import logging
import os
import shutil
from typing import Optional

from celery import states
from celery.signals import before_task_publish
from celery.signals import task_failure
from celery.signals import task_postrun
from celery.signals import task_prerun
from django.conf import settings
from django.contrib.admin.models import ADDITION
from django.contrib.admin.models import LogEntry
from django.contrib.auth.models import User
from django.contrib.contenttypes.models import ContentType
from django.db import DatabaseError
from django.db import close_old_connections
from django.db import models
from django.db.models import Q
from django.dispatch import receiver
from django.utils import termcolors
from django.utils import timezone
from filelock import FileLock

from documents import matching
from documents.classifier import DocumentClassifier
from documents.file_handling import create_source_path_directory
from documents.file_handling import delete_empty_directories
from documents.file_handling import generate_unique_filename
from documents.models import Document
from documents.models import MatchingModel
from documents.models import PaperlessTask
from documents.models import Tag
from documents.permissions import get_objects_for_user_owner_aware

logger = logging.getLogger("paperless.handlers")


def add_inbox_tags(sender, document: Document, logging_group=None, **kwargs):
    if document.owner is not None:
        tags = get_objects_for_user_owner_aware(
            document.owner,
            "documents.view_tag",
            Tag,
        )
    else:
        tags = Tag.objects.all()
    inbox_tags = tags.filter(is_inbox_tag=True)
    document.tags.add(*inbox_tags)


def set_correspondent(
    sender,
    document: Document,
    logging_group=None,
    classifier: Optional[DocumentClassifier] = None,
    replace=False,
    use_first=True,
    suggest=False,
    base_url=None,
    color=False,
    **kwargs,
):
    if document.correspondent and not replace:
        return

    potential_correspondents = matching.match_correspondents(document, classifier)

    potential_count = len(potential_correspondents)
    selected = potential_correspondents[0] if potential_correspondents else None
    if potential_count > 1:
        if use_first:
            logger.debug(
                f"Detected {potential_count} potential correspondents, "
                f"so we've opted for {selected}",
                extra={"group": logging_group},
            )
        else:
            logger.debug(
                f"Detected {potential_count} potential correspondents, "
                f"not assigning any correspondent",
                extra={"group": logging_group},
            )
            return

    if selected or replace:
        if suggest:
            if base_url:
                print(
                    termcolors.colorize(str(document), fg="green")
                    if color
                    else str(document),
                )
                print(f"{base_url}/documents/{document.pk}")
            else:
                print(
                    (
                        termcolors.colorize(str(document), fg="green")
                        if color
                        else str(document)
                    )
                    + f" [{document.pk}]",
                )
            print(f"Suggest correspondent {selected}")
        else:
            logger.info(
                f"Assigning correspondent {selected} to {document}",
                extra={"group": logging_group},
            )

            document.correspondent = selected
            document.save(update_fields=("correspondent",))


def set_document_type(
    sender,
    document: Document,
    logging_group=None,
    classifier: Optional[DocumentClassifier] = None,
    replace=False,
    use_first=True,
    suggest=False,
    base_url=None,
    color=False,
    **kwargs,
):
    if document.document_type and not replace:
        return

    potential_document_type = matching.match_document_types(document, classifier)

    potential_count = len(potential_document_type)
    selected = potential_document_type[0] if potential_document_type else None

    if potential_count > 1:
        if use_first:
            logger.info(
                f"Detected {potential_count} potential document types, "
                f"so we've opted for {selected}",
                extra={"group": logging_group},
            )
        else:
            logger.info(
                f"Detected {potential_count} potential document types, "
                f"not assigning any document type",
                extra={"group": logging_group},
            )
            return

    if selected or replace:
        if suggest:
            if base_url:
                print(
                    termcolors.colorize(str(document), fg="green")
                    if color
                    else str(document),
                )
                print(f"{base_url}/documents/{document.pk}")
            else:
                print(
                    (
                        termcolors.colorize(str(document), fg="green")
                        if color
                        else str(document)
                    )
                    + f" [{document.pk}]",
                )
            print(f"Suggest document type {selected}")
        else:
            logger.info(
                f"Assigning document type {selected} to {document}",
                extra={"group": logging_group},
            )

            document.document_type = selected
            document.save(update_fields=("document_type",))


def set_tags(
    sender,
    document: Document,
    logging_group=None,
    classifier: Optional[DocumentClassifier] = None,
    replace=False,
    suggest=False,
    base_url=None,
    color=False,
    **kwargs,
):
    if replace:
        Document.tags.through.objects.filter(document=document).exclude(
            Q(tag__is_inbox_tag=True),
        ).exclude(
            Q(tag__match="") & ~Q(tag__matching_algorithm=Tag.MATCH_AUTO),
        ).delete()

    current_tags = set(document.tags.all())

    matched_tags = matching.match_tags(document, classifier)

    relevant_tags = set(matched_tags) - current_tags

    if suggest:
        extra_tags = current_tags - set(matched_tags)
        extra_tags = [
            t for t in extra_tags if t.matching_algorithm == MatchingModel.MATCH_AUTO
        ]
        if not relevant_tags and not extra_tags:
            return
        if base_url:
            print(
                termcolors.colorize(str(document), fg="green")
                if color
                else str(document),
            )
            print(f"{base_url}/documents/{document.pk}")
        else:
            print(
                (
                    termcolors.colorize(str(document), fg="green")
                    if color
                    else str(document)
                )
                + f" [{document.pk}]",
            )
        if relevant_tags:
            print("Suggest tags: " + ", ".join([t.name for t in relevant_tags]))
        if extra_tags:
            print("Extra tags: " + ", ".join([t.name for t in extra_tags]))
    else:
        if not relevant_tags:
            return

        message = 'Tagging "{}" with "{}"'
        logger.info(
            message.format(document, ", ".join([t.name for t in relevant_tags])),
            extra={"group": logging_group},
        )

        document.tags.add(*relevant_tags)


def set_storage_path(
    sender,
    document: Document,
    logging_group=None,
    classifier: Optional[DocumentClassifier] = None,
    replace=False,
    use_first=True,
    suggest=False,
    base_url=None,
    color=False,
    **kwargs,
):
    if document.storage_path and not replace:
        return

    potential_storage_path = matching.match_storage_paths(
        document,
        classifier,
    )

    potential_count = len(potential_storage_path)
    selected = potential_storage_path[0] if potential_storage_path else None

    if potential_count > 1:
        if use_first:
            logger.info(
                f"Detected {potential_count} potential storage paths, "
                f"so we've opted for {selected}",
                extra={"group": logging_group},
            )
        else:
            logger.info(
                f"Detected {potential_count} potential storage paths, "
                f"not assigning any storage directory",
                extra={"group": logging_group},
            )
            return

    if selected or replace:
        if suggest:
            if base_url:
                print(
                    termcolors.colorize(str(document), fg="green")
                    if color
                    else str(document),
                )
                print(f"{base_url}/documents/{document.pk}")
            else:
                print(
                    (
                        termcolors.colorize(str(document), fg="green")
                        if color
                        else str(document)
                    )
                    + f" [{document.pk}]",
                )
            print(f"Suggest storage directory {selected}")
        else:
            logger.info(
                f"Assigning storage path {selected} to {document}",
                extra={"group": logging_group},
            )

            document.storage_path = selected
            document.save(update_fields=("storage_path",))


@receiver(models.signals.post_delete, sender=Document)
def cleanup_document_deletion(sender, instance, using, **kwargs):
    with FileLock(settings.MEDIA_LOCK):
        if settings.TRASH_DIR:
            # Find a non-conflicting filename in case a document with the same
            # name was moved to trash earlier
            counter = 0
            old_filename = os.path.split(instance.source_path)[1]
            (old_filebase, old_fileext) = os.path.splitext(old_filename)

            while True:
                new_file_path = os.path.join(
                    settings.TRASH_DIR,
                    old_filebase + (f"_{counter:02}" if counter else "") + old_fileext,
                )

                if os.path.exists(new_file_path):
                    counter += 1
                else:
                    break

            logger.debug(f"Moving {instance.source_path} to trash at {new_file_path}")
            try:
                shutil.move(instance.source_path, new_file_path)
            except OSError as e:
                logger.error(
                    f"Failed to move {instance.source_path} to trash at "
                    f"{new_file_path}: {e}. Skipping cleanup!",
                )
                return

        for filename in (
            instance.source_path,
            instance.archive_path,
            instance.thumbnail_path,
        ):
            if filename and os.path.isfile(filename):
                try:
                    os.unlink(filename)
                    logger.debug(f"Deleted file {filename}.")
                except OSError as e:
                    logger.warning(
                        f"While deleting document {instance!s}, the file "
                        f"{filename} could not be deleted: {e}",
                    )

        delete_empty_directories(
            os.path.dirname(instance.source_path),
            root=settings.ORIGINALS_DIR,
        )

        if instance.has_archive_version:
            delete_empty_directories(
                os.path.dirname(instance.archive_path),
                root=settings.ARCHIVE_DIR,
            )


class CannotMoveFilesException(Exception):
    pass


def validate_move(instance, old_path, new_path):
    if not os.path.isfile(old_path):
        # Can't do anything if the old file does not exist anymore.
        logger.fatal(f"Document {instance!s}: File {old_path} has gone.")
        raise CannotMoveFilesException

    if os.path.isfile(new_path):
        # Can't do anything if the new file already exists. Skip updating file.
        logger.warning(
            f"Document {instance!s}: Cannot rename file "
            f"since target path {new_path} already exists.",
        )
        raise CannotMoveFilesException


@receiver(models.signals.m2m_changed, sender=Document.tags.through)
@receiver(models.signals.post_save, sender=Document)
def update_filename_and_move_files(sender, instance: Document, **kwargs):
    if not instance.filename:
        # Can't update the filename if there is no filename to begin with
        # This happens when the consumer creates a new document.
        # The document is modified and saved multiple times, and only after
        # everything is done (i.e., the generated filename is final),
        # filename will be set to the location where the consumer has put
        # the file.
        #
        # This will in turn cause this logic to move the file where it belongs.
        return

    with FileLock(settings.MEDIA_LOCK):
        try:
            # If this was waiting for the lock, the filename or archive_filename
            # of this document may have been updated.  This happens if multiple updates
            # get queued from the UI for the same document
            # So freshen up the data before doing anything
            instance.refresh_from_db()

            old_filename = instance.filename
            old_source_path = instance.source_path

            instance.filename = generate_unique_filename(instance)
            move_original = old_filename != instance.filename

            old_archive_filename = instance.archive_filename
            old_archive_path = instance.archive_path

            if instance.has_archive_version:
                instance.archive_filename = generate_unique_filename(
                    instance,
                    archive_filename=True,
                )

                move_archive = old_archive_filename != instance.archive_filename
            else:
                move_archive = False

            if not move_original and not move_archive:
                # Don't do anything if filenames did not change.
                return

            if move_original:
                validate_move(instance, old_source_path, instance.source_path)
                create_source_path_directory(instance.source_path)
                shutil.move(old_source_path, instance.source_path)

            if move_archive:
                validate_move(instance, old_archive_path, instance.archive_path)
                create_source_path_directory(instance.archive_path)
                shutil.move(old_archive_path, instance.archive_path)

            # Don't save() here to prevent infinite recursion.
            Document.objects.filter(pk=instance.pk).update(
                filename=instance.filename,
                archive_filename=instance.archive_filename,
            )

        except (OSError, DatabaseError, CannotMoveFilesException) as e:
            logger.warning(f"Exception during file handling: {e}")
            # This happens when either:
            #  - moving the files failed due to file system errors
            #  - saving to the database failed due to database errors
            # In both cases, we need to revert to the original state.

            # Try to move files to their original location.
            try:
                if move_original and os.path.isfile(instance.source_path):
                    logger.info("Restoring previous original path")
                    shutil.move(instance.source_path, old_source_path)

                if move_archive and os.path.isfile(instance.archive_path):
                    logger.info("Restoring previous archive path")
                    shutil.move(instance.archive_path, old_archive_path)

            except Exception:
                # This is fine, since:
                # A: if we managed to move source from A to B, we will also
                #  manage to move it from B to A. If not, we have a serious
                #  issue that's going to get caught by the santiy checker.
                #  All files remain in place and will never be overwritten,
                #  so this is not the end of the world.
                # B: if moving the original file failed, nothing has changed
                #  anyway.
                pass

            # restore old values on the instance
            instance.filename = old_filename
            instance.archive_filename = old_archive_filename

        # finally, remove any empty sub folders. This will do nothing if
        # something has failed above.
        if not os.path.isfile(old_source_path):
            delete_empty_directories(
                os.path.dirname(old_source_path),
                root=settings.ORIGINALS_DIR,
            )

        if instance.has_archive_version and not os.path.isfile(
            old_archive_path,
        ):
            delete_empty_directories(
                os.path.dirname(old_archive_path),
                root=settings.ARCHIVE_DIR,
            )


def set_log_entry(sender, document: Document, logging_group=None, **kwargs):
    ct = ContentType.objects.get(model="document")
    user = User.objects.get(username="consumer")

    LogEntry.objects.create(
        action_flag=ADDITION,
        action_time=timezone.now(),
        content_type=ct,
        object_id=document.pk,
        user=user,
        object_repr=document.__str__(),
    )


def add_to_index(sender, document, **kwargs):
    from documents import index

    index.add_or_update_document(document)


@before_task_publish.connect
def before_task_publish_handler(sender=None, headers=None, body=None, **kwargs):
    """
    Creates the PaperlessTask object in a pending state.  This is sent before
    the task reaches the broker, but before it begins executing on a worker.

    https://docs.celeryq.dev/en/stable/userguide/signals.html#before-task-publish

    https://docs.celeryq.dev/en/stable/internals/protocol.html#version-2

    """
    if "task" not in headers or headers["task"] != "documents.tasks.consume_file":
        # Assumption: this is only ever a v2 message
        return

    try:
        close_old_connections()

        task_args = body[0]
        input_doc, _ = task_args

        task_file_name = input_doc.original_file.name

        PaperlessTask.objects.create(
            task_id=headers["id"],
            status=states.PENDING,
            task_file_name=task_file_name,
            task_name=headers["task"],
            result=None,
            date_created=timezone.now(),
            date_started=None,
            date_done=None,
        )
    except Exception:  # pragma: no cover
        # Don't let an exception in the signal handlers prevent
        # a document from being consumed.
        logger.exception("Creating PaperlessTask failed")


@task_prerun.connect
def task_prerun_handler(sender=None, task_id=None, task=None, **kwargs):
    """

    Updates the PaperlessTask to be started.  Sent before the task begins execution
    on a worker.

    https://docs.celeryq.dev/en/stable/userguide/signals.html#task-prerun
    """
    try:
        close_old_connections()
        task_instance = PaperlessTask.objects.filter(task_id=task_id).first()

        if task_instance is not None:
            task_instance.status = states.STARTED
            task_instance.date_started = timezone.now()
            task_instance.save()
    except Exception:  # pragma: no cover
        # Don't let an exception in the signal handlers prevent
        # a document from being consumed.
        logger.exception("Setting PaperlessTask started failed")


@task_postrun.connect
def task_postrun_handler(
    sender=None,
    task_id=None,
    task=None,
    retval=None,
    state=None,
    **kwargs,
):
    """
    Updates the result of the PaperlessTask.

    https://docs.celeryq.dev/en/stable/userguide/signals.html#task-postrun
    """
    try:
        close_old_connections()
        task_instance = PaperlessTask.objects.filter(task_id=task_id).first()

        if task_instance is not None:
            task_instance.status = state
            task_instance.result = retval
            task_instance.date_done = timezone.now()
            task_instance.save()
    except Exception:  # pragma: no cover
        # Don't let an exception in the signal handlers prevent
        # a document from being consumed.
        logger.exception("Updating PaperlessTask failed")


@task_failure.connect
def task_failure_handler(
    sender=None,
    task_id=None,
    exception=None,
    args=None,
    traceback=None,
    **kwargs,
):
    """
    Updates the result of a failed PaperlessTask.

    https://docs.celeryq.dev/en/stable/userguide/signals.html#task-failure
    """
    try:
        close_old_connections()
        task_instance = PaperlessTask.objects.filter(task_id=task_id).first()

        if task_instance is not None and task_instance.result is None:
            task_instance.status = states.FAILURE
            task_instance.result = traceback
            task_instance.date_done = timezone.now()
            task_instance.save()
    except Exception:  # pragma: no cover
        logger.exception("Updating PaperlessTask failed")