# -*- coding: utf-8 -*-
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# the extent that dedication to the public domain is not available,
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from Crypto.Util.py3compat import bord

from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
                                  VoidPointer, SmartPointer,
                                  create_string_buffer,
                                  get_raw_buffer, c_size_t,
                                  c_uint8_ptr)

from Crypto.Hash.keccak import _raw_keccak_lib

class SHA3_256_Hash(object):
    """A SHA3-256 hash object.
    Do not instantiate directly.
    Use the :func:`new` function.

    :ivar oid: ASN.1 Object ID
    :vartype oid: string

    :ivar digest_size: the size in bytes of the resulting hash
    :vartype digest_size: integer
    """

    # The size of the resulting hash in bytes.
    digest_size = 32

    # ASN.1 Object ID
    oid = "2.16.840.1.101.3.4.2.8"

    def __init__(self, data, update_after_digest):
        self._update_after_digest = update_after_digest
        self._digest_done = False

        state = VoidPointer()
        result = _raw_keccak_lib.keccak_init(state.address_of(),
                                             c_size_t(self.digest_size * 2),
                                             0x06)
        if result:
            raise ValueError("Error %d while instantiating SHA-3/256"
                             % result)
        self._state = SmartPointer(state.get(),
                                   _raw_keccak_lib.keccak_destroy)
        if data:
            self.update(data)

    def update(self, data):
        """Continue hashing of a message by consuming the next chunk of data.

        Args:
            data (byte string/byte array/memoryview): The next chunk of the message being hashed.
        """

        if self._digest_done and not self._update_after_digest:
            raise TypeError("You can only call 'digest' or 'hexdigest' on this object")

        result = _raw_keccak_lib.keccak_absorb(self._state.get(),
                                               c_uint8_ptr(data),
                                               c_size_t(len(data)))
        if result:
            raise ValueError("Error %d while updating SHA-3/256"
                             % result)
        return self

    def digest(self):
        """Return the **binary** (non-printable) digest of the message that has been hashed so far.

        :return: The hash digest, computed over the data processed so far.
                 Binary form.
        :rtype: byte string
        """

        self._digest_done = True

        bfr = create_string_buffer(self.digest_size)
        result = _raw_keccak_lib.keccak_digest(self._state.get(),
                                               bfr,
                                               c_size_t(self.digest_size))
        if result:
            raise ValueError("Error %d while instantiating SHA-3/256"
                             % result)

        self._digest_value = get_raw_buffer(bfr)
        return self._digest_value

    def hexdigest(self):
        """Return the **printable** digest of the message that has been hashed so far.

        :return: The hash digest, computed over the data processed so far.
                 Hexadecimal encoded.
        :rtype: string
        """

        return "".join(["%02x" % bord(x) for x in self.digest()])

    def new(self):
        """Create a fresh SHA3-256 hash object."""

        return type(self)(None, self._update_after_digest)


def new(*args, **kwargs):
    """Create a new hash object.

    Args:
        data (byte string/byte array/memoryview):
            The very first chunk of the message to hash.
            It is equivalent to an early call to :meth:`update`.
        update_after_digest (boolean):
            Whether :meth:`digest` can be followed by another :meth:`update`
            (default: ``False``).

    :Return: A :class:`SHA3_256_Hash` hash object
    """

    data = kwargs.pop("data", None)
    update_after_digest = kwargs.pop("update_after_digest", False)
    if len(args) == 1:
        if data:
            raise ValueError("Initial data for hash specified twice")
        data = args[0]

    if kwargs:
        raise TypeError("Unknown parameters: " + str(kwargs))

    return SHA3_256_Hash(data, update_after_digest)

# The size of the resulting hash in bytes.
digest_size = SHA3_256_Hash.digest_size
