/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2014 Damien P. George
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <stdlib.h>
#include <assert.h>

#include "py/runtime.h"

#if MICROPY_PY_BUILTINS_REVERSED

typedef struct _mp_obj_reversed_t {
 mp_obj_base_t base;
 mp_obj_t seq; // sequence object that we are reversing
 mp_uint_t cur_index; // current index, plus 1; 0=no more, 1=last one (index 0)
} mp_obj_reversed_t;

STATIC mp_obj_t reversed_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
 mp_arg_check_num(n_args, n_kw, 1, 1, false);

 // check if __reversed__ exists, and if so delegate to it
 mp_obj_t dest[2];
 mp_load_method_maybe(args[0], MP_QSTR___reversed__, dest);
 if (dest[0] != MP_OBJ_NULL) {
 return mp_call_method_n_kw(0, 0, dest);
 }

 mp_obj_reversed_t *o = m_new_obj(mp_obj_reversed_t);
 o->base.type = type;
 o->seq = args[0];
 o->cur_index = mp_obj_get_int(mp_obj_len(args[0])); // start at the end of the sequence

 return MP_OBJ_FROM_PTR(o);
}

STATIC mp_obj_t reversed_iternext(mp_obj_t self_in) {
 mp_check_self(mp_obj_is_type(self_in, &mp_type_reversed));
 mp_obj_reversed_t *self = MP_OBJ_TO_PTR(self_in);

 // "raise" stop iteration if we are at the end (the start) of the sequence
 if (self->cur_index == 0) {
 return MP_OBJ_STOP_ITERATION;
 }

 // pre-decrement and index sequence
 self->cur_index -= 1;
 return mp_obj_subscr(self->seq, MP_OBJ_NEW_SMALL_INT(self->cur_index), MP_OBJ_SENTINEL);
}

const mp_obj_type_t mp_type_reversed = {
 { &mp_type_type },
 .name = MP_QSTR_reversed,
 .make_new = reversed_make_new,
 .getiter = mp_identity_getiter,
 .iternext = reversed_iternext,
};

#endif // MICROPY_PY_BUILTINS_REVERSED