# Copyright 2013-2019 The Meson development team

# 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 glob
import re
import os

from .. import mlog
from .. import mesonlib
from ..environment import detect_cpu_family

from .base import (DependencyException, ExternalDependency, HasNativeKwarg)


class CudaDependency(ExternalDependency):

    supported_languages = ['cuda', 'cpp', 'c'] # see also _default_language

    def __init__(self, environment, kwargs):
        HasNativeKwarg.__init__(self, kwargs) # initialize self.for_machine
        compilers = environment.coredata.compilers[self.for_machine]
        language = self._detect_language(compilers)
        if language not in self.supported_languages:
            raise DependencyException('Language \'{}\' is not supported by the CUDA Toolkit. Supported languages are {}.'.format(language, self.supported_languages))

        super().__init__('cuda', environment, language, kwargs)
        self.requested_modules = self.get_requested(kwargs)
        if 'cudart' not in self.requested_modules:
            self.requested_modules = ['cudart'] + self.requested_modules

        (self.cuda_path, self.version, self.is_found) = self._detect_cuda_path_and_version()
        if not self.is_found:
            return

        if not os.path.isabs(self.cuda_path):
            raise DependencyException('CUDA Toolkit path must be absolute, got \'{}\'.'.format(self.cuda_path))

        # nvcc already knows where to find the CUDA Toolkit, but if we're compiling
        # a mixed C/C++/CUDA project, we still need to make the include dir searchable
        if self.language != 'cuda' or len(compilers) > 1:
            self.incdir = os.path.join(self.cuda_path, 'include')
            self.compile_args += ['-I{}'.format(self.incdir)]

        if self.language != 'cuda':
            arch_libdir = self._detect_arch_libdir()
            self.libdir = os.path.join(self.cuda_path, arch_libdir)
            mlog.debug('CUDA library directory is', mlog.bold(self.libdir))
        else:
            self.libdir = None

        self.is_found = self._find_requested_libraries()

    @classmethod
    def _detect_language(cls, compilers):
        for lang in cls.supported_languages:
            if lang in compilers:
                return lang
        return list(compilers.keys())[0]

    def _detect_cuda_path_and_version(self):
        self.env_var = self._default_path_env_var()
        mlog.debug('Default path env var:', mlog.bold(self.env_var))

        version_reqs = self.version_reqs
        if self.language == 'cuda':
            nvcc_version = self._strip_patch_version(self.get_compiler().version)
            mlog.debug('nvcc version:', mlog.bold(nvcc_version))
            if version_reqs:
                # make sure nvcc version satisfies specified version requirements
                (found_some, not_found, found) = mesonlib.version_compare_many(nvcc_version, version_reqs)
                if not_found:
                    msg = 'The current nvcc version {} does not satisfy the specified CUDA Toolkit version requirements {}.'.format(nvcc_version, version_reqs)
                    return self._report_dependency_error(msg, (None, None, False))

            # use nvcc version to find a matching CUDA Toolkit
            version_reqs = ['={}'.format(nvcc_version)]
        else:
            nvcc_version = None

        paths = [(path, self._cuda_toolkit_version(path), default) for (path, default) in self._cuda_paths()]
        if version_reqs:
            return self._find_matching_toolkit(paths, version_reqs, nvcc_version)

        defaults = [(path, version) for (path, version, default) in paths if default]
        if defaults:
            return (*defaults[0], True)

        platform_msg = 'set the CUDA_PATH environment variable' if self._is_windows() \
            else 'set the CUDA_PATH environment variable/create the \'/usr/local/cuda\' symbolic link'
        msg = 'Please specify the desired CUDA Toolkit version (e.g. dependency(\'cuda\', version : \'>=10.1\')) or {} to point to the location of your desired version.'.format(platform_msg)
        return self._report_dependency_error(msg, (None, None, False))

    def _find_matching_toolkit(self, paths, version_reqs, nvcc_version):
        # keep the default paths order intact, sort the rest in the descending order
        # according to the toolkit version
        defaults, rest = mesonlib.partition(lambda t: not t[2], paths)
        defaults = list(defaults)
        paths = defaults + sorted(rest, key=lambda t: mesonlib.Version(t[1]), reverse=True)
        mlog.debug('Search paths: {}'.format(paths))

        if nvcc_version and defaults:
            default_src = "the {} environment variable".format(self.env_var) if self.env_var else "the \'/usr/local/cuda\' symbolic link"
            nvcc_warning = 'The default CUDA Toolkit as designated by {} ({}) doesn\'t match the current nvcc version {} and will be ignored.'.format(default_src, os.path.realpath(defaults[0][0]), nvcc_version)
        else:
            nvcc_warning = None

        for (path, version, default) in paths:
            (found_some, not_found, found) = mesonlib.version_compare_many(version, version_reqs)
            if not not_found:
                if not default and nvcc_warning:
                    mlog.warning(nvcc_warning)
                return (path, version, True)

        if nvcc_warning:
            mlog.warning(nvcc_warning)
        return (None, None, False)

    def _default_path_env_var(self):
        env_vars = ['CUDA_PATH'] if self._is_windows() else ['CUDA_PATH', 'CUDA_HOME', 'CUDA_ROOT']
        env_vars = [var for var in env_vars if var in os.environ]
        user_defaults = set([os.environ[var] for var in env_vars])
        if len(user_defaults) > 1:
            mlog.warning('Environment variables {} point to conflicting toolkit locations ({}). Toolkit selection might produce unexpected results.'.format(', '.join(env_vars), ', '.join(user_defaults)))
        return env_vars[0] if env_vars else None

    def _cuda_paths(self):
        return ([(os.environ[self.env_var], True)] if self.env_var else []) \
            + (self._cuda_paths_win() if self._is_windows() else self._cuda_paths_nix())

    def _cuda_paths_win(self):
        env_vars = os.environ.keys()
        return [(os.environ[var], False) for var in env_vars if var.startswith('CUDA_PATH_')]

    def _cuda_paths_nix(self):
        # include /usr/local/cuda default only if no env_var was found
        pattern = '/usr/local/cuda-*' if self.env_var else '/usr/local/cuda*'
        return [(path, os.path.basename(path) == 'cuda') for path in glob.iglob(pattern)]

    toolkit_version_regex = re.compile(r'^CUDA Version\s+(.*)$')
    path_version_win_regex = re.compile(r'^v(.*)$')
    path_version_nix_regex = re.compile(r'^cuda-(.*)$')

    def _cuda_toolkit_version(self, path):
        version = self._read_toolkit_version_txt(path)
        if version:
            return version

        mlog.debug('Falling back to extracting version from path')
        path_version_regex = self.path_version_win_regex if self._is_windows() else self.path_version_nix_regex
        m = path_version_regex.match(os.path.basename(path))
        if m:
            return m[1]

        mlog.warning('Could not detect CUDA Toolkit version for {}'.format(path))
        return '0.0'

    def _read_toolkit_version_txt(self, path):
        # Read 'version.txt' at the root of the CUDA Toolkit directory to determine the tookit version
        version_file_path = os.path.join(path, 'version.txt')
        try:
            with open(version_file_path) as version_file:
                version_str = version_file.readline() # e.g. 'CUDA Version 10.1.168'
                m = self.toolkit_version_regex.match(version_str)
                if m:
                    return self._strip_patch_version(m[1])
        except Exception as e:
            mlog.debug('Could not read CUDA Toolkit\'s version file {}: {}'.format(version_file_path, str(e)))

        return None

    @classmethod
    def _strip_patch_version(cls, version):
        return '.'.join(version.split('.')[:2])

    def _detect_arch_libdir(self):
        arch = detect_cpu_family(self.env.coredata.compilers.host)
        machine = self.env.machines[self.for_machine]
        msg = '{} architecture is not supported in {} version of the CUDA Toolkit.'
        if machine.is_windows():
            libdirs = {'x86': 'Win32', 'x86_64': 'x64'}
            if arch not in libdirs:
                raise DependencyException(msg.format(arch, 'Windows'))
            return os.path.join('lib', libdirs[arch])
        elif machine.is_linux():
            libdirs = {'x86_64': 'lib64', 'ppc64': 'lib'}
            if arch not in libdirs:
                raise DependencyException(msg.format(arch, 'Linux'))
            return libdirs[arch]
        elif machine.is_osx():
            libdirs = {'x86_64': 'lib64'}
            if arch not in libdirs:
                raise DependencyException(msg.format(arch, 'macOS'))
            return libdirs[arch]
        else:
            raise DependencyException('CUDA Toolkit: unsupported platform.')

    def _find_requested_libraries(self):
        self.lib_modules = {}
        all_found = True

        for module in self.requested_modules:
            args = self.clib_compiler.find_library(module, self.env, [self.libdir] if self.libdir else [])
            if args is None:
                self._report_dependency_error('Couldn\'t find requested CUDA module \'{}\''.format(module))
                all_found = False
            else:
                mlog.debug('Link args for CUDA module \'{}\' are {}'.format(module, args))
                self.lib_modules[module] = args

        return all_found

    def _is_windows(self):
        return self.env.machines[self.for_machine].is_windows()

    def _report_dependency_error(self, msg, ret_val=None):
        if self.required:
            raise DependencyException(msg)

        mlog.debug(msg)
        return ret_val

    def log_details(self):
        module_str = ', '.join(self.requested_modules)
        return 'modules: ' + module_str

    def log_info(self):
        return self.cuda_path if self.cuda_path else ''

    def get_requested(self, kwargs):
        candidates = mesonlib.extract_as_list(kwargs, 'modules')
        for c in candidates:
            if not isinstance(c, str):
                raise DependencyException('CUDA module argument is not a string.')
        return candidates

    def get_link_args(self, **kwargs):
        args = []
        if self.libdir:
            args += self.clib_compiler.get_linker_search_args(self.libdir)
        for lib in self.requested_modules:
            args += self.lib_modules[lib]
        return args