/*
 * Show the data boundries for a given child table as well as the suffix that will be used.
 * Passing the parent table argument improves performance by avoiding a catalog lookup.
 * Passing an interval lets you set one different than the default configured one if desired.
 */
CREATE FUNCTION show_partition_info(p_child_table text
    , p_partition_interval text DEFAULT NULL
    , p_parent_table text DEFAULT NULL
    , OUT child_start_time timestamptz
    , OUT child_end_time timestamptz
    , OUT child_start_id bigint
    , OUT child_end_id bigint 
    , OUT suffix text)
RETURNS record
    LANGUAGE plpgsql STABLE SECURITY DEFINER
    AS $$
DECLARE

v_child_schema          text;
v_child_tablename       text;
v_datetime_string       text;
v_new_search_path       text := '@extschema@,pg_temp';
v_old_search_path       text;
v_parent_table          text;
v_partition_interval    text;
v_partition_type        text;
v_quarter               text;
v_suffix                text;
v_suffix_position       int;
v_year                  text;

BEGIN

SELECT current_setting('search_path') INTO v_old_search_path;
EXECUTE format('SELECT set_config(%L, %L, %L)', 'search_path', v_new_search_path, 'false');

SELECT schemaname, tablename INTO v_child_schema, v_child_tablename
FROM pg_catalog.pg_tables
WHERE schemaname = split_part(p_child_table, '.', 1)::name
AND tablename = split_part(p_child_table, '.', 2)::name;
IF v_child_tablename IS NULL THEN
    EXECUTE format('SELECT set_config(%L, %L, %L)', 'search_path', v_old_search_path, 'false');
    RAISE EXCEPTION 'Child table given does not exist (%)', p_child_table;
END IF;

IF p_parent_table IS NULL THEN
    SELECT n.nspname||'.'|| c.relname INTO v_parent_table
    FROM pg_catalog.pg_inherits h
    JOIN pg_catalog.pg_class c ON c.oid = h.inhparent
    JOIN pg_catalog.pg_namespace n ON c.relnamespace = n.oid
    WHERE h.inhrelid::regclass = p_child_table::regclass;
ELSE
    v_parent_table := p_parent_table;
END IF;

IF p_partition_interval IS NULL THEN
    SELECT partition_interval, partition_type, datetime_string INTO v_partition_interval, v_partition_type, v_datetime_string 
    FROM @extschema@.part_config WHERE parent_table = v_parent_table;
ELSE
    v_partition_interval := p_partition_interval;
    SELECT partition_type, datetime_string INTO v_partition_type, v_datetime_string 
    FROM @extschema@.part_config WHERE parent_table = v_parent_table;
END IF;

IF v_partition_type IS NULL THEN
    RAISE EXCEPTION 'Parent table of given child not managed by pg_partman: %', v_parent_table;
END IF;

v_suffix_position := (length(v_child_tablename) - position('p_' in reverse(v_child_tablename))) + 2;
v_suffix := substring(v_child_tablename from v_suffix_position);

IF v_partition_type = 'time' OR v_partition_type = 'time-custom' THEN

        IF v_partition_interval::interval <> '3 months' OR (v_partition_interval::interval = '3 months' AND v_partition_type = 'time-custom') THEN
           child_start_time := to_timestamp(v_suffix, v_datetime_string);
        ELSE
            -- to_timestamp doesn't recognize 'Q' date string formater. Handle it
            v_year := split_part(v_suffix, 'q', 1);
            v_quarter := split_part(v_suffix, 'q', 2);
            CASE
                WHEN v_quarter = '1' THEN
                    child_start_time := to_timestamp(v_year || '-01-01', 'YYYY-MM-DD');
                WHEN v_quarter = '2' THEN
                    child_start_time := to_timestamp(v_year || '-04-01', 'YYYY-MM-DD');
                WHEN v_quarter = '3' THEN
                    child_start_time := to_timestamp(v_year || '-07-01', 'YYYY-MM-DD');
                WHEN v_quarter = '4' THEN
                    child_start_time := to_timestamp(v_year || '-10-01', 'YYYY-MM-DD');
            END CASE;
        END IF;

        child_end_time := (child_start_time + v_partition_interval::interval) - '1 second'::interval;

ELSIF v_partition_type = 'id' THEN

    child_start_id := v_suffix::bigint;
    child_end_id := (child_start_id + v_partition_interval::bigint) - 1;

ELSE
    RAISE EXCEPTION 'Invalid partition type encountered in show_partition_info()';
END IF;

suffix = v_suffix;

EXECUTE format('SELECT set_config(%L, %L, %L)', 'search_path', v_old_search_path, 'false');

RETURN;

END
$$;