/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2013, 2014 Damien P. George
 * Copyright (c) 2014 Paul Sokolovsky
 * Copyright (c) 2017 Michael McWethy
 *
 * 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 <assert.h>
#include <string.h>

#include "py/runtime.h"
#include "py/builtin.h"
#include "py/objtuple.h"
#include "py/binary.h"
#include "py/parsenum.h"
#include "shared-bindings/struct/__init__.h"
#include "shared-module/struct/__init__.h"

//| :mod:`struct` --- manipulation of c-style data
//| ========================================================
//|
//| .. module:: struct
//|   :synopsis: byte data control
//|   :platform: SAMD21
//|
//| This module implements a subset of the corresponding CPython module,
//| as described below. For more information, refer to the original CPython
//| documentation: struct.
//|
//| Supported size/byte order prefixes: *@*, *<*, *>*, *!*.
//|
//| Supported format codes: *b*, *B*, *h*, *H*, *i*, *I*, *l*, *L*, *q*, *Q*,
//| *s*, *P*, *f*, *d* (the latter 2 depending on the floating-point support).
//|


//| .. function:: calcsize(fmt)
//|
//|   Return the number of bytes needed to store the given fmt.
//|

STATIC mp_obj_t struct_calcsize(mp_obj_t fmt_in) {

    return MP_OBJ_NEW_SMALL_INT(shared_modules_struct_calcsize(fmt_in));
}
MP_DEFINE_CONST_FUN_OBJ_1(struct_calcsize_obj, struct_calcsize);

//| .. function:: pack(fmt, v1, v2, ...)
//|
//|   Pack the values v1, v2, ... according to the format string fmt.
//|   The return value is a bytes object encoding the values.
//|

STATIC mp_obj_t struct_pack(size_t n_args, const mp_obj_t *args) {
    // TODO: "The arguments must match the values required by the format exactly."
    mp_int_t size = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
    vstr_t vstr;
    vstr_init_len(&vstr, size);
    byte *p = (byte*)vstr.buf;
    memset(p, 0, size);
    byte *end_p = &p[size];
    shared_modules_struct_pack_into(args[0], p, end_p, n_args - 1, &args[1]);
    return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(struct_pack_obj, 1, MP_OBJ_FUN_ARGS_MAX, struct_pack);


//| .. function:: pack_into(fmt, buffer, offset, v1, v2, ...)
//|
//|   Pack the values v1, v2, ... according to the format string fmt into a buffer
//|   starting at offset. offset may be negative to count from the end of buffer.
//|

STATIC mp_obj_t struct_pack_into(size_t n_args, const mp_obj_t *args) {
    mp_buffer_info_t bufinfo;
    mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
    mp_int_t offset = mp_obj_get_int(args[2]);
    if (offset < 0) {
        // negative offsets are relative to the end of the buffer
        offset = (mp_int_t)bufinfo.len + offset;
        if (offset < 0) {
            mp_raise_RuntimeError("buffer too small");
        }
    }
    byte *p = (byte *)bufinfo.buf;
    byte *end_p = &p[bufinfo.len];
    p += offset;

    shared_modules_struct_pack_into(args[0], p, end_p, n_args - 3, &args[3]);
    return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(struct_pack_into_obj, 3, MP_OBJ_FUN_ARGS_MAX, struct_pack_into);

//| .. function:: unpack(fmt, data)
//|
//|   Unpack from the data according to the format string fmt. The return value
//|   is a tuple of the unpacked values.
//|

//| .. function:: unpack_from(fmt, data, offset)
//|
//|   Unpack from the data starting at offset according to the format string fmt.
//|   offset may be negative to count from the end of buffer. The return value is
//|   a tuple of the unpacked values.
//|

STATIC mp_obj_t struct_unpack_from(size_t n_args, const mp_obj_t *args) {
    // unpack requires that the buffer be exactly the right size.
    // unpack_from requires that the buffer be "big enough".
    // Since we implement unpack and unpack_from using the same function
    // we relax the "exact" requirement, and only implement "big enough".
    mp_buffer_info_t bufinfo;
    mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_READ);
    byte *p = bufinfo.buf;
    byte *end_p = &p[bufinfo.len];

    if (n_args > 2) {
        mp_int_t offset = mp_obj_get_int(args[2]);
        // offset arg provided
        if (offset < 0) {
            // negative offsets are relative to the end of the buffer
            offset = bufinfo.len + offset;
            if (offset < 0) {
                mp_raise_RuntimeError("buffer too small");
            }
        }
        p += offset;
    }

    return MP_OBJ_FROM_PTR(shared_modules_struct_unpack_from(args[0] , p, end_p));
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(struct_unpack_from_obj, 2, 3, struct_unpack_from);

STATIC const mp_rom_map_elem_t mp_module_struct_globals_table[] = {
    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_struct) },
    { MP_ROM_QSTR(MP_QSTR_calcsize), MP_ROM_PTR(&struct_calcsize_obj) },
    { MP_ROM_QSTR(MP_QSTR_pack), MP_ROM_PTR(&struct_pack_obj) },
    { MP_ROM_QSTR(MP_QSTR_pack_into), MP_ROM_PTR(&struct_pack_into_obj) },
    { MP_ROM_QSTR(MP_QSTR_unpack), MP_ROM_PTR(&struct_unpack_from_obj) },
    { MP_ROM_QSTR(MP_QSTR_unpack_from), MP_ROM_PTR(&struct_unpack_from_obj) },
};

STATIC MP_DEFINE_CONST_DICT(mp_module_struct_globals, mp_module_struct_globals_table);

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