from __future__ import absolute_import, unicode_literals

import logging

from furl import furl

from django.core.files.base import ContentFile
from django.db import models
from django.urls import reverse
from django.utils.encoding import force_text, python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _

from mayan.apps.converter.literals import DEFAULT_ZOOM_LEVEL, DEFAULT_ROTATION
from mayan.apps.converter.models import Transformation
from mayan.apps.converter.transformations import (
    BaseTransformation, TransformationResize, TransformationRotate,
    TransformationZoom
)
from mayan.apps.converter.utils import get_converter_class

from ..managers import DocumentPageCachedImage, DocumentPageManager
from ..settings import (
    setting_disable_base_image_cache, setting_disable_transformed_image_cache,
    setting_display_width, setting_display_height, setting_zoom_max_level,
    setting_zoom_min_level
)
from ..storages import storage_documentimagecache

from .document_version_models import DocumentVersion

__all__ = ('DocumentPage', 'DocumentPageCachedImage', 'DocumentPageResult')
logger = logging.getLogger(__name__)


@python_2_unicode_compatible
class DocumentPage(models.Model):
    """
    Model that describes a document version page
    """
    document_version = models.ForeignKey(
        on_delete=models.CASCADE, related_name='pages', to=DocumentVersion,
        verbose_name=_('Document version')
    )
    page_number = models.PositiveIntegerField(
        db_index=True, default=1, editable=False,
        verbose_name=_('Page number')
    )

    objects = DocumentPageManager()

    class Meta:
        ordering = ('page_number',)
        verbose_name = _('Document page')
        verbose_name_plural = _('Document pages')

    def __str__(self):
        return self.get_label()

    @property
    def cache_filename(self):
        return 'page-cache-{}'.format(self.uuid)

    def delete(self, *args, **kwargs):
        self.invalidate_cache()
        super(DocumentPage, self).delete(*args, **kwargs)

    def detect_orientation(self):
        with self.document_version.open() as file_object:
            converter = get_converter_class()(
                file_object=file_object,
                mime_type=self.document_version.mimetype
            )
            return converter.detect_orientation(
                page_number=self.page_number
            )

    @property
    def document(self):
        return self.document_version.document

    def generate_image(self, *args, **kwargs):
        transformation_list = self.get_combined_transformation_list(*args, **kwargs)

        cache_filename = '{}-{}'.format(
            self.cache_filename, BaseTransformation.combine(transformation_list)
        )

        # Check is transformed image is available
        logger.debug('transformations cache filename: %s', cache_filename)

        if not setting_disable_transformed_image_cache.value and storage_documentimagecache.exists(cache_filename):
            logger.debug(
                'transformations cache file "%s" found', cache_filename
            )
        else:
            logger.debug(
                'transformations cache file "%s" not found', cache_filename
            )
            image = self.get_image(transformations=transformation_list)
            with storage_documentimagecache.open(cache_filename, 'wb+') as file_object:
                file_object.write(image.getvalue())

            self.cached_images.create(filename=cache_filename)

        return cache_filename

    def get_absolute_url(self):
        return reverse(
            viewname='documents:document_page_view', kwargs={'pk': self.pk}
        )

    def get_api_image_url(self, *args, **kwargs):
        """
        Create an unique URL combining:
        - the page's image URL
        - the interactive argument
        - a hash from the server side and interactive transformations
        The purpose of this unique URL is to allow client side caching
        if document page images.
        """
        transformations_hash = BaseTransformation.combine(
            self.get_combined_transformation_list(*args, **kwargs)
        )

        kwargs.pop('transformations', None)

        final_url = furl()
        final_url.args = kwargs
        final_url.path = reverse(
            viewname='rest_api:documentpage-image', kwargs={
                'pk': self.document.pk, 'version_pk': self.document_version.pk,
                'page_pk': self.pk
            }
        )
        final_url.args['_hash'] = transformations_hash

        return final_url.tostr()

    def get_combined_transformation_list(self, *args, **kwargs):
        """
        Return a list of transformation containing the server side
        document page transformation as well as tranformations created
        from the arguments as transient interactive transformation.
        """
        # Convert arguments into transformations
        transformations = kwargs.get('transformations', [])

        # Set sensible defaults if the argument is not specified or if the
        # argument is None
        width = kwargs.get('width', setting_display_width.value) or setting_display_width.value
        height = kwargs.get('height', setting_display_height.value) or setting_display_height.value
        rotation = kwargs.get('rotation', DEFAULT_ROTATION) or DEFAULT_ROTATION
        zoom_level = kwargs.get('zoom', DEFAULT_ZOOM_LEVEL) or DEFAULT_ZOOM_LEVEL

        if zoom_level < setting_zoom_min_level.value:
            zoom_level = setting_zoom_min_level.value

        if zoom_level > setting_zoom_max_level.value:
            zoom_level = setting_zoom_max_level.value

        # Generate transformation hash

        transformation_list = []

        # Stored transformations first
        for stored_transformation in Transformation.objects.get_for_object(self, as_classes=True):
            transformation_list.append(stored_transformation)

        # Interactive transformations second
        for transformation in transformations:
            transformation_list.append(transformation)

        if rotation:
            transformation_list.append(
                TransformationRotate(degrees=rotation)
            )

        if width:
            transformation_list.append(
                TransformationResize(width=width, height=height)
            )

        if zoom_level:
            transformation_list.append(TransformationZoom(percent=zoom_level))

        return transformation_list

    def get_image(self, transformations=None):
        cache_filename = self.cache_filename
        logger.debug('Page cache filename: %s', cache_filename)

        if not setting_disable_base_image_cache.value and storage_documentimagecache.exists(cache_filename):
            logger.debug('Page cache file "%s" found', cache_filename)

            with storage_documentimagecache.open(cache_filename) as file_object:
                converter = get_converter_class()(
                    file_object=file_object
                )

                converter.seek_page(page_number=0)

                # This code is also repeated below to allow using a context
                # manager with storage_documentimagecache.open and close it
                # automatically.
                for transformation in transformations:
                    converter.transform(transformation=transformation)

                return converter.get_page()
        else:
            logger.debug('Page cache file "%s" not found', cache_filename)

            try:
                with self.document_version.get_intermediate_file() as file_object:
                    converter = get_converter_class()(
                        file_object=file_object
                    )
                    converter.seek_page(page_number=self.page_number - 1)

                    page_image = converter.get_page()

                    # Since open "wb+" doesn't create files, check if the file
                    # exists, if not then create it
                    if not storage_documentimagecache.exists(cache_filename):
                        storage_documentimagecache.save(name=cache_filename, content=ContentFile(content=''))

                    with storage_documentimagecache.open(cache_filename, 'wb+') as file_object:
                        file_object.write(page_image.getvalue())

                    for transformation in transformations:
                        converter.transform(transformation=transformation)

                    return converter.get_page()
            except Exception as exception:
                # Cleanup in case of error
                logger.error(
                    'Error creating page cache file "%s"; %s',
                    cache_filename, exception
                )
                storage_documentimagecache.delete(cache_filename)
                raise

    def invalidate_cache(self):
        storage_documentimagecache.delete(self.cache_filename)
        for cached_image in self.cached_images.all():
            cached_image.delete()

    @property
    def is_in_trash(self):
        return self.document.is_in_trash

    def get_label(self):
        return _(
            'Page %(page_num)d out of %(total_pages)d of %(document)s'
        ) % {
            'document': force_text(self.document),
            'page_num': self.page_number,
            'total_pages': self.document_version.pages.count()
        }
    get_label.short_description = _('Label')

    def natural_key(self):
        return (self.page_number, self.document_version.natural_key())
    natural_key.dependencies = ['documents.DocumentVersion']

    @property
    def siblings(self):
        return DocumentPage.objects.filter(
            document_version=self.document_version
        )

    @property
    def uuid(self):
        """
        Make cache UUID a mix of version ID and page ID to avoid using stale
        images
        """
        return '{}-{}'.format(self.document_version.uuid, self.pk)


class DocumentPageCachedImage(models.Model):
    document_page = models.ForeignKey(
        on_delete=models.CASCADE, related_name='cached_images',
        to=DocumentPage, verbose_name=_('Document page')
    )
    datetime = models.DateTimeField(
        auto_now_add=True, db_index=True, verbose_name=_('Date time')
    )
    filename = models.CharField(max_length=128, verbose_name=_('Filename'))
    file_size = models.PositiveIntegerField(
        db_index=True, default=0, verbose_name=_('File size')
    )

    objects = DocumentPageCachedImage()

    class Meta:
        verbose_name = _('Document page cached image')
        verbose_name_plural = _('Document page cached images')

    def delete(self, *args, **kwargs):
        storage_documentimagecache.delete(self.filename)
        return super(DocumentPageCachedImage, self).delete(*args, **kwargs)

    def natural_key(self):
        return (self.filename, self.document_page.natural_key())
    natural_key.dependencies = ['documents.DocumentPage']

    def save(self, *args, **kwargs):
        self.file_size = storage_documentimagecache.size(self.filename)
        return super(DocumentPageCachedImage, self).save(*args, **kwargs)


class DocumentPageResult(DocumentPage):
    class Meta:
        ordering = ('document_version__document', 'page_number')
        proxy = True
        verbose_name = _('Document page')
        verbose_name_plural = _('Document pages')