import importlib
import pickle
import re
import subprocess
import sys
import traceback

from .. import exceptionHandling as exceptionHandling
from .. import getConfigOption
from ..functions import SignalBlock
from ..Qt import QT_LIB, QtCore, QtGui, QtWidgets

ui_template = importlib.import_module(
    f'.template_{QT_LIB.lower()}', package=__package__)


class ConsoleWidget(QtWidgets.QWidget):
    """
    Widget displaying console output and accepting command input.
    Implements:
        
      - eval python expressions / exec python statements
      - storable history of commands
      - exception handling allowing commands to be interpreted in the context of any level in the exception stack frame
    
    Why not just use python in an interactive shell (or ipython) ? There are a few reasons:
       
      - pyside does not yet allow Qt event processing and interactive shell at the same time
      - on some systems, typing in the console _blocks_ the qt event loop until the user presses enter. This can
        be baffling and frustrating to users since it would appear the program has frozen.
      - some terminals (eg windows cmd.exe) have notoriously unfriendly interfaces
      - ability to add extra features like exception stack introspection
      - ability to have multiple interactive prompts, including for spawned sub-processes
    """
    _threadException = QtCore.Signal(object)
    
    def __init__(self, parent=None, namespace=None, historyFile=None, text=None, editor=None):
        """
        ==============  ============================================================================
        **Arguments:**
        namespace       dictionary containing the initial variables present in the default namespace
        historyFile     optional file for storing command history
        text            initial text to display in the console window
        editor          optional string for invoking code editor (called when stack trace entries are 
                        double-clicked). May contain {fileName} and {lineNum} format keys. Example:: 
                      
                            editorCommand --loadfile {fileName} --gotoline {lineNum}
        ==============  =============================================================================
        """
        QtWidgets.QWidget.__init__(self, parent)
        if namespace is None:
            namespace = {}
        namespace['__console__'] = self
        self.localNamespace = namespace
        self.editor = editor
        self.multiline = None
        self.inCmd = False
        self.frames = []  # stack frames to access when an item in the stack list is selected
        
        self.ui = ui_template.Ui_Form()
        self.ui.setupUi(self)
        self.output = self.ui.output
        self.input = self.ui.input
        self.input.setFocus()
        
        if text is not None:
            self.output.setPlainText(text)

        self.historyFile = historyFile
        
        history = self.loadHistory()
        if history is not None:
            self.input.history = [""] + history
            self.ui.historyList.addItems(history[::-1])
        self.ui.historyList.hide()
        self.ui.exceptionGroup.hide()
        
        self.input.sigExecuteCmd.connect(self.runCmd)
        self.ui.historyBtn.toggled.connect(self.ui.historyList.setVisible)
        self.ui.historyList.itemClicked.connect(self.cmdSelected)
        self.ui.historyList.itemDoubleClicked.connect(self.cmdDblClicked)
        self.ui.exceptionBtn.toggled.connect(self.ui.exceptionGroup.setVisible)
        
        self.ui.catchAllExceptionsBtn.toggled.connect(self.catchAllExceptions)
        self.ui.catchNextExceptionBtn.toggled.connect(self.catchNextException)
        self.ui.clearExceptionBtn.clicked.connect(self.clearExceptionClicked)
        self.ui.exceptionStackList.itemClicked.connect(self.stackItemClicked)
        self.ui.exceptionStackList.itemDoubleClicked.connect(self.stackItemDblClicked)
        self.ui.onlyUncaughtCheck.toggled.connect(self.updateSysTrace)
        
        self.currentTraceback = None

        # send exceptions raised in non-gui threads back to the main thread by signal.
        self._threadException.connect(self._threadExceptionHandler)
        
    def loadHistory(self):
        """Return the list of previously-invoked command strings (or None)."""
        if self.historyFile is not None:
            with open(self.historyFile, 'rb') as pf:
                return pickle.load(pf)
        
    def saveHistory(self, history):
        """Store the list of previously-invoked command strings."""
        if self.historyFile is not None:
            with open(self.historyFile, 'wb') as pf:
                pickle.dump(pf, history)
        
    def runCmd(self, cmd):
        #cmd = str(self.input.lastCmd)

        orig_stdout = sys.stdout
        orig_stderr = sys.stderr
        encCmd = re.sub(r'>', '&gt;', re.sub(r'<', '&lt;', cmd))
        encCmd = re.sub(r' ', '&nbsp;', encCmd)
        
        self.ui.historyList.addItem(cmd)
        self.saveHistory(self.input.history[1:100])
        
        try:
            sys.stdout = self
            sys.stderr = self
            if self.multiline is not None:
                self.write("<br><b>%s</b>\n"%encCmd, html=True, scrollToBottom=True)
                self.execMulti(cmd)
            else:
                self.write("<br><div style='background-color: #CCF; color: black'><b>%s</b>\n"%encCmd, html=True, scrollToBottom=True)
                self.inCmd = True
                self.execSingle(cmd)
            
            if not self.inCmd:
                self.write("</div>\n", html=True, scrollToBottom=True)
                
        finally:
            sys.stdout = orig_stdout
            sys.stderr = orig_stderr
            
            sb = self.ui.historyList.verticalScrollBar()
            sb.setValue(sb.maximum())
            
    def globals(self):
        frame = self.currentFrame()
        if frame is not None and self.ui.runSelectedFrameCheck.isChecked():
            return self.currentFrame().f_globals
        else:
            return self.localNamespace
        
    def locals(self):
        frame = self.currentFrame()
        if frame is not None and self.ui.runSelectedFrameCheck.isChecked():
            return self.currentFrame().f_locals
        else:
            return self.localNamespace
            
    def currentFrame(self):
        ## Return the currently selected exception stack frame (or None if there is no exception)
        index = self.ui.exceptionStackList.currentRow()
        if index >= 0 and index < len(self.frames):
            return self.frames[index]
        else:
            return None
        
    def execSingle(self, cmd):
        try:
            output = eval(cmd, self.globals(), self.locals())
            self.write(repr(output) + '\n')
            return
        except SyntaxError:
            pass
        except:
            self.displayException()
            return

        # eval failed with syntax error; try exec instead
        try:
            exec(cmd, self.globals(), self.locals())
        except SyntaxError as exc:
            if 'unexpected EOF' in exc.msg:
                self.multiline = cmd
            else:
                self.displayException()
        except:
            self.displayException()
            
    def execMulti(self, nextLine):
        if nextLine.strip() != '':
            self.multiline += "\n" + nextLine
            return
        else:
            cmd = self.multiline
            
        try:
            output = eval(cmd, self.globals(), self.locals())
            self.write(str(output) + '\n')
            self.multiline = None
            return
        except SyntaxError:
            pass
        except:
            self.displayException()
            self.multiline = None
            return

        # eval failed with syntax error; try exec instead
        try:
            exec(cmd, self.globals(), self.locals())
            self.multiline = None
        except SyntaxError as exc:
            if 'unexpected EOF' in exc.msg:
                self.multiline = cmd
            else:
                self.displayException()
                self.multiline = None
        except:
            self.displayException()
            self.multiline = None


    def write(self, strn, html=False, scrollToBottom='auto'):
        """Write a string into the console.

        If scrollToBottom is 'auto', then the console is automatically scrolled
        to fit the new text only if it was already at the bottom.
        """
        isGuiThread = QtCore.QThread.currentThread() == QtCore.QCoreApplication.instance().thread()
        if not isGuiThread:
            sys.__stdout__.write(strn)
            return

        sb = self.output.verticalScrollBar()
        scroll = sb.value()
        if scrollToBottom == 'auto':
            atBottom = scroll == sb.maximum()
            scrollToBottom = atBottom

        self.output.moveCursor(QtGui.QTextCursor.MoveOperation.End)
        if html:
            self.output.textCursor().insertHtml(strn)
        else:
            if self.inCmd:
                self.inCmd = False
                self.output.textCursor().insertHtml("</div><br><div style='font-weight: normal; background-color: #FFF; color: black'>")
            self.output.insertPlainText(strn)

        if scrollToBottom:
            sb.setValue(sb.maximum())
        else:
            sb.setValue(scroll)

    
    def fileno(self):
        # Need to implement this since we temporarily occlude sys.stdout, and someone may be looking for it (faulthandler, for example)
        return 1

    def displayException(self):
        """
        Display the current exception and stack.
        """
        tb = traceback.format_exc()
        lines = []
        indent = 4
        prefix = '' 
        for l in tb.split('\n'):
            lines.append(" "*indent + prefix + l)
        self.write('\n'.join(lines))
        self.exceptionHandler(*sys.exc_info())
        
    def cmdSelected(self, item):
        index = -(self.ui.historyList.row(item)+1)
        self.input.setHistory(index)
        self.input.setFocus()
        
    def cmdDblClicked(self, item):
        index = -(self.ui.historyList.row(item)+1)
        self.input.setHistory(index)
        self.input.execCmd()
        
    def flush(self):
        pass

    def catchAllExceptions(self, catch=True):
        """
        If True, the console will catch all unhandled exceptions and display the stack
        trace. Each exception caught clears the last.
        """
        with SignalBlock(self.ui.catchAllExceptionsBtn.toggled, self.catchAllExceptions):
            self.ui.catchAllExceptionsBtn.setChecked(catch)
        
        if catch:
            with SignalBlock(self.ui.catchNextExceptionBtn.toggled, self.catchNextException):
                self.ui.catchNextExceptionBtn.setChecked(False)
            self.enableExceptionHandling()
            self.ui.exceptionBtn.setChecked(True)
        else:
            self.disableExceptionHandling()
        
    def catchNextException(self, catch=True):
        """
        If True, the console will catch the next unhandled exception and display the stack
        trace.
        """
        with SignalBlock(self.ui.catchNextExceptionBtn.toggled, self.catchNextException):
            self.ui.catchNextExceptionBtn.setChecked(catch)
        if catch:
            with SignalBlock(self.ui.catchAllExceptionsBtn.toggled, self.catchAllExceptions):
                self.ui.catchAllExceptionsBtn.setChecked(False)
            self.enableExceptionHandling()
            self.ui.exceptionBtn.setChecked(True)
        else:
            self.disableExceptionHandling()
        
    def enableExceptionHandling(self):
        exceptionHandling.register(self.exceptionHandler)
        self.updateSysTrace()
        
    def disableExceptionHandling(self):
        exceptionHandling.unregister(self.exceptionHandler)
        self.updateSysTrace()
        
    def clearExceptionClicked(self):
        self.currentTraceback = None
        self.frames = []
        self.ui.exceptionInfoLabel.setText("[No current exception]")
        self.ui.exceptionStackList.clear()
        self.ui.clearExceptionBtn.setEnabled(False)
        
    def stackItemClicked(self, item):
        pass
    
    def stackItemDblClicked(self, item):
        editor = self.editor
        if editor is None:
            editor = getConfigOption('editorCommand')
        if editor is None:
            return
        tb = self.currentFrame()
        lineNum = tb.f_lineno
        fileName = tb.f_code.co_filename
        subprocess.Popen(self.editor.format(fileName=fileName, lineNum=lineNum), shell=True)
        
    def updateSysTrace(self):
        ## Install or uninstall  sys.settrace handler 
        
        if not self.ui.catchNextExceptionBtn.isChecked() and not self.ui.catchAllExceptionsBtn.isChecked():
            if sys.gettrace() == self.systrace:
                sys.settrace(None)
            return
        
        if self.ui.onlyUncaughtCheck.isChecked():
            if sys.gettrace() == self.systrace:
                sys.settrace(None)
        else:
            if sys.gettrace() is not None and sys.gettrace() != self.systrace:
                self.ui.onlyUncaughtCheck.setChecked(False)
                raise Exception("sys.settrace is in use; cannot monitor for caught exceptions.")
            else:
                sys.settrace(self.systrace)
        
    def exceptionHandler(self, excType, exc, tb, systrace=False, frame=None):
        if frame is None:
            frame = sys._getframe()

        # exceptions raised in non-gui threads must be handled separately
        isGuiThread = QtCore.QThread.currentThread() == QtCore.QCoreApplication.instance().thread()
        if not isGuiThread:
            # sending a frame from one thread to another.. probably not safe, but better than just
            # dropping the exception?
            self._threadException.emit((excType, exc, tb, systrace, frame.f_back))
            return

        if self.ui.catchNextExceptionBtn.isChecked():
            self.ui.catchNextExceptionBtn.setChecked(False)
        elif not self.ui.catchAllExceptionsBtn.isChecked():
            return
        
        self.currentTraceback = tb
        
        excMessage = ''.join(traceback.format_exception_only(excType, exc))
        self.ui.exceptionInfoLabel.setText(excMessage)

        if systrace:
            # exceptions caught using systrace don't need the usual 
            # call stack + traceback handling
            self.setStack(frame.f_back.f_back)
        else:
            self.setStack(frame=frame.f_back, tb=tb)
    
    def _threadExceptionHandler(self, args):
        self.exceptionHandler(*args)

    def setStack(self, frame=None, tb=None):
        """Display a call stack and exception traceback.

        This allows the user to probe the contents of any frame in the given stack.

        *frame* may either be a Frame instance or None, in which case the current 
        frame is retrieved from ``sys._getframe()``. 

        If *tb* is provided then the frames in the traceback will be appended to 
        the end of the stack list. If *tb* is None, then sys.exc_info() will 
        be checked instead.
        """
        self.ui.clearExceptionBtn.setEnabled(True)
        
        if frame is None:
            frame = sys._getframe().f_back

        if tb is None:
            tb = sys.exc_info()[2]

        self.ui.exceptionStackList.clear()
        self.frames = []

        # Build stack up to this point
        for index, line in enumerate(traceback.extract_stack(frame)):
            # extract_stack return value changed in python 3.5
            if 'FrameSummary' in str(type(line)):
                line = (line.filename, line.lineno, line.name, line._line)
            
            self.ui.exceptionStackList.addItem('File "%s", line %s, in %s()\n  %s' % line)
        while frame is not None:
            self.frames.insert(0, frame)
            frame = frame.f_back

        if tb is None:
            return

        self.ui.exceptionStackList.addItem('-- exception caught here: --')
        item = self.ui.exceptionStackList.item(self.ui.exceptionStackList.count()-1)
        item.setBackground(QtGui.QBrush(QtGui.QColor(200, 200, 200)))
        item.setForeground(QtGui.QBrush(QtGui.QColor(50, 50, 50)))
        self.frames.append(None)

        # And finish the rest of the stack up to the exception
        for index, line in enumerate(traceback.extract_tb(tb)):
            # extract_stack return value changed in python 3.5
            if 'FrameSummary' in str(type(line)):
                line = (line.filename, line.lineno, line.name, line._line)
            
            self.ui.exceptionStackList.addItem('File "%s", line %s, in %s()\n  %s' % line)
        while tb is not None:
            self.frames.append(tb.tb_frame)
            tb = tb.tb_next

    def systrace(self, frame, event, arg):
        if event == 'exception' and self.checkException(*arg):
            self.exceptionHandler(*arg, systrace=True)
        return self.systrace
        
    def checkException(self, excType, exc, tb):
        ## Return True if the exception is interesting; False if it should be ignored.
        
        filename = tb.tb_frame.f_code.co_filename
        function = tb.tb_frame.f_code.co_name
        
        filterStr = str(self.ui.filterText.text())
        if filterStr != '':
            if isinstance(exc, Exception):
                msg = traceback.format_exception_only(type(exc), exc)
            elif isinstance(exc, str):
                msg = exc
            else:
                msg = repr(exc)
            match = re.search(filterStr, "%s:%s:%s" % (filename, function, msg))
            return match is not None

        ## Go through a list of common exception points we like to ignore:
        if excType is GeneratorExit or excType is StopIteration:
            return False
        if excType is KeyError:
            if filename.endswith('python2.7/weakref.py') and function in ('__contains__', 'get'):
                return False
            if filename.endswith('python2.7/copy.py') and function == '_keep_alive':
                return False
        if excType is AttributeError:
            if filename.endswith('python2.7/collections.py') and function == '__init__':
                return False
            if filename.endswith('numpy/core/fromnumeric.py') and function in ('all', '_wrapit', 'transpose', 'sum'):
                return False
            if filename.endswith('numpy/core/arrayprint.py') and function in ('_array2string'):
                return False
            if filename.endswith('MetaArray.py') and function == '__getattr__':
                for name in ('__array_interface__', '__array_struct__', '__array__'):  ## numpy looks for these when converting objects to array
                    if name in exc:
                        return False
            if filename.endswith('flowchart/eq.py'):
                return False
            if filename.endswith('pyqtgraph/functions.py') and function == 'makeQImage':
                return False
        if excType is TypeError:
            if filename.endswith('numpy/lib/function_base.py') and function == 'iterable':
                return False
        if excType is ZeroDivisionError:
            if filename.endswith('python2.7/traceback.py'):
                return False
            
        return True
    
