-- +goose Up
-- +goose StatementBegin

CREATE TABLE IF NOT EXISTS chat_admin_conversation_states (
  id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
  conversation_id BIGINT UNSIGNED NOT NULL COMMENT '会话ID',
  admin_user_id BIGINT UNSIGNED NOT NULL COMMENT '管理员ID',
  remark VARCHAR(128) NOT NULL DEFAULT '' COMMENT '管理员个人备注',
  last_read_message_id BIGINT UNSIGNED NOT NULL DEFAULT 0 COMMENT '最后已读消息ID',
  last_read_at DATETIME NULL COMMENT '最后已读时间',
  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
  updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  UNIQUE KEY uk_chat_admin_conversation_state (conversation_id, admin_user_id),
  KEY idx_chat_admin_state_admin (admin_user_id, conversation_id),
  KEY idx_chat_admin_state_read (admin_user_id, last_read_message_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='管理员会话个人状态';

INSERT INTO chat_admin_conversation_states (
  conversation_id, admin_user_id, remark, last_read_message_id, last_read_at
)
SELECT
  cp.conversation_id,
  cp.participant_id,
  cp.remark,
  COALESCE((
    SELECT MAX(cm.id)
    FROM chat_messages cm
    WHERE cm.conversation_id = cp.conversation_id
      AND cp.last_read_at IS NOT NULL
      AND cm.created_at <= cp.last_read_at
  ), 0),
  cp.last_read_at
FROM chat_participants cp
WHERE cp.participant_type = 'admin'
  AND (cp.remark <> '' OR cp.last_read_at IS NOT NULL)
ON DUPLICATE KEY UPDATE
  remark = VALUES(remark),
  last_read_message_id = GREATEST(
    chat_admin_conversation_states.last_read_message_id,
    VALUES(last_read_message_id)
  ),
  last_read_at = CASE
    WHEN chat_admin_conversation_states.last_read_at IS NULL THEN VALUES(last_read_at)
    WHEN VALUES(last_read_at) IS NULL THEN chat_admin_conversation_states.last_read_at
    ELSE GREATEST(chat_admin_conversation_states.last_read_at, VALUES(last_read_at))
  END;

ALTER TABLE chat_conversations
  ADD INDEX idx_chat_conversations_status_activity (status, last_message_at, id),
  ADD INDEX idx_chat_conversations_type_scene_activity (type, support_scene, last_message_at, id);

-- 后台客服列表需要按商品快速定位最新订单，避免为每个会话执行全表排序。
ALTER TABLE rental_orders
  ADD INDEX idx_rental_orders_listing_id_id (listing_id, id);

-- +goose StatementEnd

-- +goose Down
-- +goose StatementBegin

ALTER TABLE rental_orders
  DROP INDEX idx_rental_orders_listing_id_id;

ALTER TABLE chat_conversations
  DROP INDEX idx_chat_conversations_type_scene_activity,
  DROP INDEX idx_chat_conversations_status_activity;

DROP TABLE IF EXISTS chat_admin_conversation_states;

-- +goose StatementEnd