✨ feat(cache): add database integration for translation cache

- introduce peewee ORM for database management
- add `_TranslationCache` model with unique constraints
- implement `TranslationCache` class for clean API usage
- add `init_db` function to initialize database
- improve translation cache handling with database storage

pdf2zh/cache.py

@@ -1,91 +1,69 @@
-import tempfile
 import os
-import time
-import hashlib
-import shutil
-
-cache_dir = os.path.join(tempfile.gettempdir(), "cache")
-os.makedirs(cache_dir, exist_ok=True)
-time_filename = "update_time"
-max_cache = 5
-
-
-def deterministic_hash(obj):
-    hash_object = hashlib.sha256()
-    hash_object.update(str(obj).encode())
-    return hash_object.hexdigest()[0:20]
-
-
-def get_dirs():
-    dirs = [
-        os.path.join(cache_dir, dir)
-        for dir in os.listdir(cache_dir)
-        if os.path.isdir(os.path.join(cache_dir, dir))
-    ]
-    return dirs
-
-
-def get_time(dir):
-    try:
-        timefile = os.path.join(dir, time_filename)
-        t = float(open(timefile, encoding="utf-8").read())
-        return t
-    except FileNotFoundError:
-        # handle the error as needed, for now we'll just return a default value
-        return float(
-            "inf"
-        )  # This ensures that this directory will be the first to be removed if required
-
-
-def write_time(dir):
-    timefile = os.path.join(dir, time_filename)
-    t = time.time()
-    print(t, file=open(timefile, "w", encoding="utf-8"), end="")
-
-
-def argmin(iterable):
-    return min(enumerate(iterable), key=lambda x: x[1])[0]
-
-
-def remove_extra():
-    dirs = get_dirs()
-    for dir in dirs:
-        if not os.path.isdir(
-            dir
-        ):  # This line might be redundant now, as get_dirs() ensures only directories are returned
-            os.remove(dir)
-        try:
-            get_time(dir)
-        except BaseException:
-            shutil.rmtree(dir)
-    while True:
-        dirs = get_dirs()
-        if len(dirs) <= max_cache:
-            break
-        times = [get_time(dir) for dir in dirs]
-        arg = argmin(times)
-        shutil.rmtree(dirs[arg])
-
-
-def is_cached(hash_key):
-    dir = os.path.join(cache_dir, hash_key)
-    return os.path.exists(dir)
-
-
-def create_cache(hash_key):
-    dir = os.path.join(cache_dir, hash_key)
-    os.makedirs(dir, exist_ok=True)
-    write_time(dir)
-
-
-def load_paragraph(hash_key, hash_key_paragraph):
-    filename = os.path.join(cache_dir, hash_key, hash_key_paragraph)
-    if os.path.exists(filename):
-        return open(filename, encoding="utf-8").read()
-    else:
-        return None
-
-
-def write_paragraph(hash_key, hash_key_paragraph, paragraph):
-    filename = os.path.join(cache_dir, hash_key, hash_key_paragraph)
-    print(paragraph, file=open(filename, "w", encoding="utf-8"), end="")
+from peewee import Model, SqliteDatabase, AutoField, CharField, TextField, SQL
+
+# we don't init the database here
+db = SqliteDatabase(None)
+
+
+class _TranslationCache(Model):
+    id = AutoField()
+    translate_engine = CharField(max_length=20)
+    translate_engine_params = TextField()
+    original_text = TextField()
+    translation = TextField()
+
+    class Meta:
+        database = db
+        constraints = [
+            SQL(
+                """
+            UNIQUE (
+                translate_engine,
+                translate_engine_params,
+                original_text
+                )
+            ON CONFLICT REPLACE
+            """
+            )
+        ]
+
+
+class TranslationCache:
+    def __init__(self, translate_engine, translate_engine_params):
+        self.translate_engine = translate_engine
+        self.translate_engine_params = translate_engine_params
+
+    def get(self, original_text):
+        return _TranslationCache.get_or_none(
+            translate_engine=self.translate_engine,
+            translate_engine_params=self.translate_engine_params,
+            original_text=original_text,
+        )
+
+    def set(self, original_text, translation):
+        _TranslationCache.create(
+            translate_engine=self.translate_engine,
+            translate_engine_params=self.translate_engine_params,
+            original_text=original_text,
+            translation=translation,
+        )
+
+
+def init_db(remove_exists=False):
+    cache_folder = os.path.join(os.path.expanduser("~"), ".cache", "pdf2zh")
+    os.makedirs(cache_folder, exist_ok=True)
+    # The current version does not support database migration, so add the version number to the file name.
+    cache_db_path = os.path.join(cache_folder, "cache.v1.db")
+    if remove_exists and os.path.exists(cache_db_path):
+        os.remove(cache_db_path)
+    db.init(
+        cache_db_path,
+        pragmas={
+            "journal_mode": "wal",
+            "busy_timeout": 1000,
+        },
+    )
+    db.create_tables([_TranslationCache], safe=True)
+
+
+init_db()