-- 该迁移用于已有数据库；新数据库请直接使用 001_schema.sql 中的最终结构。
-- 执行前应确认 live_session 没有重复活动会话，再创建活动机巢唯一约束。

ALTER TABLE live_session
    ADD COLUMN requested_by BIGINT NULL COMMENT '请求人用户 ID',
    ADD COLUMN stop_deadline DATETIME NULL COMMENT '停止截止时间',
    ADD COLUMN updated_at DATETIME NULL COMMENT '更新时间',
    ADD COLUMN active_dock_id VARCHAR(64) GENERATED ALWAYS AS (
        CASE WHEN phase IN ('starting', 'streaming', 'reconnecting', 'stopping') THEN dock_id ELSE NULL END
    ) STORED COMMENT '活动机巢标识（生成列）',
    ADD KEY idx_live_session_dock_phase (dock_id, phase, created_at),
    ADD KEY idx_live_session_phase_deadline (phase, stop_deadline),
    ADD UNIQUE KEY uk_live_session_active_dock (active_dock_id);

CREATE TABLE IF NOT EXISTS live_viewer_lease (
    id BIGINT PRIMARY KEY COMMENT '主键 ID',
    stream_session_id VARCHAR(128) NOT NULL COMMENT '直播会话 ID',
    viewer_id BIGINT NOT NULL COMMENT '观看用户 ID',
    expires_at DATETIME NOT NULL COMMENT '过期时间戳',
    released_at DATETIME NULL COMMENT '释放时间',
    created_at DATETIME NULL COMMENT '创建时间',
    updated_at DATETIME NULL COMMENT '更新时间',
    UNIQUE KEY uk_live_viewer (stream_session_id, viewer_id),
    KEY idx_live_lease_expire (stream_session_id, expires_at),
    KEY idx_live_lease_active (stream_session_id, released_at, expires_at),
    CONSTRAINT fk_live_lease_session FOREIGN KEY (stream_session_id) REFERENCES live_session(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;