--
-- 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/>
--

BEGIN;

SELECT _v.register_patch('exchange-0001', NULL, NULL);

CREATE SCHEMA exchange;
COMMENT ON SCHEMA exchange IS 'taler-exchange data';

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, constrain, foreign, or drop). Create is done for the master table 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 -- SQL template for table creation
  ,IN table_name VARCHAR -- base name of the table
  ,IN main_table_partition_str VARCHAR -- declaration for how to partition the table
  ,IN partition_suffix VARCHAR DEFAULT NULL -- NULL: no partitioning, 0: yes partitioning, no sharding, >0: sharding
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF partition_suffix IS NULL
  THEN
    -- no partitioning, disable option
    main_table_partition_str = '';
  ELSE
    IF partition_suffix > 0
    THEN
      -- sharding, add shard name
      table_name=table_name || '_' || partition_suffix;
    END IF;
  END IF;
  EXECUTE FORMAT(
    table_definition,
    table_name,
    main_table_partition_str
  );
END $$;

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


CREATE FUNCTION comment_partitioned_table(
   IN table_comment VARCHAR
  ,IN table_name VARCHAR
  ,IN partition_suffix VARCHAR DEFAULT NULL
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF ( (partition_suffix IS NOT NULL) AND
       (partition_suffix > 0) )
  THEN
    -- sharding, add shard name
    table_name=table_name || '_' || partition_suffix;
  END IF;
  EXECUTE FORMAT(
     'COMMENT ON TABLE %s IS %s'
    ,table_name
    ,quote_literal(table_comment)
  );
END $$;

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 partition_suffix VARCHAR DEFAULT NULL
)
RETURNS VOID
LANGUAGE plpgsql
AS $$
BEGIN
  IF ( (partition_suffix IS NOT NULL) AND
       (partition_suffix > 0) )
  THEN
    -- sharding, add shard name
    table_name=table_name || '_' || partition_suffix;
  END IF;
  EXECUTE FORMAT(
     'COMMENT ON COLUMN %s.%s IS %s'
    ,table_name
    ,column_name
    ,quote_literal(table_comment)
  );
END $$;

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


---------------------------------------------------------------------------
--                   Main DB setup loop
---------------------------------------------------------------------------


CREATE FUNCTION create_tables(
  num_partitions INTEGER
-- 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
  tc CURSOR FOR
    SELECT table_serial_id
          ,name
          ,action
          ,partitioned
          ,by_range
      FROM exchange_tables
     WHERE NOT finished
     ORDER BY table_serial_id ASC;
BEGIN
  FOR rec IN tc
  LOOP
    CASE rec.action
    -- "create" actions apply to master and partitions
    WHEN "create"
    THEN
      IF (rec.partitioned AND
          (num_partitions IS NOT NULL))
      THEN
        -- Create master table with partitioning.
        EXECUTE FORMAT(
          'PERFORM %s_table_%s (%s)'::text
          ,rec.action
          ,rec.name
          ,0
        );
        IF (rec.by_range OR
            (num_partitions = 0))
        THEN
          -- Create default partition.
          IF (rec.by_range)
          THEN
            -- Range partition
            EXECUTE FORMAT(
              'CREATE TABLE IF NOT EXISTS %s_default'
              ' PARTITION OF %s'
              ' FOR DEFAULT'
             ,rec.name
             ,rec.name
            );
          ELSE
            -- Hash 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;
        ELSE
          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;
      ELSE
        -- Only create master table. No partitions.
        EXECUTE FORMAT(
          'PERFORM %s_table_%s (%s)'::text
          ,rec.action
          ,rec.name
          ,NULL
        );
      END IF;
    -- Constrain action apply to master OR each partition
    WHEN "constrain"
    THEN
      ASSERT rec.partitioned, 'constrain action only applies to partitioned tables';
      IF (num_partitions IS NULL)
      THEN
        -- Constrain master table
        EXECUTE FORMAT(
          'PERFORM %s_table_%s (%s)'::text
          ,rec.action
          ,rec.name
          ,NULL
        );
      ELSE
        IF (num_partitions = 0)
        THEN
          -- Constrain default table
          EXECUTE FORMAT(
            'PERFORM %s_table_%s (%s)'::text
            ,rec.action
            ,rec.name
            ,'default'
          );
        ELSE
          -- Constrain each partition
          FOR i IN 1..num_partitions LOOP
            EXECUTE FORMAT(
              'PERFORM %s_table_%s (%s)'::text
              ,rec.action
              ,rec.name
              ,i
            );
          END LOOP;
        END IF;
      END IF;
    -- Foreign actions only apply if partitioning is off
    WHEN "foreign"
    THEN
      IF (num_partitions IS NULL)
      THEN
        -- Only create master table. No partitions.
        EXECUTE FORMAT(
          'PERFORM %s_table_%s (%s)'::text
          ,rec.action
          ,rec.name
          ,NULL
        );
      END IF;
    WHEN "master"
    THEN
      EXECUTE FORMAT(
        'PERFORM %s_table_%s'::text
        ,rec.action
        ,rec.name
      );
    ELSE
      ASSERT FALSE, 'unsupported action type: ' || rec.action;
    END CASE;  -- END CASE (rec.action)
    -- Mark as finished
    UPDATE exchange_tables
       SET finished=TRUE
     WHERE table_serial_id=rec.table_serial_id;
  END LOOP; -- create/alter/drop actions
END $$;

COMMENT ON FUNCTION create_tables
  IS 'Creates all tables for the given number of partitions that need creating. Does NOT support sharding.';


COMMIT;
