import platform

import numpy

from brian2.core.base import BrianObjectException
from brian2.core.variables import (DynamicArrayVariable, ArrayVariable,
                                   AuxiliaryVariable, Subexpression)
from brian2.core.functions import Function
from brian2.core.preferences import prefs, BrianPreference
from brian2.utils.logger import get_logger
from brian2.utils.stringtools import get_identifiers

from ...codeobject import constant_or_scalar, check_compiler_kwds
from ..numpy_rt import NumpyCodeObject
from ...templates import Templater
from ...generators.cython_generator import (CythonCodeGenerator, get_cpp_dtype,
                                            get_numpy_dtype)
from ...targets import codegen_targets
from ...cpp_prefs import get_compiler_and_args
from .extension_manager import cython_extension_manager

__all__ = ['CythonCodeObject']


logger = get_logger(__name__)

# Preferences
prefs.register_preferences(
    'codegen.runtime.cython',
    'Cython runtime codegen preferences',
    multiprocess_safe = BrianPreference(
        default=True,
        docs="""
        Whether to use a lock file to prevent simultaneous write access
        to cython .pyx and .so files.
        """
        ),
    cache_dir = BrianPreference(
        default=None,
        validator=lambda x: x is None or isinstance(x, str),
        docs="""
        Location of the cache directory for Cython files. By default,
        will be stored in a ``brian_extensions`` subdirectory
        where Cython inline stores its temporary files
        (the result of ``get_cython_cache_dir()``).
        """
        ),
    delete_source_files = BrianPreference(
        default=True,
        docs="""
        Whether to delete source files after compiling. The Cython
        source files can take a significant amount of disk space, and
        are not used anymore when the compiled library file exists.
        They are therefore deleted by default, but keeping them around
        can be useful for debugging.
        """
        )
    )


class CythonCodeObject(NumpyCodeObject):
    """
    Execute code using Cython.
    """
    templater = Templater('brian2.codegen.runtime.cython_rt', '.pyx',
                          env_globals={'cpp_dtype': get_cpp_dtype,
                                       'numpy_dtype': get_numpy_dtype,
                                       'dtype': numpy.dtype,
                                       'constant_or_scalar': constant_or_scalar})
    generator_class = CythonCodeGenerator
    class_name = 'cython'

    def __init__(self, owner, code, variables, variable_indices,
                 template_name, template_source, compiler_kwds,
                 name='cython_code_object*'):
        check_compiler_kwds(compiler_kwds, ['libraries', 'include_dirs',
                                            'library_dirs',
                                            'runtime_library_dirs',
                                            'sources'],
                            'Cython')
        super(CythonCodeObject, self).__init__(owner, code, variables,
                                               variable_indices,
                                               template_name, template_source,
                                               compiler_kwds={}, # do not pass the actual args
                                               name=name)
        self.compiler, self.extra_compile_args = get_compiler_and_args()
        self.define_macros = list(prefs['codegen.cpp.define_macros'])
        self.extra_link_args = list(prefs['codegen.cpp.extra_link_args'])
        self.headers = []  # not actually used

        self.include_dirs = (list(prefs['codegen.cpp.include_dirs']) +
                             compiler_kwds.get('include_dirs', []))
        self.include_dirs = list(prefs['codegen.cpp.include_dirs'])

        self.library_dirs = (list(prefs['codegen.cpp.library_dirs']) +
                             compiler_kwds.get('library_dirs', []))

        self.runtime_library_dirs = (list(prefs['codegen.cpp.runtime_library_dirs']) +
                                     compiler_kwds.get('runtime_library_dirs', []))

        self.libraries = (list(prefs['codegen.cpp.libraries']) +
                          compiler_kwds.get('libraries', []))
        self.sources = compiler_kwds.get('sources', [])

    @classmethod
    def is_available(cls):
        try:
            compiler, extra_compile_args = get_compiler_and_args()
            code = """
            #cython: language_level=3
            def main():
                cdef int x
                x = 0"""
            compiled = cython_extension_manager.create_extension(code,
                                                                 compiler=compiler,
                                                                 extra_compile_args=extra_compile_args,
                                                                 extra_link_args=prefs['codegen.cpp.extra_link_args'],
                                                                 include_dirs=prefs['codegen.cpp.include_dirs'],
                                                                 library_dirs=prefs['codegen.cpp.library_dirs'],
                                                                 runtime_library_dirs=prefs['codegen.cpp.runtime_library_dirs'])
            compiled.main()
            return True
        except Exception as ex:
            msg = (f"Cannot use Cython, a test compilation failed: {str(ex)} " 
                   f"({ex.__class__.__name__})")
            if platform.system() != 'Windows':
                msg += ("\nCertain compiler configurations (e.g. clang in a conda "
                        "environment on OS X) are known to be problematic. Note that "
                        "you can switch the compiler by setting the 'CC' and 'CXX' "
                        "environment variables. For example, you may want to try "
                        "'CC=gcc' and 'CXX=g++'.")
            logger.warn(msg, 'failed_compile_test')
            return False

    def compile_block(self, block):
        code = getattr(self.code, block, '').strip()
        if not code or 'EMPTY_CODE_BLOCK' in code:
            return None
        return cython_extension_manager.create_extension(
            code,
            define_macros=self.define_macros,
            libraries=self.libraries,
            extra_compile_args=self.extra_compile_args,
            extra_link_args=self.extra_link_args,
            include_dirs=self.include_dirs,
            library_dirs=self.library_dirs,
            runtime_library_dirs=self.runtime_library_dirs,
            compiler=self.compiler,
            owner_name=f"{self.owner.name}_{self.template_name}",
            sources=self.sources
            )
        
    def run_block(self, block):
        compiled_code = self.compiled_code[block]
        if compiled_code:
            try:
                return compiled_code.main(self.namespace)
            except Exception as exc:
                message = (f"An exception occured during the execution of the "
                           f"'{block}' block of code object '{self.name}'.\n")
                raise BrianObjectException(message, self.owner) from exc

    def _insert_func_namespace(self, func):
        impl = func.implementations[self]
        func_namespace = impl.get_namespace(self.owner)
        if func_namespace is not None:
            self.namespace.update(func_namespace)
        if impl.dependencies is not None:
            for dep in impl.dependencies.values():
                self._insert_func_namespace(dep)

    def variables_to_namespace(self):

        # Variables can refer to values that are either constant (e.g. dt)
        # or change every timestep (e.g. t). We add the values of the
        # constant variables here and add the names of non-constant variables
        # to a list

        # A list containing tuples of name and a function giving the value
        self.nonconstant_values = []

        for name, var in self.variables.items():
            if isinstance(var, Function):
                self._insert_func_namespace(var)
            if isinstance(var, (AuxiliaryVariable, Subexpression)):
                continue
            try:
                value = var.get_value()
            except (TypeError, AttributeError):
                # A dummy Variable without value or a function
                self.namespace[name] = var
                continue

            if isinstance(var, ArrayVariable):
                self.namespace[self.device.get_array_name(var,
                                                            self.variables)] = value
                self.namespace[f"_num{name}"] = var.get_len()
                if var.scalar and var.constant:
                    self.namespace[name] = value.item()
            else:
                self.namespace[name] = value

            if isinstance(var, DynamicArrayVariable):
                dyn_array_name = self.generator_class.get_array_name(var,
                                                                    access_data=False)
                self.namespace[dyn_array_name] = self.device.get_value(var,
                                                                       access_data=False)

            # Also provide the Variable object itself in the namespace (can be
            # necessary for resize operations, for example)
            self.namespace[f"_var_{name}"] = var

        # Get all identifiers in the code -- note that this is not a smart
        # function, it will get identifiers from strings, comments, etc. This
        # is not a problem here, since we only use this list to filter out
        # things. If we include something incorrectly, this only means that we
        # will pass something into the namespace unnecessarily.
        all_identifiers = get_identifiers(self.code.run)
        # Filter out all unneeded objects
        self.namespace = {k: v for k, v in self.namespace.items()
                          if k in all_identifiers}

        # There is one type of objects that we have to inject into the
        # namespace with their current value at each time step: dynamic
        # arrays that change in size during runs, where the size change is not
        # initiated by the template itself
        for name, var in self.variables.items():
            if (isinstance(var, DynamicArrayVariable) and
                    var.needs_reference_update):
                array_name = self.device.get_array_name(var, self.variables)
                if array_name in self.namespace:
                    self.nonconstant_values.append((array_name, var.get_value))
                if f"_num{name}" in self.namespace:
                    self.nonconstant_values.append((f"_num{name}", var.get_len))

    def update_namespace(self):
        # update the values of the non-constant values in the namespace
        for name, func in self.nonconstant_values:
            self.namespace[name] = func()


codegen_targets.add(CythonCodeObject)
