import os
from datetime import datetime
from django.db import models
from django.db.models.base import ModelBase
from django.utils.translation import ugettext_lazy as _


class IKSpec(object):
    def __init__(self, spec=None):
        self.name = 'thumbnail'
        self.width = 100
        self.height = 100
        self.quality = 70
        self.upscale = False
        self.crop = False
        self.pre_cache = False
        self.increment_count = False
        self.effects = []
        
        if spec is not None:
            for key, value in spec.items():
                setattr(self, key, value)


class SpecAccessor(object):
    def __init__(self, instance, spec):
        self._instance = instance
        self._spec = spec
        
    @property
    def url(self):
        return '/'.join([self._instance._cache_url(),
                         self._instance._spec_filename(spec)])
    
    @property
    def path(self):
        return self._instance._spec_path(spec)
        
    @property
    def size(self):
        return self._instance._spec_size(spec)
        
    @property
    def spec(self):
        pass


class IKOptions(object):
    def __init__(self, config=None):
        self.max_image_size = (100, 100)
        self.image_dir = 'images'
        self.cache_dir = 'cache'
        self.save_count_as = None # Field name on subclass where count is stored
        self.cache_filename_format = "%(filename)s_%(specname)s.%(extension)s"
        self.spec_filename = "imagekit.yaml"
        if config is not None:
            for key, value in config.__dict__.iteritems():
                setattr(self, key, value)


class IKModelBase(ModelBase):
    def __init__(cls, name, bases, attrs):
        import os
        import inspect
        import yaml
    
        opts = IKOptions(getattr(cls, 'IK', None))
        
        # load configuration file
        try:
            file_obj = open(opts.spec_filename)
        except:
            try:                
                filename = os.path.join(os.path.dirname(inspect.getabsfile(cls)),
                                                        opts.spec_filename)
                file_obj = open(filename)
            except:
                return
                
        spec = yaml.load(file_obj)
        
        for size in spec['sizes']:
            for name, spec = size.items():
                spec =  IKSpec(spec)
                accessor = SpecAccessor(spec)
                setattr(cls, name, accessor)

        
class IKModel(models.Model):
    """ Abstract base class implementing all core ImageKit functionality
    
    Subclasses of IKModel can override the inner IKConfig class to customize
    storage locations and other options.
    
    """
    __metaclass__ = IKModelBase
    
    CROP_X_NONE   = 0
    CROP_X_LEFT   = 1
    CROP_X_CENTER = 2
    CROP_X_RIGHT  = 3

    CROP_Y_NONE   = 0
    CROP_Y_TOP    = 1
    CROP_Y_CENTER = 2
    CROP_Y_BOTTOM = 3 

    CROP_X_CHOICES = (
        (CROP_X_NONE, 'None'),
        (CROP_X_LEFT, 'Left'),
        (CROP_X_CENTER, 'Center'),
        (CROP_X_RIGHT, 'Right'),
    )

    CROP_Y_CHOICES = (
        (CROP_Y_NONE, 'None'),
        (CROP_Y_TOP, 'Top'),
        (CROP_Y_CENTER,  'Center'),
        (CROP_Y_BOTTOM, 'Bottom'),
    )

    image = models.ImageField(_('image'), upload_to='photos')
    crop_x = models.PositiveSmallIntegerField(choices=CROP_X_CHOICES,
                                              default=CROP_X_CENTER)
    crop_y = models.PositiveSmallIntegerField(choices=CROP_Y_CHOICES,
                                              default=CROP_Y_CENTER)

    class Meta:
        abstract = True
        
    class IK:
        config_file_name = 'imagekit.yaml'

    def _image_basename(self):
        """ Returns the basename of the original image file """
        return os.path.basename(self.image.path)

    def _cache_dir(self):
        """ Returns the path to the image cache directory """
        return os.path.join(os.path.dirname(self.image.path), self.IKConfig.cache_dir)

    def _cache_url(self):
        """ Returns a url pointing to the image cache directory """
        return '/'.join([os.path.dirname(self.image.url), self.IKConfig.cache_dir])
        
    def _spec_url(self, spec):
        return '/'.join([self._cache_url(), self._spec_filename(spec)])
        
    def _spec_path(self, spec):
        return os.path.join(self._cache_dir(),
                            self._spec_filename(spec))

    def _spec_filename(self, spec):
        """ Returns a formatted filename for a specific ImageSpec """
        filename, extension = os.path.splitext(self._image_basename())
        return self.IKConfig.cache_filename_format % \
          {'filename': filename,
           'specname': spec.name,
           'extension': extension.lstrip('.')}

    def _increment_view_count(self):
        """ Increment the view count If a field name is supplied in IKConfig """
        field_name = IKConfig.save_count_as
        if field_name is not None:
            new_count = getattr(self, field_name) + 1
            setattr(self, field_name, new_count)
        models.Model.save(self)
        
    def _file_exists(self, spec):
        accessor = getattr(self, spec.name)
        return os.path.isfile(accessor.path)
        
    def _cache_spec(self, spec):
        if self._file_exists(spec):
            return
                        
        # create cache directory if it does not exist
        if not os.path.isdir(self._cache_path()):
            os.makedirs(self._cache_path())
            
        img = Image.open(self.image.path)
        
        if img.size != spec.size and spec.size != (0, 0):
            resized = resize_image(img, spec)
            
        output_filename = self._spec_filename(spec)
        
        try:
            if img.format == 'JPEG':
                resized.save(output_filename, img.format, quality=int(spec.quality))
            else:
                try:
                    im.save(im_filename)
                except KeyError:
                    pass
        except IOError, e:
            if os.path.isfile(output_filename):
                os.unlink(output_filename)
            raise e
            
    def _delete_spec(self, spec, remove_dirs=True):
        if not self._file_exists(spec):
            return
        accessor = getattr(self, spec.name)
        if os.path.isfile(accessor.path):
            os.remove(accessor.path)
        if remove_dirs:
            self._cleanup_cache_dirs
            
    def _cleanup_cache_dirs(self):
        try:
            os.removedirs(self._cache_path())
        except:
            pass

    def _clear_cache(self):
        cache = SpecCache()
        for photosize in cache.sizes.values():
            self._delete_spec(spec, False)
        self._cleanup_cache_dirs()

    def _pre_cache(self):
        cache = SpecCache()
        for spec in cache.specs.values():
            if spec.cache_on_save:
                self._cache_spec(spec)

    def save(self, *args, **kwargs):
        if self._get_pk_val():
            self._clear_cache()
        super(ImageModel, self).save(*args, **kwargs)
        self._pre_cache()

    def delete(self):
        assert self._get_pk_val() is not None, "%s object can't be deleted because its %s attribute is set to None." % (self._meta.object_name, self._meta.pk.attname)
        self._clear_cache()
        super(ImageModel, self).delete()