WHERE TABLE_SCHEMA = DATABASE()
      AND TABLE_NAME REGEXP '^im_group_messages_[0-9]{6}$';
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

  CALL migrate_message_crypto_table('im_messages');
  CALL migrate_message_crypto_table('im_message_revisions');
  CALL migrate_message_crypto_table('im_group_messages');

  OPEN shard_cursor;
  shard_loop: LOOP
    FETCH shard_cursor INTO table_name_value;
    IF done = 1 THEN
      LEAVE shard_loop;
    END IF;
    CALL migrate_message_crypto_table(table_name_value);
  END LOOP;
  CLOSE shard_cursor;
END$$

CALL migrate_message_crypto_schema()$$
DROP PROCEDURE migrate_message_crypto_schema$$
DROP PROCEDURE migrate_message_crypto_table$$
DROP PROCEDURE drop_message_crypto_column$$
DROP PROCEDURE add_message_crypto_column$$

DELIMITER ;