-- This program is open source, licensed under the PostgreSQL License.
-- For license terms, see the LICENSE file.
--
-- Copyright (C) 2015-2022: Julien Rouhaud

-- complain if script is sourced in psql, rather than via ALTER EXTENSION
\echo Use "ALTER EXTENSION pg_track_settings" to load this file. \quit

SET client_encoding = 'UTF8';

CREATE OR REPLACE FUNCTION pg_track_settings_snapshot() RETURNS boolean AS
$_$
BEGIN
    -- Handle dropped GUC
    WITH dropped AS (
        SELECT l.name
        FROM pg_track_settings_list l
        LEFT JOIN pg_settings s ON s.name = l.name
        WHERE s.name IS NULL
    ),
    mark_dropped AS (
        INSERT INTO pg_track_settings_history (ts, name, setting, is_dropped)
        SELECT now(), name, NULL, true
        FROM dropped
    )
    DELETE FROM pg_track_settings_list l
    USING dropped d
    WHERE d.name = l.name;

    -- Insert missing settings
    INSERT INTO pg_track_settings_list (name)
    SELECT name
    FROM pg_settings s
    WHERE NOT EXISTS (SELECT 1
        FROM pg_track_settings_list l
        WHERE l.name = s.name
    );

    -- Detect changed GUC, insert new vals
    WITH last_snapshot AS (
        SELECT name, setting
        FROM (
            SELECT name, setting, row_number() OVER (PARTITION BY NAME ORDER BY ts DESC) rownum
            FROM pg_track_settings_history
        ) all_snapshots
        WHERE rownum = 1
    )
    INSERT INTO pg_track_settings_history (ts, name, setting)
    SELECT now(), s.name, s.setting
    FROM pg_settings s
    LEFT JOIN last_snapshot l ON l.name = s.name
    WHERE l.name IS NULL
    OR l.setting IS DISTINCT FROM s.setting;

    -- Handle dropped db_role_setting
    WITH rds AS (
        SELECT setdatabase, setrole,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[1] as name,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[2] as setting
        FROM pg_db_role_setting
    ),
    dropped AS (
        SELECT l.setdatabase, l.setrole, l.name
        FROM pg_track_db_role_settings_list l
        LEFT JOIN rds s ON (
            s.setdatabase = l.setdatabase
            AND s.setrole = l.setrole
            AND s.name = l.name
        )
        WHERE s.setdatabase IS NULL
            AND s.setrole IS NULL
            AND s.name IS NULL
    ),
    mark_dropped AS (
        INSERT INTO pg_track_db_role_settings_history
            (ts, setdatabase, setrole, name, setting, is_dropped)
        SELECT now(), setdatabase, setrole, name, NULL, true
        FROM dropped
    )
    DELETE FROM pg_track_db_role_settings_list l
    USING dropped d
    WHERE
        d.setdatabase = l.setdatabase
        AND d.setrole = l.setrole
        AND d.name = l.name;

    -- Insert missing settings
    WITH rds AS (
        SELECT setdatabase, setrole,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[1] as name,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[2] as setting
        FROM pg_db_role_setting
    )
    INSERT INTO pg_track_db_role_settings_list
        (setdatabase, setrole, name)
    SELECT setdatabase, setrole, name
    FROM rds s
    WHERE NOT EXISTS (SELECT 1
        FROM pg_track_db_role_settings_list l
        WHERE
            l.setdatabase = s.setdatabase
            AND l.setrole = l.setrole
            AND l.name = s.name
    );

    -- Detect changed GUC, insert new vals
    WITH rds AS (
        SELECT setdatabase, setrole,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[1] as name,
            (regexp_split_to_array(unnest(setconfig),'=')::text[])[2] as setting
        FROM pg_db_role_setting
    ),
    last_snapshot AS (
        SELECT setdatabase, setrole, name, setting
        FROM (
            SELECT setdatabase, setrole, name, setting,
                row_number() OVER (PARTITION BY name, setdatabase, setrole ORDER BY ts DESC) rownum
            FROM pg_track_db_role_settings_history
        ) all_snapshots
        WHERE rownum = 1
    )
    INSERT INTO pg_track_db_role_settings_history
        (ts, setdatabase, setrole, name, setting)
    SELECT now(), s.setdatabase, s.setrole, s.name, s.setting
    FROM rds s
    LEFT JOIN last_snapshot l ON
        l.setdatabase = s.setdatabase
        AND l.setrole = s.setrole
        AND l.name = s.name
    WHERE l.setdatabase IS NULL
        AND l.setrole IS NULL
        AND l.name IS NULL
    OR l.setting IS DISTINCT FROM s.setting;

    -- Detect is postmaster restarted since last call
    WITH last_reboot AS (
        SELECT t FROM pg_postmaster_start_time() t
    )
    INSERT INTO pg_reboot (ts)
    SELECT t FROM last_reboot lr
    WHERE NOT EXISTS (SELECT 1
        FROM pg_reboot r
        WHERE r.ts = lr.t
    );

    RETURN true;
END;
$_$
LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION pg_track_db_role_settings(_ts timestamp with time zone DEFAULT now())
RETURNS TABLE (setdatabase oid, setrole oid, name text, setting text) AS
$_$
BEGIN
    RETURN QUERY
        SELECT s.setdatabase, s.setrole, s.name, s.setting
        FROM (
            SELECT h.setdatabase, h.setrole, h.name, h.setting, h.is_dropped,
                row_number() OVER (PARTITION BY h.name, h.setdatabase, h.setrole ORDER BY h.ts DESC) AS rownum
            FROM pg_track_db_role_settings_history h
            WHERE ts <= _ts
        ) s
        WHERE s.rownum = 1
        AND NOT s.is_dropped
        ORDER BY s.setdatabase, s.setrole, s.name;
END;
$_$
LANGUAGE plpgsql;
