/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2014 Damien P. George
 * Copyright (c) 2016-2017 Paul Sokolovsky
 * Copyright (c) Quectel Wireless Solution, Co., Ltd.All Rights Reserved.
 *
 * 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 <string.h>

#include "py/objlist.h"
#include "py/runtime.h"
#include "py/smallint.h"

#if MICROPY_PY_UTIMEQ

#define MODULO MICROPY_PY_UTIME_TICKS_PERIOD

#define DEBUG 0

// the algorithm here is modelled on CPython's heapq.py

struct qentry {
 mp_uint_t time;
 mp_uint_t id;
 mp_obj_t callback;
 mp_obj_t args;
};

typedef struct _mp_obj_utimeq_t {
 mp_obj_base_t base;
 mp_uint_t alloc;
 mp_uint_t len;
 struct qentry items[];
} mp_obj_utimeq_t;

STATIC mp_uint_t utimeq_id;

STATIC mp_obj_utimeq_t *utimeq_get_heap(mp_obj_t heap_in) {
 return MP_OBJ_TO_PTR(heap_in);
}

STATIC bool time_less_than(struct qentry *item, struct qentry *parent) {
 mp_uint_t item_tm = item->time;
 mp_uint_t parent_tm = parent->time;
 mp_uint_t res = parent_tm - item_tm;
 if (res == 0) {
 // TODO: This actually should use the same "ring" logic
 // as for time, to avoid artifacts when id's overflow.
 return item->id < parent->id;
 }
 if ((mp_int_t)res < 0) {
 res += MODULO;
 }
 return res && res < (MODULO / 2);
}

STATIC mp_obj_t utimeq_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);
 mp_uint_t alloc = mp_obj_get_int(args[0]);
 mp_obj_utimeq_t *o = m_new_obj_var(mp_obj_utimeq_t, struct qentry, alloc);
 o->base.type = type;
 memset(o->items, 0, sizeof(*o->items) * alloc);
 o->alloc = alloc;
 o->len = 0;
 return MP_OBJ_FROM_PTR(o);
}

STATIC void utimeq_heap_siftdown(mp_obj_utimeq_t *heap, mp_uint_t start_pos, mp_uint_t pos) {
 struct qentry item = heap->items[pos];
 while (pos > start_pos) {
 mp_uint_t parent_pos = (pos - 1) >> 1;
 struct qentry *parent = &heap->items[parent_pos];
 bool lessthan = time_less_than(&item, parent);
 if (lessthan) {
 heap->items[pos] = *parent;
 pos = parent_pos;
 } else {
 break;
 }
 }
 heap->items[pos] = item;
}

STATIC void utimeq_heap_siftup(mp_obj_utimeq_t *heap, mp_uint_t pos) {
 mp_uint_t start_pos = pos;
 mp_uint_t end_pos = heap->len;
 struct qentry item = heap->items[pos];
 for (mp_uint_t child_pos = 2 * pos + 1; child_pos < end_pos; child_pos = 2 * pos + 1) {
 // choose right child if it's <= left child
 if (child_pos + 1 < end_pos) {
 bool lessthan = time_less_than(&heap->items[child_pos], &heap->items[child_pos + 1]);
 if (!lessthan) {
 child_pos += 1;
 }
 }
 // bubble up the smaller child
 heap->items[pos] = heap->items[child_pos];
 pos = child_pos;
 }
 heap->items[pos] = item;
 utimeq_heap_siftdown(heap, start_pos, pos);
}

STATIC mp_obj_t mod_utimeq_heappush(size_t n_args, const mp_obj_t *args) {
 (void)n_args;
 mp_obj_t heap_in = args[0];
 mp_obj_utimeq_t *heap = utimeq_get_heap(heap_in);
 if (heap->len == heap->alloc) {
 mp_raise_msg(&mp_type_IndexError, MP_ERROR_TEXT("queue overflow"));
 }
 mp_uint_t l = heap->len;
 heap->items[l].time = MP_OBJ_SMALL_INT_VALUE(args[1]);
 heap->items[l].id = utimeq_id++;
 heap->items[l].callback = args[2];
 heap->items[l].args = args[3];
 utimeq_heap_siftdown(heap, 0, heap->len);
 heap->len++;
 return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_utimeq_heappush_obj, 4, 4, mod_utimeq_heappush);

STATIC mp_obj_t mod_utimeq_heappop(mp_obj_t heap_in, mp_obj_t list_ref) {
 mp_obj_utimeq_t *heap = utimeq_get_heap(heap_in);
 if (heap->len == 0) {
 mp_raise_msg(&mp_type_IndexError, MP_ERROR_TEXT("empty heap"));
 }
 mp_obj_list_t *ret = MP_OBJ_TO_PTR(list_ref);
 if (!mp_obj_is_type(list_ref, &mp_type_list) || ret->len < 3) {
 mp_raise_TypeError(NULL);
 }

 struct qentry *item = &heap->items[0];
 ret->items[0] = MP_OBJ_NEW_SMALL_INT(item->time);
 ret->items[1] = item->callback;
 ret->items[2] = item->args;
 heap->len -= 1;
 heap->items[0] = heap->items[heap->len];
 heap->items[heap->len].callback = MP_OBJ_NULL; // so we don't retain a pointer
 heap->items[heap->len].args = MP_OBJ_NULL;
 if (heap->len) {
 utimeq_heap_siftup(heap, 0);
 }
 return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_utimeq_heappop_obj, mod_utimeq_heappop);

STATIC mp_obj_t mod_utimeq_peektime(mp_obj_t heap_in) {
 mp_obj_utimeq_t *heap = utimeq_get_heap(heap_in);
 if (heap->len == 0) {
 mp_raise_msg(&mp_type_IndexError, MP_ERROR_TEXT("empty heap"));
 }

 struct qentry *item = &heap->items[0];
 return MP_OBJ_NEW_SMALL_INT(item->time);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_utimeq_peektime_obj, mod_utimeq_peektime);

#if DEBUG
STATIC mp_obj_t mod_utimeq_dump(mp_obj_t heap_in) {
 mp_obj_utimeq_t *heap = utimeq_get_heap(heap_in);
 for (int i = 0; i < heap->len; i++) {
 printf(UINT_FMT "\t%p\t%p\n", heap->items[i].time,
 MP_OBJ_TO_PTR(heap->items[i].callback), MP_OBJ_TO_PTR(heap->items[i].args));
 }
 return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_utimeq_dump_obj, mod_utimeq_dump);
#endif

STATIC mp_obj_t utimeq_unary_op(mp_unary_op_t op, mp_obj_t self_in) {
 mp_obj_utimeq_t *self = MP_OBJ_TO_PTR(self_in);
 switch (op) {
 case MP_UNARY_OP_BOOL:
 return mp_obj_new_bool(self->len != 0);
 case MP_UNARY_OP_LEN:
 return MP_OBJ_NEW_SMALL_INT(self->len);
 default:
 return MP_OBJ_NULL; // op not supported
 }
}

STATIC const mp_rom_map_elem_t utimeq_locals_dict_table[] = {
 { MP_ROM_QSTR(MP_QSTR_push), MP_ROM_PTR(&mod_utimeq_heappush_obj) },
 { MP_ROM_QSTR(MP_QSTR_pop), MP_ROM_PTR(&mod_utimeq_heappop_obj) },
 { MP_ROM_QSTR(MP_QSTR_peektime), MP_ROM_PTR(&mod_utimeq_peektime_obj) },
 #if DEBUG
 { MP_ROM_QSTR(MP_QSTR_dump), MP_ROM_PTR(&mod_utimeq_dump_obj) },
 #endif
};

STATIC MP_DEFINE_CONST_DICT(utimeq_locals_dict, utimeq_locals_dict_table);

STATIC const mp_obj_type_t utimeq_type = {
 { &mp_type_type },
 .name = MP_QSTR_utimeq,
 .make_new = utimeq_make_new,
 .unary_op = utimeq_unary_op,
 .locals_dict = (void *)&utimeq_locals_dict,
};

STATIC const mp_rom_map_elem_t mp_module_utimeq_globals_table[] = {
 { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_utimeq) },
 { MP_ROM_QSTR(MP_QSTR_utimeq), MP_ROM_PTR(&utimeq_type) },
};

STATIC MP_DEFINE_CONST_DICT(mp_module_utimeq_globals, mp_module_utimeq_globals_table);

const mp_obj_module_t mp_module_utimeq = {
 .base = { &mp_type_module },
 .globals = (mp_obj_dict_t *)&mp_module_utimeq_globals,
};

#endif // MICROPY_PY_UTIMEQ