--
-- This file is part of TALER
-- Copyright (C) 2014--2022 Taler Systems SA
--
-- TALER is free software; you can redistribute it and/or modify it under the
-- terms of the GNU General Public License as published by the Free Software
-- Foundation; either version 3, or (at your option) any later version.
--
-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-- A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License along with
-- TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
--

-- Everything in one big transaction
BEGIN;

SET search_path TO exchange;

---------------------------------------------------------------------------
--                   General procedures for DB setup
---------------------------------------------------------------------------

CREATE TABLE exchange_tables
  (table_serial_id BIGINT GENERATED BY DEFAULT AS IDENTITY
  ,name VARCHAR NOT NULL
  ,version VARCHAR NOT NULL
  ,action VARCHAR NOT NULL
  ,partitioned BOOL NOT NULL
  ,by_range BOOL NOT NULL
  ,finished BOOL NOT NULL DEFAULT(FALSE));
COMMENT ON TABLE exchange_tables
  IS 'Tables of the exchange and their status';
COMMENT ON COLUMN exchange_tables.name
  IS 'Base name of the table (without partition/shard)';
COMMENT ON COLUMN exchange_tables.version
  IS 'Version of the DB in which the given action happened';
COMMENT ON COLUMN exchange_tables.action
  IS 'Action to take on the table (e.g. create, alter, constrain, foreign, or drop). Create, alter and drop are done for master and each partition; constrain is only for partitions or for master if there are no partitions; master only on master (takes no argument); foreign only on master if there are no partitions.';
COMMENT ON COLUMN exchange_tables.partitioned
  IS 'TRUE if the table is partitioned';
COMMENT ON COLUMN exchange_tables.by_range
  IS 'TRUE if the table is partitioned by range';
COMMENT ON COLUMN exchange_tables.finished
  IS 'TRUE if the respective migration has been run';


CREATE FUNCTION create_partitioned_table(
   IN table_definition VARCHAR
  ,IN table_name VARCHAR
  ,IN main_table_partition_str VARCHAR -- Used only when it is the main table - we do not partition shard tables
  ,IN shard_suffix VARCHAR DEFAULT NULL
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF shard_suffix IS NOT NULL THEN
    table_name=table_name || '_' || shard_suffix;
    main_table_partition_str = '';
  END IF;
  EXECUTE FORMAT(
    table_definition,
    table_name,
    main_table_partition_str
  );
END
$$;

COMMENT ON FUNCTION create_partitioned_table
  IS 'Generic function to create a table that is partitioned.';


CREATE FUNCTION comment_partitioned_table(
   IN table_comment VARCHAR
  ,IN table_name VARCHAR
  ,IN shard_suffix VARCHAR DEFAULT NULL
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF shard_suffix IS NOT NULL THEN
    table_name=table_name || '_' || shard_suffix;
    main_table_partition_str = '';
  END IF;
  EXECUTE FORMAT(
     COMMENT ON TABLE %s IS '%s'
    ,table_name
    ,table_comment
  );
END
$$;

COMMENT ON FUNCTION comment_partitioned_table
  IS 'Generic function to create a comment on table that is partitioned.';


CREATE FUNCTION comment_partitioned_column(
   IN table_comment VARCHAR
  ,IN column_name VARCHAR
  ,IN table_name VARCHAR
  ,IN shard_suffix VARCHAR DEFAULT NULL
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF shard_suffix IS NOT NULL THEN
    table_name=table_name || '_' || shard_suffix;
    main_table_partition_str = '';
  END IF;
  EXECUTE FORMAT(
     COMMENT ON COLUMN %s.%s IS '%s'
    ,table_name
    ,column_name
    ,table_comment
  );
END
$$;

COMMENT ON FUNCTION comment_partitioned_column
  IS 'Generic function to create a comment on column of a table that is partitioned.';




CREATE FUNCTION create_tables(
  num_partitions INTEGER
-- FIXME: not implemented like this, but likely good:
-- NULL: no partitions, add foreign constraints
-- 0: no partitions, no foreign constraints
-- 1: only 1 default partition
-- > 1: normal partitions
)
  RETURNS VOID
  LANGUAGE plpgsql
AS $$
DECLARE
  -- FIXME: use only ONE cursor and then switch on action!
  tc CURSOR FOR
    SELECT table_serial_id
          ,name
          ,action
          ,by_range
      FROM exchange_tables
     WHERE NOT finished
       AND partitioned
       AND (action='create'
         OR action='alter'
         OR action='drop')
     ORDER BY table_serial_id ASC;
DECLARE
  ta CURSOR FOR
    SELECT table_serial_id
          ,name
          ,action
          ,by_range
      FROM exchange_tables
     WHERE NOT finished
       AND partitioned
       AND action='constrain'
     ORDER BY table_serial_id ASC;
DECLARE
  tf CURSOR FOR
    SELECT table_serial_id
          ,name
          ,action
          ,by_range
      FROM exchange_tables
     WHERE NOT finished
       AND partitioned
       AND action='foreign'
     ORDER BY table_serial_id ASC;
DECLARE
  tm CURSOR FOR
    SELECT table_serial_id
          ,name
          ,action
          ,by_range
      FROM exchange_tables
     WHERE NOT finished
       AND partitioned
       AND action='master'
     ORDER BY table_serial_id ASC;
BEGIN

  -- run create/alter/drop actions
  FOR rec IN tc
  LOOP
    -- First create the master table, either
    -- completely unpartitioned, or with one
    -- master and the 'default' partition
    IF IS NULL num_partitions
    THEN
      -- No partitions at all.
      EXECUTE FORMAT(
        'PERFORM %s_table_%s (%s)'::text
        ,rec.action
        ,rec.name
        ,NULL
      );
    ELSE
      -- One default partition only.
      EXECUTE FORMAT(
        'PERFORM %s_table_%s (%s)'::text
        ,rec.action
        ,rec.name
        ,0
      );

    IF NOT IS NULL num_partitions
    THEN
      IF rec.by_range
      THEN
        -- range partitions (only create default)
        -- Create default partition.
        EXECUTE FORMAT(
           'CREATE TABLE %s_default PARTITION OF %s DEFAULT'
          ,rec.name
          ,rec.name
        );
      ELSE
        -- hash partitions
        IF 0=num_partitions
        THEN
          -- Create default partition.
          EXECUTE FORMAT(
             'CREATE TABLE IF NOT EXISTS %s_default PARTITION OF %s FOR VALUES WITH (MODULUS 1, REMAINDER 0)'
            ,rec.name
            ,rec.name
          );
        END IF
        FOR i IN 1..num_partitions LOOP
          -- Create num_partitions
          EXECUTE FORMAT(
             'CREATE TABLE IF NOT EXISTS %I'
             ' PARTITION OF %I'
             ' FOR VALUES WITH (MODULUS %s, REMAINDER %s)'
            ,rec.name || '_' || i
            ,rec.name
            ,num_partitions
            ,i-1
          );
        END LOOP;
      END IF;
    END IF;
    UPDATE exchange_tables
       SET finished=TRUE
     WHERE table_serial_id=rec.table_serial_id;
  END LOOP; -- create/alter/drop actions

  -- Run constrain actions
  FOR rec IN ta
  LOOP
    IF IS NULL num_partitions
    THEN
      -- Constrain master
      EXECUTE FORMAT(
        'PERFORM %s_table_%s (%s)'::text
        ,rec.action
        ,rec.name
        ,NULL
      );
    END IF

    IF 0=num_partitions
    THEN
      -- constrain default partition
      EXECUTE FORMAT(
        'PERFORM %s_table_%s (%s)'::text
        ,rec.action
        ,rec.name
        ,0
      );
    END IF
    FOR i IN 1..num_partitions LOOP
      -- constrain each partition
      EXECUTE FORMAT(
        'PERFORM %s_table_%s (%s)'::text
        ,rec.action
        ,rec.name
        ,i::varchar
      );
    END LOOP;
    UPDATE exchange_tables
       SET finished=TRUE
     WHERE table_serial_id=rec.table_serial_id;
  END LOOP;

  -- run foreign actions
  FOR rec IN tf
  LOOP
    IF IS NULL num_partitions
    THEN
      -- Add foreign constraints
      EXECUTE FORMAT(
        'PERFORM %s_table_%s ()'::text
        ,rec.action
        ,rec.name
      );
    END IF
    UPDATE exchange_tables
       SET finished=TRUE
     WHERE table_serial_id=rec.table_serial_id;
  END LOOP;

END
$$;

COMMENT ON FUNCTION create_tables
  IS 'Creates all tables for the given number of partitions that need creating.';