# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.

"""Selection classes.

Represents an enumeration using a widget.
"""

from collections import Mapping, Iterable
try:
    from itertools import izip
except ImportError:  #python3.x
    izip = zip
from itertools import chain

from .widget_description import DescriptionWidget
from .valuewidget import ValueWidget
from .widget_core import CoreWidget
from .widget_style import Style
from .trait_types import InstanceDict
from .widget import register, widget_serialization
from traitlets import (Unicode, Bool, Int, Any, Dict, TraitError, CaselessStrEnum,
                       Tuple, List, Union, observe, validate)
from ipython_genutils.py3compat import unicode_type

_doc_snippets = {}
_doc_snippets['selection_params'] = """
    options: list or dict
        The options for the dropdown. This can either be a list of values, e.g.
        ``['Galileo', 'Brahe', 'Hubble']`` or ``[0, 1, 2]``, a list of
        (label, value) pairs, e.g.
        ``[('Galileo', 0), ('Brahe', 1), ('Hubble', 2)]``,
        or a dictionary mapping the labels to the values, e.g. ``{'Galileo': 0,
        'Brahe': 1, 'Hubble': 2}``. The labels are the strings that will be
        displayed in the UI, representing the actual Python choices, and should
        be unique. If this is a dictionary, the order in which they are
        displayed is not guaranteed.

    index: int
        The index of the current selection.

    value: any
        The value of the current selection. When programmatically setting the
        value, a reverse lookup is performed among the options to check that
        the value is valid. The reverse lookup uses the equality operator by
        default, but another predicate may be provided via the ``equals``
        keyword argument. For example, when dealing with numpy arrays, one may
        set ``equals=np.array_equal``.

    label: str
        The label corresponding to the selected value.

    disabled: bool
        Whether to disable user changes.

    description: str
        Label for this input group. This should be a string
        describing the widget.
"""

_doc_snippets['multiple_selection_params'] = """
    options: dict or list
        The options for the dropdown. This can either be a list of values, e.g.
        ``['Galileo', 'Brahe', 'Hubble']`` or ``[0, 1, 2]``, a list of
        (label, value) pairs, e.g.
        ``[('Galileo', 0), ('Brahe', 1), ('Hubble', 2)]``,
        or a dictionary mapping the labels to the values, e.g. ``{'Galileo': 0,
        'Brahe': 1, 'Hubble': 2}``. The labels are the strings that will be
        displayed in the UI, representing the actual Python choices, and should
        be unique. If this is a dictionary, the order in which they are
        displayed is not guaranteed.

    index: iterable of int
        The indices of the options that are selected.

    value: iterable
        The values that are selected. When programmatically setting the
        value, a reverse lookup is performed among the options to check that
        the value is valid. The reverse lookup uses the equality operator by
        default, but another predicate may be provided via the ``equals``
        keyword argument. For example, when dealing with numpy arrays, one may
        set ``equals=np.array_equal``.

    label: iterable of str
        The labels corresponding to the selected value.

    disabled: bool
        Whether to disable user changes.

    description: str
        Label for this input group. This should be a string
        describing the widget.
"""

_doc_snippets['slider_params'] = """
    orientation: str
        Either ``'horizontal'`` or ``'vertical'``. Defaults to ``horizontal``.

    readout: bool
        Display the current label next to the slider. Defaults to ``True``.

    continuous_update: bool
        If ``True``, update the value of the widget continuously as the user
        holds the slider. Otherwise, the model is only updated after the
        user has released the slider. Defaults to ``True``.
"""


def _doc_subst(cls):
    """ Substitute format strings in class docstring """
    # Strip the snippets to avoid trailing new lines and whitespace
    stripped_snippets = {
        key: snippet.strip() for (key, snippet) in _doc_snippets.items()
    }
    cls.__doc__ = cls.__doc__.format(**stripped_snippets)
    return cls


def _make_options(x):
    """Standardize the options tuple format.

    The returned tuple should be in the format (('label', value), ('label', value), ...).

    The input can be
    * a Mapping of labels to values
    * an iterable of (label, value) pairs
    * an iterable of values, and labels will be generated
    """
    # Check if x is a mapping of labels to values
    if isinstance(x, Mapping):
        return tuple((unicode_type(k), v) for k, v in x.items())

    # only iterate once through the options.
    xlist = tuple(x)

    # Check if x is an iterable of (label, value) pairs
    if all((isinstance(i, (list, tuple)) and len(i) == 2) for i in xlist):
        return tuple((unicode_type(k), v) for k, v in xlist)

    # Otherwise, assume x is an iterable of values
    return tuple((unicode_type(i), i) for i in xlist)

def findvalue(array, value, compare = lambda x, y: x == y):
    "A function that uses the compare function to return a value from the list."
    try:
        return next(x for x in array if compare(x, value))
    except StopIteration:
        raise ValueError('%r not in array'%value)

class _Selection(DescriptionWidget, ValueWidget, CoreWidget):
    """Base class for Selection widgets

    ``options`` can be specified as a list of values, list of (label, value)
    tuples, or a dict of {label: value}. The labels are the strings that will be
    displayed in the UI, representing the actual Python choices, and should be
    unique. If labels are not specified, they are generated from the values.

    When programmatically setting the value, a reverse lookup is performed
    among the options to check that the value is valid. The reverse lookup uses
    the equality operator by default, but another predicate may be provided via
    the ``equals`` keyword argument. For example, when dealing with numpy arrays,
    one may set equals=np.array_equal.
    """

    value = Any(None, help="Selected value", allow_none=True)
    label = Unicode(None, help="Selected label", allow_none=True)
    index = Int(None, help="Selected index", allow_none=True).tag(sync=True)

    options = Any((),
    help="""Iterable of values, (label, value) pairs, or a mapping of {label: value} pairs that the user can select.

    The labels are the strings that will be displayed in the UI, representing the
    actual Python choices, and should be unique.
    """)

    _options_full = None

    # This being read-only means that it cannot be changed from the frontend!
    _options_labels = Tuple(read_only=True, help="The labels for the options.").tag(sync=True)

    disabled = Bool(help="Enable or disable user changes").tag(sync=True)

    def __init__(self, *args, **kwargs):
        self.equals = kwargs.pop('equals', lambda x, y: x == y)
        # We have to make the basic options bookkeeping consistent
        # so we don't have errors the first time validators run
        self._initializing_traits_ = True
        options = _make_options(kwargs.get('options', ()))
        self._options_full = options
        self.set_trait('_options_labels', tuple(i[0] for i in options))
        self._options_values = tuple(i[1] for i in options)

        # Select the first item by default, if we can
        if 'index' not in kwargs and 'value' not in kwargs and 'label' not in kwargs:
            nonempty = (len(options) > 0)
            kwargs['index'] = 0 if nonempty else None
            kwargs['label'], kwargs['value'] = options[0] if nonempty else (None, None)

        super(_Selection, self).__init__(*args, **kwargs)
        self._initializing_traits_ = False

    @validate('options')
    def _validate_options(self, proposal):
        # if an iterator is provided, exhaust it
        if isinstance(proposal.value, Iterable) and not isinstance(proposal.value, Mapping):
            proposal.value = tuple(proposal.value)
        # throws an error if there is a problem converting to full form
        self._options_full = _make_options(proposal.value)
        return proposal.value

    @observe('options')
    def _propagate_options(self, change):
        "Set the values and labels, and select the first option if we aren't initializing"
        options = self._options_full
        self.set_trait('_options_labels', tuple(i[0] for i in options))
        self._options_values = tuple(i[1] for i in options)
        if self._initializing_traits_ is not True:
            self.index = 0 if len(options) > 0 else None

    @validate('index')
    def _validate_index(self, proposal):
        if proposal.value is None or 0 <= proposal.value < len(self._options_labels):
            return proposal.value
        else:
            raise TraitError('Invalid selection: index out of bounds')

    @observe('index')
    def _propagate_index(self, change):
        "Propagate changes in index to the value and label properties"
        label = self._options_labels[change.new] if change.new is not None else None
        value = self._options_values[change.new] if change.new is not None else None
        if self.label is not label:
            self.label = label
        if self.value is not value:
            self.value = value

    @validate('value')
    def _validate_value(self, proposal):
        value = proposal.value
        try:
            return findvalue(self._options_values, value, self.equals) if value is not None else None
        except ValueError:
            raise TraitError('Invalid selection: value not found')

    @observe('value')
    def _propagate_value(self, change):
        index = self._options_values.index(change.new) if change.new is not None else None
        if self.index != index:
            self.index = index

    @validate('label')
    def _validate_label(self, proposal):
        if (proposal.value is not None) and (proposal.value not in self._options_labels):
            raise TraitError('Invalid selection: label not found')
        return proposal.value

    @observe('label')
    def _propagate_label(self, change):
        index = self._options_labels.index(change.new) if change.new is not None else None
        if self.index != index:
            self.index = index

    def _repr_keys(self):
        keys = super(_Selection, self)._repr_keys()
        # Include options manually, as it isn't marked as synced:
        for key in sorted(chain(keys, ('options',))):
            if key == 'index' and self.index == 0:
                # Index 0 is default when there are options
                continue
            yield key


class _MultipleSelection(DescriptionWidget, ValueWidget, CoreWidget):
    """Base class for multiple Selection widgets

    ``options`` can be specified as a list of values, list of (label, value)
    tuples, or a dict of {label: value}. The labels are the strings that will be
    displayed in the UI, representing the actual Python choices, and should be
    unique. If labels are not specified, they are generated from the values.

    When programmatically setting the value, a reverse lookup is performed
    among the options to check that the value is valid. The reverse lookup uses
    the equality operator by default, but another predicate may be provided via
    the ``equals`` keyword argument. For example, when dealing with numpy arrays,
    one may set equals=np.array_equal.
    """

    value = Tuple(help="Selected values")
    label = Tuple(help="Selected labels")
    index = Tuple(help="Selected indices").tag(sync=True)

    options = Any((),
    help="""Iterable of values, (label, value) pairs, or a mapping of {label: value} pairs that the user can select.

    The labels are the strings that will be displayed in the UI, representing the
    actual Python choices, and should be unique.
    """)
    _options_full = None

    # This being read-only means that it cannot be changed from the frontend!
    _options_labels = Tuple(read_only=True, help="The labels for the options.").tag(sync=True)

    disabled = Bool(help="Enable or disable user changes").tag(sync=True)

    def __init__(self, *args, **kwargs):
        self.equals = kwargs.pop('equals', lambda x, y: x == y)

        # We have to make the basic options bookkeeping consistent
        # so we don't have errors the first time validators run
        self._initializing_traits_ = True
        options = _make_options(kwargs.get('options', ()))
        self._full_options = options
        self.set_trait('_options_labels', tuple(i[0] for i in options))
        self._options_values = tuple(i[1] for i in options)

        super(_MultipleSelection, self).__init__(*args, **kwargs)
        self._initializing_traits_ = False

    @validate('options')
    def _validate_options(self, proposal):
        if isinstance(proposal.value, Iterable) and not isinstance(proposal.value, Mapping):
            proposal.value = tuple(proposal.value)
        # throws an error if there is a problem converting to full form
        self._options_full = _make_options(proposal.value)
        return proposal.value

    @observe('options')
    def _propagate_options(self, change):
        "Unselect any option"
        options = self._options_full
        self.set_trait('_options_labels', tuple(i[0] for i in options))
        self._options_values = tuple(i[1] for i in options)
        if self._initializing_traits_ is not True:
            self.index = ()

    @validate('index')
    def _validate_index(self, proposal):
        "Check the range of each proposed index."
        if all(0 <= i < len(self._options_labels) for i in proposal.value):
            return proposal.value
        else:
            raise TraitError('Invalid selection: index out of bounds')

    @observe('index')
    def _propagate_index(self, change):
        "Propagate changes in index to the value and label properties"
        label = tuple(self._options_labels[i] for i in change.new)
        value = tuple(self._options_values[i] for i in change.new)
        # we check equality so we can avoid validation if possible
        if self.label != label:
            self.label = label
        if self.value != value:
            self.value = value

    @validate('value')
    def _validate_value(self, proposal):
        "Replace all values with the actual objects in the options list"
        try:
            return tuple(findvalue(self._options_values, i, self.equals) for i in proposal.value)
        except ValueError:
            raise TraitError('Invalid selection: value not found')

    @observe('value')
    def _propagate_value(self, change):
        index = tuple(self._options_values.index(i) for i in change.new)
        if self.index != index:
            self.index = index

    @validate('label')
    def _validate_label(self, proposal):
        if any(i not in self._options_labels for i in proposal.value):
            raise TraitError('Invalid selection: label not found')
        return proposal.value

    @observe('label')
    def _propagate_label(self, change):
        index = tuple(self._options_labels.index(i) for i in change.new)
        if self.index != index:
            self.index = index

    def _repr_keys(self):
        keys = super(_MultipleSelection, self)._repr_keys()
        # Include options manually, as it isn't marked as synced:
        for key in sorted(chain(keys, ('options',))):
            yield key

@register
class ToggleButtonsStyle(Style, CoreWidget):
    """Button style widget.

    Parameters
    ----------
    button_width: str
        The width of each button. This should be a valid CSS
        width, e.g. '10px' or '5em'.
    """
    _model_name = Unicode('ToggleButtonsStyleModel').tag(sync=True)
    button_width = Unicode(help="The width of each button.").tag(sync=True)

@register
@_doc_subst
class ToggleButtons(_Selection):
    """Group of toggle buttons that represent an enumeration.

    Only one toggle button can be toggled at any point in time.

    Parameters
    ----------
    {selection_params}

    tooltips: list
        Tooltip for each button. If specified, must be the
        same length as `options`.

    icons: list
        Icons to show on the buttons. This must be the name
        of a font-awesome icon. See `http://fontawesome.io/icons/`
        for a list of icons.

    button_style: str
        One of 'primary', 'success', 'info', 'warning' or
        'danger'. Applies a predefined style to every button.

    style: ToggleButtonsStyle
        Style parameters for the buttons.
    """
    _view_name = Unicode('ToggleButtonsView').tag(sync=True)
    _model_name = Unicode('ToggleButtonsModel').tag(sync=True)

    tooltips = List(Unicode(), help="Tooltips for each button.").tag(sync=True)
    icons = List(Unicode(), help="Icons names for each button (FontAwesome names without the fa- prefix).").tag(sync=True)
    style = InstanceDict(ToggleButtonsStyle).tag(sync=True, **widget_serialization)

    button_style = CaselessStrEnum(
        values=['primary', 'success', 'info', 'warning', 'danger', ''],
        default_value='', allow_none=True, help="""Use a predefined styling for the buttons.""").tag(sync=True)


@register
@_doc_subst
class Dropdown(_Selection):
    """Allows you to select a single item from a dropdown.

    Parameters
    ----------
    {selection_params}
    """
    _view_name = Unicode('DropdownView').tag(sync=True)
    _model_name = Unicode('DropdownModel').tag(sync=True)


@register
@_doc_subst
class RadioButtons(_Selection):
    """Group of radio buttons that represent an enumeration.

    Only one radio button can be toggled at any point in time.

    Parameters
    ----------
    {selection_params}
    """
    _view_name = Unicode('RadioButtonsView').tag(sync=True)
    _model_name = Unicode('RadioButtonsModel').tag(sync=True)


@register
@_doc_subst
class Select(_Selection):
    """
    Listbox that only allows one item to be selected at any given time.

    Parameters
    ----------
    {selection_params}

    rows: int
        The number of rows to display in the widget.
    """
    _view_name = Unicode('SelectView').tag(sync=True)
    _model_name = Unicode('SelectModel').tag(sync=True)
    rows = Int(5, help="The number of rows to display.").tag(sync=True)

@register
@_doc_subst
class SelectMultiple(_MultipleSelection):
    """
    Listbox that allows many items to be selected at any given time.

    The ``value``, ``label`` and ``index`` attributes are all iterables.

    Parameters
    ----------
    {multiple_selection_params}

    rows: int
        The number of rows to display in the widget.
    """
    _view_name = Unicode('SelectMultipleView').tag(sync=True)
    _model_name = Unicode('SelectMultipleModel').tag(sync=True)
    rows = Int(5, help="The number of rows to display.").tag(sync=True)


class _SelectionNonempty(_Selection):
    """Selection that is guaranteed to have a value selected."""
    # don't allow None to be an option.
    value = Any(help="Selected value")
    label = Unicode(help="Selected label")
    index = Int(help="Selected index").tag(sync=True)

    def __init__(self, *args, **kwargs):
        if len(kwargs.get('options', ())) == 0:
            raise TraitError('options must be nonempty')
        super(_SelectionNonempty, self).__init__(*args, **kwargs)

    @validate('options')
    def _validate_options(self, proposal):
        if isinstance(proposal.value, Iterable) and not isinstance(proposal.value, Mapping):
            proposal.value = tuple(proposal.value)
        self._options_full = _make_options(proposal.value)
        if len(self._options_full) == 0:
            raise TraitError("Option list must be nonempty")
        return proposal.value

class _MultipleSelectionNonempty(_MultipleSelection):
    """Selection that is guaranteed to have an option available."""

    def __init__(self, *args, **kwargs):
        if len(kwargs.get('options', ())) == 0:
            raise TraitError('options must be nonempty')
        super(_MultipleSelectionNonempty, self).__init__(*args, **kwargs)

    @validate('options')
    def _validate_options(self, proposal):
        if isinstance(proposal.value, Iterable) and not isinstance(proposal.value, Mapping):