import logging

from tfw.networking import Scope
from tfw.components import FileManager
from tfw.components.inotify import InotifyObserver

from .event_handler import EventHandler

LOG = logging.getLogger(__name__)

BUILD_ARTIFACTS = (
    "*.a",
    "*.class",
    "*.dll",
    "*.dylib",
    "*.elf",
    "*.exe",
    "*.jar",
    "*.ko",
    "*.la",
    "*.lib",
    "*.lo",
    "*.o",
    "*.obj",
    "*.out",
    "*.py[cod]",
    "*.so",
    "*.so.*",
    "*.tar.gz",
    "*.zip",
    "*__pycache__*"
)


class IdeEventHandler(EventHandler):
    # pylint: disable=too-many-arguments,anomalous-backslash-in-string
    """
    Event handler implementing the backend of our browser based IDE.
    By default all files in the directory specified in __init__ are displayed
    on the fontend. Note that this is a stateful component.

    When any file in the selected directory changes they are automatically refreshed
    on the frontend (this is done by listening to inotify events).

    This EventHandler accepts messages that have a data['command'] key specifying
    a command to be executed.

    The API of each command is documented in their respective handler.
    """
    def __init__(self, key, directory, allowed_directories, selected_file=None, exclude=None):
        """
        :param key: the key this instance should listen to
        :param directory: working directory which the EventHandler should serve files from
        :param allowed_directories: list of directories that can be switched to using selectdir
        :param selected_file: file that is selected by default
        :param exclude: list of filenames that should not appear between files (for .o, .pyc, etc.)
        """
        super().__init__(key, scope=Scope.WEBSOCKET)
        try:
            self.filemanager = FileManager(
                allowed_directories=allowed_directories,
                working_directory=directory,
                selected_file=selected_file,
                exclude=exclude
            )
        except IndexError:
            raise EnvironmentError(
                f'No file(s) in IdeEventHandler working_directory "{directory}"!'
            )

        self.monitor = InotifyObserver(
            self.filemanager.allowed_directories,
            exclude=BUILD_ARTIFACTS
        )
        self.monitor.on_modified = self._reload_frontend
        self.monitor.start()

        self.commands = {
            'read':      self.read,
            'write':     self.write,
            'select':    self.select,
            'selectdir': self.select_dir,
            'exclude':   self.exclude
        }

    def _reload_frontend(self, event):  # pylint: disable=unused-argument
        self.server_connector.send_message({
            'key': 'ide',
            'data': {'command': 'reload'}
        }, Scope.WEBSOCKET)

    def read(self, data):
        """
        Read the currently selected file.

        :return dict: TFW message data containing key 'content'
                      (contents of the selected file)
        """
        try:
            data['content'] = self.filemanager.file_contents
        except PermissionError:
            data['content'] = 'You have no permission to open that file :('
        except FileNotFoundError:
            data['content'] = 'This file was removed :('
        except Exception: # pylint: disable=broad-except
            data['content'] = 'Failed to read file :('
        return data

    def write(self, data):
        """
        Overwrites a file with the desired string.

        :param data: TFW message data containing key 'content'
                     (new file content)

        """
        try:
            self.filemanager.file_contents = data['content']
        except Exception: # pylint: disable=broad-except
            LOG.exception('Error writing file!')
        del data['content']
        return data

    def select(self, data):
        """
        Selects a file from the current directory.

        :param data: TFW message data containing 'filename'
                     (name of file to select relative to the current directory)
        """
        try:
            self.filemanager.filename = data['filename']
        except EnvironmentError:
            LOG.exception('Failed to select file "%s"', data['filename'])
        return data

    def select_dir(self, data):
        """
        Select a new working directory to display files from.

        :param data: TFW message data containing 'directory'
                     (absolute path of diretory to select.
                     must be a path whitelisted in
                     self.allowed_directories)
        """
        try:
            self.filemanager.workdir = data['directory']
            try:
                self.filemanager.filename = self.filemanager.files[0]
                self.read(data)
            except IndexError:
                data['content'] = 'No files in this directory :('
        except EnvironmentError as err:
            LOG.error(
                'Failed to select directory "%s". Reason: %s',
                data['directory'], str(err)
            )
        return data

    def exclude(self, data):
        """
        Overwrite list of excluded files

        :param data: TFW message data containing 'exclude'
                     (list of unix-style filename patterns to be excluded,
                     e.g.: ["\*.pyc", "\*.o")
        """
        try:
            self.filemanager.exclude = list(data['exclude'])
        except TypeError:
            LOG.error('Exclude must be Iterable!')
        return data

    def attach_fileinfo(self, data):
        """
        Basic information included in every response to the frontend.
        """
        data['filename'] = self.filemanager.filename
        data['files'] = self.filemanager.files
        data['directory'] = self.filemanager.workdir

    def handle_event(self, message):
        try:
            data = message['data']
            message['data'] = self.commands[data['command']](data)
            self.attach_fileinfo(data)
            self.send_message(message)
        except KeyError:
            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)

    def cleanup(self):
        self.monitor.stop()