# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import collections
import os

import pytest


HashVector = collections.namedtuple("HashVector", ["message", "digest"])
KeyedHashVector = collections.namedtuple(
    "KeyedHashVector", ["message", "digest", "key"]
)


def select_backends(names, backend_list):
    if names is None:
        return backend_list
    split_names = [x.strip() for x in names.split(',')]
    # this must be duplicated and then removed to preserve the metadata
    # pytest associates. Appending backends to a new list doesn't seem to work
    selected_backends = []
    for backend in backend_list:
        if backend.name in split_names:
            selected_backends.append(backend)

    if len(selected_backends) > 0:
        return selected_backends
    else:
        raise ValueError(
            "No backend selected. Tried to select: {0}".format(split_names)
        )


def check_for_iface(name, iface, item):
    if name in item.keywords and "backend" in item.funcargs:
        if not isinstance(item.funcargs["backend"], iface):
            pytest.skip("{0} backend does not support {1}".format(
                item.funcargs["backend"], name
            ))


def check_backend_support(item):
    supported = item.keywords.get("supported")
    if supported and "backend" in item.funcargs:
        if not supported.kwargs["only_if"](item.funcargs["backend"]):
            pytest.skip("{0} ({1})".format(
                supported.kwargs["skip_message"], item.funcargs["backend"]
            ))
    elif supported:
        raise ValueError("This mark is only available on methods that take a "
                         "backend")


def load_vectors_from_file(filename, loader):
    base = os.path.join(
        os.path.dirname(__file__), "hazmat", "primitives", "vectors",
    )
    with open(os.path.join(base, filename), "r") as vector_file:
        return loader(vector_file)


def load_nist_vectors(vector_data):
    test_data = None
    data = []

    for line in vector_data:
        line = line.strip()

        # Blank lines, comments, and section headers are ignored
        if not line or line.startswith("#") or (line.startswith("[")
                                                and line.endswith("]")):
            continue

        if line.strip() == "FAIL":
            test_data["fail"] = True
            continue

        # Build our data using a simple Key = Value format
        name, value = [c.strip() for c in line.split("=")]

        # Some tests (PBKDF2) contain \0, which should be interpreted as a
        # null character rather than literal.
        value = value.replace("\\0", "\0")

        # COUNT is a special token that indicates a new block of data
        if name.upper() == "COUNT":
            test_data = {}
            data.append(test_data)
            continue
        # For all other tokens we simply want the name, value stored in
        # the dictionary
        else:
            test_data[name.lower()] = value.encode("ascii")

    return data


def load_cryptrec_vectors(vector_data):
    cryptrec_list = []

    for line in vector_data:
        line = line.strip()

        # Blank lines and comments are ignored
        if not line or line.startswith("#"):
            continue

        if line.startswith("K"):
            key = line.split(" : ")[1].replace(" ", "").encode("ascii")
        elif line.startswith("P"):
            pt = line.split(" : ")[1].replace(" ", "").encode("ascii")
        elif line.startswith("C"):
            ct = line.split(" : ")[1].replace(" ", "").encode("ascii")
            # after a C is found the K+P+C tuple is complete
            # there are many P+C pairs for each K
            cryptrec_list.append({
                "key": key,
                "plaintext": pt,
                "ciphertext": ct
            })
        else:
            raise ValueError("Invalid line in file '{}'".format(line))
    return cryptrec_list


def load_openssl_vectors(vector_data):
    vectors = []

    for line in vector_data:
        line = line.strip()

        # Blank lines and comments are ignored
        if not line or line.startswith("#"):
            continue

        vector = line.split(":")
        vectors.append({
            "key": vector[1].encode("ascii"),
            "iv": vector[2].encode("ascii"),
            "plaintext": vector[3].encode("ascii"),
            "ciphertext": vector[4].encode("ascii"),
        })
    return vectors


def load_hash_vectors(vector_data):
    vectors = []
    key = None
    msg = None
    md = None

    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#") or line.startswith("["):
            continue

        if line.startswith("Len"):
            length = int(line.split(" = ")[1])
        elif line.startswith("Key"):
            # HMAC vectors contain a key attribute. Hash vectors do not.
            key = line.split(" = ")[1].encode("ascii")
        elif line.startswith("Msg"):
            # In the NIST vectors they have chosen to represent an empty
            # string as hex 00, which is of course not actually an empty
            # string. So we parse the provided length and catch this edge case.
            msg = line.split(" = ")[1].encode("ascii") if length > 0 else b""
        elif line.startswith("MD"):
            md = line.split(" = ")[1]
            # after MD is found the Msg+MD (+ potential key) tuple is complete
            if key is not None:
                vectors.append(KeyedHashVector(msg, md, key))
                key = None
                msg = None
                md = None
            else:
                vectors.append(HashVector(msg, md))
                msg = None
                md = None
        else:
            raise ValueError("Unknown line in hash vector")
    return vectors