[booru] add base classes for tag/pool/post extractors

gallery_dl/extractor/booru.py

@@ -22,7 +22,8 @@ class BooruExtractor(Extractor):
     def __init__(self):
         Extractor.__init__(self)
         self.page = "page"
-        self.headers = self.params = {}
+        self.params = {"limit": 50}
+        self.headers = {}
 
     def items(self):
         yield Message.Version, 1
@@ -50,12 +51,12 @@ class BooruExtractor(Extractor):
         """Collect metadata for extractor-job"""
         # Override this method in derived classes
         return {
-            "category": self.info["category"],
+            "category": self.category,
         }
 
     def get_file_metadata(self, data):
         """Collect metadata for a downloadable file"""
-        data["category"] = self.info["category"]
+        data["category"] = self.category
         return text.nameext_from_url(self.get_file_url(data), data)
 
     def get_file_url(self, data):
@@ -75,10 +76,10 @@ class JSONBooruExtractor(BooruExtractor):
                 self.request(self.api_url, verify=True, params=self.params,
                              headers=self.headers).text
             )
-            if len(images) == 0:
-                return
             for data in images:
                 yield data
+            if len(images) < self.params["limit"]:
+                return
             self.update_page()
 
 
@@ -90,8 +91,56 @@ class XMLBooruExtractor(BooruExtractor):
             root = ET.fromstring(
                 self.request(self.api_url, verify=True, params=self.params).text
             )
-            if len(root) == 0:
-                return
             for item in root:
                 yield item.attrib
+            if len(root) < self.params["limit"]:
+                return
             self.update_page()
+
+
+class BooruTagExtractor(BooruExtractor):
+    """Extract images based on search-tags"""
+
+    directory_fmt = ["{category}", "{tags}"]
+    filename_fmt = "{category}_{id}_{md5}.{extension}"
+
+    def __init__(self, match):
+        BooruExtractor.__init__(self)
+        self.tags = text.unquote(match.group(1))
+        self.params["tags"] = self.tags
+
+    def get_job_metadata(self):
+        return {
+            "category": self.category,
+            "tags": self.tags,
+        }
+
+
+class BooruPoolExtractor(BooruExtractor):
+    """Extract image-pools"""
+
+    directory_fmt = ["{category}", "pool", "{pool}"]
+    filename_fmt = "{category}_{id}_{md5}.{extension}"
+
+    def __init__(self, match):
+        BooruExtractor.__init__(self)
+        self.pool = match.group(1)
+        self.params["tags"] = "pool:" + self.pool
+
+    def get_job_metadata(self):
+        return {
+            "category": self.category,
+            "pool": self.pool,
+        }
+
+
+class BooruPostExtractor(BooruExtractor):
+    """Extract single images"""
+
+    directory_fmt = ["{category}"]
+    filename_fmt = "{category}_{id}_{md5}.{extension}"
+
+    def __init__(self, match):
+        BooruExtractor.__init__(self)
+        self.post = match.group(1)
+        self.params["tags"] = "id:" + self.post