module LMDB

@overload new(path, opts)

Open an LMDB database environment.
The database environment is the root object for all operations on
a collection of databases.  It has to be opened first, before
individual databases can be opened or created in the environment.
The database should be closed when it is no longer needed.

The options hash on this method includes all the flags listed in
{Environment#flags} as well as the options documented here.
@return [Environment]
@param [String] path the path to the files containing the database
@param [Hash] opts options for the database environment
@option opts [Number] :mode The Posix permissions to set on created files.
@option opts [Number] :maxreaders The maximum number of concurrent threads
    that can be executing transactions at once.  Default is 126.
@option opts [Number] :maxdbs The maximum number of named databases in the
    environment.  Not needed if only one database is being used.
@option opts [Number] :mapsize The size of the memory map to be allocated
    for this environment, in bytes.  The memory map size is the
    maximum total size of the database.  The size should be a
    multiple of the OS page size.  The default size is about
    10MiB.
@yield [env] The block to be executed with the environment. The environment is closed afterwards.
@yieldparam env [Environment] The environment
@see #close
@see Environment#flags
@example Open environment and pass options
   env = LMDB.new "dbdir", :maxdbs => 30, :mapasync => true, :writemap => true
@example Pass environment to block
   LMDB.new "dbdir" do |env|
     # ...
   end

static VALUE environment_new(int argc, VALUE *argv, VALUE klass) {
    VALUE path, option_hash;

#ifdef RB_SCAN_ARGS_KEYWORDS
    rb_scan_args_kw(RB_SCAN_ARGS_LAST_HASH_KEYWORDS,
                    argc, argv, "1:", &path, &option_hash);
#else
    rb_scan_args(argc, argv, "1:", &path, &option_hash);
#endif

    EnvironmentOptions options = {
        .flags = MDB_NOTLS,
        .maxreaders = -1,
        .maxdbs = 128,
        .mapsize = 0,
        .mode = 0755,
    };
    if (!NIL_P(option_hash))
        rb_hash_foreach(option_hash, (int (*)(ANYARGS))environment_options,
                        (VALUE)&options);

    MDB_env* env;
    check(mdb_env_create(&env));

    Environment* environment;
    VALUE venv = Data_Make_Struct(cEnvironment, Environment, environment_mark,
                                  environment_free, environment);
    environment->env = env;
    environment->thread_txn_hash = rb_hash_new();
    environment->txn_thread_hash = rb_hash_new();

    if (options.maxreaders > 0)
        check(mdb_env_set_maxreaders(env, options.maxreaders));
    if (options.mapsize > 0)
        check(mdb_env_set_mapsize(env, options.mapsize));

    check(mdb_env_set_maxdbs(env, options.maxdbs <= 0 ? 1 : options.maxdbs));
    VALUE expanded_path = rb_file_expand_path(path, Qnil);
    check(mdb_env_open(env, StringValueCStr(expanded_path), options.flags,
                       options.mode));

    if (rb_block_given_p())
        return rb_ensure(rb_yield, venv, environment_close, venv);

    return venv;
}