# pylint: disable=too-many-branches,too-many-statements,protected-access
"""
Proof of work calculation
"""

import ctypes
import hashlib
import os
import sys
import tempfile
import time
from struct import pack, unpack
from subprocess import call

import openclpow
import paths
import queues
import state
import tr
from bmconfigparser import BMConfigParser
from debug import logger

bitmsglib = 'bitmsghash.so'
bmpow = None


class LogOutput(object):  # pylint: disable=too-few-public-methods
    """
    A context manager that block stdout for its scope
    and appends it's content to log before exit. Usage::

    with LogOutput():
        os.system('ls -l')

    https://stackoverflow.com/questions/5081657
    """

    def __init__(self, prefix='PoW'):
        self.prefix = prefix
        try:
            sys.stdout.flush()
            self._stdout = sys.stdout
            self._stdout_fno = os.dup(sys.stdout.fileno())
        except AttributeError:
            # NullWriter instance has no attribute 'fileno' on Windows
            self._stdout = None
        else:
            self._dst, self._filepath = tempfile.mkstemp()

    def __enter__(self):
        if not self._stdout:
            return
        stdout = os.dup(1)
        os.dup2(self._dst, 1)
        os.close(self._dst)
        sys.stdout = os.fdopen(stdout, 'w')

    def __exit__(self, exc_type, exc_val, exc_tb):
        if not self._stdout:
            return
        sys.stdout.close()
        sys.stdout = self._stdout
        sys.stdout.flush()
        os.dup2(self._stdout_fno, 1)

        with open(self._filepath) as out:
            for line in out:
                logger.info('%s: %s', self.prefix, line)
        os.remove(self._filepath)


def _set_idle():
    if 'linux' in sys.platform:
        os.nice(20)
    else:
        try:
            # pylint: disable=no-member,import-error
            sys.getwindowsversion()
            import win32api
            import win32process
            import win32con
            pid = win32api.GetCurrentProcessId()
            handle = win32api.OpenProcess(win32con.PROCESS_ALL_ACCESS, True, pid)
            win32process.SetPriorityClass(handle, win32process.IDLE_PRIORITY_CLASS)
        except:  # noqa:E722
            # Windows 64-bit
            pass


def _pool_worker(nonce, initialHash, target, pool_size):
    _set_idle()
    trialValue = float('inf')
    while trialValue > target:
        nonce += pool_size
        trialValue, = unpack('>Q', hashlib.sha512(hashlib.sha512(
            pack('>Q', nonce) + initialHash).digest()).digest()[0:8])
    return [trialValue, nonce]


def _doSafePoW(target, initialHash):
    logger.debug("Safe PoW start")
    nonce = 0
    trialValue = float('inf')
    while trialValue > target and state.shutdown == 0:
        nonce += 1
        trialValue, = unpack('>Q', hashlib.sha512(hashlib.sha512(
            pack('>Q', nonce) + initialHash).digest()).digest()[0:8])
    if state.shutdown != 0:
        raise StopIteration("Interrupted")  # pylint: misplaced-bare-raise
    logger.debug("Safe PoW done")
    return [trialValue, nonce]


def _doFastPoW(target, initialHash):
    logger.debug("Fast PoW start")
    from multiprocessing import Pool, cpu_count
    try:
        pool_size = cpu_count()
    except:  # noqa:E722
        pool_size = 4
    try:
        maxCores = BMConfigParser().getint('bitmessagesettings', 'maxcores')
    except:  # noqa:E722
        maxCores = 99999
    if pool_size > maxCores:
        pool_size = maxCores

    pool = Pool(processes=pool_size)
    result = []
    for i in range(pool_size):
        result.append(pool.apply_async(_pool_worker, args=(i, initialHash, target, pool_size)))

    while True:
        if state.shutdown > 0:
            try:
                pool.terminate()
                pool.join()
            except:  # noqa:E722
                pass
            raise StopIteration("Interrupted")
        for i in range(pool_size):
            if result[i].ready():
                try:
                    result[i].successful()
                except AssertionError:
                    pool.terminate()
                    pool.join()
                    raise StopIteration("Interrupted")
                result = result[i].get()
                pool.terminate()
                pool.join()
                logger.debug("Fast PoW done")
                return result[0], result[1]
        time.sleep(0.2)


def _doCPoW(target, initialHash):
    with LogOutput():
        h = initialHash
        m = target
        out_h = ctypes.pointer(ctypes.create_string_buffer(h, 64))
        out_m = ctypes.c_ulonglong(m)
        logger.debug("C PoW start")
        nonce = bmpow(out_h, out_m)

    trialValue, = unpack('>Q', hashlib.sha512(hashlib.sha512(pack('>Q', nonce) + initialHash).digest()).digest()[0:8])
    if state.shutdown != 0:
        raise StopIteration("Interrupted")
    logger.debug("C PoW done")
    return [trialValue, nonce]


def _doGPUPoW(target, initialHash):
    logger.debug("GPU PoW start")
    nonce = openclpow.do_opencl_pow(initialHash.encode("hex"), target)
    trialValue, = unpack('>Q', hashlib.sha512(hashlib.sha512(pack('>Q', nonce) + initialHash).digest()).digest()[0:8])
    if trialValue > target:
        deviceNames = ", ".join(gpu.name for gpu in openclpow.enabledGpus)
        queues.UISignalQueue.put((
            'updateStatusBar', (
                tr._translate(
                    "MainWindow",
                    'Your GPU(s) did not calculate correctly, disabling OpenCL. Please report to the developers.'
                ),
                1)))
        logger.error(
            "Your GPUs (%s) did not calculate correctly, disabling OpenCL. Please report to the developers.",
            deviceNames)
        openclpow.enabledGpus = []
        raise Exception("GPU did not calculate correctly.")
    if state.shutdown != 0:
        raise StopIteration("Interrupted")
    logger.debug("GPU PoW done")
    return [trialValue, nonce]


def estimate(difficulty, format=False):  # pylint: disable=redefined-builtin
    """
    .. todo: fix unused variable
    """
    ret = difficulty / 10
    if ret < 1:
        ret = 1

    if format:
        # pylint: disable=unused-variable
        out = str(int(ret)) + " seconds"
        if ret > 60:
            ret /= 60
            out = str(int(ret)) + " minutes"
        if ret > 60:
            ret /= 60
            out = str(int(ret)) + " hours"
        if ret > 24:
            ret /= 24
            out = str(int(ret)) + " days"
        if ret > 7:
            out = str(int(ret)) + " weeks"
        if ret > 31:
            out = str(int(ret)) + " months"
        if ret > 366:
            ret /= 366
            out = str(int(ret)) + " years"
        ret = None  # Ensure legacy behaviour

    return ret


def getPowType():
    """Get the proof of work implementation"""

    if openclpow.openclEnabled():
        return "OpenCL"
    if bmpow:
        return "C"
    return "python"


def notifyBuild(tried=False):
    """Notify the user of the success or otherwise of building the PoW C module"""

    if bmpow:
        queues.UISignalQueue.put(('updateStatusBar', (tr._translate(
            "proofofwork", "C PoW module built successfully."), 1)))
    elif tried:
        queues.UISignalQueue.put(
            (
                'updateStatusBar', (
                    tr._translate(
                        "proofofwork",
                        "Failed to build C PoW module. Please build it manually."
                    ),
                    1
                )
            )
        )
    else:
        queues.UISignalQueue.put(('updateStatusBar', (tr._translate(
            "proofofwork", "C PoW module unavailable. Please build it."), 1)))


def buildCPoW():
    """Attempt to build the PoW C module"""
    if bmpow is not None:
        return
    if paths.frozen is not None:
        notifyBuild(False)
        return
    if sys.platform in ["win32", "win64"]:
        notifyBuild(False)
        return
    try:
        if "bsd" in sys.platform:
            # BSD make
            call(["make", "-C", os.path.join(paths.codePath(), "bitmsghash"), '-f', 'Makefile.bsd'])
        else:
            # GNU make
            call(["make", "-C", os.path.join(paths.codePath(), "bitmsghash")])
        if os.path.exists(os.path.join(paths.codePath(), "bitmsghash", "bitmsghash.so")):
            init()
            notifyBuild(True)
        else:
            notifyBuild(True)
    except:  # noqa:E722
        notifyBuild(True)


def run(target, initialHash):
    """Run the proof of work thread"""

    if state.shutdown != 0:
        raise  # pylint: disable=misplaced-bare-raise
    target = int(target)
    if openclpow.openclEnabled():
        try:
            return _doGPUPoW(target, initialHash)
        except StopIteration:
            raise
        except:  # noqa:E722
            pass  # fallback
    if bmpow:
        try:
            return _doCPoW(target, initialHash)
        except StopIteration:
            raise
        except:  # noqa:E722
            pass  # fallback
    if paths.frozen == "macosx_app" or not paths.frozen:
        # on my (Peter Surda) Windows 10, Windows Defender
        # does not like this and fights with PyBitmessage
        # over CPU, resulting in very slow PoW
        # added on 2015-11-29: multiprocesing.freeze_support() doesn't help
        try:
            return _doFastPoW(target, initialHash)
        except StopIteration:
            logger.error("Fast PoW got StopIteration")
            raise
        except:  # noqa:E722
            logger.error("Fast PoW got exception:", exc_info=True)
    try:
        return _doSafePoW(target, initialHash)
    except StopIteration:
        raise
    except:  # noqa:E722
        pass  # fallback


def resetPoW():
    """Initialise the OpenCL PoW"""
    openclpow.initCL()


# init


def init():
    """Initialise PoW"""
    # pylint: disable=global-statement
    global bitmsglib, bmpow

    openclpow.initCL()
    if sys.platform == "win32":
        if ctypes.sizeof(ctypes.c_voidp) == 4:
            bitmsglib = 'bitmsghash32.dll'
        else:
            bitmsglib = 'bitmsghash64.dll'
        try:
            # MSVS
            bso = ctypes.WinDLL(os.path.join(paths.codePath(), "bitmsghash", bitmsglib))
            logger.info("Loaded C PoW DLL (stdcall) %s", bitmsglib)
            bmpow = bso.BitmessagePOW
            bmpow.restype = ctypes.c_ulonglong
            _doCPoW(2**63, "")
            logger.info("Successfully tested C PoW DLL (stdcall) %s", bitmsglib)
        except ValueError:
            try:
                # MinGW
                bso = ctypes.CDLL(os.path.join(paths.codePath(), "bitmsghash", bitmsglib))
                logger.info("Loaded C PoW DLL (cdecl) %s", bitmsglib)
                bmpow = bso.BitmessagePOW
                bmpow.restype = ctypes.c_ulonglong
                _doCPoW(2**63, "")
                logger.info("Successfully tested C PoW DLL (cdecl) %s", bitmsglib)
            except Exception as e:
                logger.error("Error: %s", e, exc_info=True)
                bso = None
        except Exception as e:
            logger.error("Error: %s", e, exc_info=True)
            bso = None
    else:
        try:
            bso = ctypes.CDLL(os.path.join(paths.codePath(), "bitmsghash", bitmsglib))
        except OSError:
            import glob
            try:
                bso = ctypes.CDLL(glob.glob(os.path.join(
                    paths.codePath(), "bitmsghash", "bitmsghash*.so"
                ))[0])
            except (OSError, IndexError):
                bso = None
        except:  # noqa:E722
            bso = None
        else:
            logger.info("Loaded C PoW DLL %s", bitmsglib)
    if bso:
        try:
            bmpow = bso.BitmessagePOW
            bmpow.restype = ctypes.c_ulonglong
        except:  # noqa:E722
            bmpow = None
    else:
        bmpow = None
    if bmpow is None:
        buildCPoW()