from collections.abc import Callable
from types import MappingProxyType
from typing import (
    Any,
    Dict,
)

from PySide6.QtCore import (
    QDir,
    Qt,
    Signal,
)
from PySide6.QtWidgets import (
    QCheckBox,
    QComboBox,
    QFileDialog,
    QHBoxLayout,
    QLineEdit,
    QSpinBox,
    QToolButton,
    QWidget,
)

from .resource_provider import gooey_resources
from .utils import _NoValue


class GooeyParamWidgetMixin:
    """API mixin for QWidget to get/set parameter specifications

    Any parameter widget implementation should also derive from the class,
    and implement, at minimum, `_set_gooey_param_value()` and
    `get_gooey_param_value()` for compatibility with the command parameter
    UI generator.

    The main API used by the GUI generator are `set_gooey_param_spec()`
    and `get_gooey_param_spec()`. They take care of providing a standard
    widget behavior across all widget types, such as, not returning values if
    they do not deviate from the default.
    """

    value_changed = Signal(MappingProxyType)
    """Signal to be emitted whenever a parameter value is changed. The signal
    payload type matches the return value of `get_gooey_param_spec()`"""

    def set_gooey_param_value(self, value):
        """Implement to set a particular value in the target widget.

        The `value_changed` signal is emitted a the given value differs
        from the current value.
        """
        # what we had
        try:
            prev = self.get_gooey_param_value()
        except ValueError:
            prev = _NoValue
        # let widget implementation actually set the value
        self._set_gooey_param_value(value)
        if prev != value:
            # an actual change, emit corresponding signal
            self.emit_gooey_value_changed()

    def _set_gooey_param_value(self, value):
        """Implement to set a particular value in the target widget.

        By default, this method is also used to set a default value.
        If that is not desirable for a particular widget type,
        override `set_gooey_param_default()`.
        """
        raise NotImplementedError

    def get_gooey_param_value(self):
        """Implement to get the parameter value from the widget.

        Raises
        ------
        ValueError
          The implementation must raise this exception, when no value
          has been entered/is available.
        """
        raise NotImplementedError

    def set_gooey_param_default(self, value):
        """Implement to set a parameter default value in the widget
        """
        pass

    def set_gooey_param_spec(
            self, name: str, default=_NoValue):
        """Called by the command UI generator to set parameter
        name, and a default.
        """
        self._gooey_param_name = name
        # always store here for later inspection by get_gooey_param_spec()
        self._gooey_param_default = default
        self.set_gooey_param_default(default)

    def get_gooey_param_spec(self) -> Dict:
        """Called by the command UI generator to get a parameter specification

        Return a mapping of the parameter name to the gathered value or _NoValue
        when no value was gathered, or the gather value is not different from
        the default)
        is a mapping of parameter name to the gather value.
        """
        try:
            val = self.get_gooey_param_value()
        except ValueError:
            # class signals that no value was set
            return {self._gooey_param_name: _NoValue}
        return {self._gooey_param_name: val} \
            if val != self._gooey_param_default \
            else {self._gooey_param_name: _NoValue}

    def set_gooey_param_validator(self, validator: Callable) -> None:
        """Set a validator callable that can be used by the widget
        for input validation
        """
        self._gooey_param_validator = validator

    def set_gooey_param_docs(self, docs: str) -> None:
        """Present documentation on the parameter in the widget

        The default implementation assigns the documentation to a widget-wide
        tooltip.
        """
        # recycle the docs as widget tooltip, this is more compact than
        # having to integrate potentially lengthy text into the layout
        self.setToolTip(docs)

    def init_gooey_from_other_param(self, spec: Dict) -> None:
        """Slot to receive changes of other parameter values

        Can be implemented to act on context changes that require a
        reinitialization of a widget. For example, update a list
        of remotes after changing the reference dataset.

        Parameters
        ----------
        spec: dict
          Mapping of parameter names to new values, in the same format
          and semantics as the return value of get_gooey_param_spec().
        """
        pass

    def emit_gooey_value_changed(self):
        """Slot to connect "changed" signals of underlying input widgets too

        It emits the standard Gooey `value_changed` signal with the
        current Gooey `param_spec` as value.
        """
        self.value_changed.emit(MappingProxyType(self.get_gooey_param_spec()))


def load_parameter_widget(
        parent: QWidget,
        pwid_factory: Callable,
        name: str,
        docs: str,
        default: Any = _NoValue,
        validator: Callable or None = None) -> QWidget:
    """ """
    pwid = pwid_factory(parent=parent)
    if validator:
        pwid.set_gooey_param_validator(validator)
    pwid.set_gooey_param_docs(docs)
    # set any default last, as they might need a validator,
    # docs, and all other bits in place already for an editor or
    # validation to work
    pwid.set_gooey_param_spec(name, default)
    return pwid


#
# Parameter widget implementations
#

class ChoiceParamWidget(QComboBox, GooeyParamWidgetMixin):
    def __init__(self, choices=None, parent=None):
        super().__init__(parent)
        self.setInsertPolicy(QComboBox.NoInsert)
        # TODO: We may need to always have --none-- as an option.
        #       That's b/c of specs like EnsureChoice('a', 'b') | EnsureNone()
        #       with default None.
        if choices:
            for c in choices:
                self._add_item(c)
        else:
            # avoid making the impression something could be selected
            self.setPlaceholderText('No known choices')
            self.setDisabled(True)

    def _add_item(self, value) -> None:
        # we add items, and we stick their real values in too
        # to avoid tricky conversion via str
        self.addItem(self._gooey_map_val2label(value), userData=value)

    def _set_gooey_param_value(self, value):
        self.setCurrentText(self._gooey_map_val2label(value))

    def get_gooey_param_value(self):
        return self.currentData()

    def set_gooey_param_spec(self, name: str, default=_NoValue):
        super().set_gooey_param_spec(name, default)
        # QComboBox will report the first choice to be selected by default.
        # Set the specified default instead.
        if default is _NoValue:
            default = None
        self._set_gooey_param_value(default)

    def _gooey_map_val2label(self, val):
        return '--none--' if val is None else str(val)


class PosIntParamWidget(QSpinBox, GooeyParamWidgetMixin):
    def __init__(self, allow_none=False, parent=None):
        super().__init__(parent)
        if allow_none:
            self.setMinimum(-1)
            self.setSpecialValueText('none')
        else:
            # this is not entirely correct, but large enough for any practical
            # purpose
            # TODO libshiboken: Overflow: Value 9223372036854775807 exceedsi
            # limits of type  [signed] "i" (4bytes).
            # Do we need to set a maximum value at all?
            #self.setMaximum(sys.maxsize)
            pass
        self._allow_none = allow_none

    def _set_gooey_param_value(self, value):
        # generally assumed to be int and fit in the range
        self.setValue(-1 if value is None and self._allow_none else value)

    def set_gooey_param_spec(self, name: str, default=_NoValue):
        # QSpinBox' values is set to 0 by default. Hence, we need to overwrite
        # here.
        super().set_gooey_param_spec(name, default)
        if default is _NoValue:
            default = None
        self.setValue(default if default is not None else -1)

    def get_gooey_param_value(self):
        val = self.value()
        # convert special value -1 back to None
        return None if val == -1 and self._allow_none else val


class BoolParamWidget(QCheckBox, GooeyParamWidgetMixin):

    def __init__(self, parent=None) -> None:
        super().__init__(parent)
        # set to no value initially
        self._set_gooey_param_value(None)

    def _set_gooey_param_value(self, value):
        if value not in (True, False):
            # if the value is not representable by a checkbox
            # leave it in "partiallychecked". In cases where the
            # default is something like `None`, we can distinguish
            # a user not having set anything different from the default,
            # even if the default is not a bool
            self.setTristate(True)
            self.setCheckState(Qt.PartiallyChecked)
        else:
            # otherwise flip the switch accordingly
            self.setChecked(value)

    def get_gooey_param_value(self):
        state = self.checkState()
        if state == Qt.PartiallyChecked:
            # TODO error if partiallychecked still (means a
            # value with no default was not set)
            # a default `validator` could handle that
            # Mixin picks this up and communicates: nothing was set
            raise ValueError
        # convert to bool
        return state == Qt.Checked

    def set_gooey_param_spec(self, name: str, default=_NoValue):
        super().set_gooey_param_spec(name, default)
        self._set_gooey_param_value(default)


class StrParamWidget(QLineEdit, GooeyParamWidgetMixin):
    def _set_gooey_param_value(self, value):
        self.setText(str(value))
        self.setModified(True)

    def set_gooey_param_default(self, value):
        if value != _NoValue:
            self.setPlaceholderText(str(value))

    def get_gooey_param_value(self):
        # return the value if it was set be the caller, or modified
        # by the user -- otherwise stay silent and let the command
        # use its default
        if self.isEnabled() and not self.isModified():
            raise ValueError('Present value was not modified')
        return self.text()


class PathParamWidget(QWidget, GooeyParamWidgetMixin):
    def __init__(self, basedir=None,
                 pathtype: QFileDialog.FileMode = QFileDialog.AnyFile,
                 disable_manual_edit: bool = False,
                 parent=None):
        """Supported `pathtype` values are

        - `QFileDialog.AnyFile`
        - `QFileDialog.ExistingFile`
        - `QFileDialog.Directory`
        """
        super().__init__(parent)
        self._basedir = basedir
        self._pathtype = pathtype

        hl = QHBoxLayout()
        # squash the margins to fit into a list widget item as much as possible
        margins = hl.contentsMargins()
        # we stay with the default left/right, but minimize vertically
        hl.setContentsMargins(margins.left(), 0, margins.right(), 0)
        self.setLayout(hl)

        # the main widget is a simple line edit
        self._edit = QLineEdit(self)
        if disable_manual_edit:
            # in e.g. simplified mode we do not allow manual entry of paths
            # to avoid confusions re interpretation of relative paths
            # https://github.com/datalad/datalad-gooey/issues/106
            self._edit.setDisabled(True)
        hl.addWidget(self._edit)
        self._edit.editingFinished.connect(self.emit_gooey_value_changed)

        # next to the line edit, we place to small button to facilitate
        # selection of file/directory paths by a browser dialog.
        if pathtype in (
                QFileDialog.AnyFile,
                QFileDialog.ExistingFile):
            file_button = QToolButton(self)
            file_button.setToolTip(
                'Select path'
                if pathtype == QFileDialog.AnyFile
                else 'Select file')
            file_button.setIcon(
                gooey_resources.get_best_icon(
                    'path' if pathtype == QFileDialog.AnyFile else 'file'))
            hl.addWidget(file_button)
            # wire up the slots
            file_button.clicked.connect(self._select_path)
        if pathtype in (
                QFileDialog.AnyFile,
                QFileDialog.Directory):
            # we use a dedicated directory selector.
            # on some platforms the respected native
            # dialogs are different... so we go with two for the best "native"
            # experience
            dir_button = QToolButton(self)
            dir_button.setToolTip('Choose directory')
            dir_button.setIcon(gooey_resources.get_best_icon('directory'))
            hl.addWidget(dir_button)
            dir_button.clicked.connect(
                lambda: self._select_path(dirs_only=True))

    def _set_gooey_param_value(self, value):
        self._edit.setText(str(value))
        self._edit.setModified(True)

    def set_gooey_param_default(self, value):
        placeholder = 'Select path'
        if value not in (_NoValue, None):
            placeholder += f'(default: {value})'
        self._edit.setPlaceholderText(placeholder)

    def get_gooey_param_value(self):
        # return the value if it was set be the caller, or modified
        # by the user -- otherwise stay silent and let the command
        # use its default
        edit = self._edit
        if not edit.isModified():
            raise ValueError
        return edit.text()

    def set_gooey_param_docs(self, docs: str) -> None:
        # only use edit tooltip for the docs, and let the buttons
        # have their own
        self._edit.setToolTip(docs)

    def _select_path(self, dirs_only=False):
        dialog = QFileDialog(self)
        dialog.setFileMode(
            QFileDialog.Directory if dirs_only else self._pathtype)
        dialog.setOption(QFileDialog.DontResolveSymlinks)
        if self._basedir:
            # we have a basedir, so we can be clever
            dialog.setDirectory(str(self._basedir))
        # we need to turn on 'System' in order to get broken symlinks
        # too
        if not dirs_only:
            dialog.setFilter(dialog.filter() | QDir.System)
        dialog.finished.connect(self._select_path_receiver)
        dialog.open()

    def _select_path_receiver(self):
        """Internal slot to receive the outcome of _select_path() dialog"""
        dialog = self.sender()
        paths = dialog.selectedFiles()
        if paths:
            # ignores any multi-selection
            # TODO prevent or support specifically
            self.set_gooey_param_value(paths[0])
            self._edit.setModified(True)

    def init_gooey_from_other_param(self, spec: Dict) -> None:
        if self._gooey_param_name == 'dataset':
            # prevent update from self
            return

        if 'dataset' in spec:
            self._basedir = spec['dataset']


class CfgProcParamWidget(ChoiceParamWidget):
    """Choice widget with items from `run_procedure(discover=True)`"""
    def __init__(self, choices=None, parent=None):
        super().__init__(parent=parent)
        self.init_gooey_from_other_param({})

    def init_gooey_from_other_param(self, spec: Dict) -> None:
        if self.count() and 'dataset' not in spec:
            # we have items and no context change is required
            return

        # we have no items yet, or the dataset has changed: query!
        # reset first
        while self.count():
            self.removeItem(0)
        from datalad.local.run_procedure import RunProcedure
        for res in RunProcedure.__call__(
            dataset=spec.get('dataset'),
            discover=True,
            return_type='generator',
            result_renderer='disabled',
            on_failure='ignore',
        ):
            proc_name = res.get('procedure_name', '')
            if res.get('status') != 'ok' \
                    or not proc_name.startswith('cfg_'):
                # not a good config procedure
                continue
            # strip 'cfg_' prefix, even when reporting, we do not want it
            # because commands like `create()` put it back themselves
            self._add_item(proc_name[4:])
        if self.count():
            self.setEnabled(True)
            self.setPlaceholderText('Select procedure')


class SiblingChoiceParamWidget(ChoiceParamWidget):
    """Choice widget with items from `siblings()`"""
    def __init__(self, choices=None, parent=None):
        super().__init__(parent=parent)
        self.init_gooey_from_other_param({})
        self._saw_dataset = False
        self._set_placeholder_msg()

    def _set_placeholder_msg(self):
        if not self._saw_dataset:
            self.setPlaceholderText('Select dataset first')
        elif not self.count():
            self.setPlaceholderText('No known siblings')
        else:
            self.setPlaceholderText('Select sibling')

    def init_gooey_from_other_param(self, spec: Dict) -> None:
        if 'dataset' not in spec:
            # we have items and no context change is required
            return

        self._saw_dataset = True
        # the dataset has changed: query!
        # reset first
        while self.count():
            self.removeItem(0)
        from datalad.distribution.siblings import Siblings
        for res in Siblings.__call__(
            dataset=spec['dataset'],
            action='query',
            return_type='generator',
            result_renderer='disabled',
            on_failure='ignore',
        ):
            sibling_name = res.get('name')
            if (not sibling_name or res.get('status') != 'ok'
                    or res.get('type') != 'sibling'
                    or (sibling_name == 'here'
                        and res.get('path') == spec['dataset'])):
                # not a good sibling
                continue
            self._add_item(sibling_name)
        if self.count():
            self.setEnabled(True)
            self._set_placeholder_msg()