import warnings

import numpy as np
import operator

from numba.core import types, utils, config
from numba.core.typing.templates import (AttributeTemplate, AbstractTemplate,
                                         CallableTemplate, Registry, signature)

from numba.np.numpy_support import (ufunc_find_matching_loop,
                             supported_ufunc_loop, as_dtype,
                             from_dtype, as_dtype, resolve_output_type,
                             carray, farray, _ufunc_loop_sig)
from numba.core.errors import (TypingError, NumbaPerformanceWarning,
                               NumbaTypeError, NumbaAssertionError)
from numba import pndindex

registry = Registry()
infer = registry.register
infer_global = registry.register_global
infer_getattr = registry.register_attr


class Numpy_rules_ufunc(AbstractTemplate):
    @classmethod
    def _handle_inputs(cls, ufunc, args, kws):
        """
        Process argument types to a given *ufunc*.
        Returns a (base types, explicit outputs, ndims, layout) tuple where:
        - `base types` is a tuple of scalar types for each input
        - `explicit outputs` is a tuple of explicit output types (arrays)
        - `ndims` is the number of dimensions of the loop and also of
          any outputs, explicit or implicit
        - `layout` is the layout for any implicit output to be allocated
        """
        nin = ufunc.nin
        nout = ufunc.nout
        nargs = ufunc.nargs

        # preconditions
        assert nargs == nin + nout

        if len(args) < nin:
            msg = "ufunc '{0}': not enough arguments ({1} found, {2} required)"
            raise TypingError(msg=msg.format(ufunc.__name__, len(args), nin))

        if len(args) > nargs:
            msg = "ufunc '{0}': too many arguments ({1} found, {2} maximum)"
            raise TypingError(msg=msg.format(ufunc.__name__, len(args), nargs))

        args = [a.as_array if isinstance(a, types.ArrayCompatible) else a
                for a in args]
        arg_ndims = [a.ndim if isinstance(a, types.ArrayCompatible) else 0
                     for a in args]
        ndims = max(arg_ndims)

        # explicit outputs must be arrays (no explicit scalar return values supported)
        explicit_outputs = args[nin:]

        # all the explicit outputs must match the number max number of dimensions
        if not all(d == ndims for d in arg_ndims[nin:]):
            msg = "ufunc '{0}' called with unsuitable explicit output arrays."
            raise TypingError(msg=msg.format(ufunc.__name__))

        if not all(isinstance(output, types.ArrayCompatible)
                   for output in explicit_outputs):
            msg = "ufunc '{0}' called with an explicit output that is not an array"
            raise TypingError(msg=msg.format(ufunc.__name__))

        if not all(output.mutable for output in explicit_outputs):
            msg = "ufunc '{0}' called with an explicit output that is read-only"
            raise TypingError(msg=msg.format(ufunc.__name__))

        # find the kernel to use, based only in the input types (as does NumPy)
        base_types = [x.dtype if isinstance(x, types.ArrayCompatible) else x
                      for x in args]

        # Figure out the output array layout, if needed.
        layout = None
        if ndims > 0 and (len(explicit_outputs) < ufunc.nout):
            layout = 'C'
            layouts = [x.layout if isinstance(x, types.ArrayCompatible) else ''
                       for x in args]

            # Prefer C contig if any array is C contig.
            # Next, prefer F contig.
            # Defaults to C contig if not layouts are C/F.
            if 'C' not in layouts and 'F' in layouts:
                layout = 'F'

        return base_types, explicit_outputs, ndims, layout

    @property
    def ufunc(self):
        return self.key

    def generic(self, args, kws):
        # First, strip optional types, ufunc loops are typed on concrete types
        args = [x.type if isinstance(x, types.Optional) else x for x in args]

        ufunc = self.ufunc
        base_types, explicit_outputs, ndims, layout = self._handle_inputs(
            ufunc, args, kws)
        ufunc_loop = ufunc_find_matching_loop(ufunc, base_types)
        if ufunc_loop is None:
            raise TypingError("can't resolve ufunc {0} for types {1}".format(ufunc.__name__, args))

        # check if all the types involved in the ufunc loop are supported in this mode
        if not supported_ufunc_loop(ufunc, ufunc_loop):
            msg = "ufunc '{0}' using the loop '{1}' not supported in this mode"
            raise TypingError(msg=msg.format(ufunc.__name__, ufunc_loop.ufunc_sig))

        # if there is any explicit output type, check that it is valid
        explicit_outputs_np = [as_dtype(tp.dtype) for tp in explicit_outputs]

        # Numpy will happily use unsafe conversions (although it will actually warn)
        if not all (np.can_cast(fromty, toty, 'unsafe') for (fromty, toty) in
                    zip(ufunc_loop.numpy_outputs, explicit_outputs_np)):
            msg = "ufunc '{0}' can't cast result to explicit result type"
            raise TypingError(msg=msg.format(ufunc.__name__))

        # A valid loop was found that is compatible. The result of type inference should
        # be based on the explicit output types, and when not available with the type given
        # by the selected NumPy loop
        out = list(explicit_outputs)
        implicit_output_count = ufunc.nout - len(explicit_outputs)
        if implicit_output_count > 0:
            # XXX this is sometimes wrong for datetime64 and timedelta64,
            # as ufunc_find_matching_loop() doesn't do any type inference
            ret_tys = ufunc_loop.outputs[-implicit_output_count:]
            if ndims > 0:
                assert layout is not None
                # If either of the types involved in the ufunc operation have a
                # __array_ufunc__ method then invoke the first such one to
                # determine the output type of the ufunc.
                array_ufunc_type = None
                for a in args:
                    if hasattr(a, "__array_ufunc__"):
                        array_ufunc_type = a
                        break
                output_type = types.Array
                if array_ufunc_type is not None:
                    output_type = array_ufunc_type.__array_ufunc__(ufunc, "__call__", *args, **kws)
                    if output_type is NotImplemented:
                        msg = (f"unsupported use of ufunc {ufunc} on "
                               f"{array_ufunc_type}")
                        # raise TypeError here because
                        # NumpyRulesArrayOperator.generic is capturing
                        # TypingError
                        raise NumbaTypeError(msg)
                    elif not issubclass(output_type, types.Array):
                        msg = (f"ufunc {ufunc} on {array_ufunc_type}"
                               f"cannot return non-array {output_type}")
                        # raise TypeError here because
                        # NumpyRulesArrayOperator.generic is capturing
                        # TypingError
                        raise TypeError(msg)

                ret_tys = [output_type(dtype=ret_ty, ndim=ndims, layout=layout)
                           for ret_ty in ret_tys]
                ret_tys = [resolve_output_type(self.context, args, ret_ty)
                           for ret_ty in ret_tys]
            out.extend(ret_tys)

        return _ufunc_loop_sig(out, args)


class NumpyRulesArrayOperator(Numpy_rules_ufunc):
    _op_map = {
        operator.add: "add",
        operator.sub: "subtract",
        operator.mul: "multiply",
        operator.truediv: "true_divide",
        operator.floordiv: "floor_divide",
        operator.mod: "remainder",
        operator.pow: "power",
        operator.lshift: "left_shift",
        operator.rshift: "right_shift",
        operator.and_: "bitwise_and",
        operator.or_: "bitwise_or",
        operator.xor: "bitwise_xor",
        operator.eq: "equal",
        operator.gt: "greater",
        operator.ge: "greater_equal",
        operator.lt: "less",
        operator.le: "less_equal",
        operator.ne: "not_equal",
    }

    @property
    def ufunc(self):
        return getattr(np, self._op_map[self.key])

    @classmethod
    def install_operations(cls):
        for op, ufunc_name in cls._op_map.items():
            infer_global(op)(
                type("NumpyRulesArrayOperator_" + ufunc_name, (cls,), dict(key=op))
            )

    def generic(self, args, kws):
        '''Overloads and calls base class generic() method, returning
        None if a TypingError occurred.

        Returning None for operators is important since operators are
        heavily overloaded, and by suppressing type errors, we allow
        type inference to check other possibilities before giving up
        (particularly user-defined operators).
        '''
        try:
            sig = super(NumpyRulesArrayOperator, self).generic(args, kws)
        except TypingError:
            return None
        if sig is None:
            return None
        args = sig.args
        # Only accept at least one array argument, otherwise the operator
        # doesn't involve Numpy's ufunc machinery.
        if not any(isinstance(arg, types.ArrayCompatible)
                   for arg in args):
            return None
        return sig


_binop_map = NumpyRulesArrayOperator._op_map

class NumpyRulesInplaceArrayOperator(NumpyRulesArrayOperator):
    _op_map = {
        operator.iadd: "add",
        operator.isub: "subtract",
        operator.imul: "multiply",
        operator.itruediv: "true_divide",
        operator.ifloordiv: "floor_divide",
        operator.imod: "remainder",
        operator.ipow: "power",
        operator.ilshift: "left_shift",
        operator.irshift: "right_shift",
        operator.iand: "bitwise_and",
        operator.ior: "bitwise_or",
        operator.ixor: "bitwise_xor",
    }

    def generic(self, args, kws):
        # Type the inplace operator as if an explicit output was passed,
        # to handle type resolution correctly.
        # (for example int8[:] += int16[:] should use an int8[:] output,
        #  not int16[:])
        lhs, rhs = args
        if not isinstance(lhs, types.ArrayCompatible):
            return
        args = args + (lhs,)
        sig = super(NumpyRulesInplaceArrayOperator, self).generic(args, kws)
        # Strip off the fake explicit output
        assert len(sig.args) == 3
        real_sig = signature(sig.return_type, *sig.args[:2])
        return real_sig


class NumpyRulesUnaryArrayOperator(NumpyRulesArrayOperator):
    _op_map = {
        operator.pos: "positive",
        operator.neg: "negative",
        operator.invert: "invert",
    }

    def generic(self, args, kws):
        assert not kws
        if len(args) == 1 and isinstance(args[0], types.ArrayCompatible):
            return super(NumpyRulesUnaryArrayOperator, self).generic(args, kws)


# list of unary ufuncs to register

math_operations = [ "add", "subtract", "multiply",
                    "logaddexp", "logaddexp2", "true_divide",
                    "floor_divide", "negative", "positive", "power",
                    "float_power", "remainder", "fmod", "absolute",
                    "rint", "sign", "conjugate", "exp", "exp2",
                    "log", "log2", "log10", "expm1", "log1p",
                    "sqrt", "square", "cbrt", "reciprocal",
                    "divide", "mod", "divmod", "abs", "fabs" , "gcd", "lcm"]

trigonometric_functions = [ "sin", "cos", "tan", "arcsin",
                            "arccos", "arctan", "arctan2",
                            "hypot", "sinh", "cosh", "tanh",
                            "arcsinh", "arccosh", "arctanh",
                            "deg2rad", "rad2deg", "degrees",
                            "radians" ]

bit_twiddling_functions = ["bitwise_and", "bitwise_or",
                           "bitwise_xor", "invert",
                           "left_shift", "right_shift",
                           "bitwise_not" ]

comparison_functions = [ "greater", "greater_equal", "less",
                         "less_equal", "not_equal", "equal",
                         "logical_and", "logical_or",
                         "logical_xor", "logical_not",
                         "maximum", "minimum", "fmax", "fmin" ]

floating_functions = [ "isfinite", "isinf", "isnan", "signbit",
                       "copysign", "nextafter", "modf", "ldexp",
                       "frexp", "floor", "ceil", "trunc",
                       "spacing" ]

logic_functions = [ "isnat" ]


# This is a set of the ufuncs that are not yet supported by Lowering. In order
# to trigger no-python mode we must not register them until their Lowering is
# implemented.
#
# It also works as a nice TODO list for ufunc support :)
_unsupported = set([ 'frexp',
                     'modf',
                 ])


def register_numpy_ufunc(name, register_global=infer_global):
    func = getattr(np, name)
    class typing_class(Numpy_rules_ufunc):
        key = func

    typing_class.__name__ = "resolve_{0}".format(name)

    # A list of ufuncs that are in fact aliases of other ufuncs. They need to
    # insert the resolve method, but not register the ufunc itself
    aliases = ("abs", "bitwise_not", "divide", "abs")

    if name not in aliases:
        register_global(func, types.Function(typing_class))

all_ufuncs = sum([math_operations, trigonometric_functions,
                  bit_twiddling_functions, comparison_functions,
                  floating_functions, logic_functions], [])

supported_ufuncs = [x for x in all_ufuncs if x not in _unsupported]

for func in supported_ufuncs:
    register_numpy_ufunc(func)

all_ufuncs = [getattr(np, name) for name in all_ufuncs]
supported_ufuncs = [getattr(np, name) for name in supported_ufuncs]

NumpyRulesUnaryArrayOperator.install_operations()
NumpyRulesArrayOperator.install_operations()
NumpyRulesInplaceArrayOperator.install_operations()

supported_array_operators = set(
    NumpyRulesUnaryArrayOperator._op_map.keys()
).union(
    NumpyRulesArrayOperator._op_map.keys()
).union(
    NumpyRulesInplaceArrayOperator._op_map.keys()
)

del _unsupported


# -----------------------------------------------------------------------------
# Install global helpers for array methods.

class Numpy_method_redirection(AbstractTemplate):
    """
    A template redirecting a Numpy global function (e.g. np.sum) to an
    array method of the same name (e.g. ndarray.sum).
    """

    # Arguments like *axis* can specialize on literals but also support
    # non-literals
    prefer_literal = True

    def generic(self, args, kws):
        pysig = None
        if kws:
            if self.method_name == 'sum':
                if 'axis' in kws and 'dtype' not in kws:
                    def sum_stub(arr, axis):
                        pass
                    pysig = utils.pysignature(sum_stub)
                elif 'dtype' in kws and 'axis' not in kws:
                    def sum_stub(arr, dtype):
                        pass
                    pysig = utils.pysignature(sum_stub)
                elif 'dtype' in kws and 'axis' in kws:
                    def sum_stub(arr, axis, dtype):
                        pass
                    pysig = utils.pysignature(sum_stub)
            elif self.method_name == 'argsort':
                def argsort_stub(arr, kind='quicksort'):
                    pass
                pysig = utils.pysignature(argsort_stub)
            else:
                fmt = "numba doesn't support kwarg for {}"
                raise TypingError(fmt.format(self.method_name))

        arr = args[0]
        # This will return a BoundFunction
        meth_ty = self.context.resolve_getattr(arr, self.method_name)
        # Resolve arguments on the bound function
        meth_sig = self.context.resolve_function_type(meth_ty, args[1:], kws)
        if meth_sig is not None:
            return meth_sig.as_function().replace(pysig=pysig)


# Function to glue attributes onto the numpy-esque object
def _numpy_redirect(fname):
    numpy_function = getattr(np, fname)
    cls = type("Numpy_redirect_{0}".format(fname), (Numpy_method_redirection,),
               dict(key=numpy_function, method_name=fname))
    infer_global(numpy_function, types.Function(cls))


for func in ['sum', 'argsort', 'nonzero', 'ravel']:
    _numpy_redirect(func)


# -----------------------------------------------------------------------------
# Numpy scalar constructors

# Register np.int8, etc. as converters to the equivalent Numba types
np_types = set(getattr(np, str(nb_type)) for nb_type in types.number_domain)
np_types.add(np.bool_)
# Those may or may not be aliases (depending on the Numpy build / version)
np_types.add(np.intc)
np_types.add(np.intp)
np_types.add(np.uintc)
np_types.add(np.uintp)


def register_number_classes(register_global):
    for np_type in np_types:
        nb_type = getattr(types, np_type.__name__)

        register_global(np_type, types.NumberClass(nb_type))


register_number_classes(infer_global)


# -----------------------------------------------------------------------------
# Numpy array constructors

def parse_shape(shape):
    """
    Given a shape, return the number of dimensions.
    """
    ndim = None
    if isinstance(shape, types.Integer):
        ndim = 1
    elif isinstance(shape, (types.Tuple, types.UniTuple)):
        int_tys = (types.Integer, types.IntEnumMember)
        if all(isinstance(s, int_tys) for s in shape):
            ndim = len(shape)
    return ndim

def parse_dtype(dtype):
    """
    Return the dtype of a type, if it is either a DtypeSpec (used for most
    dtypes) or a TypeRef (used for record types).
    """
    if isinstance(dtype, types.DTypeSpec):
        return dtype.dtype
    elif isinstance(dtype, types.TypeRef):
        return dtype.instance_type
    elif isinstance(dtype, types.StringLiteral):
        dtstr = dtype.literal_value
        try:
            dt = np.dtype(dtstr)
        except TypeError:
            msg = f"Invalid NumPy dtype specified: '{dtstr}'"
            raise TypingError(msg)
        return from_dtype(dt)

def _parse_nested_sequence(context, typ):
    """
    Parse a (possibly 0d) nested sequence type.
    A (ndim, dtype) tuple is returned.  Note the sequence may still be
    heterogeneous, as long as it converts to the given dtype.
    """
    if isinstance(typ, (types.Buffer,)):
        raise TypingError("%s not allowed in a homogeneous sequence" % typ)
    elif isinstance(typ, (types.Sequence,)):
        n, dtype = _parse_nested_sequence(context, typ.dtype)
        return n + 1, dtype
    elif isinstance(typ, (types.BaseTuple,)):
        if typ.count == 0:
            # Mimic Numpy's behaviour
            return 1, types.float64
        n, dtype = _parse_nested_sequence(context, typ[0])
        dtypes = [dtype]
        for i in range(1, typ.count):
            _n, dtype = _parse_nested_sequence(context, typ[i])
            if _n != n:
                raise TypingError("type %s does not have a regular shape"
                                  % (typ,))
            dtypes.append(dtype)
        dtype = context.unify_types(*dtypes)
        if dtype is None:
            raise TypingError("cannot convert %s to a homogeneous type" % typ)
        return n + 1, dtype
    else:
        # Scalar type => check it's valid as a Numpy array dtype
        as_dtype(typ)
        return 0, typ


def _infer_dtype_from_inputs(inputs):
    return dtype


def _homogeneous_dims(context, func_name, arrays):
    ndim = arrays[0].ndim
    for a in arrays:
        if a.ndim != ndim:
            msg = (f"{func_name}(): all the input arrays must have same number "
                   "of dimensions")
            raise NumbaTypeError(msg)
    return ndim

def _sequence_of_arrays(context, func_name, arrays,
                        dim_chooser=_homogeneous_dims):
    if (not isinstance(arrays, types.BaseTuple)
        or not len(arrays)
        or not all(isinstance(a, types.Array) for a in arrays)):
        raise TypeError("%s(): expecting a non-empty tuple of arrays, "
                        "got %s" % (func_name, arrays))

    ndim = dim_chooser(context, func_name, arrays)

    dtype = context.unify_types(*(a.dtype for a in arrays))
    if dtype is None:
        raise TypeError("%s(): input arrays must have "
                        "compatible dtypes" % func_name)

    return dtype, ndim

def _choose_concatenation_layout(arrays):
    # Only create a F array if all input arrays have F layout.
    # This is a simplified version of Numpy's behaviour,
    # while Numpy's actually processes the input strides to
    # decide on optimal output strides
    # (see PyArray_CreateMultiSortedStridePerm()).
    return 'F' if all(a.layout == 'F' for a in arrays) else 'C'


class BaseStackTemplate(CallableTemplate):

    def generic(self):
        def typer(arrays):
            dtype, ndim = _sequence_of_arrays(self.context,
                                              self.func_name, arrays)

            ndim = max(ndim, self.ndim_min)
            layout = _choose_concatenation_layout(arrays)

            return types.Array(dtype, ndim, layout)

        return typer


# -----------------------------------------------------------------------------
# Linear algebra


class MatMulTyperMixin(object):

    def matmul_typer(self, a, b, out=None):
        """
        Typer function for Numpy matrix multiplication.
        """
        if not isinstance(a, types.Array) or not isinstance(b, types.Array):
            return
        if not all(x.ndim in (1, 2) for x in (a, b)):
            raise TypingError("%s only supported on 1-D and 2-D arrays"
                              % (self.func_name, ))
        # Output dimensionality
        ndims = set([a.ndim, b.ndim])
        if ndims == set([2]):
            # M * M
            out_ndim = 2
        elif ndims == set([1, 2]):
            # M* V and V * M
            out_ndim = 1
        elif ndims == set([1]):
            # V * V
            out_ndim = 0

        if out is not None:
            if out_ndim == 0:
                raise TypeError("explicit output unsupported for vector * vector")
            elif out.ndim != out_ndim:
                raise TypeError("explicit output has incorrect dimensionality")
            if not isinstance(out, types.Array) or out.layout != 'C':
                raise TypeError("output must be a C-contiguous array")
            all_args = (a, b, out)
        else:
            all_args = (a, b)

        if not (config.DISABLE_PERFORMANCE_WARNINGS or
                all(x.layout in 'CF' for x in (a, b))):
            msg = ("%s is faster on contiguous arrays, called on %s" %
                   (self.func_name, (a, b)))
            warnings.warn(NumbaPerformanceWarning(msg))
        if not all(x.dtype == a.dtype for x in all_args):
            raise TypingError("%s arguments must all have "
                              "the same dtype" % (self.func_name,))
        if not isinstance(a.dtype, (types.Float, types.Complex)):
            raise TypingError("%s only supported on "
                              "float and complex arrays"
                              % (self.func_name,))
        if out:
            return out
        elif out_ndim > 0:
            return types.Array(a.dtype, out_ndim, 'C')
        else:
            return a.dtype


def _check_linalg_matrix(a, func_name):
    if not isinstance(a, types.Array):
        return
    if not a.ndim == 2:
        raise TypingError("np.linalg.%s() only supported on 2-D arrays"
                          % func_name)
    if not isinstance(a.dtype, (types.Float, types.Complex)):
        raise TypingError("np.linalg.%s() only supported on "
                          "float and complex arrays" % func_name)

# -----------------------------------------------------------------------------
# Miscellaneous functions

@infer_global(np.ndenumerate)
class NdEnumerate(AbstractTemplate):

    def generic(self, args, kws):
        assert not kws
        arr, = args

        if isinstance(arr, types.Array):
            enumerate_type = types.NumpyNdEnumerateType(arr)
            return signature(enumerate_type, *args)


@infer_global(np.nditer)
class NdIter(AbstractTemplate):

    def generic(self, args, kws):
        assert not kws
        if len(args) != 1:
            return
        arrays, = args

        if isinstance(arrays, types.BaseTuple):
            if not arrays:
                return
            arrays = list(arrays)
        else:
            arrays = [arrays]
        nditerty = types.NumpyNdIterType(arrays)
        return signature(nditerty, *args)


@infer_global(pndindex)
@infer_global(np.ndindex)
class NdIndex(AbstractTemplate):

    def generic(self, args, kws):
        assert not kws

        # Either ndindex(shape) or ndindex(*shape)
        if len(args) == 1 and isinstance(args[0], types.BaseTuple):
            tup = args[0]
            if tup.count > 0 and not isinstance(tup, types.UniTuple):
                # Heterogeneous tuple
                return
            shape = list(tup)
        else:
            shape = args

        if all(isinstance(x, types.Integer) for x in shape):
            iterator_type = types.NumpyNdIndexType(len(shape))
            return signature(iterator_type, *args)
