# SPDX-FileCopyrightText: Freya Bruhin (The Compiler) <mail@qutebrowser.org>
#
# SPDX-License-Identifier: GPL-3.0-or-later

"""Debugging console."""

import sys
import code
from typing import Optional
from collections.abc import MutableSequence

from qutebrowser.qt.core import pyqtSignal, pyqtSlot, Qt
from qutebrowser.qt.widgets import QTextEdit, QWidget, QVBoxLayout, QApplication
from qutebrowser.qt.gui import QTextCursor

from qutebrowser.config import stylesheet
from qutebrowser.misc import cmdhistory, miscwidgets
from qutebrowser.utils import utils, objreg


console_widget: Optional["ConsoleWidget"] = None


class ConsoleLineEdit(miscwidgets.CommandLineEdit):

    """A QLineEdit which executes entered code and provides a history.

    Attributes:
        _history: The command history of executed commands.

    Signals:
        execute: Emitted when a commandline should be executed.
    """

    execute = pyqtSignal(str)

    def __init__(self, _namespace, parent):
        """Constructor.

        Args:
            _namespace: The local namespace of the interpreter.
        """
        super().__init__(parent=parent)
        self._history = cmdhistory.History(parent=self)
        self.returnPressed.connect(self.on_return_pressed)

    @pyqtSlot()
    def on_return_pressed(self):
        """Execute the line of code which was entered."""
        self._history.stop()
        text = self.text()
        if text:
            self._history.append(text)
        self.execute.emit(text)
        self.setText('')

    def history_prev(self):
        """Go back in the history."""
        try:
            if not self._history.is_browsing():
                item = self._history.start(self.text().strip())
            else:
                item = self._history.previtem()
        except (cmdhistory.HistoryEmptyError,
                cmdhistory.HistoryEndReachedError):
            return
        self.setText(item)

    def history_next(self):
        """Go forward in the history."""
        if not self._history.is_browsing():
            return
        try:
            item = self._history.nextitem()
        except cmdhistory.HistoryEndReachedError:
            return
        self.setText(item)

    def keyPressEvent(self, e):
        """Override keyPressEvent to handle special keypresses."""
        if e.key() == Qt.Key.Key_Up:
            self.history_prev()
            e.accept()
        elif e.key() == Qt.Key.Key_Down:
            self.history_next()
            e.accept()
        elif e.modifiers() & Qt.KeyboardModifier.ControlModifier and e.key() == Qt.Key.Key_C:
            self.setText('')
            e.accept()
        else:
            super().keyPressEvent(e)


class ConsoleTextEdit(QTextEdit):

    """Custom QTextEdit for console output."""

    def __init__(self, parent=None):
        super().__init__(parent)
        self.setAcceptRichText(False)
        self.setReadOnly(True)
        self.setFocusPolicy(Qt.FocusPolicy.ClickFocus)

    def __repr__(self):
        return utils.get_repr(self)

    def append_text(self, text):
        """Append new text and scroll output to bottom.

        We can't use Qt's way to append stuff because that inserts weird
        newlines.
        """
        self.moveCursor(QTextCursor.MoveOperation.End)
        self.insertPlainText(text)
        scrollbar = self.verticalScrollBar()
        assert scrollbar is not None
        scrollbar.setValue(scrollbar.maximum())


class ConsoleWidget(QWidget):

    """A widget with an interactive Python console.

    Attributes:
        _lineedit: The line edit in the console.
        _output: The output widget in the console.
        _vbox: The layout which contains everything.
        _more: A flag which is set when more input is expected.
        _buffer: The buffer for multi-line commands.
        _interpreter: The InteractiveInterpreter to execute code with.
    """

    STYLESHEET = """
        ConsoleWidget > ConsoleTextEdit, ConsoleWidget > ConsoleLineEdit {
            font: {{ conf.fonts.debug_console }};
        }
    """

    def __init__(self, parent=None):
        super().__init__(parent)
        if not hasattr(sys, 'ps1'):
            sys.ps1 = '>>> '
        if not hasattr(sys, 'ps2'):
            sys.ps2 = '... '
        namespace = {
            '__name__': '__console__',
            '__doc__': None,
            'q_app': QApplication.instance(),
            # We use parent as self here because the user "feels" the whole
            # console, not just the line edit.
            'self': parent,
            'objreg': objreg,
        }
        self._more = False
        self._buffer: MutableSequence[str] = []
        self._lineedit = ConsoleLineEdit(namespace, self)
        self._lineedit.execute.connect(self.push)
        self._output = ConsoleTextEdit()
        self.write(self._curprompt())
        self._vbox = QVBoxLayout()
        self._vbox.setSpacing(0)
        self._vbox.addWidget(self._output)
        self._vbox.addWidget(self._lineedit)
        stylesheet.set_register(self)
        self.setLayout(self._vbox)
        self._lineedit.setFocus()
        self._interpreter = code.InteractiveInterpreter(namespace)

    def __repr__(self):
        return utils.get_repr(self, visible=self.isVisible())

    def write(self, line):
        """Write a line of text (without added newline) to the output."""
        self._output.append_text(line)

    @pyqtSlot(str)
    def push(self, line):
        """Push a line to the interpreter."""
        self._buffer.append(line)
        source = '\n'.join(self._buffer)
        self.write(line + '\n')
        # We do two special things with the context managers here:
        #   - We replace stdout/stderr to capture output. Even if we could
        #     override InteractiveInterpreter's write method, most things are
        #     printed elsewhere (e.g. by exec). Other Python GUI shells do the
        #     same.
        #   - We disable our exception hook, so exceptions from the console get
        #     printed and don't open a crashdialog.
        with utils.fake_io(self.write), utils.disabled_excepthook():
            self._more = self._interpreter.runsource(source, '<console>')
        self.write(self._curprompt())
        if not self._more:
            self._buffer = []

    def _curprompt(self):
        """Get the prompt which is visible currently."""
        return sys.ps2 if self._more else sys.ps1


def init():
    """Initialize a global console."""
    global console_widget
    console_widget = ConsoleWidget()
