# -*- coding: utf-8 -*-

# Copyright © Spyder Project Contributors
# Licensed under the terms of the MIT License
# (see spyder/__init__.py for details)

"""
Fallback completion actor.

This takes a plain text/source file and returns the individual words
written on it and the keywords associated by Pygments to the
programming language of that file.
"""

# Standard library imports
import logging

# Qt imports
from qtpy.QtCore import QObject, QThread, QMutex, QMutexLocker, Signal, Slot

# Other imports
from pygments.lexers import get_lexer_by_name
from diff_match_patch import diff_match_patch

# Local imports
from spyder.plugins.completion.api import CompletionItemKind
from spyder.plugins.completion.api import CompletionRequestTypes
from spyder.plugins.completion.providers.fallback.utils import (
    get_keywords, get_words, is_prefix_valid)


FALLBACK_COMPLETION = "Fallback"

logger = logging.getLogger(__name__)


class FallbackActor(QObject):
    #: Signal emitted when the Thread is ready
    sig_fallback_ready = Signal()
    sig_set_tokens = Signal(int, dict)
    sig_mailbox = Signal(dict)

    def __init__(self, parent):
        QObject.__init__(self)
        self.stopped = False
        self.daemon = True
        self.mutex = QMutex()
        self.file_tokens = {}
        self.diff_patch = diff_match_patch()
        self.thread = QThread()
        self.moveToThread(self.thread)

        self.thread.started.connect(self.started)
        self.sig_mailbox.connect(self.handle_msg)

    def tokenize(self, text, offset, language, current_word):
        """
        Return all tokens in `text` and all keywords associated by
        Pygments to `language`.
        """
        valid = is_prefix_valid(text, offset, language)
        if not valid:
            return []

        # Get language keywords provided by Pygments
        try:
            lexer = get_lexer_by_name(language)
            keywords = get_keywords(lexer)
        except Exception:
            keywords = []
        keyword_set = set(keywords)
        keywords = [{'kind': CompletionItemKind.KEYWORD,
                     'insertText': keyword,
                     'label': keyword,
                     'sortText': keyword,
                     'filterText': keyword,
                     'documentation': '',
                     'provider': FALLBACK_COMPLETION}
                    for keyword in keywords]

        # Get file tokens
        tokens = get_words(text, offset, language)
        tokens = [{'kind': CompletionItemKind.TEXT,
                   'insertText': token,
                   'label': token,
                   'sortText': token,
                   'filterText': token,
                   'documentation': '',
                   'provider': FALLBACK_COMPLETION}
                  for token in tokens]
        for token in tokens:
            if token['insertText'] not in keyword_set:
                keywords.append(token)

        # Filter matching results
        if current_word is not None:
            current_word = current_word.lower()
            keywords = [k for k in keywords
                        if current_word in k['insertText'].lower()]

        return keywords

    def stop(self):
        """Stop actor."""
        with QMutexLocker(self.mutex):
            logger.debug("Fallback plugin stopping...")
            self.thread.quit()

    def start(self):
        """Start thread."""
        self.thread.start()

    def started(self):
        """Thread started."""
        logger.debug('Fallback plugin starting...')
        self.sig_fallback_ready.emit()

    @Slot(dict)
    def handle_msg(self, message):
        """Handle one message"""
        msg_type, _id, file, msg = [
            message[k] for k in ('type', 'id', 'file', 'msg')]
        logger.debug(u'Perform request {0} with id {1}'.format(msg_type, _id))
        if msg_type == CompletionRequestTypes.DOCUMENT_DID_OPEN:
            self.file_tokens[file] = {
                'text': msg['text'],
                'offset': msg['offset'],
                'language': msg['language'],
            }
        elif msg_type == CompletionRequestTypes.DOCUMENT_DID_CHANGE:
            if file not in self.file_tokens:
                self.file_tokens[file] = {
                    'text': '',
                    'offset': msg['offset'],
                    'language': msg['language'],
                }
            diff = msg['diff']
            text = self.file_tokens[file]
            text['offset'] = msg['offset']
            text, _ = self.diff_patch.patch_apply(
                diff, text['text'])
            self.file_tokens[file]['text'] = text
        elif msg_type == CompletionRequestTypes.DOCUMENT_DID_CLOSE:
            self.file_tokens.pop(file, {})
        elif msg_type == CompletionRequestTypes.DOCUMENT_COMPLETION:
            tokens = []
            if file in self.file_tokens:
                text_info = self.file_tokens[file]
                tokens = self.tokenize(
                    text_info['text'],
                    text_info['offset'],
                    text_info['language'],
                    msg['current_word'])
            tokens = {'params': tokens}
            self.sig_set_tokens.emit(_id, tokens)