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"""
Methods for layout swizzling
"""

from .layout import *


def shiftr(a, s):
  return a >> s if s > 0 else shiftl(a, -s)


def shiftl(a, s):
  return a << s if s > 0 else shiftr(a, -s)


## A generic Swizzle functor
 # 0bxxxxxxxxxxxxxxxYYYxxxxxxxZZZxxxx
 #                               ^--^  Base is the number of least-sig bits to keep constant
 #                  ^-^       ^-^      Bits is the number of bits in the mask
 #                    ^---------^      Shift is the distance to shift the YYY mask
 #                                       (pos shifts YYY to the right, neg shifts YYY to the left)
 #
 # e.g. Given
 # 0bxxxxxxxxxxxxxxxxYYxxxxxxxxxZZxxx
 # the result is
 # 0bxxxxxxxxxxxxxxxxYYxxxxxxxxxAAxxx where AA = ZZ xor YY
 #
class Swizzle:
  def __init__(self, bits, base, shift):
    assert bits >= 0
    assert base >= 0
    assert abs(shift) >= bits
    self.bits = bits
    self.base = base
    self.shift = shift
    bit_msk = (1 << bits) - 1
    self.yyy_msk = bit_msk << (base + max(0,shift))
    self.zzz_msk = bit_msk << (base - min(0,shift))

  # operator ()    (transform integer)
  def __call__(self, offset):
    return offset ^ shiftr(offset & self.yyy_msk, self.shift)

  # Size of the domain
  def size(self):
    return 1 << (bits + base + abs(shift))

  # Size of the codomain
  def cosize(self):
    return self.size()

  # print and str
  def __str__(self):
    return f"SW_{self.bits}_{self.base}_{self.shift}"

  # error msgs and representation
  def __repr__(self):
    return f"Swizzle({self.bits},{self.base},{self.shift})"


class ComposedLayout(LayoutBase):
  def __init__(self, layoutB, offset, layoutA):
    self.layoutB = layoutB
    self.offset  = offset
    self.layoutA = layoutA

  # operator ==
  def __eq__(self, other):
    return self.layoutB == other.layoutB and self.offset == other.offset and self.layoutA == other.layoutA

  # operator len(L)  (len [rank] like tuples)
  def __len__(self):
    return len(self.layoutA)

  # operator ()    (map coord to idx)
  def __call__(self, *args):
    return self.layoutB(self.offset + self.layoutA(*args))

  # operator []    (get-i like tuples)
  def __getitem__(self, i):
    return ComposedLayout(self.layoutB, self.offset, self.layoutA[i])

  # size(layout)   Size of the domain
  def size(self):
    return size(self.layoutA)

  # cosize(layout)   Size of the codomain
  def cosize(self):
    return cosize(self.layoutB)

  # print and str
  def __str__(self):
    return f"{self.layoutB} o {self.offset} o {self.layoutA}"

  # error msgs and representation
  def __repr__(self):
    return f"ComposedLayout({repr(self.layoutB)},{repr(self.offset)},{repr(self.layoutA)})"
