Make backend more modular

backend.py

@@ -8,6 +8,10 @@ import os.path
 import sqlite3
 import werkzeug.exceptions as exceptions
 
+DEFAULT_WEBP_QUALITY = 80
+DEFAULT_WEBP_METHOD = 0
+DEFAULT_WEBP_SIZE = 1906  # width of FullHD monitor without scroll bar
+
 mimetypes['.webp'] = 'image/webp'
 
 if os.environ.get('DISK_CACHE', '1') == '0':
@@ -25,35 +29,8 @@ def dict_factory(cursor, row):
     return d
 
 
-def generate_thumbnail(filepath):
-    if filepath not in thumbnail_cache:
-        image = Image.open(filepath)
-        image.thumbnail((512, 512))
-        thumbnail = BytesIO()
-        image.save(thumbnail, 'webp')
-        thumbnail.seek(0)
-
-        data = thumbnail.read()
-        etag = str(crc32(data))
-
-        thumbnail_cache[filepath] = {
-            'data_raw': data,
-            'etag': etag,
-            'mimetype': 'image/webp'
-        }
-
-    thumbnail = thumbnail_cache[filepath]
-    thumbnail['data'] = BytesIO()
-    thumbnail['data'].write(thumbnail['data_raw'])
-    thumbnail['data'].seek(0)
-
-    return thumbnail
-
-
-class CalibreDB:
-    def __init__(self, path='metadata.db', webp_quality=80, webp_method=0, webp_size=2048):
-        self.database_path = f'file:{path}?mode=ro'
-
+class BaseDB:
+    def __init__(self, webp_quality, webp_method, webp_size):
         # lossy: 0-100 (used as quality)
         # lossless: 101-201 (101 subtracted and used as quality)
         if webp_quality > 100:
@@ -69,6 +46,65 @@ class CalibreDB:
             'size': webp_size
         }
 
+    def _generate_webp(self, fp, max_size=None):
+        if max_size is None:
+            max_size = tuple([self.webp_config['size']] * 2)
+
+        image = Image.open(fp)
+        image.thumbnail(max_size)
+        image_buffer = BytesIO()
+        image.save(
+            image_buffer,
+            format='webp',
+            save_all=True,          #
+            append_images=[image],  # https://github.com/python-pillow/Pillow/issues/4042
+            quality=self.webp_config['quality'],
+            method=self.webp_config['method'],
+            lossless=self.webp_config['lossless']
+        )
+
+        image_buffer.seek(0)
+
+        return image_buffer
+
+    def _generate_thumbnail(self, filepath):
+        if filepath not in thumbnail_cache:
+            thumbnail_buffer = self._generate_webp(filepath, max_size=(512, 512))
+
+            data = thumbnail_buffer.read()
+            etag = str(crc32(data))
+
+            thumbnail_cache[filepath] = {
+                'data_raw': data,
+                'etag': etag,
+                'mimetype': 'image/webp'
+            }
+
+        thumbnail = thumbnail_cache[filepath]
+        thumbnail['buffer'] = BytesIO()
+        thumbnail['buffer'].write(thumbnail['data_raw'])
+        thumbnail['buffer'].seek(0)
+
+        return thumbnail
+
+    def _generate_page(self, page_buffer, volume, page):
+        page_buffer = self._generate_webp(page_buffer)
+        disk_cache.set(f'{volume}-{page}', page_buffer)
+        page_buffer.seek(0)
+
+        return page_buffer
+
+
+class CalibreDB(BaseDB):
+    def __init__(self, path='metadata.db', webp_quality=DEFAULT_WEBP_QUALITY, webp_method=DEFAULT_WEBP_METHOD, webp_size=DEFAULT_WEBP_SIZE):
+        super().__init__(
+            webp_quality=webp_quality,
+            webp_method=webp_method,
+            webp_size=webp_size
+        )
+
+        self.database_path = f'file:{path}?mode=ro'
+
     def create_cursor(self):
         conn = sqlite3.connect(self.database_path, uri=True)
         conn.row_factory = dict_factory
@@ -120,7 +156,7 @@ class CalibreDB:
         return self.get_volume_cover(first_volume['id'])
 
     def get_series_cover_thumbnail(self, series_id):
-        return generate_thumbnail(self.get_series_cover(series_id))
+        return self._generate_thumbnail(self.get_series_cover(series_id))
 
     def get_series_volumes(self, series_id):
         cursor = self.create_cursor()
@@ -172,7 +208,7 @@ class CalibreDB:
             raise exceptions.NotFound()
 
     def get_volume_cover_thumbnail(self, volume_id):
-        return generate_thumbnail(self.get_volume_cover(volume_id))
+        return self._generate_thumbnail(self.get_volume_cover(volume_id))
 
     def get_volume_filepath(self, volume_id):
         cursor = self.create_cursor()
@@ -229,38 +265,24 @@ class CalibreDB:
                 return None
 
             page_filename = zip_info.filename
+
+            if original is True:
                 mimetype = mimetypes[os.path.splitext(page_filename)[1]]
 
-            if original is False:
+                page_buffer = BytesIO()
+                page_buffer.write(volume.read(page_filename))
+                page_buffer.seek(0)
+            else:
                 mimetype = 'image/webp'
 
                 try:
-                    page_data = disk_cache.get(f'{volume_id}-{page_number}')
+                    page_buffer = disk_cache.get(f'{volume_id}-{page_number}')
                 except FileNotFoundError:
-                    with volume.open(page_filename) as orig_page_data:
-                        image = Image.open(orig_page_data)
-                        image.thumbnail(tuple([self.webp_config['size']] * 2))
-                        page_data = BytesIO()
-                        image.save(
-                            page_data,
-                            format='webp',
-                            save_all=True,         #
-                            append_images=[image], # https://github.com/python-pillow/Pillow/issues/4042
-                            quality=self.webp_config['quality'],
-                            method=self.webp_config['method'],
-                            lossless=self.webp_config['lossless']
-                        )
-
-                        page_data.seek(0)
-                        disk_cache.set(f'{volume_id}-{page_number}', page_data)
-                        page_data.seek(0)
-            else:
-                page_data = BytesIO()
-                page_data.write(volume.read(page_filename))
-                page_data.seek(0)
+                    with volume.open(page_filename) as orig_page_buffer:
+                        page_buffer = self._generate_page(orig_page_buffer, volume_id, page_number)
 
             return {
-                'data': page_data,
+                'buffer': page_buffer,
                 'mimetype': mimetype,
                 'etag': str(zip_info.CRC)
             }

mangareader.py

@@ -21,7 +21,7 @@ def send_file_with_etag(fp, etag, **kwargs):
 
 
 def send_image(image):
-    return send_file_with_etag(image['data'], image['etag'], mimetype=image['mimetype'])
+    return send_file_with_etag(image['buffer'], image['etag'], mimetype=image['mimetype'])
 
 
 app = Flask(__name__, static_folder='frontend/dist/static', template_folder='frontend/dist')