[mod] data: implement a simple currencies (SQL) database (#4836)

To reduce the memory footprint, this patch no longer loads the JSON data
completely into memory.  Instead, there is an SQL database based on
`ExpireCacheSQLite`.

The class CurrenciesDB is a simple DB application that encapsulates the
DB (queries and initialization) and provides convenient methods like
`name_to_iso4217` and `iso4217_to_name`.

Related:

- https://github.com/searxng/searxng/discussions/1892
- https://github.com/searxng/searxng/pull/3458#issuecomment-2900807671
- https://github.com/searxng/searxng/pull/4650

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

3 files changed, 90 insertions, 10 deletions

diff --git a/searx/data/__init__.py b/searx/data/__init__.py
index 48455ebe3..9be1cd67e 100644
--- a/searx/data/__init__.py
+++ b/searx/data/__init__.py
@@ -4,21 +4,17 @@
   make data.all
 
 """
-
+from __future__ import annotations
 
 __all__ = ["ahmia_blacklist_loader"]
 
 import json
-from pathlib import Path
 import typing
 
-from searx import logger
-
-log = logger.getChild("data")
+from .core import log, data_dir
+from .currencies import CurrenciesDB
 
-data_dir = Path(__file__).parent
-
-CURRENCIES: dict[str, typing.Any]
+CURRENCIES: CurrenciesDB
 USER_AGENTS: dict[str, typing.Any]
 EXTERNAL_URLS: dict[str, typing.Any]
 WIKIDATA_UNITS: dict[str, typing.Any]
@@ -29,7 +25,7 @@ ENGINE_TRAITS: dict[str, typing.Any]
 LOCALES: dict[str, typing.Any]
 
 lazy_globals = {
-    "CURRENCIES": None,
+    "CURRENCIES": CurrenciesDB(),
     "USER_AGENTS": None,
     "EXTERNAL_URLS": None,
     "WIKIDATA_UNITS": None,
@@ -41,7 +37,6 @@ lazy_globals = {
 }
 
 data_json_files = {
-    "CURRENCIES": "currencies.json",
     "USER_AGENTS": "useragents.json",
     "EXTERNAL_URLS": "external_urls.json",
     "WIKIDATA_UNITS": "wikidata_units.json",
@@ -63,6 +58,7 @@ def __getattr__(name):
         return data
 
     log.debug("init searx.data.%s", name)
+
     with open(data_dir / data_json_files[name], encoding='utf-8') as f:
         lazy_globals[name] = json.load(f)
 
diff --git a/searx/data/core.py b/searx/data/core.py
new file mode 100644
index 000000000..14cc77eb7
--- /dev/null
+++ b/searx/data/core.py
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# pylint: disable=missing-module-docstring
+from __future__ import annotations
+
+import pathlib
+
+from searx import logger
+from searx.cache import ExpireCacheCfg, ExpireCacheSQLite
+
+log = logger.getChild("data")
+
+data_dir = pathlib.Path(__file__).parent
+
+_DATA_CACHE: ExpireCacheSQLite = None  # type: ignore
+
+
+def get_cache():
+
+    global _DATA_CACHE  # pylint: disable=global-statement
+
+    if _DATA_CACHE is None:
+        _DATA_CACHE = ExpireCacheSQLite.build_cache(
+            ExpireCacheCfg(
+                name="DATA_CACHE",
+                # MAX_VALUE_LEN=1024 * 200,  # max. 200kB length for a *serialized* value.
+                # MAXHOLD_TIME=60 * 60 * 24 * 7 * 4,  # 4 weeks
+            )
+        )
+    return _DATA_CACHE
diff --git a/searx/data/currencies.py b/searx/data/currencies.py
new file mode 100644
index 000000000..a4f2901f0
--- /dev/null
+++ b/searx/data/currencies.py
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Simple implementation to store currencies data in a SQL database."""
+
+from __future__ import annotations
+
+__all__ = ["CurrenciesDB"]
+
+import json
+import pathlib
+
+from .core import get_cache, log
+
+
+class CurrenciesDB:
+    # pylint: disable=missing-class-docstring
+
+    ctx_names = "data_currencies_names"
+    ctx_iso4217 = "data_currencies_iso4217"
+
+    json_file = pathlib.Path(__file__).parent / "currencies.json"
+
+    def __init__(self):
+        self.cache = get_cache()
+
+    def init(self):
+        if self.cache.properties("currencies loaded") != "OK":
+            self.load()
+            self.cache.properties.set("currencies loaded", "OK")
+        # F I X M E:
+        #     do we need a maintenance .. rember: database is stored
+        #     in /tmp and will be rebuild during the reboot anyway
+
+    def load(self):
+        log.debug("init searx.data.CURRENCIES")
+        with open(self.json_file, encoding="utf-8") as f:
+            data_dict = json.load(f)
+        for key, value in data_dict["names"].items():
+            self.cache.set(key=key, value=value, ctx=self.ctx_names, expire=None)
+        for key, value in data_dict["iso4217"].items():
+            self.cache.set(key=key, value=value, ctx=self.ctx_iso4217, expire=None)
+
+    def name_to_iso4217(self, name):
+        self.init()
+
+        ret_val = self.cache.get(key=name, default=name, ctx=self.ctx_names)
+        if isinstance(ret_val, list):
+            # if more alternatives, use the last in the list
+            ret_val = ret_val[-1]
+        return ret_val
+
+    def iso4217_to_name(self, iso4217, language):
+        self.init()
+
+        iso4217_languages: dict = self.cache.get(key=iso4217, default={}, ctx=self.ctx_names)
+        return iso4217_languages.get(language, iso4217)