import os
from distutils.version import StrictVersion

from migen.fhdl.std import *
from migen.fhdl.specials import SynthesisDirective
from migen.genlib.cdc import *
from migen.genlib.resetsync import AsyncResetSynchronizer
from migen.genlib.io import *
from mibuild import tools

def settings(path, ver=None, sub=None):
	vers = list(tools.versions(path))
	if ver is None:
		ver = max(vers)
	else:
		ver = StrictVersion(ver)
		assert ver in vers

	full = os.path.join(path, str(ver))
	if sub:
		full = os.path.join(full, sub)

	search = [64, 32]
	if tools.arch_bits() == 32:
		search.reverse()

	for b in search:
		settings = os.path.join(full, "settings{0}.sh".format(b))
		if os.path.exists(settings):
			return settings

	raise OSError("no settings file found")

class XilinxNoRetimingImpl(Module):
	def __init__(self, reg):
		self.specials += SynthesisDirective("attribute register_balancing of {r} is no", r=reg)

class XilinxNoRetiming:
	@staticmethod
	def lower(dr):
		return XilinxNoRetimingImpl(dr.reg)

class XilinxMultiRegImpl(MultiRegImpl):
	def __init__(self, *args, **kwargs):
		MultiRegImpl.__init__(self, *args, **kwargs)
		self.specials += [SynthesisDirective("attribute shreg_extract of {r} is no", r=r)
			for r in self.regs]

class XilinxMultiReg:
	@staticmethod
	def lower(dr):
		return XilinxMultiRegImpl(dr.i, dr.o, dr.odomain, dr.n)

class XilinxAsyncResetSynchronizerImpl(Module):
	def __init__(self, cd, async_reset):
		rst1 = Signal()
		self.specials += [
			Instance("FDPE", p_INIT=1, i_D=0, i_PRE=async_reset,
				i_CE=1, i_C=cd.clk, o_Q=rst1),
			Instance("FDPE", p_INIT=1, i_D=rst1, i_PRE=async_reset,
				i_CE=1, i_C=cd.clk, o_Q=cd.rst)
		]

class XilinxAsyncResetSynchronizer:
	@staticmethod
	def lower(dr):
		return XilinxAsyncResetSynchronizerImpl(dr.cd, dr.async_reset)

class XilinxDifferentialInputImpl(Module):
	def __init__(self, i_p, i_n, o):
		self.specials += Instance("IBUFDS", i_I=i_p, i_IB=i_n, o_O=o)

class XilinxDifferentialInput:
	@staticmethod
	def lower(dr):
		return XilinxDifferentialInputImpl(dr.i_p, dr.i_n, dr.o)

class XilinxDifferentialOutputImpl(Module):
	def __init__(self, i, o_p, o_n):
		self.specials += Instance("OBUFDS", i_I=i, o_O=o_p, o_OB=o_n)

class XilinxDifferentialOutput:
	@staticmethod
	def lower(dr):
		return XilinxDifferentialOutputImpl(dr.i, dr.o_p, dr.o_n)

class XilinxDDROutputImpl(Module):
	def __init__(self, i1, i2, o, clk):
		self.specials += Instance("ODDR",
				p_DDR_CLK_EDGE="SAME_EDGE",
				i_C=clk, i_CE=1, i_S=0, i_R=0,
				i_D1=i1, i_D2=i2, o_Q=o,
		)

class XilinxDDROutput:
	@staticmethod
	def lower(dr):
		return XilinxDDROutputImpl(dr.i1, dr.i2, dr.o, dr.clk)

xilinx_special_overrides = {
	NoRetiming:					XilinxNoRetiming,
	MultiReg:					XilinxMultiReg,
	AsyncResetSynchronizer:		XilinxAsyncResetSynchronizer,
	DifferentialInput:			XilinxDifferentialInput,
	DifferentialOutput:			XilinxDifferentialOutput,
	DDROutput:					XilinxDDROutput
}