# Source code for urwidtrees.widgets

    # Copyright (C) 2013  Patrick Totzke <patricktotzke@gmail.com>
    # This file is released under the GNU GPL, version 3 or a later revision.

    import urwid
    from urwid import WidgetWrap, ListBox
    from urwid import signals

    from .decoration import DecoratedTree, CollapseMixin
    from .nested import NestedTree
    try:
        # lru_cache is part of the stdlib from v3.2 onwards
        from functools import lru_cache
    except ImportError:
        # on older versions we use a backport
        from .lru_cache import lru_cache

    # The following functions are used to check dynamically if a tree offers sub-APIs

    def implementsDecorateAPI(tree):
        """determines if given tree offers line decoration"""
        return isinstance(tree, (DecoratedTree, NestedTree))

    def implementsCollapseAPI(tree):
        """determines if given tree can collapse positions"""
        return isinstance(tree, (CollapseMixin, NestedTree))

    class TreeListWalker(urwid.ListWalker):
        """
        ListWalker to walk through a class:`Tree`.

        This translates a :class:`Tree` into a :class:`urwid.ListWalker` that is
        digestible by :class:`urwid.ListBox`.
        It uses :meth:`Tree.[next|prev]_position <Tree.next_position>` to determine
        the next/previous position in depth first order.
        """
        def __init__(self, tree, focus=None):
            """
            :param tree: the tree to be displayed
            :type tree: Tree
            :param focus: position of node to be focussed initially.
                This has to be a valid position in the Tree.
                It defaults to the value of `Tree.root`.
            """
            self._tree = tree
            self._focus = focus or tree.root
            self.root = tree.root

        @lru_cache()
        def __getitem__(self, pos):
            """gets (possibly decorated) line widget at given position"""
            if implementsDecorateAPI(self._tree):
                entry = self._tree.get_decorated(pos)
            else:
                entry = self._tree[pos]
            return entry

        def clear_cache(self):
            """removes all cached lines"""
            self.__getitem__.cache_clear()
            self._modified()

        def _get(self, pos):
            """looks up widget for given position; handling invalid arguments"""
            res = None, None
            if pos is not None:
                try:
                    res = self[pos], pos
                except (IndexError, KeyError):
                    pass
            return res

        # List Walker API.
        def get_focus(self):
            return self._get(self._focus)

        def set_focus(self, pos):
            self._focus = pos
            self._modified()

        def get_next(self, pos):
            return self._get(self._tree.next_position(pos))

        def get_prev(self, pos):
            return self._get(self._tree.prev_position(pos))

        def positions(self, reverse=False):
            """returns a generator that walks the tree's positions"""
            return self._tree.positions(reverse)

        # end of List Walker API

    class TreeBox(WidgetWrap):
        """
        A widget that displays a given :class:`Tree`.
        This is essentially a :class:`ListBox` with the ability to move the focus
        based on directions in the Tree and to collapse/expand subtrees if
        possible.

        TreeBox interprets `left/right` as well as `page up/`page down` to move the
        focus to parent/first child and next/previous sibling respectively. All
        other keys are passed to the underlying ListBox.
        """

        def __init__(self, tree, focus=None):
            """
            :param tree: tree of widgets to be displayed.
            :type tree: Tree
            :param focus: initially focussed position
            """
            self._tree = tree
            self._walker = TreeListWalker(tree)
            self._outer_list = ListBox(self._walker)
            if focus is not None:
                self.set_focus(focus)
            super().__init__(self._outer_list)

        # Widget API
        def get_focus(self):
            return self._outer_list.get_focus()

        def set_focus(self, pos, valign=None):
            position = self._outer_list.set_focus(pos)
            if valign:
                position = self._outer_list.set_focus_valign(valign)
            return position

        def refresh(self):
            self._walker.clear_cache()
            signals.emit_signal(self._walker, "modified")

        def keypress(self, size, key):
            key = self._outer_list.keypress(size, key)
            if key in ['left', 'right', '[', ']', '-', '+', 'C', 'E', ]:
                if key == 'left':
                    self.focus_parent()
                elif key == 'right':
                    self.focus_first_child()
                elif key == '[':
                    self.focus_prev_sibling()
                elif key == ']':
                    self.focus_next_sibling()
                elif key == '-':
                    self.collapse_focussed()
                elif key == '+':
                    self.expand_focussed()
                elif key == 'C':
                    self.collapse_all()
                elif key == 'E':
                    self.expand_all()
                # This is a hack around ListBox misbehaving:
                # it seems impossible to set the focus without calling keypress as
                # otherwise the change becomes visible only after the next render()
                return self._outer_list.keypress(size, None)
            else:
                return self._outer_list.keypress(size, key)

        # Collapse operations

        def collapse_focussed(self):
            """
            Collapse currently focussed position; works only if the underlying
            tree allows it.
            """
            if implementsCollapseAPI(self._tree):
                w, focuspos = self.get_focus()
                self._tree.collapse(focuspos)
                self._walker.clear_cache()
                self.refresh()

        def expand_focussed(self):
            """
            Expand currently focussed position; works only if the underlying
            tree allows it.
            """
            if implementsCollapseAPI(self._tree):
                w, focuspos = self.get_focus()
                self._tree.expand(focuspos)
                self._walker.clear_cache()
                self.refresh()

        def collapse_all(self):
            """
            Collapse all positions; works only if the underlying tree allows it.
            """
            if implementsCollapseAPI(self._tree):
                self._tree.collapse_all()
                self.set_focus(self._tree.root)
                self._walker.clear_cache()
                self.refresh()

        def expand_all(self):
            """
            Expand all positions; works only if the underlying tree allows it.
            """
            if implementsCollapseAPI(self._tree):
                self._tree.expand_all()
                self._walker.clear_cache()
                self.refresh()

        # Tree based focus movement

        def focus_parent(self):
            """move focus to parent node of currently focussed one"""
            w, focuspos = self.get_focus()
            parent = self._tree.parent_position(focuspos)
            if parent is not None:
                self.set_focus(parent)

        def focus_first_child(self):
            """move focus to first child of currently focussed one"""
            w, focuspos = self.get_focus()
            child = self._tree.first_child_position(focuspos)
            if child is not None:
                self.set_focus(child)

        def focus_last_child(self):
            """move focus to last child of currently focussed one"""
            w, focuspos = self.get_focus()
            child = self._tree.last_child_position(focuspos)
            if child is not None:
                self.set_focus(child)

        def focus_next_sibling(self):
            """move focus to next sibling of currently focussed one"""
            w, focuspos = self.get_focus()
            sib = self._tree.next_sibling_position(focuspos)
            if sib is not None:
                self.set_focus(sib)

        def focus_prev_sibling(self):
            """move focus to previous sibling of currently focussed one"""
            w, focuspos = self.get_focus()
            sib = self._tree.prev_sibling_position(focuspos)
            if sib is not None:
                self.set_focus(sib)

        def focus_next(self):
            """move focus to next position (DFO)"""
            w, focuspos = self.get_focus()
            next = self._tree.next_position(focuspos)
            if next is not None:
                self.set_focus(next)

        def focus_prev(self):
            """move focus to previous position (DFO)"""
            w, focuspos = self.get_focus()
            prev = self._tree.prev_position(focuspos)
            if prev is not None:
                self.set_focus(prev)