-- 002_daily_summary.sql
-- 状态时长定时快照表 + 聚合函数 + pg_cron 调度说明

-- ============================================================
-- 1. 快照存储表
-- ============================================================
CREATE TABLE IF NOT EXISTS state_summaries (
    id            BIGSERIAL PRIMARY KEY,
    user_id       VARCHAR(128) NOT NULL,
    state         VARCHAR(64)  NOT NULL,
    duration_secs BIGINT       NOT NULL DEFAULT 0,
    period_start  BIGINT       NOT NULL,
    period_end    BIGINT       NOT NULL,
    created_at    TIMESTAMPTZ  NOT NULL DEFAULT now(),

    UNIQUE (user_id, state, period_start, period_end)
);

CREATE INDEX IF NOT EXISTS idx_summaries_user_period
    ON state_summaries (user_id, period_start DESC);

-- ============================================================
-- 2. 聚合函数：滑动窗口计算指定时间范围内各状态时长
--    - 调度器只需传入 period_start / period_end
--    - 内部用 LEAD() 窗口函数求相邻检查点差值
--    - ON CONFLICT 保证幂等（重复执行不产生重复行）
-- ============================================================
CREATE OR REPLACE FUNCTION aggregate_checkpoint_durations(
    p_start BIGINT,
    p_end   BIGINT
) RETURNS BIGINT AS $$
DECLARE
    affected BIGINT;
BEGIN
    INSERT INTO state_summaries (user_id, state, duration_secs, period_start, period_end)
    SELECT user_id, state, SUM(duration) AS duration_secs, p_start, p_end
    FROM (
        SELECT user_id, state,
               LEAD(timestamp) OVER (PARTITION BY user_id ORDER BY timestamp) - timestamp AS duration
        FROM checkpoints
        WHERE timestamp >= p_start AND timestamp <= p_end
    ) sub
    WHERE duration > 0
    GROUP BY user_id, state
    ON CONFLICT (user_id, state, period_start, period_end) DO UPDATE
    SET duration_secs = EXCLUDED.duration_secs;

    GET DIAGNOSTICS affected = ROW_COUNT;
    RETURN affected;
END;
$$ LANGUAGE plpgsql;

-- ============================================================
-- 3. pg_cron 调度（需要超级用户手动执行一次）
-- ============================================================
-- 
-- -- 安装扩展（仅需一次）
-- CREATE EXTENSION IF NOT EXISTS pg_cron;
--
-- -- 每 5 分钟执行一次聚合
-- SELECT cron.schedule(
--     'aggregate-5min',
--     '*/5 * * * *',
--     $$ SELECT aggregate_checkpoint_durations(
--         FLOOR(EXTRACT(EPOCH FROM now() - INTERVAL '5 minutes'))::BIGINT,
--         FLOOR(EXTRACT(EPOCH FROM now()))::BIGINT
--     ); $$
-- );
--
-- -- 每小时整点执行一次（日报表用）
-- SELECT cron.schedule(
--     'aggregate-hourly',
--     '0 * * * *',
--     $$ SELECT aggregate_checkpoint_durations(
--         FLOOR(EXTRACT(EPOCH FROM now() - INTERVAL '1 hour'))::BIGINT,
--         FLOOR(EXTRACT(EPOCH FROM now()))::BIGINT
--     ); $$
-- );
--
-- -- 查看 cron 任务状态
-- SELECT * FROM cron.job;
--
-- -- 取消（如需）
-- SELECT cron.unschedule('aggregate-5min');