"""
Implementation of the range object for fixed-size integers.
"""

import operator

from numba import prange
from numba.core import types, cgutils, errors, config
from numba.core.imputils import (lower_builtin, lower_cast,
                                    iterator_impl, impl_ret_untracked)
from numba.core.typing import signature
from numba.core.extending import intrinsic, overload, overload_attribute, register_jitable
from numba.parfors.parfor import internal_prange

def make_range_iterator(typ):
    """
    Return the Structure representation of the given *typ* (an
    instance of types.RangeIteratorType).
    """
    return cgutils.create_struct_proxy(typ)


def make_range_impl(int_type, range_state_type, range_iter_type):
    RangeState = cgutils.create_struct_proxy(range_state_type)

    @lower_builtin(range, int_type)
    @lower_builtin(prange, int_type)
    @lower_builtin(internal_prange, int_type)
    def range1_impl(context, builder, sig, args):
        """
        range(stop: int) -> range object
        """
        [stop] = args
        state = RangeState(context, builder)
        state.start = context.get_constant(int_type, 0)
        state.stop = stop
        state.step = context.get_constant(int_type, 1)
        return impl_ret_untracked(context,
                                  builder,
                                  range_state_type,
                                  state._getvalue())

    @lower_builtin(range, int_type, int_type)
    @lower_builtin(prange, int_type, int_type)
    @lower_builtin(internal_prange, int_type, int_type)
    def range2_impl(context, builder, sig, args):
        """
        range(start: int, stop: int) -> range object
        """
        start, stop = args
        state = RangeState(context, builder)
        state.start = start
        state.stop = stop
        state.step = context.get_constant(int_type, 1)
        return impl_ret_untracked(context,
                                  builder,
                                  range_state_type,
                                  state._getvalue())

    @lower_builtin(range, int_type, int_type, int_type)
    @lower_builtin(prange, int_type, int_type, int_type)
    @lower_builtin(internal_prange, int_type, int_type, int_type)
    def range3_impl(context, builder, sig, args):
        """
        range(start: int, stop: int, step: int) -> range object
        """
        [start, stop, step] = args
        state = RangeState(context, builder)
        state.start = start
        state.stop = stop
        state.step = step
        return impl_ret_untracked(context,
                                  builder,
                                  range_state_type,
                                  state._getvalue())

    @lower_builtin(len, range_state_type)
    def range_len(context, builder, sig, args):
        """
        len(range)
        """
        (value,) = args
        state = RangeState(context, builder, value)
        res = RangeIter.from_range_state(context, builder, state)
        return impl_ret_untracked(context, builder, int_type, builder.load(res.count))

    @lower_builtin('getiter', range_state_type)
    def getiter_range32_impl(context, builder, sig, args):
        """
        range.__iter__
        """
        (value,) = args
        state = RangeState(context, builder, value)
        res = RangeIter.from_range_state(context, builder, state)._getvalue()
        return impl_ret_untracked(context, builder, range_iter_type, res)

    @iterator_impl(range_state_type, range_iter_type)
    class RangeIter(make_range_iterator(range_iter_type)):

        @classmethod
        def from_range_state(cls, context, builder, state):
            """
            Create a RangeIter initialized from the given RangeState *state*.
            """
            self = cls(context, builder)
            start = state.start
            stop = state.stop
            step = state.step

            startptr = cgutils.alloca_once(builder, start.type)
            builder.store(start, startptr)

            countptr = cgutils.alloca_once(builder, start.type)

            self.iter = startptr
            self.stop = stop
            self.step = step
            self.count = countptr

            diff = builder.sub(stop, start)
            zero = context.get_constant(int_type, 0)
            one = context.get_constant(int_type, 1)
            pos_diff = builder.icmp_signed('>', diff, zero)
            pos_step = builder.icmp_signed('>', step, zero)
            sign_differs = builder.xor(pos_diff, pos_step)
            zero_step = builder.icmp_unsigned('==', step, zero)

            with cgutils.if_unlikely(builder, zero_step):
                # step shouldn't be zero
                context.call_conv.return_user_exc(builder, ValueError,
                                                  ("range() arg 3 must not be zero",))

            with builder.if_else(sign_differs) as (then, orelse):
                with then:
                    builder.store(zero, self.count)

                with orelse:
                    rem = builder.srem(diff, step)
                    rem = builder.select(pos_diff, rem, builder.neg(rem))
                    uneven = builder.icmp_signed('>', rem, zero)
                    newcount = builder.add(builder.sdiv(diff, step),
                                           builder.select(uneven, one, zero))
                    builder.store(newcount, self.count)

            return self

        def iternext(self, context, builder, result):
            zero = context.get_constant(int_type, 0)
            countptr = self.count
            count = builder.load(countptr)
            is_valid = builder.icmp_signed('>', count, zero)
            result.set_valid(is_valid)

            with builder.if_then(is_valid):
                value = builder.load(self.iter)
                result.yield_(value)
                one = context.get_constant(int_type, 1)

                builder.store(builder.sub(count, one, flags=["nsw"]), countptr)
                builder.store(builder.add(value, self.step), self.iter)

range_impl_map = {
    types.int32 : (types.range_state32_type, types.range_iter32_type),
    types.int64 : (types.range_state64_type, types.range_iter64_type),
    types.uint64 : (types.unsigned_range_state64_type, types.unsigned_range_iter64_type)
}

for int_type, state_types in range_impl_map.items():
    make_range_impl(int_type, *state_types)

@lower_cast(types.RangeType, types.RangeType)
def range_to_range(context, builder, fromty, toty, val):
    olditems = cgutils.unpack_tuple(builder, val, 3)
    items = [context.cast(builder, v, fromty.dtype, toty.dtype)
             for v in olditems]
    return cgutils.make_anonymous_struct(builder, items)


def make_range_attr(index, attribute):
    @intrinsic
    def rangetype_attr_getter(typingctx, a):
        if isinstance(a, types.RangeType):
            def codegen(context, builder, sig, args):
                (val,) = args
                items = cgutils.unpack_tuple(builder, val, 3)
                return impl_ret_untracked(context, builder, sig.return_type,
                                          items[index])
            return signature(a.dtype, a), codegen

    @overload_attribute(types.RangeType, attribute)
    def range_attr(rnge):
        def get(rnge):
            return rangetype_attr_getter(rnge)
        return get


@register_jitable
def impl_contains_helper(robj, val):
    if robj.step > 0 and (val < robj.start or val >= robj.stop):
        return False
    elif robj.step < 0 and (val <= robj.stop or val > robj.start):
        return False

    return ((val - robj.start) % robj.step) == 0


@overload(operator.contains)
def impl_contains(robj, val):
    def impl_false(robj, val):
        return False

    if not isinstance(robj, types.RangeType):
        return

    elif isinstance(val, (types.Integer, types.Boolean)):
        return impl_contains_helper

    elif isinstance(val, types.Float):
        def impl(robj, val):
            if val % 1 != 0:
                return False
            else:
                return impl_contains_helper(robj, int(val))
        return impl

    elif isinstance(val, types.Complex):
        def impl(robj, val):
            if val.imag != 0:
                return False
            elif val.real % 1 != 0:
                return False
            else:
                return impl_contains_helper(robj, int(val.real))
        return impl

    elif not isinstance(val, types.Number):
        return impl_false


for ix, attr in enumerate(('start', 'stop', 'step')):
    make_range_attr(index=ix, attribute=attr)
