"""
Module for scope operations
"""

import sys
import struct
import inspect
import datetime
import itertools
import pprint

import numpy as np

import pandas
import pandas as pd  # noqa
from pandas.compat import DeepChainMap, map, StringIO
from pandas.core.base import StringMixin
import pandas.core.computation as compu


def _ensure_scope(level, global_dict=None, local_dict=None, resolvers=(),
                  target=None, **kwargs):
    """Ensure that we are grabbing the correct scope."""
    return Scope(level + 1, global_dict=global_dict, local_dict=local_dict,
                 resolvers=resolvers, target=target)


def _replacer(x):
    """Replace a number with its hexadecimal representation. Used to tag
    temporary variables with their calling scope's id.
    """
    # get the hex repr of the binary char and remove 0x and pad by pad_size
    # zeros
    try:
        hexin = ord(x)
    except TypeError:
        # bytes literals masquerade as ints when iterating in py3
        hexin = x

    return hex(hexin)


def _raw_hex_id(obj):
    """Return the padded hexadecimal id of ``obj``."""
    # interpret as a pointer since that's what really what id returns
    packed = struct.pack('@P', id(obj))
    return ''.join(map(_replacer, packed))


_DEFAULT_GLOBALS = {
    'Timestamp': pandas._libs.tslib.Timestamp,
    'datetime': datetime.datetime,
    'True': True,
    'False': False,
    'list': list,
    'tuple': tuple,
    'inf': np.inf,
    'Inf': np.inf,
}


def _get_pretty_string(obj):
    """Return a prettier version of obj

    Parameters
    ----------
    obj : object
        Object to pretty print

    Returns
    -------
    s : str
        Pretty print object repr
    """
    sio = StringIO()
    pprint.pprint(obj, stream=sio)
    return sio.getvalue()


class Scope(StringMixin):

    """Object to hold scope, with a few bells to deal with some custom syntax
    and contexts added by pandas.

    Parameters
    ----------
    level : int
    global_dict : dict or None, optional, default None
    local_dict : dict or Scope or None, optional, default None
    resolvers : list-like or None, optional, default None
    target : object

    Attributes
    ----------
    level : int
    scope : DeepChainMap
    target : object
    temps : dict
    """
    __slots__ = 'level', 'scope', 'target', 'temps'

    def __init__(self, level, global_dict=None, local_dict=None, resolvers=(),
                 target=None):
        self.level = level + 1

        # shallow copy because we don't want to keep filling this up with what
        # was there before if there are multiple calls to Scope/_ensure_scope
        self.scope = DeepChainMap(_DEFAULT_GLOBALS.copy())
        self.target = target

        if isinstance(local_dict, Scope):
            self.scope.update(local_dict.scope)
            if local_dict.target is not None:
                self.target = local_dict.target
            self.update(local_dict.level)

        frame = sys._getframe(self.level)

        try:
            # shallow copy here because we don't want to replace what's in
            # scope when we align terms (alignment accesses the underlying
            # numpy array of pandas objects)
            self.scope = self.scope.new_child((global_dict or
                                               frame.f_globals).copy())
            if not isinstance(local_dict, Scope):
                self.scope = self.scope.new_child((local_dict or
                                                   frame.f_locals).copy())
        finally:
            del frame

        # assumes that resolvers are going from outermost scope to inner
        if isinstance(local_dict, Scope):
            resolvers += tuple(local_dict.resolvers.maps)
        self.resolvers = DeepChainMap(*resolvers)
        self.temps = {}

    def __unicode__(self):
        scope_keys = _get_pretty_string(list(self.scope.keys()))
        res_keys = _get_pretty_string(list(self.resolvers.keys()))
        unicode_str = '{name}(scope={scope_keys}, resolvers={res_keys})'
        return unicode_str.format(name=type(self).__name__,
                                  scope_keys=scope_keys,
                                  res_keys=res_keys)

    @property
    def has_resolvers(self):
        """Return whether we have any extra scope.

        For example, DataFrames pass Their columns as resolvers during calls to
        ``DataFrame.eval()`` and ``DataFrame.query()``.

        Returns
        -------
        hr : bool
        """
        return bool(len(self.resolvers))

    def resolve(self, key, is_local):
        """Resolve a variable name in a possibly local context

        Parameters
        ----------
        key : text_type
            A variable name
        is_local : bool
            Flag indicating whether the variable is local or not (prefixed with
            the '@' symbol)

        Returns
        -------
        value : object
            The value of a particular variable
        """
        try:
            # only look for locals in outer scope
            if is_local:
                return self.scope[key]

            # not a local variable so check in resolvers if we have them
            if self.has_resolvers:
                return self.resolvers[key]

            # if we're here that means that we have no locals and we also have
            # no resolvers
            assert not is_local and not self.has_resolvers
            return self.scope[key]
        except KeyError:
            try:
                # last ditch effort we look in temporaries
                # these are created when parsing indexing expressions
                # e.g., df[df > 0]
                return self.temps[key]
            except KeyError:
                raise compu.ops.UndefinedVariableError(key, is_local)

    def swapkey(self, old_key, new_key, new_value=None):
        """Replace a variable name, with a potentially new value.

        Parameters
        ----------
        old_key : str
            Current variable name to replace
        new_key : str
            New variable name to replace `old_key` with
        new_value : object
            Value to be replaced along with the possible renaming
        """
        if self.has_resolvers:
            maps = self.resolvers.maps + self.scope.maps
        else:
            maps = self.scope.maps

        maps.append(self.temps)

        for mapping in maps:
            if old_key in mapping:
                mapping[new_key] = new_value
                return

    def _get_vars(self, stack, scopes):
        """Get specifically scoped variables from a list of stack frames.

        Parameters
        ----------
        stack : list
            A list of stack frames as returned by ``inspect.stack()``
        scopes : sequence of strings
            A sequence containing valid stack frame attribute names that
            evaluate to a dictionary. For example, ('locals', 'globals')
        """
        variables = itertools.product(scopes, stack)
        for scope, (frame, _, _, _, _, _) in variables:
            try:
                d = getattr(frame, 'f_' + scope)
                self.scope = self.scope.new_child(d)
            finally:
                # won't remove it, but DECREF it
                # in Py3 this probably isn't necessary since frame won't be
                # scope after the loop
                del frame

    def update(self, level):
        """Update the current scope by going back `level` levels.

        Parameters
        ----------
        level : int or None, optional, default None
        """
        sl = level + 1

        # add sl frames to the scope starting with the
        # most distant and overwriting with more current
        # makes sure that we can capture variable scope
        stack = inspect.stack()

        try:
            self._get_vars(stack[:sl], scopes=['locals'])
        finally:
            del stack[:], stack

    def add_tmp(self, value):
        """Add a temporary variable to the scope.

        Parameters
        ----------
        value : object
            An arbitrary object to be assigned to a temporary variable.

        Returns
        -------
        name : basestring
            The name of the temporary variable created.
        """
        name = '{name}_{num}_{hex_id}'.format(name=type(value).__name__,
                                              num=self.ntemps,
                                              hex_id=_raw_hex_id(self))

        # add to inner most scope
        assert name not in self.temps
        self.temps[name] = value
        assert name in self.temps

        # only increment if the variable gets put in the scope
        return name

    @property
    def ntemps(self):
        """The number of temporary variables in this scope"""
        return len(self.temps)

    @property
    def full_scope(self):
        """Return the full scope for use with passing to engines transparently
        as a mapping.

        Returns
        -------
        vars : DeepChainMap
            All variables in this scope.
        """
        maps = [self.temps] + self.resolvers.maps + self.scope.maps
        return DeepChainMap(*maps)
