"""
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License,
or (at your option) any later version.


This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
See the GNU General Public License for more details.


You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.

Copyright © 2019 Cloud Linux Software Inc.

This software is also available under ImunifyAV commercial license,
see <https://www.imunify360.com/legal/eula>

Utilities to help upload a malicious file."""
import asyncio
import json
import logging
import os
from dataclasses import dataclass
from typing import Iterable, List
from urllib.parse import quote_from_bytes, urljoin
import urllib

from defence360agent import utils
from defence360agent.contracts.config import Core, Malware as Config
from defence360agent.contracts.license import LicenseCLN, LicenseError
from defence360agent.internals.iaid import (
    IAIDTokenError,
    IndependentAgentIDAPI,
)
from imav.contracts.config import MalwareTune

logger = logging.getLogger(__name__)

if utils.OsReleaseInfo.id_like() & utils.OsReleaseInfo.DEBIAN:
    _CURL = "/opt/alt/curlssl/usr/bin/curl"
else:
    _CURL = "/opt/alt/curlssl11/usr/bin/curl"

_API_BASE_URL = os.environ.get("I360_MRS_API_BASE_URL", Core.API_BASE_URL)
_ENDPOINT_UPLOAD = os.environ.get("I360_MRS_ENDPOINT_UPLOAD", "api/v1/upload")
_ENDPOINT_CHECK = os.environ.get(
    "I360_MRS_ENDPOINT_CHECK", "api/v1/check-known-hashes"
)
_POST_FILE_TIMEOUT = int(
    os.environ.get("IMUNIFY360_POST_FILE_TIMEOUT", 60 * 60)  # hour
)
FALSE_NEGATIVE = "false_negative"
FALSE_POSITIVE = "false_positive"
UNKNOWN_REASON = "unknown"


class ClientError(OSError):
    """HTTP client error.

    It is used to hide what specific http client is used by upload_file().
    """


class FileTooLargeError(OSError):
    pass


def _token_to_headers():
    token = LicenseCLN.get_token()
    headers = {
        "I360-Id": token["id"],
        "I360-Limit": token["limit"],
        "I360-Status": token["status"],
        "I360-Token-Expire-Utc": token["token_expire_utc"],
        "I360-Token-Created-Utc": token["token_created_utc"],
        "I360-Sign": token["sign"],
    }
    headers = {key: str(value) for key, value in headers.items()}
    return headers


async def _post_file(filename, url, headers=None, timeout=None):
    """
    Post *filename* as multipart/form-data to *url* with given HTTP *headers*.

    Return server response as bytes (http body).

    Raise TimeoutError on timeout.
    Raise ConnectionError if failed to connect to host.
    Raise ClientError on error.
    """
    if headers is None:
        headers = {}
    headers_args = [
        b"-H%s: %s" % (header.encode("ascii"), value.encode("latin-1"))
        for header, value in headers.items()
    ]
    quoted_full_path = quote_from_bytes(os.fsencode(filename), safe="").encode(
        "ascii"
    )
    cmd = (
        [os.fsencode(_CURL)]
        + headers_args
        + [b"--max-time", str(timeout).encode("ascii")] * (timeout is not None)
        + [
            b"--form",
            # https://curl.haxx.se/docs/knownbugs.html#multipart_formposts_file_name_en
            b'file=@"%s";filename="%s"'
            % (
                # escape backslash, double quotes
                os.fsencode(filename)
                .replace(b"\\", b"\\\\")
                .replace(b'"', b'\\"'),
                quoted_full_path,
            ),
            b"--fail",
            # disable progress meter
            b"--silent",
            b"--show-error",
            url.encode("ascii"),
        ]
    )
    rc, out, err = await utils.run(cmd)
    if rc != 0:
        Error = (
            ConnectionError
            if rc == 7
            else TimeoutError
            if rc == 28
            else ClientError
        )
        raise Error(
            (
                "Failed to post {filename} to {url}:"
                " curl: cmd={cmd}, rc={rc}, out={out}, err={err}"
            ).format(**vars())
        )
    return out


async def upload_file(file: str, upload_reason=UNKNOWN_REASON):
    """
    Upload a file to Malware Response Service.
    :param file: path to file
    :param upload_reason: one of 'unknown', 'false_positive', 'false_negative'
    :return: dict representing json response
    :raises LicenseError:
    """
    if not LicenseCLN.is_valid():
        raise LicenseError(
            "File uploading to Malware Responce Serivce "
            "requires a valid license"
        )
    file_size = os.path.getsize(file)
    if file_size > Config.MAX_MRS_UPLOAD_FILE:
        raise FileTooLargeError(
            "File {} is {} bytes, files larger than {} bytes "
            "are not allowed.".format(
                file, file_size, Config.MAX_MRS_UPLOAD_FILE
            )
        )

    url = urljoin(_API_BASE_URL, _ENDPOINT_UPLOAD)
    headers = {
        **_token_to_headers(),
        "I360-Upload-Reason": upload_reason,
    }
    response_body = await _post_file(
        file, url, headers, timeout=_POST_FILE_TIMEOUT
    )
    result = json.loads(response_body.decode())
    logger.info(
        "Uploaded file %r to the Malware Response Service with reason: %s",
        file,
        upload_reason,
    )
    return result


async def upload_with_retries(file, upload_reason=UNKNOWN_REASON):
    """
    :raises LicenseError,
    ClientError,
    TimeoutError,
    ConnectionError,
    """
    # exponential backoff: total delay ~6 min (not including the upload time)
    delays = [0.5, 2.5, 6, 15, 40, 100, 200]
    max_tries = len(delays) + 1
    for i, pause in enumerate(delays, start=1):
        error = await _try_upload(
            file, raise_errors=False, upload_reason=upload_reason
        )

        if not error:
            break

        if isinstance(error, FileTooLargeError):
            logger.warning("File %s is too big. Stop retrying to upload", file)
            break

        logger.warning(
            "Attempt %d/%d: failed uploading file %s, reason: %s. Retrying in"
            " %s seconds",
            i,
            max_tries,
            file,
            error,
            pause,
        )
        await asyncio.sleep(pause)
    else:  # exhausted retries, one last attempt, raise error if it fails
        await _try_upload(file, raise_errors=True, upload_reason=upload_reason)


async def _try_upload(file, raise_errors, *, upload_reason=UNKNOWN_REASON):
    """Return error instead of raising it unless *raise_errors* is true.

    :raises LicenseError:
    :raises ClientError,
    TimeoutError,
    ConnectionError,
    FileTooLargeError: if raise_errors is True
    """
    try:
        await upload_file(file, upload_reason=upload_reason)
    except (
        ClientError,
        ConnectionError,
        FileTooLargeError,
        TimeoutError,
    ) as e:
        if raise_errors:
            raise e
        return e
    else:
        return None


@dataclass
class HitInfo:
    file: str
    hash: str


async def check_known_hashes(
    loop, hashes: Iterable[str], upload_reason=UNKNOWN_REASON
) -> List[str]:
    hashes = list(hashes)

    if MalwareTune.NO_CHECK_KNOWN_HASHES:
        return hashes

    try:
        token = await IndependentAgentIDAPI.get_token()
    except IAIDTokenError:
        return hashes

    url = urljoin(_API_BASE_URL, _ENDPOINT_CHECK)
    headers = {
        "X-Auth": token,
        "I360-Upload-Reason": upload_reason,
        "Content-Type": "application/json",
    }
    request = {"hashes": hashes}

    try:
        result = await loop.run_in_executor(
            None,
            _do_request,
            urllib.request.Request(
                url,
                data=json.dumps(request).encode(),
                headers=headers,
                method="POST",
            ),
        )
    except Exception as e:
        logger.warning("Failed to check known hashes: %s", e)
        return hashes

    return result["unknown_hashes"]


def _do_request(request: urllib.request.Request) -> None:
    with urllib.request.urlopen(
        request, timeout=Core.DEFAULT_SOCKET_TIMEOUT
    ) as response:
        if response.status != 200:
            raise Exception("status code is {}".format(response.status))
        return json.loads(response.read().decode())