# -*- coding: utf-8 -*-
from __future__ import print_function, division, absolute_import

import warnings
import inspect
from contextlib import contextmanager

import numpy as np

from numba.decorators import jit
from numba.targets.descriptors import TargetDescriptor
from numba.targets.options import TargetOptions
from numba.targets.registry import dispatcher_registry, cpu_target
from numba import utils, compiler, types, sigutils
from numba.numpy_support import as_dtype
from . import _internal
from .sigparse import parse_signature
from .wrappers import build_ufunc_wrapper, build_gufunc_wrapper
from numba.caching import FunctionCache, NullCache


import llvmlite.llvmpy.core as lc

class UFuncTargetOptions(TargetOptions):
    OPTIONS = {
        "nopython" : bool,
        "forceobj" : bool,
        "fastmath" : bool,
    }


class UFuncTarget(TargetDescriptor):
    options = UFuncTargetOptions

    @property
    def typing_context(self):
        return cpu_target.typing_context

    @property
    def target_context(self):
        return cpu_target.target_context

ufunc_target = UFuncTarget()


class UFuncDispatcher(object):
    """
    An object handling compilation of various signatures for a ufunc.
    """
    targetdescr = ufunc_target

    def __init__(self, py_func, locals={}, targetoptions={}):
        self.py_func = py_func
        self.overloads = utils.UniqueDict()
        self.targetoptions = targetoptions
        self.locals = locals
        self.cache = NullCache()

    def enable_caching(self):
        self.cache = FunctionCache(self.py_func)

    def compile(self, sig, locals={}, **targetoptions):
        locs = self.locals.copy()
        locs.update(locals)

        topt = self.targetoptions.copy()
        topt.update(targetoptions)

        flags = compiler.Flags()
        self.targetdescr.options.parse_as_flags(flags, topt)

        flags.set("no_cpython_wrapper")
        flags.set("error_model", "numpy")
        # Disable loop lifting
        # The feature requires a real python function
        flags.unset("enable_looplift")

        return self._compile_core(sig, flags, locals)

    def _compile_core(self, sig, flags, locals):
        """
        Trigger the compiler on the core function or load a previously
        compiled version from the cache.  Returns the CompileResult.
        """
        typingctx = self.targetdescr.typing_context
        targetctx = self.targetdescr.target_context

        @contextmanager
        def store_overloads_on_success():
            # use to ensure overloads are stored on success
            try:
                yield
            except:
                raise
            else:
                exists = self.overloads.get(cres.signature)
                if exists is None:
                    self.overloads[cres.signature] = cres

        # Use cache and compiler in a critical section
        with compiler.lock_compiler:
            with store_overloads_on_success():
                # attempt look up of existing
                cres = self.cache.load_overload(sig, targetctx)
                if cres is not None:
                    return cres

                # Compile
                args, return_type = sigutils.normalize_signature(sig)
                cres = compiler.compile_extra(typingctx, targetctx,
                                              self.py_func, args=args,
                                              return_type=return_type,
                                              flags=flags, locals=locals)

                # cache lookup failed before so safe to save
                self.cache.save_overload(sig, cres)

                return cres


dispatcher_registry['npyufunc'] = UFuncDispatcher


# Utility functions

def _compile_element_wise_function(nb_func, targetoptions, sig):
    # Do compilation
    # Return CompileResult to test
    cres = nb_func.compile(sig, **targetoptions)
    args, return_type = sigutils.normalize_signature(sig)
    return cres, args, return_type

def _finalize_ufunc_signature(cres, args, return_type):
    '''Given a compilation result, argument types, and a return type,
    build a valid Numba signature after validating that it doesn't
    violate the constraints for the compilation mode.
    '''
    if return_type is None:
        if cres.objectmode:
            # Object mode is used and return type is not specified
            raise TypeError("return type must be specified for object mode")
        else:
            return_type = cres.signature.return_type

    assert return_type != types.pyobject
    return return_type(*args)

def _build_element_wise_ufunc_wrapper(cres, signature):
    '''Build a wrapper for the ufunc loop entry point given by the
    compilation result object, using the element-wise signature.
    '''
    ctx = cres.target_context
    library = cres.library
    fname = cres.fndesc.llvm_func_name

    env = cres.environment
    envptr = env.as_pointer(ctx)

    with compiler.lock_compiler:
        ptr = build_ufunc_wrapper(library, ctx, fname, signature,
                                cres.objectmode, envptr, env)

    # Get dtypes
    dtypenums = [as_dtype(a).num for a in signature.args]
    dtypenums.append(as_dtype(signature.return_type).num)
    return dtypenums, ptr, env


_identities = {
    0: _internal.PyUFunc_Zero,
    1: _internal.PyUFunc_One,
    None: _internal.PyUFunc_None,
    "reorderable": _internal.PyUFunc_ReorderableNone,
    }

def parse_identity(identity):
    """
    Parse an identity value and return the corresponding low-level value
    for Numpy.
    """
    try:
        identity = _identities[identity]
    except KeyError:
        raise ValueError("Invalid identity value %r" % (identity,))
    return identity


# Class definitions

class _BaseUFuncBuilder(object):

    def add(self, sig=None):
        if hasattr(self, 'targetoptions'):
            targetoptions = self.targetoptions
        else:
            targetoptions = self.nb_func.targetoptions
        cres, args, return_type = _compile_element_wise_function(
            self.nb_func, targetoptions, sig)
        sig = self._finalize_signature(cres, args, return_type)
        self._sigs.append(sig)
        self._cres[sig] = cres
        return cres

    def disable_compile(self):
        """
        Disable the compilation of new signatures at call time.
        """
        # Override this for implementations that support lazy compilation


class UFuncBuilder(_BaseUFuncBuilder):

    def __init__(self, py_func, identity=None, cache=False, targetoptions={}):
        self.py_func = py_func
        self.identity = parse_identity(identity)
        self.nb_func = jit(target='npyufunc', cache=cache, **targetoptions)(py_func)
        self._sigs = []
        self._cres = {}

    def _finalize_signature(self, cres, args, return_type):
        '''Slated for deprecation, use ufuncbuilder._finalize_ufunc_signature()
        instead.
        '''
        return _finalize_ufunc_signature(cres, args, return_type)

    def build_ufunc(self):
        dtypelist = []
        ptrlist = []
        if not self.nb_func:
            raise TypeError("No definition")

        # Get signature in the order they are added
        keepalive = []
        cres = None
        for sig in self._sigs:
            cres = self._cres[sig]
            dtypenums, ptr, env = self.build(cres, sig)
            dtypelist.append(dtypenums)
            ptrlist.append(utils.longint(ptr))
            keepalive.append((cres.library, env))

        datlist = [None] * len(ptrlist)

        if cres is None:
            argspec = inspect.getargspec(self.py_func)
            inct = len(argspec.args)
        else:
            inct = len(cres.signature.args)
        outct = 1

        # Becareful that fromfunc does not provide full error checking yet.
        # If typenum is out-of-bound, we have nasty memory corruptions.
        # For instance, -1 for typenum will cause segfault.
        # If elements of type-list (2nd arg) is tuple instead,
        # there will also memory corruption. (Seems like code rewrite.)
        ufunc = _internal.fromfunc(self.py_func.__name__, self.py_func.__doc__,
                                   ptrlist, dtypelist, inct, outct, datlist,
                                   keepalive, self.identity)

        return ufunc

    def build(self, cres, signature):
        '''Slated for deprecation, use
        ufuncbuilder._build_element_wise_ufunc_wrapper().
        '''
        return _build_element_wise_ufunc_wrapper(cres, signature)


class GUFuncBuilder(_BaseUFuncBuilder):

    # TODO handle scalar
    def __init__(self, py_func, signature, identity=None, cache=False,
                 targetoptions={}):
        self.py_func = py_func
        self.identity = parse_identity(identity)
        self.nb_func = jit(target='npyufunc', cache=cache)(py_func)
        self.signature = signature
        self.sin, self.sout = parse_signature(signature)
        self.targetoptions = targetoptions
        self.cache = cache
        self._sigs = []
        self._cres = {}

    def _finalize_signature(self, cres, args, return_type):
        if not cres.objectmode and cres.signature.return_type != types.void:
            raise TypeError("gufunc kernel must have void return type")

        if return_type is None:
            return_type = types.void

        return return_type(*args)

    def build_ufunc(self):
        dtypelist = []
        ptrlist = []
        if not self.nb_func:
            raise TypeError("No definition")

        # Get signature in the order they are added
        keepalive = []
        for sig in self._sigs:
            cres = self._cres[sig]
            dtypenums, ptr, env = self.build(cres)
            dtypelist.append(dtypenums)
            ptrlist.append(utils.longint(ptr))
            keepalive.append((cres.library, env))

        datlist = [None] * len(ptrlist)

        inct = len(self.sin)
        outct = len(self.sout)

        # Pass envs to fromfuncsig to bind to the lifetime of the ufunc object
        ufunc = _internal.fromfunc(self.py_func.__name__, self.py_func.__doc__,
                                   ptrlist, dtypelist, inct, outct, datlist,
                                   keepalive, self.identity, self.signature)
        return ufunc

    def build(self, cres):
        """
        Returns (dtype numbers, function ptr, EnvironmentObject)
        """
        # Buider wrapper for ufunc entry point
        signature = cres.signature
        with compiler.lock_compiler:
            ptr, env, wrapper_name = build_gufunc_wrapper(self.py_func, cres,
                                                          self.sin, self.sout,
                                                          cache=self.cache)

        # Get dtypes
        dtypenums = []
        for a in signature.args:
            if isinstance(a, types.Array):
                ty = a.dtype
            else:
                ty = a
            dtypenums.append(as_dtype(ty).num)
        return dtypenums, ptr, env
