"""Internal utilities for parsing Python subset to HalideIR"""

import ast
import inspect
import logging
import sys
import numpy
from .intrin import HYBRID_GLOBALS
from .._ffi.base import numeric_types
from .. import api as _api
from .. import make as _make
from .. import expr as _expr
from .. import stmt as _stmt
from ..tensor import Tensor


#pylint: disable=invalid-name
np_arg_types = tuple(list(numeric_types) + [numpy.ndarray])
tvm_arg_types = (Tensor, _expr.Var, _expr.ConstExpr)
halide_imm_types = (_expr.IntImm, _expr.FloatImm, _expr.UIntImm)

def _internal_assert(cond, err):
    """Simplify the code segment like if not XXX then raise an error"""
    if not cond:
        raise ValueError(err)


# Useful constants. In avoid of runtime dependences, we use function calls to return them.
def make_nop():
    """Returns a 'no operation' node in HalideIR."""
    return _make.Evaluate(_api.const(0, dtype='int32'))


def is_docstring(node):
    """Checks if a Python AST node is a docstring"""
    return isinstance(node, ast.Expr) and isinstance(node.value, ast.Str)


def _pruned_source(func):
    """Prune source code's extra leading spaces"""
    try:
        lines = inspect.getsource(func).split('\n')
        leading_space = len(lines[0]) - len(lines[0].lstrip(' '))
        lines = [line[leading_space:] for line in lines]
        return '\n'.join(lines)
    except IOError as err:
        if sys.version_info[0] == 2 and str(err) == 'could not get source code':
            logging.log(logging.CRITICAL, \
                        'This module is not fully operated under Python2... ' \
                        'Please move to Python3!')
            raise err


def _is_tvm_arg_types(args):
    """Determine a list of element is either a list of tvm arguments of a list of numpy arguments.
    If neither is true, raise a value error."""
    if isinstance(args[0], tvm_arg_types):
        for elem in args[1:]:
            _internal_assert(isinstance(elem, tvm_arg_types),
                             "Expecting a Var, Tensor or ConstExpr instance but %s get!" \
                             % str(type(elem)))
        return True

    _internal_assert(isinstance(args[0], np_arg_types), \
                     "Expect a numpy type but %s get!" % str(type(args[0])))
    for elem in args[1:]:
        _internal_assert(isinstance(elem, np_arg_types), \
                         "Expect a numpy type but %s get!" % str(type(elem)))
    return False


def _enter_hybrid_runtime(func):
    """Put hybrid runtime variables into the global scope"""
    _globals = func.__globals__
    intersect = []
    for elem in list(HYBRID_GLOBALS.keys()):
        if elem in _globals.keys():
            intersect.append((elem, _globals[elem]))
        _globals[elem] = HYBRID_GLOBALS[elem]
    return intersect


def _restore_runtime(func, intersect):
    """Rollback the modification caused by hybrid runtime"""
    _globals = func.__globals__
    for elem in list(HYBRID_GLOBALS.keys()):
        _globals.pop(elem)
    for k, v in intersect:
        _globals[k] = v


def replace_io(body, rmap):
    """Replacing tensors usage according to the dict given"""
    from .. import ir_pass

    def replace(op):
        if isinstance(op, _stmt.Provide) and op.func in rmap.keys():
            buf = rmap[op.func]
            return _make.Provide(buf.op, op.value_index, op.value, op.args)
        elif isinstance(op, _expr.Call) and  op.func in rmap.keys():
            buf = rmap[op.func]
            return _make.Call(buf.dtype, buf.name, op.args, \
                              _expr.Call.Halide, buf.op, buf.value_index)
        return None

    return ir_pass.IRTransform(body, None, replace, ['Provide', 'Call'])
