""" manage PyTables query interface via Expressions """

import ast
from functools import partial

import numpy as np

from pandas.compat import DeepChainMap, string_types, u

from pandas.core.dtypes.common import is_list_like

import pandas as pd
from pandas.core.base import StringMixin
import pandas.core.common as com
from pandas.core.computation import expr, ops
from pandas.core.computation.common import _ensure_decoded
from pandas.core.computation.expr import BaseExprVisitor
from pandas.core.computation.ops import UndefinedVariableError, is_term

from pandas.io.formats.printing import pprint_thing, pprint_thing_encoded


class Scope(expr.Scope):
    __slots__ = 'queryables',

    def __init__(self, level, global_dict=None, local_dict=None,
                 queryables=None):
        super(Scope, self).__init__(level + 1, global_dict=global_dict,
                                    local_dict=local_dict)
        self.queryables = queryables or dict()


class Term(ops.Term):

    def __new__(cls, name, env, side=None, encoding=None):
        klass = Constant if not isinstance(name, string_types) else cls
        supr_new = StringMixin.__new__
        return supr_new(klass)

    def __init__(self, name, env, side=None, encoding=None):
        super(Term, self).__init__(name, env, side=side, encoding=encoding)

    def _resolve_name(self):
        # must be a queryables
        if self.side == 'left':
            if self.name not in self.env.queryables:
                raise NameError('name {name!r} is not defined'
                                .format(name=self.name))
            return self.name

        # resolve the rhs (and allow it to be None)
        try:
            return self.env.resolve(self.name, is_local=False)
        except UndefinedVariableError:
            return self.name

    @property
    def value(self):
        return self._value


class Constant(Term):

    def __init__(self, value, env, side=None, encoding=None):
        super(Constant, self).__init__(value, env, side=side,
                                       encoding=encoding)

    def _resolve_name(self):
        return self._name


class BinOp(ops.BinOp):

    _max_selectors = 31

    def __init__(self, op, lhs, rhs, queryables, encoding):
        super(BinOp, self).__init__(op, lhs, rhs)
        self.queryables = queryables
        self.encoding = encoding
        self.filter = None
        self.condition = None

    def _disallow_scalar_only_bool_ops(self):
        pass

    def prune(self, klass):

        def pr(left, right):
            """ create and return a new specialized BinOp from myself """

            if left is None:
                return right
            elif right is None:
                return left

            k = klass
            if isinstance(left, ConditionBinOp):
                if (isinstance(left, ConditionBinOp) and
                        isinstance(right, ConditionBinOp)):
                    k = JointConditionBinOp
                elif isinstance(left, k):
                    return left
                elif isinstance(right, k):
                    return right

            elif isinstance(left, FilterBinOp):
                if (isinstance(left, FilterBinOp) and
                        isinstance(right, FilterBinOp)):
                    k = JointFilterBinOp
                elif isinstance(left, k):
                    return left
                elif isinstance(right, k):
                    return right

            return k(self.op, left, right, queryables=self.queryables,
                     encoding=self.encoding).evaluate()

        left, right = self.lhs, self.rhs

        if is_term(left) and is_term(right):
            res = pr(left.value, right.value)
        elif not is_term(left) and is_term(right):
            res = pr(left.prune(klass), right.value)
        elif is_term(left) and not is_term(right):
            res = pr(left.value, right.prune(klass))
        elif not (is_term(left) or is_term(right)):
            res = pr(left.prune(klass), right.prune(klass))

        return res

    def conform(self, rhs):
        """ inplace conform rhs """
        if not is_list_like(rhs):
            rhs = [rhs]
        if isinstance(rhs, np.ndarray):
            rhs = rhs.ravel()
        return rhs

    @property
    def is_valid(self):
        """ return True if this is a valid field """
        return self.lhs in self.queryables

    @property
    def is_in_table(self):
        """ return True if this is a valid column name for generation (e.g. an
        actual column in the table) """
        return self.queryables.get(self.lhs) is not None

    @property
    def kind(self):
        """ the kind of my field """
        return getattr(self.queryables.get(self.lhs), 'kind', None)

    @property
    def meta(self):
        """ the meta of my field """
        return getattr(self.queryables.get(self.lhs), 'meta', None)

    @property
    def metadata(self):
        """ the metadata of my field """
        return getattr(self.queryables.get(self.lhs), 'metadata', None)

    def generate(self, v):
        """ create and return the op string for this TermValue """
        val = v.tostring(self.encoding)
        return "({lhs} {op} {val})".format(lhs=self.lhs, op=self.op, val=val)

    def convert_value(self, v):
        """ convert the expression that is in the term to something that is
        accepted by pytables """

        def stringify(value):
            if self.encoding is not None:
                encoder = partial(pprint_thing_encoded,
                                  encoding=self.encoding)
            else:
                encoder = pprint_thing
            return encoder(value)

        kind = _ensure_decoded(self.kind)
        meta = _ensure_decoded(self.meta)
        if kind == u('datetime64') or kind == u('datetime'):
            if isinstance(v, (int, float)):
                v = stringify(v)
            v = _ensure_decoded(v)
            v = pd.Timestamp(v)
            if v.tz is not None:
                v = v.tz_convert('UTC')
            return TermValue(v, v.value, kind)
        elif kind == u('timedelta64') or kind == u('timedelta'):
            v = pd.Timedelta(v, unit='s').value
            return TermValue(int(v), v, kind)
        elif meta == u('category'):
            metadata = com.values_from_object(self.metadata)
            result = metadata.searchsorted(v, side='left')

            # result returns 0 if v is first element or if v is not in metadata
            # check that metadata contains v
            if not result and v not in metadata:
                result = -1
            return TermValue(result, result, u('integer'))
        elif kind == u('integer'):
            v = int(float(v))
            return TermValue(v, v, kind)
        elif kind == u('float'):
            v = float(v)
            return TermValue(v, v, kind)
        elif kind == u('bool'):
            if isinstance(v, string_types):
                v = not v.strip().lower() in [u('false'), u('f'), u('no'),
                                              u('n'), u('none'), u('0'),
                                              u('[]'), u('{}'), u('')]
            else:
                v = bool(v)
            return TermValue(v, v, kind)
        elif isinstance(v, string_types):
            # string quoting
            return TermValue(v, stringify(v), u('string'))
        else:
            raise TypeError("Cannot compare {v} of type {typ} to {kind} column"
                            .format(v=v, typ=type(v), kind=kind))

    def convert_values(self):
        pass


class FilterBinOp(BinOp):

    def __unicode__(self):
        return pprint_thing("[Filter : [{lhs}] -> [{op}]"
                            .format(lhs=self.filter[0], op=self.filter[1]))

    def invert(self):
        """ invert the filter """
        if self.filter is not None:
            f = list(self.filter)
            f[1] = self.generate_filter_op(invert=True)
            self.filter = tuple(f)
        return self

    def format(self):
        """ return the actual filter format """
        return [self.filter]

    def evaluate(self):

        if not self.is_valid:
            raise ValueError("query term is not valid [{slf}]"
                             .format(slf=self))

        rhs = self.conform(self.rhs)
        values = [TermValue(v, v, self.kind) for v in rhs]

        if self.is_in_table:

            # if too many values to create the expression, use a filter instead
            if self.op in ['==', '!='] and len(values) > self._max_selectors:

                filter_op = self.generate_filter_op()
                self.filter = (
                    self.lhs,
                    filter_op,
                    pd.Index([v.value for v in values]))

                return self
            return None

        # equality conditions
        if self.op in ['==', '!=']:

            filter_op = self.generate_filter_op()
            self.filter = (
                self.lhs,
                filter_op,
                pd.Index([v.value for v in values]))

        else:
            raise TypeError("passing a filterable condition to a non-table "
                            "indexer [{slf}]".format(slf=self))

        return self

    def generate_filter_op(self, invert=False):
        if (self.op == '!=' and not invert) or (self.op == '==' and invert):
            return lambda axis, vals: ~axis.isin(vals)
        else:
            return lambda axis, vals: axis.isin(vals)


class JointFilterBinOp(FilterBinOp):

    def format(self):
        raise NotImplementedError("unable to collapse Joint Filters")

    def evaluate(self):
        return self


class ConditionBinOp(BinOp):

    def __unicode__(self):
        return pprint_thing("[Condition : [{cond}]]"
                            .format(cond=self.condition))

    def invert(self):
        """ invert the condition """
        # if self.condition is not None:
        #    self.condition = "~(%s)" % self.condition
        # return self
        raise NotImplementedError("cannot use an invert condition when "
                                  "passing to numexpr")

    def format(self):
        """ return the actual ne format """
        return self.condition

    def evaluate(self):

        if not self.is_valid:
            raise ValueError("query term is not valid [{slf}]"
                             .format(slf=self))

        # convert values if we are in the table
        if not self.is_in_table:
            return None

        rhs = self.conform(self.rhs)
        values = [self.convert_value(v) for v in rhs]

        # equality conditions
        if self.op in ['==', '!=']:

            # too many values to create the expression?
            if len(values) <= self._max_selectors:
                vs = [self.generate(v) for v in values]
                self.condition = "({cond})".format(cond=' | '.join(vs))

            # use a filter after reading
            else:
                return None
        else:
            self.condition = self.generate(values[0])