From b0815fdac4cc0554f90176c6350ccd73b8e8ca59 Mon Sep 17 00:00:00 2001
From: Lars Noack <lars@webcontact.de>
Date: Wed, 17 Jan 2024 12:46:55 +0100
Subject: [PATCH] feat: implemented caching

---
 src/music_kraken/utils/cache.py | 109 ++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/src/music_kraken/utils/cache.py b/src/music_kraken/utils/cache.py
index e69de29..dbf2c26 100644
--- a/src/music_kraken/utils/cache.py
+++ b/src/music_kraken/utils/cache.py
@@ -0,0 +1,109 @@
+import json
+from pathlib import Path
+from dataclasses import dataclass
+from datetime import datetime, timedelta
+from typing import List, Optional
+
+from .config import main_settings
+
+
+@dataclass
+class CacheAttribute:
+    module: str
+    name: str
+
+    created: datetime
+    expires: datetime
+
+    @property
+    def id(self):
+        return f"{self.module}_{self.name}"
+
+    @property
+    def is_valid(self):
+        return datetime.now() < self.expires
+
+    def __eq__(self, other):
+        return self.__dict__ == other.__dict__
+
+
+class Cache:
+    def __init__(self):
+        self._dir = main_settings["cache_directory"]
+        self.index = Path(self._dir, "index.json")
+
+        if not self.index.is_file():
+            with self.index.open("w") as i:
+                i.write(json.dumps([]))
+
+        self.cached_attributes: List[CacheAttribute] = []
+        self._id_to_attribute = {}
+
+        self._time_fields = {"created", "expires"}
+        with self.index.open("r") as i:
+            for c in json.loads(i.read()):
+                for key in self._time_fields:
+                    c[key] = datetime.fromisoformat(c[key])
+
+                self.cached_attributes.append(**c)
+
+    def _init_module(self, module: str) -> Path:
+        """
+        :param module:
+        :return: the module path
+        """
+        r = Path(self._dir, module)
+        r.mkdir(exist_ok=True)
+        return r
+
+    def _write_attribute(self, cached_attribute: CacheAttribute, write: bool = True) -> bool:
+        existing_attribute: Optional[CacheAttribute] = self._id_to_attribute.get(cached_attribute.id)
+        if existing_attribute is not None:
+            # the attribute exists
+            if existing_attribute == cached_attribute:
+                return True
+
+            if existing_attribute.is_valid:
+                return False
+
+            existing_attribute.__dict__ = cached_attribute.__dict__
+            cached_attribute = existing_attribute
+        else:
+            self.cached_attributes.append(cached_attribute)
+            self._id_to_attribute[cached_attribute.id] = cached_attribute
+
+        if write:
+            _json = []
+            for c in self.cached_attributes:
+                d = c.__dict__
+                for key in self._time_fields:
+                    d[key] = d[key].isoformat()
+
+                _json.append(d)
+
+            with self.index.open("w") as f:
+                f.write(json.dumps(_json, indent=4))
+
+        return True
+
+    def set(self, content: bytes, module: str, name: str, expires_in: int = 10):
+        """
+        :param content:
+        :param module:
+        :param name:
+        :param expires_in: the unit is days
+        :return:
+        """
+
+        module_path = self._init_module(module)
+
+        cache_attribute = CacheAttribute(
+            module=module,
+            name=name,
+            created=datetime.now(),
+            expires=datetime.now() + timedelta(days=expires_in),
+        )
+        self._write_attribute(cache_attribute)
+
+        with Path(module_path, name).open("wb") as content_file:
+            content_file.write(content)