"""
Preferences related to C++ compilation

Preferences
--------------------
.. document_brian_prefs:: codegen.cpp

"""
from setuptools import msvc
import distutils
from distutils.ccompiler import get_default_compiler
import json
import os
import re
import platform
import socket
import struct
import subprocess
import sys
import tempfile

from brian2.core.preferences import prefs, BrianPreference
from brian2.utils.filetools import ensure_directory
from brian2.utils.logger import get_logger, std_silent

__all__ = ['get_compiler_and_args', 'get_msvc_env', 'compiler_supports_c99',
           'C99Check']


logger = get_logger(__name__)

# default_buildopts stores default build options for Gcc compiler
default_buildopts = []

# Try to get architecture information to get the best compiler setting for
# Windows
msvc_arch_flag = ''
if platform.system() == 'Windows':
    flags = None
    previously_stored_flags = None

    # Check whether we've already stored the CPU flags previously
    user_dir = os.path.join(os.path.expanduser('~'), '.brian')
    ensure_directory(user_dir)
    flag_file = os.path.join(user_dir, 'cpu_flags.txt')
    hostname = socket.gethostname()
    if os.path.isfile(flag_file):
        try:
            with open(flag_file, 'r', encoding='utf-8') as f:
                previously_stored_flags = json.load(f)
            if hostname not in previously_stored_flags:
                logger.debug('Ignoring stored CPU flags for a different host')
            else:
                flags = previously_stored_flags[hostname]
        except (IOError, OSError) as ex:
            logger.debug(f'Opening file "{flag_file}" to get CPU flags failed with error "{str(ex)}".')

    if flags is None:  # If we don't have stored info, run get_cpu_flags.py
        get_cpu_flags_script = os.path.join(os.path.dirname(__file__),
                                            'get_cpu_flags.py')
        get_cpu_flags_script = os.path.abspath(get_cpu_flags_script)
        try:
            output = subprocess.check_output([sys.executable,
                                              get_cpu_flags_script],
                                             universal_newlines=True,
                                             encoding='utf-8')
            flags = json.loads(output)
            # Store flags to a file so we don't have to call cpuinfo next time
            try:
                if previously_stored_flags is not None:
                    to_store = previously_stored_flags
                    to_store[hostname] = flags
                else:
                    to_store = {hostname: flags}
                with open(flag_file, 'w', encoding='utf-8') as f:
                    json.dump(to_store, f)
            except (IOError, OSError) as ex:
                logger.debug(f'Writing file "{flag_file}" to store CPU flags failed with error "{str(ex)}".')
        except subprocess.CalledProcessError as ex:
            logger.debug(f'Could not determine optimized MSVC flags, get_cpu_flags failed with: {str(ex)}')

    if flags is not None:
        # Note that this overwrites the arch_flag, i.e. only the best option
        # will be used
        if 'sse' in flags:
            msvc_arch_flag = '/arch:SSE'
        if 'sse2' in flags:
            msvc_arch_flag = '/arch:SSE2'
        if 'avx' in flags:
            msvc_arch_flag = '/arch:AVX'
        if 'avx2' in flags:
            msvc_arch_flag = '/arch:AVX2'

else:
    # Optimized default build options for a range a CPU architectures
    machine = os.uname().machine
    if re.match('^(x86_64|aarch64|arm.*|s390.*|i.86.*)$', machine):
        default_buildopts = ['-w', '-O3', '-ffast-math',
                             '-fno-finite-math-only', '-march=native',
                             '-std=c++11']
    elif re.match('^(alpha|ppc.*|sparc.*)$', machine):
        default_buildopts = ['-w', '-O3', '-ffast-math',
                             '-fno-finite-math-only', '-mcpu=native',
                             '-mtune=native', '-std=c++11']
    elif re.match('^(parisc.*|riscv.*|mips.*)$', machine):
        default_buildopts = ['-w', '-O3', '-ffast-math',
                             '-fno-finite-math-only', '-std=c++11']
    else:
        default_buildopts = ['-w']

if os.environ.get('READTHEDOCS', 'False').lower() == 'true':
    # We are getting imported during a documentation build. Set a fake prefix
    # to avoid having the name of the local environment in the documentation
    sys_prefix = '/path/to/your/Python/environment'
else:
    sys_prefix = sys.prefix

if sys.platform == 'win32':
    prefix_dir = os.path.join(sys_prefix, 'Library')
else:
    prefix_dir = sys_prefix

# Preferences
prefs.register_preferences(
    'codegen.cpp',
    'C++ compilation preferences',
    compiler = BrianPreference(
        default='',
        docs="""
        Compiler to use (uses default if empty).
        Should be ``'unix'`` or ``'msvc'``.

        To specify a specific compiler binary on unix systems, set the `CXX` environment
        variable instead.
        """
        ),
    extra_compile_args=BrianPreference(
        default=None,
        validator=lambda v: True,
        docs="""
        Extra arguments to pass to compiler (if None, use either
        ``extra_compile_args_gcc`` or ``extra_compile_args_msvc``).
        """
        ),
    extra_compile_args_gcc=BrianPreference(
        default=default_buildopts,
        docs="""
        Extra compile arguments to pass to GCC compiler
        """
        ),
    extra_compile_args_msvc=BrianPreference(
        default=['/Ox', '/w', msvc_arch_flag, '/MP'],
        docs="""
        Extra compile arguments to pass to MSVC compiler (the default
        ``/arch:`` flag is determined based on the processor architecture)
        """
        ),
    extra_link_args=BrianPreference(
        default=[],
        docs="""
        Any extra platform- and compiler-specific information to use when
        linking object files together.
        """
    ),
    include_dirs=BrianPreference(
        default=[os.path.join(prefix_dir, 'include')],
        docs="""
        Include directories to use.
        The default value is ``$prefix/include`` (or ``$prefix/Library/include``
        on Windows), where ``$prefix`` is Python's site-specific directory
        prefix as returned by `sys.prefix`. This will make compilation use
        library files installed into a conda environment.
        """
        ),
    library_dirs=BrianPreference(
        default=[os.path.join(prefix_dir, 'lib')],
        docs="""
        List of directories to search for C/C++ libraries at link time.
        The default value is ``$prefix/lib`` (or ``$prefix/Library/lib``
        on Windows), where ``$prefix`` is Python's site-specific directory
        prefix as returned by `sys.prefix`. This will make compilation use
        library files installed into a conda environment.
        """
    ),
    runtime_library_dirs=BrianPreference(
        default=[os.path.join(prefix_dir, 'lib')]
                    if sys.platform != 'win32' else [],
        docs="""
        List of directories to search for C/C++ libraries at run time.
        The default value is ``$prefix/lib`` (not used on Windows), where
        ``$prefix`` is Python's site-specific directory prefix as returned by
        `sys.prefix`. This will make compilation use library files installed
        into a conda environment.
        """
    ),
    libraries=BrianPreference(
        default=[],
        docs="""
        List of library names (not filenames or paths) to link against.
        """
    ),
    headers=BrianPreference(
        default=[],
        docs="""
        A list of strings specifying header files to use when compiling the
        code. The list might look like ["<vector>","'my_header'"]. Note that
        the header strings need to be in a form than can be pasted at the end
        of a #include statement in the C++ code.
        """
    ),
    define_macros=BrianPreference(
        default=[],
        docs="""
        List of macros to define; each macro is defined using a 2-tuple,
        where 'value' is either the string to define it to or None to
        define it without a particular value (equivalent of "#define
        FOO" in source or -DFOO on Unix C compiler command line).
        """
    ),
    msvc_vars_location=BrianPreference(
        default='',
        docs="""
        Location of the MSVC command line tool (or search for best by default).
        """),
    msvc_architecture=BrianPreference(
        default='',
        docs="""
        MSVC architecture name (or use system architectue by default).
        
        Could take values such as x86, amd64, etc.
        """),
    )

# check whether compiler supports a flag
# Adapted from https://github.com/pybind/pybind11/
def _determine_flag_compatibility(compiler, flagname):
    import tempfile
    from distutils.errors import CompileError
    with tempfile.NamedTemporaryFile('w', suffix='.cpp') as f, std_silent():
        f.write('int main (int argc, char **argv) { return 0; }')
        try:
            compiler.compile([f.name], extra_postargs=[flagname])
        except CompileError:
            logger.warn(f"Removing unsupported flag '{flagname}' from "
                        f'compiler flags.')
            return False
    return True

_compiler_flag_compatibility = {}
def has_flag(compiler, flagname):
    if compiler.compiler_type == 'msvc':
        # MSVC does not raise an error for illegal flags, so determining
        # whether it accepts a flag would mean parsing the output for warnings
        # This is non-trivial so we don't do it (the main reason to check
        # flags in the first place are differences between gcc and clang)
        return True
    else:
        compiler_exe = ' '.join(compiler.executables['compiler_cxx'])

    if (compiler_exe, flagname) not in _compiler_flag_compatibility:
        compatibility = _determine_flag_compatibility(compiler, flagname)
        _compiler_flag_compatibility[(compiler_exe, flagname)] = compatibility

    return _compiler_flag_compatibility[(compiler_exe, flagname)]


def get_compiler_and_args():
    """
    Returns the computed compiler and compilation flags
    """
    compiler = prefs['codegen.cpp.compiler']
    if compiler == '':
        compiler = get_default_compiler()
    extra_compile_args = prefs['codegen.cpp.extra_compile_args']
    if extra_compile_args is None:
        if compiler in ('gcc', 'unix'):
            extra_compile_args = prefs['codegen.cpp.extra_compile_args_gcc']
        elif compiler == 'msvc':
            extra_compile_args = prefs['codegen.cpp.extra_compile_args_msvc']
        else:
            extra_compile_args = []
            logger.warn(f"Unsupported compiler '{compiler}'.")

    from distutils.ccompiler import new_compiler
    from distutils.sysconfig import customize_compiler
    compiler_obj = new_compiler(compiler=compiler, verbose=0)
    customize_compiler(compiler_obj)
    extra_compile_args = [flag
                          for flag in extra_compile_args
                          if has_flag(compiler_obj, flag)]

    return compiler, extra_compile_args


_msvc_env = None
def get_msvc_env():
    global _msvc_env
    arch_name = prefs['codegen.cpp.msvc_architecture']
    if arch_name == '':
        bits = struct.calcsize('P') * 8
        if bits == 64:
            arch_name = 'x86_amd64'
        else:
            arch_name = 'x86'
    # Manual specification of vcvarsall.bat location by the user
    vcvars_loc = prefs['codegen.cpp.msvc_vars_location']
    if vcvars_loc:
        vcvars_cmd = f'"{vcvars_loc}" {arch_name}'
        return None, vcvars_cmd

    # Search for MSVC environment if not already cached
    if _msvc_env is None:
        try:
            _msvc_env = msvc.msvc14_get_vc_env(arch_name)
        except distutils.errors.DistutilsPlatformError:
            raise IOError("Cannot find Microsoft Visual Studio, You "
                          "can try to set the path to vcvarsall.bat "
                          "via the codegen.cpp.msvc_vars_location "
                          "preference explicitly.")
    return _msvc_env, None


_compiler_supports_c99 = None
def compiler_supports_c99():
    global _compiler_supports_c99
    if _compiler_supports_c99 is None:
        if platform.system() == 'Windows':
            fd, tmp_file = tempfile.mkstemp(suffix='.cpp')
            os.write(fd, """
            #if _MSC_VER < 1800
            #error
            #endif
            """.encode())
            os.close(fd)
            msvc_env, vcvars_cmd = get_msvc_env()
            if vcvars_cmd:
                cmd = f'{vcvars_cmd} && cl /E {tmp_file} > NUL 2>&1'
            else:
                os.environ.update(msvc_env)
                cmd = f'cl /E {tmp_file} > NUL 2>&1'
            return_value = os.system(cmd)
            _compiler_supports_c99 = return_value == 0
            os.remove(tmp_file)
        else:
            cmd = ('echo "#if (__STDC_VERSION__ < 199901L)\n#error\n#endif" | '
                  'cc -xc -E - > /dev/null 2>&1')
            return_value = os.system(cmd)
            _compiler_supports_c99 = return_value == 0
    return _compiler_supports_c99


class C99Check(object):
    """
    Helper class to create objects that can be passed as an ``availability_check`` to
    a `FunctionImplementation`.
    """
    def __init__(self, name):
        self.name = name

    def __call__(self, *args, **kwargs):
        if not compiler_supports_c99():
            raise NotImplementedError(f'The "{self.name}" function needs C99 compiler support')
