import re
import warnings
import weakref
from collections import OrderedDict

from .. import functions as fn
from ..Qt import QtCore
from .ParameterItem import ParameterItem

PARAM_TYPES = {}
PARAM_NAMES = {}

_PARAM_ITEM_TYPES = {}


def registerParameterItemType(name, itemCls, parameterCls=None, override=False):
    """
    Similar to :func:`registerParameterType`, but works on ParameterItems. This is useful for Parameters where the
    `itemClass` does all the heavy lifting, and a redundant Parameter class must be defined just to house `itemClass`.
    Instead, use `registerParameterItemType`. If this should belong to a subclass of `Parameter`, specify which one
    in `parameterCls`.
    """
    global _PARAM_ITEM_TYPES
    if name in _PARAM_ITEM_TYPES and not override:
        raise ValueError(
            f"Parameter item type '{name}' already exists (use override=True to replace)"
        )

    parameterCls = parameterCls or Parameter
    _PARAM_ITEM_TYPES[name] = itemCls
    registerParameterType(name, parameterCls, override)


def registerParameterType(name, cls, override=False):
    """Register a parameter type in the parametertree system.

    This enables construction of custom Parameter classes by name in
    :meth:`~pyqtgraph.parametertree.Parameter.create`.
    """
    global PARAM_TYPES
    if name in PARAM_TYPES and not override:
        raise ValueError(f"Parameter type '{name}' already exists (use override=True to replace)")
    PARAM_TYPES[name] = cls
    PARAM_NAMES[cls] = name


def __reload__(old):
    PARAM_TYPES.update(old.get('PARAM_TYPES', {}))
    PARAM_NAMES.update(old.get('PARAM_NAMES', {}))


class Parameter(QtCore.QObject):
    """
    A Parameter is the basic unit of data in a parameter tree. Each parameter has
    a name, a type, a value, and several other properties that modify the behavior of the 
    Parameter. Parameters may have parent / child / sibling relationships to construct
    organized hierarchies. Parameters generally do not have any inherent GUI or visual
    interpretation; instead they manage ParameterItem instances which take care of
    display and user interaction.
    
    Note: It is fairly uncommon to use the Parameter class directly; mostly you 
    will use subclasses which provide specialized type and data handling. The static
    method Parameter.create(...) is an easy way to generate instances of these subclasses.
       
    For more Parameter types, see ParameterTree.parameterTypes module.
    
    ===================================  =========================================================
    **Signals:**
    sigStateChanged(self, change, info)  Emitted when anything changes about this parameter at 
                                         all.
                                         The second argument is a string indicating what changed 
                                         ('value', 'childAdded', etc..)
                                         The third argument can be any extra information about 
                                         the change
    sigTreeStateChanged(self, changes)   Emitted when any child in the tree changes state
                                         (but only if monitorChildren() is called)
                                         the format of *changes* is [(param, change, info), ...]
    sigValueChanged(self, value)         Emitted when value is finished changing
    sigValueChanging(self, value)        Emitted immediately for all value changes, 
                                         including during editing.
    sigChildAdded(self, child, index)    Emitted when a child is added
    sigChildRemoved(self, child)         Emitted when a child is removed
    sigRemoved(self)                     Emitted when this parameter is removed
    sigParentChanged(self, parent)       Emitted when this parameter's parent has changed
    sigLimitsChanged(self, limits)       Emitted when this parameter's limits have changed
    sigDefaultChanged(self, default)     Emitted when this parameter's default value has changed
    sigNameChanged(self, name)           Emitted when this parameter's name has changed
    sigOptionsChanged(self, opts)        Emitted when any of this parameter's options have changed
    sigContextMenu(self, name)           Emitted when a context menu was clicked
    ===================================  =========================================================
    """
    ## name, type, limits, etc.
    ## can also carry UI hints (slider vs spinbox, etc.)

    sigValueChanged = QtCore.Signal(object, object)  ## self, value   emitted when value is finished being edited
    sigValueChanging = QtCore.Signal(object, object)  ## self, value  emitted as value is being edited
    
    sigChildAdded = QtCore.Signal(object, object, object)  ## self, child, index
    sigChildRemoved = QtCore.Signal(object, object)  ## self, child
    sigRemoved = QtCore.Signal(object) ## self
    sigParentChanged = QtCore.Signal(object, object)  ## self, parent
    sigLimitsChanged = QtCore.Signal(object, object)  ## self, limits
    sigDefaultChanged = QtCore.Signal(object, object)  ## self, default
    sigNameChanged = QtCore.Signal(object, object)  ## self, name
    sigOptionsChanged = QtCore.Signal(object, object)  ## self, {opt:val, ...}
    
    ## Emitted when anything changes about this parameter at all.
    ## The second argument is a string indicating what changed ('value', 'childAdded', etc..)
    ## The third argument can be any extra information about the change
    sigStateChanged = QtCore.Signal(object, object, object) ## self, change, info
    
    ## emitted when any child in the tree changes state
    ## (but only if monitorChildren() is called)
    sigTreeStateChanged = QtCore.Signal(object, object)  # self, changes
                                                         # changes = [(param, change, info), ...]
    sigContextMenu = QtCore.Signal(object, object)       # self, name

    # bad planning.
    #def __new__(cls, *args, **opts):
        #try:
            #cls = PARAM_TYPES[opts['type']]
        #except KeyError:
            #pass
        #return QtCore.QObject.__new__(cls, *args, **opts)

    @staticmethod
    def create(**opts):
        """
        Static method that creates a new Parameter (or subclass) instance using 
        opts['type'] to select the appropriate class.
        
        All options are passed directly to the new Parameter's __init__ method.
        Use registerParameterType() to add new class types.
        """
        typ = opts.get('type', None)
        if typ is None:
            cls = Parameter
        else:
            cls = PARAM_TYPES[opts['type']]
        return cls(**opts)

    def __init__(self, **opts):
        """
        Initialize a Parameter object. Although it is rare to directly create a
        Parameter instance, the options available to this method are also allowed
        by most Parameter subclasses.
        
        =======================      =========================================================
        **Keyword Arguments:**
        name                         The name to give this Parameter. This is the name that
                                     will appear in the left-most column of a ParameterTree
                                     for this Parameter.
        value                        The value to initially assign to this Parameter.
        default                      The default value for this Parameter (most Parameters
                                     provide an option to 'reset to default').
        children                     A list of children for this Parameter. Children
                                     may be given either as a Parameter instance or as a
                                     dictionary to pass to Parameter.create(). In this way,
                                     it is possible to specify complex hierarchies of
                                     Parameters from a single nested data structure.
        readonly                     If True, the user will not be allowed to edit this
                                     Parameter. (default=False)
        enabled                      If False, any widget(s) for this parameter will appear
                                     disabled. (default=True)
        visible                      If False, the Parameter will not appear when displayed
                                     in a ParameterTree. (default=True)
        renamable                    If True, the user may rename this Parameter.
                                     (default=False)
        removable                    If True, the user may remove this Parameter.
                                     (default=False)
        expanded                     If True, the Parameter will initially be expanded in
                                     ParameterTrees: Its children will be visible.
                                     (default=True)
        syncExpanded                 If True, the `expanded` state of this Parameter is
                                     synchronized with all ParameterTrees it is displayed in.
                                     (default=False)
        title                        (str or None) If specified, then the parameter will be 
                                     displayed to the user using this string as its name. 
                                     However, the parameter will still be referred to 
                                     internally using the *name* specified above. Note that
                                     this option is not compatible with renamable=True.
                                     (default=None; added in version 0.9.9)
        =======================      =========================================================
        """
        QtCore.QObject.__init__(self)
        
        self.opts = {
            'type': None,
            'readonly': False,
            'visible': True,
            'enabled': True,
            'renamable': False,
            'removable': False,
            'strictNaming': False,  # forces name to be usable as a python variable
            'expanded': True,
            'syncExpanded': False,
            'title': None,
            # The following intentionally excluded; each parameter type may have a different data type for limits.
            # 'limits': None,
        }
        name = opts.get('name', None)
        if not isinstance(name, str):
            raise TypeError("Parameter must have a string name specified in opts.")
        self.opts.update(opts)
        self.opts['name'] = None

        self.childs = []
        self.names = {}   ## map name:child
        self.items = weakref.WeakKeyDictionary()  ## keeps track of tree items representing this parameter
        self._parent = None
        self.treeStateChanges = []  ## cache of tree state changes to be delivered on next emit
        self.blockTreeChangeEmit = 0
        self.setName(name)

        self.addChildren(self.opts.pop('children', []))
        if 'value' in self.opts and 'default' not in self.opts:
            warnings.warn(
                "Parameter has no default value. Pass a default, or use setDefault(). This will no longer set "
                "an implicit default after January 2025.",
                DeprecationWarning,
                stacklevel=2,
            )
            self.opts['default'] = self.opts['value']
        value = self.opts.get('value', self.opts.get('default', None))
        modified = 'value' in self.opts
        if value is not None:
            self.setValue(value)
        self._modifiedSinceReset = modified

        # Connect all state changed signals to the general sigStateChanged
        self.sigValueChanged.connect(self._emitValueChanged)
        self.sigChildAdded.connect(self._emitChildAddedChanged)
        self.sigChildRemoved.connect(self._emitChildRemovedChanged)
        self.sigParentChanged.connect(self._emitParentChanged)
        self.sigLimitsChanged.connect(self._emitLimitsChanged)
        self.sigDefaultChanged.connect(self._emitDefaultChanged)
        self.sigNameChanged.connect(self._emitNameChanged)
        self.sigOptionsChanged.connect(self._emitOptionsChanged)
        self.sigContextMenu.connect(self._emitContextMenuChanged)

    @property
    def itemClass(self):
        """
        The class of ParameterItem to use when displaying this parameter in a ParameterTree.
        """
        return ParameterItem

    def name(self):
        """Return the name of this Parameter."""
        return self.opts['name']

    def title(self):
        """Return the title of this Parameter.
        
        By default, the title is the same as the name unless it has been explicitly specified
        otherwise."""
        title = self.opts.get('title', None)
        if title is None:
            title = self.name()
        return title

    def contextMenu(self, name):
        """"A context menu entry was clicked"""
        self.sigContextMenu.emit(self, name)

    def setName(self, name):
        """Attempt to change the name of this parameter; return the actual name. 
        (The parameter may reject the name change or automatically pick a different name)"""
        if self.opts['strictNaming'] and (len(name) < 1 or re.search(r'\W', name) or re.match(r'\d', name[0])):
            raise ValueError(
                f"Parameter name '{name}' is invalid. (Must contain only alphanumeric and underscore characters and "
                f"may not start with a number)")
        parent = self.parent()
        if parent is not None:
            name = parent._renameChild(self, name)  # first ask parent if it's ok to rename
        if self.opts['name'] != name:
            self.opts['name'] = name
            self.sigNameChanged.emit(self, name)
        return name

    def type(self):
        """Return the type string for this Parameter."""
        return self.opts['type']
        
    def isType(self, typ):
        """
        Return True if this parameter type matches the name *typ*.
        This can occur either of two ways:
        
          - If self.type() == *typ*
          - If this parameter's class is registered with the name *typ*
        """
        if self.type() == typ:
            return True
        global PARAM_TYPES
        cls = PARAM_TYPES.get(typ, None)
        if cls is None:
            raise ValueError(f"Type name '{typ}' is not registered.")
        return self.__class__ is cls
        
    def childPath(self, child):
        """
        Return the path of parameter names from self to child.
        If child is not a (grand)child of self, return None.
        """
        path = []
        while child is not self:
            path.insert(0, child.name())
            child = child.parent()
            if child is None:
                return None
        return path

    def setValue(self, value, blockSignal=None):
        """
        Set the value of this Parameter; return the actual value that was set.
        (this may be different from the value that was requested)
        """
        try:
            if blockSignal is not None:
                self.sigValueChanged.disconnect(blockSignal)
            value = self._interpretValue(value)
            if fn.eq(self.opts.get('value', None), value):
                return value
            self._modifiedSinceReset = True
            self.opts['value'] = value
            self.sigValueChanged.emit(self, value)  # value might change after signal is received by tree item
        finally:
            if blockSignal is not None:
                self.sigValueChanged.connect(blockSignal)
            
        return self.opts['value']

    def _interpretValue(self, v):
        return v

    def hasValue(self):
        """Return True if this Parameter has a value set."""
        return 'value' in self.opts

    def value(self):
        """
        Return the value of this Parameter. Raises ValueError if no value has been set.
        """
        if 'value' not in self.opts:
            warnings.warn(
                "Parameter has no value set. Pass an initial value or default, or use setValue() or setDefault(). "
                "This will be an error after January 2025.",
                DeprecationWarning,
                stacklevel=2,
            )
        return self.opts.get('value')

    def getValues(self):
        """
        Return a tree of all values that are children of this parameter. Raises ValueError if any child has no value.
        """
        vals = OrderedDict()
        for ch in self:
            vals[ch.name()] = (ch.value(), ch.getValues())
        return vals
    
    def saveState(self, filter=None):
        """
        Return a structure representing the entire state of the parameter tree.
        The tree state may be restored from this structure using restoreState().

        If *filter* is set to 'user', then only user-settable data will be included in the
        returned state.
        """
        if filter is None:
            state = self.opts.copy()
            if state['type'] is None:
                global PARAM_NAMES
                state['type'] = PARAM_NAMES.get(type(self), None)
        elif filter == 'user':
            if self.hasValue():
                state = {'value': self.value()}
            else:
                state = {}
        else:
            raise ValueError(f"Unrecognized filter argument: '{filter}'")

        ch = OrderedDict([(ch.name(), ch.saveState(filter=filter)) for ch in self])
        if len(ch) > 0:
            state['children'] = ch
        return state

    def restoreState(self, state, recursive=True, addChildren=True, removeChildren=True, blockSignals=True):
        """
        Restore the state of this parameter and its children from a structure generated using saveState()
        If recursive is True, then attempt to restore the state of child parameters as well.
        If addChildren is True, then any children which are referenced in the state object will be
        created if they do not already exist.
        If removeChildren is True, then any children which are not referenced in the state object will 
        be removed.
        If blockSignals is True, no signals will be emitted until the tree has been completely restored. 
        This prevents signal handlers from responding to a partially-rebuilt network.
        """
        state = state.copy()
        childState = state.pop('children', [])
        
        ## list of children may be stored either as list or dict.
        if isinstance(childState, dict):
            cs = []
            for k,v in childState.items():
                cs.append(v.copy())
                cs[-1].setdefault('name', k)
            childState = cs
        
        if blockSignals:
            self.blockTreeChangeSignal()
            
        try:
            self.setOpts(**state)
            
            if not recursive:
                return
            
            ptr = 0  ## pointer to first child that has not been restored yet
            foundChilds = set()
            #print "==============", self.name()
            
            for ch in childState:
                name = ch['name']
                #typ = ch.get('type', None)
                #print('child: %s, %s' % (self.name()+'.'+name, typ))
                
                ## First, see if there is already a child with this name
                gotChild = False
                for i, ch2 in enumerate(self.childs[ptr:]):
                    #print "  ", ch2.name(), ch2.type()
                    if ch2.name() != name: # or not ch2.isType(typ):
                        continue
                    gotChild = True
                    #print "    found it"
                    if i != 0:  ## move parameter to next position
                        #self.removeChild(ch2)
                        self.insertChild(ptr, ch2)
                        #print "  moved to position", ptr
                    ch2.restoreState(ch, recursive=recursive, addChildren=addChildren, removeChildren=removeChildren)
                    foundChilds.add(ch2)
                    
                    break
                
                if not gotChild:
                    if not addChildren:
                        #print "  ignored child"
                        continue
                    #print "    created new"
                    ch2 = Parameter.create(**ch)
                    self.insertChild(ptr, ch2)
                    foundChilds.add(ch2)
                    
                ptr += 1
                
            if removeChildren:
                for ch in self.childs[:]:
                    if ch not in foundChilds:
                        #print "  remove:", ch
                        self.removeChild(ch)
        finally:
            if blockSignals:
                self.unblockTreeChangeSignal()

    def valueModifiedSinceResetToDefault(self):
        """Return True if this parameter's value has been changed since the last time
        it was reset to its default value."""
        return self._modifiedSinceReset

    def defaultValue(self):
        """Return the default value for this parameter. Raises ValueError if no default."""
        if 'default' not in self.opts:
            warnings.warn("Parameter has no default value. This will be a ValueError after January 2025.",
                          DeprecationWarning,
                          stacklevel=2)
        return self.opts.get('default')
        
    def setDefault(self, val, updatePristineValues=False):
        """Set the default value for this parameter. If updatePristineValues is True, then
        any values that haven't been modified since the last time they were reset to default
        will be updated to the new default value (default: False)."""
        if self.opts.get('default', None) == val:
            return
        self.opts['default'] = val
        if 'value' not in self.opts or (updatePristineValues and not self.valueModifiedSinceResetToDefault()):
            self.setToDefault()
        if not self.valueIsDefault():
            self._modifiedSinceReset = True
        self.sigDefaultChanged.emit(self, val)

    def setToDefault(self):
        """Set this parameter's value to the default. Raises ValueError if no default is set."""
        with self.treeChangeBlocker():
            self.setValue(self.defaultValue())
            self._modifiedSinceReset = False

    def hasDefault(self):
        """Returns True if this parameter has a default value."""
        return self.opts.get('default', None) is not None
        
    def valueIsDefault(self):
        """Returns True if this parameter's value is equal to the default value."""
        if not self.hasValue() or not self.hasDefault():
            return False
        return fn.eq(self.value(), self.defaultValue())

    def setLimits(self, limits):
        """Set limits on the acceptable values for this parameter. 
        The format of limits depends on the type of the parameter and
        some parameters do not make use of limits at all."""
        if 'limits' in self.opts and fn.eq(self.opts['limits'], limits):
            return
        self.opts['limits'] = limits
        self.sigLimitsChanged.emit(self, limits)
        return limits

    def writable(self):
        """
        Returns True if this parameter's value can be changed by the user.
        Note that the value of the parameter can *always* be changed by
        calling setValue().
        """
        return not self.readonly()

    def setWritable(self, writable=True):
        """Set whether this Parameter should be editable by the user. (This is 
        exactly the opposite of setReadonly)."""
        self.setOpts(readonly=not writable)
        
    def readonly(self):
        """
        Return True if this parameter is read-only. (this is the opposite of writable())
        """
        return self.opts.get('readonly', False)
        
    def setReadonly(self, readonly=True):
        """Set whether this Parameter's value may be edited by the user
        (this is the opposite of setWritable())."""
        self.setOpts(readonly=readonly)
        
    def setOpts(self, **opts):
        """
        Set any arbitrary options on this parameter.
        The exact behavior of this function will depend on the parameter type, but
        most parameters will accept a common set of options: value, name, limits,
        default, readonly, removable, renamable, visible, enabled, expanded and
        syncExpanded.
        
        See :func:`Parameter.__init__ <pyqtgraph.parametertree.Parameter.__init__>`
        for more information on default options.
        """
        changed = OrderedDict()
        for k in opts:
            if k == 'value':
                self.setValue(opts[k])
            elif k == 'name':
                self.setName(opts[k])
            elif k == 'limits':
                self.setLimits(opts[k])
            elif k == 'default':
                self.setDefault(opts[k])
            elif k not in self.opts or not fn.eq(self.opts[k], opts[k]):
                self.opts[k] = opts[k]
                changed[k] = opts[k]
                
        if len(changed) > 0:
            self.sigOptionsChanged.emit(self, changed)
        
    def emitStateChanged(self, changeDesc, data):
        ## Emits stateChanged signal and 
        ## requests emission of new treeStateChanged signal
        self.sigStateChanged.emit(self, changeDesc, data)
        #self.treeStateChanged(self, changeDesc, data)
        self.treeStateChanges.append((self, changeDesc, data))
        self.emitTreeChanges()

    @QtCore.Slot(object, object)
    def _emitValueChanged(self, param, data):
        self.emitStateChanged("value", data)

    @QtCore.Slot(object, object, object)
    def _emitChildAddedChanged(self, param, *data):
        self.emitStateChanged("childAdded", data)

    @QtCore.Slot(object, object)
    def _emitChildRemovedChanged(self, param, data):
        self.emitStateChanged("childRemoved", data)

    @QtCore.Slot(object, object)
    def _emitParentChanged(self, param, data):
        self.emitStateChanged("parent", data)

    @QtCore.Slot(object, object)
    def _emitLimitsChanged(self, param, data):
        self.emitStateChanged("limits", data)

    @QtCore.Slot(object, object)
    def _emitDefaultChanged(self, param, data):
        self.emitStateChanged("default", data)

    @QtCore.Slot(object, object)
    def _emitNameChanged(self, param, data):
        self.emitStateChanged("name", data)

    @QtCore.Slot(object, object)
    def _emitOptionsChanged(self, param, data):
        self.emitStateChanged("options", data)

    @QtCore.Slot(object, object)
    def _emitContextMenuChanged(self, param, data):
        self.emitStateChanged("contextMenu", data)

    def makeTreeItem(self, depth):
        """
        Return a TreeWidgetItem suitable for displaying/controlling the content of 
        this parameter. This is called automatically when a ParameterTree attempts
        to display this Parameter.
        Most subclasses will want to override this function.
        """
        # Default to user-specified itemClass. If not present, check for a registered item class. Finally,
        # revert to ParameterItem if both fail
        itemClass = self.itemClass or _PARAM_ITEM_TYPES.get(self.opts['type'], ParameterItem)
        return itemClass(self, depth)

    def addChild(self, child, autoIncrementName=None, existOk=False):
        """
        Add another parameter to the end of this parameter's child list.
        
        See insertChild() for a description of the *autoIncrementName* and *existOk*
        arguments.
        """
        return self.insertChild(len(self.childs), child, autoIncrementName=autoIncrementName, existOk=existOk)

    def addChildren(self, children):
        """
        Add a list or dict of children to this parameter. This method calls
        addChild once for each value in *children*.
        """
        ## If children was specified as dict, then assume keys are the names.
        if isinstance(children, dict):
            ch2 = []
            for name, opts in children.items():
                if isinstance(opts, dict) and 'name' not in opts:
                    opts = opts.copy()
                    opts['name'] = name
                ch2.append(opts)
            children = ch2
        
        for chOpts in children:
            #print self, "Add child:", type(chOpts), id(chOpts)
            self.addChild(chOpts)

    def insertChild(self, pos, child, autoIncrementName=None, existOk=False):
        """
        Insert a new child at pos.
        If pos is a Parameter, then insert at the position of that Parameter.
        If child is a dict, then a parameter is constructed using
        :func:`Parameter.create <pyqtgraph.parametertree.Parameter.create>`.
        
        By default, the child's 'autoIncrementName' option determines whether
        the name will be adjusted to avoid prior name collisions. This 
        behavior may be overridden by specifying the *autoIncrementName* 
        argument. This argument was added in version 0.9.9.

        If 'autoIncrementName' is *False*, an error is raised when the inserted child already exists. However, if
        'existOk' is *True*, the existing child will be returned instead, and this child will *not* be inserted.
        """
        if isinstance(child, dict):
            child = Parameter.create(**child)
        
        name = child.name()
        if name in self.names and child is not self.names[name]:
            if autoIncrementName is True or (autoIncrementName is None and child.opts.get('autoIncrementName', False)):
                name = self.incrementName(name)
                child.setName(name)
            elif existOk:
                return self.names[name]
            else:
                raise ValueError("Already have child named %s" % str(name))
        if isinstance(pos, Parameter):
            pos = self.childs.index(pos)
            
        with self.treeChangeBlocker():
            if child.parent() is not None:
                child.remove()
                
            self.names[name] = child
            self.childs.insert(pos, child)
            
            child.parentChanged(self)
            child.sigTreeStateChanged.connect(self.treeStateChanged)
            self.sigChildAdded.emit(self, child, pos)
        return child
        
    def removeChild(self, child):
        """Remove a child parameter."""
        name = child.name()
        if name not in self.names or self.names[name] is not child:
            raise Exception("Parameter %s is not my child; can't remove." % str(child))
        del self.names[name]
        self.childs.pop(self.childs.index(child))
        child.parentChanged(None)
        try:
            child.sigTreeStateChanged.disconnect(self.treeStateChanged)
        except (TypeError, RuntimeError):  ## already disconnected
            pass
        self.sigChildRemoved.emit(self, child)

    def clearChildren(self):
        """Remove all child parameters."""
        for ch in self.childs[:]:
            self.removeChild(ch)

    def children(self):  
        """Return a list of this parameter's children.
        Warning: this overrides QObject.children
        """
        return self.childs[:]
    
    def hasChildren(self):
        """Return True if this Parameter has children."""
        return len(self.childs) > 0

    def parentChanged(self, parent):
        """This method is called when the parameter's parent has changed.
        It may be useful to extend this method in subclasses."""
        self._parent = parent
        self.sigParentChanged.emit(self, parent)
        
    def parent(self):
        """Return the parent of this parameter."""
        return self._parent
        
    def remove(self):
        """Remove this parameter from its parent's child list"""
        parent = self.parent()
        if parent is None:
            raise Exception("Cannot remove; no parent.")
        parent.removeChild(self)
        self.sigRemoved.emit(self)

    def incrementName(self, name):
        ## return an unused name by adding a number to the name given
        base, num = re.match(r'([^\d]*)(\d*)', name).groups()
        numLen = len(num)
        if numLen == 0:
            num = 2
            numLen = 1
        else:
            num = int(num)
        while True:
            newName = base + ("%%0%dd"%numLen) % num
            if newName not in self.names:
                return newName
            num += 1

    def __iter__(self):
        yield from self.childs

    def __getitem__(self, names):
        """Get the value of a child parameter. The name may also be a tuple giving
        the path to a sub-parameter::
        
            value = param[('child', 'grandchild')]

        Raises ValueError if the child value is not set.
        """
        if not isinstance(names, tuple):
            names = (names,)
        return self.param(*names).value()

    def __setitem__(self, names, value):
        """Set the value of a child parameter. The name may also be a tuple giving
        the path to a sub-parameter::
        
            param[('child', 'grandchild')] = value
        """
        if isinstance(names, str):
            names = (names,)
        return self.param(*names).setValue(value)

    def keys(self):
        return self.names

    def child(self, *names):
        """Return a child parameter. 
        Accepts the name of the child or a tuple (path, to, child)

        Added in version 0.9.9. Earlier versions used the 'param' method, which is still
        implemented for backward compatibility.
        """
        try:
            param = self.names[names[0]]
        except KeyError as e:
            raise KeyError(f"Parameter {self.name()} has no child named {names[0]}") from e

        if len(names) > 1:
            return param.child(*names[1:])
        else:
            return param

    def param(self, *names):
        # for backward compatibility.
        return self.child(*names)

    def __repr__(self):
        return "<%s '%s' at 0x%x>" % (self.__class__.__name__, self.name(), id(self))
       
    def _renameChild(self, child, name):
        ## Only to be called from Parameter.rename
        if name in self.names:
            return child.name()
        self.names[name] = child
        del self.names[child.name()]
        return name

    def registerItem(self, item):
        self.items[item] = None
        
    def hide(self):
        """Hide this parameter. It and its children will no longer be visible in any ParameterTree
        widgets it is connected to."""
        self.show(False)
        
    def show(self, s=True):
        """Show this parameter. """
        self.opts['visible'] = s
        self.sigOptionsChanged.emit(self, {'visible': s})


    def treeChangeBlocker(self):
        """
        Return an object that can be used to temporarily block and accumulate
        sigTreeStateChanged signals. This is meant to be used when numerous changes are 
        about to be made to the tree and only one change signal should be
        emitted at the end.
        
        Example::

            with param.treeChangeBlocker():
                param.addChild(...)
                param.removeChild(...)
                param.setValue(...)
        """
        return SignalBlocker(self.blockTreeChangeSignal, self.unblockTreeChangeSignal)

    def blockTreeChangeSignal(self):
        """
        Used to temporarily block and accumulate tree change signals.
        *You must remember to unblock*, so it is advisable to use treeChangeBlocker() instead.
        """
        self.blockTreeChangeEmit += 1

    def unblockTreeChangeSignal(self):
        """Unblocks enission of sigTreeStateChanged and flushes the changes out through a single signal."""
        self.blockTreeChangeEmit -= 1
        self.emitTreeChanges()
        
        
    @QtCore.Slot(object, object)
    def treeStateChanged(self, param, changes):
        """
        Called when the state of any sub-parameter has changed. 
        
        ==============  ================================================================
        **Arguments:**
        param           The immediate child whose tree state has changed.
                        note that the change may have originated from a grandchild.
        changes         List of tuples describing all changes that have been made
                        in this event: (param, changeDescr, data)
        ==============  ================================================================
                     
        This function can be extended to react to tree state changes.
        """
        self.treeStateChanges.extend(changes)
        self.emitTreeChanges()
    
    def emitTreeChanges(self):
        if self.blockTreeChangeEmit == 0:
            changes = self.treeStateChanges
            self.treeStateChanges = []
            if len(changes) > 0:
                self.sigTreeStateChanged.emit(self, changes)


class SignalBlocker(object):
    def __init__(self, enterFn, exitFn):
        self.enterFn = enterFn
        self.exitFn = exitFn
        
    def __enter__(self):
        self.enterFn()
        
    def __exit__(self, exc_type, exc_value, tb):
        self.exitFn()
    
