1 files changed, 102 insertions, 0 deletions
diff --git a/python/knot_resolver/manager/config_store.py b/python/knot_resolver/manager/config_store.py
new file mode 100644
index 00000000..214062b2
--- /dev/null
+++ b/python/knot_resolver/manager/config_store.py
@@ -0,0 +1,102 @@
+import asyncio
+from asyncio import Lock
+from typing import Any, Awaitable, Callable, List, Tuple
+
+from knot_resolver.datamodel import KresConfig
+from knot_resolver.utils.functional import Result
+from knot_resolver.utils.modeling.exceptions import DataParsingError
+from knot_resolver.utils.modeling.types import NoneType
+
+from .exceptions import KresManagerException
+
+VerifyCallback = Callable[[KresConfig, KresConfig], Awaitable[Result[None, str]]]
+UpdateCallback = Callable[[KresConfig], Awaitable[None]]
+
+
+class ConfigStore:
+    def __init__(self, initial_config: KresConfig):
+        self._config = initial_config
+        self._verifiers: List[VerifyCallback] = []
+        self._callbacks: List[UpdateCallback] = []
+        self._update_lock: Lock = Lock()
+
+    async def update(self, config: KresConfig) -> None:
+        # invoke pre-change verifiers
+        results: Tuple[Result[None, str], ...] = tuple(
+            await asyncio.gather(*[ver(self._config, config) for ver in self._verifiers])
+        )
+        err_res = filter(lambda r: r.is_err(), results)
+        errs = list(map(lambda r: r.unwrap_err(), err_res))
+        if len(errs) > 0:
+            raise KresManagerException("Configuration validation failed. The reasons are:\n - " + "\n - ".join(errs))
+
+        async with self._update_lock:
+            # update the stored config with the new version
+            self._config = config
+
+            # invoke change callbacks
+            for call in self._callbacks:
+                await call(config)
+
+    async def renew(self) -> None:
+        await self.update(self._config)
+
+    async def register_verifier(self, verifier: VerifyCallback) -> None:
+        self._verifiers.append(verifier)
+        res = await verifier(self.get(), self.get())
+        if res.is_err():
+            raise DataParsingError(f"Initial config verification failed with error: {res.unwrap_err()}")
+
+    async def register_on_change_callback(self, callback: UpdateCallback) -> None:
+        """
+        Registers new callback and immediatelly calls it with current config
+        """
+
+        self._callbacks.append(callback)
+        await callback(self.get())
+
+    def get(self) -> KresConfig:
+        return self._config
+
+
+def only_on_real_changes_update(selector: Callable[[KresConfig], Any]) -> Callable[[UpdateCallback], UpdateCallback]:
+    def decorator(orig_func: UpdateCallback) -> UpdateCallback:
+        original_value_set: Any = False
+        original_value: Any = None
+
+        async def new_func_update(config: KresConfig) -> None:
+            nonlocal original_value_set
+            nonlocal original_value
+            if not original_value_set:
+                original_value_set = True
+                original_value = selector(config)
+                await orig_func(config)
+            elif original_value != selector(config):
+                original_value = selector(config)
+                await orig_func(config)
+
+        return new_func_update
+
+    return decorator
+
+
+def only_on_real_changes_verifier(selector: Callable[[KresConfig], Any]) -> Callable[[VerifyCallback], VerifyCallback]:
+    def decorator(orig_func: VerifyCallback) -> VerifyCallback:
+        original_value_set: Any = False
+        original_value: Any = None
+
+        async def new_func_verifier(old: KresConfig, new: KresConfig) -> Result[NoneType, str]:
+            nonlocal original_value_set
+            nonlocal original_value
+            if not original_value_set:
+                original_value_set = True
+                original_value = selector(new)
+                await orig_func(old, new)
+            elif original_value != selector(new):
+                original_value = selector(new)
+                await orig_func(old, new)
+            return Result.ok(None)
+
+        return new_func_verifier
+
+    return decorator