[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>

1 files changed, 55 insertions, 0 deletions

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)