-- Complain if script is sourced in `psql`, rather than via `CREATE EXTENSION`.
\echo Use "CREATE EXTENSION pg_mockable" to load this file. \quit

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create or replace function mock_memory__after_magic()
    returns trigger
    set search_path to pg_catalog
    language plpgsql
    as $$
declare
    _mock_mem mockable.mock_memory;
    _proc_schema name := 'mockable';
    _pg_proc pg_proc := mockable.pg_proc(NEW.routine_signature::regprocedure);
    _signature_changed bool := tg_op = 'UPDATE' and (
        NEW.routine_signature != OLD.routine_signature
        or NEW.unmock_statement != OLD.unmock_statement
    );
    _must_mock bool := NEW.mock_value is not null
        and (_signature_changed or NEW.mock_value is distinct from OLD.mock_value);
    _must_unmock bool := NEW.mock_value is null and (OLD.mock_value is not null or tg_op = 'INSERT');
    _extension_context_detection_object name;
    _extension_context name;
    _proc_grantee oid;
begin
    assert tg_when = 'AFTER';
    assert tg_op in ('INSERT', 'UPDATE');
    assert tg_level = 'ROW';
    assert tg_table_schema = 'mockable';
    assert tg_table_name = 'mock_memory';

    -- The extension context may be:
    --    a) outside of a `CREATE EXTENSION` / `ALTER EXTENSION` context (`_extension_context IS NULL`);
    --    b) inside the `CREATE EXTENSION` / `ALTER EXTENSION` context of the extension owning the config
    --       table to which this trigger is attached; or
    --    c) inside the `CREATE EXTENSION` / `ALTER EXTENSION` context of extension that changes settings in
    --       another extension's configuration table.
    _extension_context_detection_object := format(
        'extension_context_detector_%s'
        ,floor(pg_catalog.random() * 1000)
    );
    execute format('CREATE TEMPORARY TABLE %I (col int) ON COMMIT DROP', _extension_context_detection_object);
    select
        pg_extension.extname
    into
        _extension_context
    from
        pg_catalog.pg_depend
    inner join
        pg_catalog.pg_extension
        on pg_extension.oid = pg_depend.refobjid
    where
        pg_depend.classid = 'pg_catalog.pg_class'::regclass
        and pg_depend.objid = _extension_context_detection_object::regclass
        and pg_depend.refclassid = 'pg_catalog.pg_extension'::regclass
    ;
    execute format('DROP TABLE %I', _extension_context_detection_object);

    if _signature_changed then
        execute 'DROP FUNCTION ' || NEW.mock_signature;
    end if;

    if _must_mock or _must_unmock then
        if NEW.pg_extension_name is not null and _extension_context is distinct from NEW.pg_extension_name
        then
            execute 'ALTER EXTENSION ' || NEW.pg_extension_name || ' DROP '
                || case _pg_proc.prokind when 'f' then 'FUNCTION' when 'p' then 'PROCEDURE' end
                || ' ' || NEW.mock_signature;
            if _extension_context is not null then
                execute 'ALTER EXTENSION ' || _extension_context || ' ADD '
                    || case _pg_proc.prokind when 'f' then 'FUNCTION' when 'p' then 'PROCEDURE' end
                    || ' ' || NEW.mock_signature;
            end if;
        end if;

        if _must_mock then
            execute 'CREATE OR REPLACE '
                || case _pg_proc.prokind
                    when 'f' then 'FUNCTION'
                    when 'p' then 'PROCEDURE'
                end
                || ' ' || NEW.mock_signature
                || ' RETURNS ' || pg_get_function_result(_pg_proc.oid)
                || ' LANGUAGE SQL'
                || ' IMMUTABLE'
                || ' SET search_path FROM CURRENT'
                || ' RETURN ' || quote_literal(NEW.mock_value)
                || '::' || pg_get_function_result(_pg_proc.oid)
            ;
        elsif _must_unmock then
            execute NEW.unmock_statement;

            execute 'COMMENT ON FUNCTION mockable.' || quote_ident(_pg_proc.proname)
                || ' IS $md$Mockable wrapper function for `' || NEW.routine_signature || '`.$md$';
        end if;

        if NEW.pg_extension_name is not null and _extension_context is distinct from NEW.pg_extension_name
        then
            if _extension_context is not null then
                execute 'ALTER EXTENSION ' || _extension_context || ' DROP '
                    || case _pg_proc.prokind when 'f' then 'FUNCTION' when 'p' then 'PROCEDURE' end
                    || ' ' || NEW.mock_signature;
            end if;
            execute 'ALTER EXTENSION ' || NEW.pg_extension_name || ' ADD '
                || case _pg_proc.prokind when 'f' then 'FUNCTION' when 'p' then 'PROCEDURE' end
                || ' ' || NEW.mock_signature;
        end if;
    end if;

    if _pg_proc.proacl is not null then
        execute 'REVOKE EXECUTE ON '
                || case _pg_proc.prokind
                    when 'f' then 'FUNCTION'
                    when 'p' then 'PROCEDURE'
                end
                || ' mockable.' || quote_ident(_pg_proc.proname)
                || ' FROM PUBLIC';

        for _proc_grantee in
            select
                routine_grant.grantee
            from
                pg_catalog.pg_proc
            cross join
                pg_catalog.aclexplode(pg_proc.proacl) as routine_grant
            where
                pg_proc.oid = NEW.routine_signature
        loop
            execute 'GRANT EXECUTE ON '
                || case _pg_proc.prokind
                    when 'f' then 'FUNCTION'
                    when 'p' then 'PROCEDURE'
                end
                || ' mockable.' || quote_ident(_pg_proc.proname)
                || ' TO '
                || case
                    when _proc_grantee = 0
                    then 'PUBLIC'
                    else _proc_grantee::regrole::text
                end
                ;
        end loop;
    end if;

    return null;
end;
$$;

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create or replace procedure test__pg_mockable()
    set search_path to pg_catalog
    set plpgsql.check_asserts to true
    set pg_readme.include_this_routine_definition to true
    language plpgsql
    as $plpgsql$
declare
    _now timestamptz;
begin
    assert mockable.now() = pg_catalog.now();
    assert mockable.current_date() = current_date;

    assert mockable.mock('pg_catalog.now()', '2022-01-02 10:20'::timestamptz)
        = '2022-01-02 10:20'::timestamptz;
    perform mockable.mock('pg_catalog.now()', '2022-01-02 10:30'::timestamptz);

    assert mockable.now() = '2022-01-02 10:30'::timestamptz,
        'Failed to mock `pg_catalog.now()` as `mockable.now()`.';
    assert mockable.current_date() = '2022-01-02'::date;
    assert mockable.localtime() = '10:30'::time;

    call mockable.unmock('pg_catalog.now()');
    assert pg_catalog.now() = mockable.now();
    assert current_date = mockable.current_date();

    create schema test__schema;
    create function test__schema.func() returns int return 8;
    perform mockable.wrap_function('test__schema.func()');

    --
    -- Now, let's demonstrate how to use the `search_path` to alltogether skip the mocking layer…
    --

    _now := now();  -- just to not have to use qualified names

    perform mockable.mock('pg_catalog.now()', '2022-01-02 10:20'::timestamptz);

    perform set_config('search_path', 'pg_catalog', true);
    assert now() = _now;

    perform set_config('search_path', 'mockable, pg_catalog', true);
    assert now() = '2022-01-02 10:20'::timestamptz;

    <<test_that_grants_are_copied>>
    begin
        create role underling;

        create function test__schema.private_func() returns int return 100;
        revoke execute on function test__schema.private_func() from public;
        assert not has_function_privilege('underling', 'test__schema.private_func()', 'EXECUTE');

        perform mockable.wrap_function('test__schema.private_func()');
        assert not has_function_privilege('underling', 'mockable.private_func()', 'EXECUTE');
        perform mockable.mock('test__schema.private_func()', 1000::int);
        assert not has_function_privilege('underling', 'mockable.private_func()', 'EXECUTE');

        grant execute on function test__schema.private_func() to underling;
        assert has_function_privilege('underling', 'test__schema.private_func()', 'EXECUTE');

        perform mockable.mock('test__schema.private_func()', 1000::int);
        assert has_function_privilege('underling', 'mockable.private_func()', 'EXECUTE');

    end test_that_grants_are_copied;

    <<recursive_mock_attempt>>
    begin
        assert current_schema = 'mockable';
        assert 'now()'::regprocedure = 'mockable.now()'::regprocedure;
        assert 'now()'::regprocedure != 'pg_catalog.now()'::regprocedure;

        perform mockable.mock('now()', '2021-01-01 00:00'::timestamptz);

        raise assert_failure using
            message = 'Mocking an unwrapped function should have been forbidden.';
    exception
        when no_data_found then  -- Good.
    end recursive_mock_attempt;

    <<recursive_wrap_attempt>>
    begin
        assert current_schema = 'mockable';
        assert 'now()'::regprocedure = 'mockable.now()'::regprocedure;
        assert 'now()'::regprocedure != 'pg_catalog.now()'::regprocedure;

        perform mockable.wrap_function('now()');

        raise assert_failure using
            message = 'Wrapping a wrapper function should have been forbidden.';
    exception
        when invalid_recursion then  -- Good.
    end recursive_wrap_attempt;

    create extension pg_mockable_dependent_test_extension
        with version 'constver';

    raise transaction_rollback;
exception
    when transaction_rollback then
end;
$plpgsql$;

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