# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


from operator import attrgetter
from contextlib import contextmanager
from collections import namedtuple, Counter, defaultdict
from functools import total_ordering
import itertools as it
from weakref import ref
import threading
import types

from . import linear_util as lu
from .util import safe_zip, safe_map, partial, curry
from .pprint_util import pp, vcat, hcat, pp_kv_pairs

# TODO(dougalm): the trace cache breaks the leak detector. Consisder solving.
check_leaks = False
# TODO(dougalm): put this behind a flag that's enabled during testing
skip_checks = True  # not __debug__  # google doesn't use -O

zip = safe_zip
map = safe_map


# -------------------- jaxprs --------------------

class Jaxpr(object):
  def __init__(self, constvars, invars, outvars, eqns):
    """
    Params:
      constvars: list of variables introduced for constants (either literals
        in the Python program, or the result of constant folding during the
        generation of the Jaxpr). Array constants are replaced with such variables
        while scalar constants are kept inline.
      invars: list of input variables. Together, `constvars` and `invars` are
        the inputs to the Jaxpr.
      outvars: list of output variables.
      eqns: list of equations."""
    self.constvars = list(constvars)
    self.invars = list(invars)
    self.outvars = list(outvars)
    self.eqns = list(eqns)

  def __str__(self):
    return str(pp_jaxpr(self))
  __repr__ = __str__


def subjaxprs(jaxpr):
  """Generator for all subjaxprs found in the params of jaxpr.eqns.
  Does not descend recursively into the found subjaxprs.
  """
  for eqn in jaxpr.eqns:
    for param in eqn.params.values():
      if type(param) is Jaxpr:
        yield param
      elif type(param) is TypedJaxpr:
        yield param.jaxpr


class TypedJaxpr(object):
  def __init__(self, jaxpr, literals, in_avals, out_avals):
    assert type(jaxpr) is Jaxpr
    assert len(literals) == len(jaxpr.constvars)
    assert len(in_avals) == len(jaxpr.invars)
    assert all(isinstance(aval, AbstractValue) for aval in in_avals)
    assert all(isinstance(aval, AbstractValue) for aval in out_avals)

    self.jaxpr = jaxpr
    self.literals = list(literals)
    self.in_avals = list(in_avals)
    self.out_avals = list(out_avals)

  def __iter__(self):
    return iter((self.jaxpr, self.literals, self.in_avals, self.out_avals))

  def __str__(self):
    # TODO(mattjj): improve this with type annotations?
    return str(pp_jaxpr(self.jaxpr))
  __repr__ = __str__

@curry
def jaxpr_as_fun(typed_jaxpr, *args):
  return eval_jaxpr(typed_jaxpr.jaxpr, typed_jaxpr.literals, *args)



JaxprEqn = namedtuple('JaxprEqn', ['invars', 'outvars', 'primitive', 'params'])
JaxprEqn.__repr__ = JaxprEqn.__str__ = lambda eqn: str(pp_eqn(eqn)).rstrip()
new_jaxpr_eqn = JaxprEqn


@total_ordering
class Var(object):
  # TODO(frostig,mattjj): We don't override __eq__ or __hash__, so comparison is
  # by object id, but pretty printing might collide.

  def __init__(self, count, suffix):
    self.count = count
    self.suffix = suffix

  def __lt__(self, other):
    if not isinstance(other, Var):
      return NotImplemented
    else:
      return (self.count, self.suffix) < (other.count, other.suffix)

  def __repr__(self):
    rem = self.count
    s = ''
    while True:
      rem, i = rem // 26, rem % 26
      s = chr(97 + i % 26) + s
      if not rem:
        break
    return s + self.suffix

def gensym(suffix):
  counter = it.count()
  return lambda: Var(next(counter), suffix)

class Literal(object):
  __slots__ = ["val", "hash"]

  def __init__(self, val):
    self.val = val
    try:
      self.hash = hash(val)
    except TypeError:
      if type(val) in literalable_types:
        try:
          self.hash = hash((val.item(), val.dtype))
        except (TypeError, AttributeError):
          self.hash = None

  def __hash__(self):
    assert False

  def __eq__(self, other):
    assert False

  def __repr__(self):
    if self.hash is None:
      return 'Literal(val={})'.format(self.val)
    else:
      return '{}'.format(self.val)

literalable_types = set()

class Primitive(object):
  multiple_results = False  # override for multi-output primitives
  call_primitive = False  # override for higher-order primitives that are
                          # processed in final style.

  def __init__(self, name):
    self.name = name

  def __repr__(self):
    return '{}'.format(self.name)

  def bind(self, *args, **kwargs):
    assert skip_checks or all(isinstance(arg, Tracer)
                              or valid_jaxtype(arg) for arg in args), args
    top_trace = find_top_trace(args)
    if top_trace is None:
      return self.impl(*args, **kwargs)

    tracers = map(top_trace.full_raise, args)
    out_tracer = top_trace.process_primitive(self, tracers, kwargs)
    if self.multiple_results:
      return map(full_lower, out_tracer)
    else:
      return full_lower(out_tracer)

  def def_impl(self, impl):
    self.impl = impl
    return impl

  def def_abstract_eval(self, abstract_eval):
    self.abstract_eval = abstract_eval
    return abstract_eval

  def def_custom_bind(self, bind):
    self.bind = bind
    return bind

  def impl(self, *args, **kwargs):
    raise NotImplementedError("Evaluation rule for '{}' not implemented"
                              .format(self.name))

  def abstract_eval(self, *args, **kwargs):
    raise NotImplementedError("Abstract evaluation for '{}' not implemented"
                              .format(self.name))


# -------------------- lifting --------------------

# TODO(necula): this belongs next to pe.new_eqn_recipe, but is needed in
# core.py. Plan to move all these utilities to jaxpr.py.
def extract_call_jaxpr(primitive, params):
  """Extract the call primitive subjaxpr from the params.

  Params:
    params: a parameter dictionary for a primitive.
  Returns: the subjaxpr and the params without the "jaxpr" value. If this is
    not a call primitive then returns (None, params).
  """
  if not primitive.call_primitive:
    return (None, params)
  else:
    assert "call_jaxpr" in params
    new_params = dict(params)
    del new_params["call_jaxpr"]
    return (params["call_jaxpr"], new_params)


def eval_jaxpr(jaxpr, consts, *args):
  def read(v):
    if type(v) is Literal:
      return v.val
    else:
      return env[v]

  def write(v, val):
    env[v] = val

  env = {}
  write(unitvar, unit)
  map(write, jaxpr.constvars, consts)
  map(write, jaxpr.invars, args)
  for eqn in jaxpr.eqns:
    in_vals = map(read, eqn.invars)
    call_jaxpr, params = extract_call_jaxpr(eqn.primitive, eqn.params)
    if call_jaxpr:
      subfuns = [lu.wrap_init(partial(eval_jaxpr, call_jaxpr, ()))]
    else:
      subfuns = []
    ans = eqn.primitive.bind(*(subfuns + in_vals), **params)
    if eqn.primitive.multiple_results:
      map(write, eqn.outvars, ans)
    else:
      write(eqn.outvars[0], ans)
  return map(read, jaxpr.outvars)


def full_lower(val):
  if isinstance(val, Tracer):
    return val.full_lower()
  else:
    return val


def find_top_trace(xs):
 try:
   top_trace = max((x._trace for x in xs if isinstance(x, Tracer)),
                   key=attrgetter('level'))
 except ValueError:
   return None
 else:
   return type(top_trace)(top_trace.master, cur_sublevel())


# -------------------- tracing --------------------


class Trace(object):
  def __init__(self, master, sublevel):
    self.master = master
    self.level = master.level
    self.sublevel = sublevel

  def full_raise(self, val):
    if not isinstance(val, Tracer):
      return self.pure(val)
    level = self.level
    sublevel = self.sublevel
    if val._trace.master is self.master:
      if val._trace.sublevel == sublevel:
        return val
      elif val._trace.sublevel < sublevel:
        return self.sublift(val)
      else:
        raise Exception("Can't lift sublevels {} to {}"
                        .format(val._trace.sublevel, sublevel))
    elif val._trace.level < level:
      if val._trace.sublevel > sublevel:
        raise Exception("Incompatible sublevel: {}, {}"
                        .format(val._trace, (level, sublevel)))
      return self.lift(val)
    elif val._trace.level > level:
      raise Exception("Can't lift {} to {}".format(val, self))
    elif val._trace.level == self.level:
      raise Exception("Different traces at same level: {}, {}".format(val, self))
    else:
      raise Exception("Can't lift {} to {}".format(val, self))


  def pure(self, val):
    assert False

  def lift(self, tracer):
    assert False

  def sublift(self, tracer):
    assert False

  def __repr__(self):
    return '{}(level={}/{})'.format(
        self.__class__.__name__, self.level, self.sublevel)


class Tracer(object):
  __array_priority__ = 1000
  __slots__ = ['_trace', '__weakref__']

  def __array__(self, *args, **kw):
    raise Exception("Tracer can't be used with raw numpy functions. "
                    "You might have\n  import numpy as np\ninstead of\n  import jax.numpy as np")

  def __init__(self, trace):
    self._trace = trace

  def __iter__(self):
    return iter(self.aval._iter(self))

  def __len__(self):
    return self.aval._len(self)

  @property
  def aval(self):
    assert False

  def __neg__(self): return self.aval._neg(self)
  def __pos__(self): return self.aval._pos(self)
  def __eq__(self, other): return self.aval._eq(self, other)
  def __ne__(self, other): return self.aval._ne(self, other)
  def __lt__(self, other): return self.aval._lt(self, other)
  def __le__(self, other): return self.aval._le(self, other)
  def __gt__(self, other): return self.aval._gt(self, other)
  def __ge__(self, other): return self.aval._ge(self, other)
  def __abs__(self): return self.aval._abs(self)
  def __add__(self, other): return self.aval._add(self, other)
  def __radd__(self, other): return self.aval._radd(self, other)
  def __sub__(self, other): return self.aval._sub(self, other)
  def __rsub__(self, other): return self.aval._rsub(self, other)
  def __mul__(self, other): return self.aval._mul(self, other)
  def __rmul__(self, other): return self.aval._rmul(self, other)
  def __div__(self, other): return self.aval._div(self, other)
  def __rdiv__(self, other): return self.aval._rdiv(self, other)
  def __truediv__(self, other): return self.aval._truediv(self, other)
  def __rtruediv__(self, other): return self.aval._rtruediv(self, other)
  def __floordiv__(self, other): return self.aval._floordiv(self, other)
  def __rfloordiv__(self, other): return self.aval._rfloordiv(self, other)
  def __divmod__(self, other): return self.aval._divmod(self, other)
  def __rdivmod__(self, other): return self.aval._rdivmod(self, other)
  def __mod__(self, other): return self.aval._mod(self, other)
  def __rmod__(self, other): return self.aval._rmod(self, other)
  def __pow__(self, other): return self.aval._pow(self, other)
  def __rpow__(self, other): return self.aval._rpow(self, other)
  def __matmul__(self, other): return self.aval._matmul(self, other)
  def __rmatmul__(self, other): return self.aval._rmatmul(self, other)
  def __and__(self, other): return self.aval._and(self, other)
  def __rand__(self, other): return self.aval._rand(self, other)
  def __or__(self, other): return self.aval._or(self, other)
  def __ror__(self, other): return self.aval._ror(self, other)
  def __xor__(self, other): return self.aval._xor(self, other)
  def __rxor__(self, other): return self.aval._rxor(self, other)
  def __invert__(self): return self.aval._invert(self)
  def __lshift__(self, other): return self.aval._lshift(self, other)
  def __rshift__(self, other): return self.aval._rshift(self, other)
  def __getitem__(self, idx): return self.aval._getitem(self, idx)
  def __nonzero__(self): return self.aval._nonzero(self)
  def __bool__(self): return self.aval._bool(self)
  def __float__(self): return self.aval._float(self)
  def __int__(self): return self.aval._int(self)
  def __long__(self): return self.aval._long(self)
  def __complex__(self): return self.aval._complex(self)
  def __hex__(self): return self.aval._hex(self)
  def __oct__(self): return self.aval._oct(self)

  def __setitem__(self, idx, val):
    raise TypeError("JAX 'Tracer' objects do not support item assignment")

  def __getattr__(self, name):
    # if the aval property raises an AttributeError, gets caught here
    assert skip_checks or name != "aval"

    try:
      attr = getattr(self.aval, name)
    except KeyError:
      raise AttributeError(
          "{} has no attribute {}".format(self.__class__.__name__, name))
    else:
      t = type(attr)
      if t is aval_property:
        return attr.fget(self)
      elif t is aval_method:
        return types.MethodType(attr.fun, self)
      else:
        return attr

  def __repr__(self):
    return 'Traced<{}>with<{}>'.format(self.aval, self._trace)

  def __copy__(self):
    return self

  def __deepcopy__(self, unused_memo):
    return self


# these can be used to set up forwarding of properties and instance methods from
# Tracer instances to the underlying avals
aval_property = namedtuple("aval_property", ["fget"])
aval_method = namedtuple("aval_method", ["fun"])


class MasterTrace(object):
  def __init__(self, level, trace_type):
    self.level = level
    self.trace_type = trace_type

  def __repr__(self):
    return "MasterTrace({},{})".format(self.level, self.trace_type.__name__)

  def __hash__(self):
    return hash((self.level, self.trace_type))

  def __eq__(self, other):
    return self.level == other.level and self.trace_type == other.trace_type


class TraceStack(object):
  def __init__(self):
    self.upward = []
    self.downward = []

  def next_level(self, bottom):
    if bottom:
      return - (len(self.downward) + 1)
    else:
      return len(self.upward)

  def push(self, val, bottom):
    if bottom:
      self.downward.append(val)
    else:
      self.upward.append(val)

  def pop(self, bottom):
    if bottom:
      self.downward.pop()
    else:
      self.upward.pop()

  def __repr__(self):
    return  'Trace stack\n{} ---\n{}'.format(
      map('  {}\n'.format, self.upward[::-1]),
      map('  {}\n'.format, self.downward))


class Sublevel(int): pass

# The global state of the tracer is accessed by a thread-local object.
# This allows concurrent tracing in separate threads; passing traced objects
# between threads is forbidden.
class TraceState(threading.local):
  def __init__(self):
    self.trace_stack = TraceStack()
    self.substack = [Sublevel(0)]

trace_state = TraceState()


def cur_sublevel():
  return trace_state.substack[-1]


@contextmanager
def new_master(trace_type, bottom=False):
  level = trace_state.trace_stack.next_level(bottom)
  master = MasterTrace(level, trace_type)
  trace_state.trace_stack.push(master, bottom)

  try:
    yield master
  finally:
    trace_state.trace_stack.pop(bottom)

  if check_leaks:
    t = ref(master)
    del master
    if t() is not None:
      print(trace_state.trace_stack)
      raise Exception('Leaked trace {}'.format(t()))


@contextmanager
def new_sublevel():
  sublevel = Sublevel(len(trace_state.substack))
  trace_state.substack.append(sublevel)
  try:
    yield
  finally:
    trace_state.substack.pop()

  if check_leaks:
    t = ref(sublevel)
    del sublevel
    if t() is not None:
      raise Exception('Leaked sublevel {}'.format(t()))

# -------------------- abstract values --------------------


class AbstractValue(object):
  __slots__ = []

  def at_least_vspace(self):
    assert False

  def __repr__(self):
    try:
      kv_pairs = ('{}={}'.format(k, v) for k, v in self.__dict__.items())
      return '{}({})'.format(self.__class__.__name__, ','.join(kv_pairs))
    except AttributeError:
      return self.__class__.__name__

  def strip_weak_type(self):
    return self

class Bot(AbstractValue): pass

bot = Bot()

class AbstractUnit(AbstractValue):
  def join(self, other): return self
  def _eq(self, self_traced, other): return get_aval(other) is self

abstract_unit = AbstractUnit()

def lattice_join(x, y):
  if x is None:
    return y
  elif y is None:
    return x
  elif isinstance(x, type(y)):
    return y.join(x)
  elif isinstance(y, type(x)):
    return x.join(y)
  else:
    raise TypeError((x, y))


def valid_jaxtype(x):
  try:
    concrete_aval(x)
  except TypeError:
    return False
  else:
    return True


def concrete_aval(x):
  try:
    return pytype_aval_mappings[type(x)](x)
  except KeyError:
    raise TypeError("{} is not a valid Jax type".format(type(x)))


def get_aval(x):
  if isinstance(x, Tracer):
    return x.aval
  else:
    return concrete_aval(x)


pytype_aval_mappings = {}


class Unit(object):
  def __repr__(self): return '*'
unit = Unit()
literalable_types.add(Unit)

class UnitVar(object):
  def __repr__(self): return '*'
unitvar = UnitVar()

pytype_aval_mappings[Unit] = lambda _: abstract_unit

identity_p = Primitive('id')
identity_p.def_impl(lambda x: x)
identity_p.def_custom_bind(lambda x: x)

# ------------------- Call -------------------


def apply_todos(todos, outs):
  todos_list = list(todos)
  while todos_list:
    outs = map(full_lower, todos_list.pop()(outs))
  return outs

@lu.transformation_with_aux
def process_env_traces(primitive, level, params_tuple, *args):
  outs = yield args, {}
  params = dict(params_tuple)
  todo = []
  while True:
    tracers = [x for x in outs if isinstance(x, Tracer) and x._trace.level > level]
    if tracers:
      ans = max(tracers, key=lambda x: x._trace.level)
    else:
      break
    trace = type(ans._trace)(ans._trace.master, cur_sublevel())
    outs = map(trace.full_raise, outs)
    outs, cur_todo = trace.post_process_call(primitive, outs, params)
    todo.append(cur_todo)
  yield outs, tuple(todo)  # Ensure the aux output is immutable

def call_bind(primitive, f, *args, **params):
  top_trace = find_top_trace(args)
  level = trace_state.trace_stack.next_level(True) if top_trace is None else top_trace.level
  params_tuple = tuple(params.items())
  f, env_trace_todo = process_env_traces(f, primitive, level, params_tuple)
  if top_trace is None:
    with new_sublevel():
      outs = primitive.impl(f, *args, **params)
  else:
    tracers = map(top_trace.full_raise, args)
    outs = map(full_lower, top_trace.process_call(primitive, f, tracers, params))
  return apply_todos(env_trace_todo(), outs)


def call_impl(f, *args, **params):
  del params  # params parameterize the call primitive, not the function
  return f.call_wrapped(*args)


call_p = Primitive('call')
call = partial(call_bind, call_p)
call_p.def_custom_bind(call)
call_p.def_impl(call_impl)


# ------------------- Jaxpr printed representation -------------------

def check_jaxpr(jaxpr):
  """Checks well-formedness of a jaxpr.

  Specifically it checks that all variabled used are previously defined.
  """
  def context():
    return "\njaxpr:\n{}\n".format(jaxpr)

  def read_env(env, v):
    if type(v) is not Literal and v not in env:
      raise Exception("Variable '{}' not defined".format(v) + context())

  def write_env(env, v):
    if v in env:
      raise Exception("Variable {} already bound".format(v) + context())
    env.add(v)

  env = set()
  read = partial(read_env, env)
  write = partial(write_env, env)

  write(unitvar)
  map(write, jaxpr.constvars)
  map(write, jaxpr.invars)
  for eqn in jaxpr.eqns:
    if eqn.primitive.call_primitive:
      if "call_jaxpr" not in eqn.params:
        raise Exception("Call primitive {} should have a 'call_jaxpr' parameter"
                        .format(eqn.primitive))
    map(read, eqn.invars)
    map(write, eqn.outvars)

  for subjaxpr in subjaxprs(jaxpr):
    check_jaxpr(subjaxpr)

  map(read, jaxpr.outvars)


def pp_vars(vs):
    return ' '.join(map(str, vs))

def pp_eqn_compact(primitive_name, params):
  filtered_params = {k: v for k, v in params.items()
                     if not isinstance(v, (Jaxpr, TypedJaxpr))}
  return pp(primitive_name) >> pp_kv_pairs(sorted(filtered_params.items()))

def pp_eqn(eqn):
  lhs = pp_vars(eqn.outvars)
  pp_subexpr = pp('')
  return (pp('{} = '.format(lhs)) >>
          pp(eqn.primitive.name) >> pp_kv_pairs(sorted(eqn.params.items()))
          >> pp(' ') >> pp(pp_vars(eqn.invars))) + pp_subexpr

def pp_jaxpr(jaxpr):
  return (pp('{{ lambda {} ; {}.'.format(pp_vars(jaxpr.constvars),
                                         pp_vars(jaxpr.invars))) +
          ((pp('let ') >>
            vcat(map(pp_eqn, jaxpr.eqns))) +
           pp('in {} }}'.format(jaxpr.outvars))).indent(2))