From ace0062f379154cd2c3e84d982340aaf79a48092 Mon Sep 17 00:00:00 2001
From: Linus Vogel <linus@linvogel.ch>
Date: Sun, 15 Feb 2026 11:13:22 +0100
Subject: [PATCH] implemented utility function for merging dictionaries

---
 pillar_tool/routers/pillar.py        | 43 +++++++++++++++++++++++
 pillar_tool/schemas.py               |  6 +++-
 pillar_tool/util/pillar_utilities.py | 52 ++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 pillar_tool/util/pillar_utilities.py

diff --git a/pillar_tool/routers/pillar.py b/pillar_tool/routers/pillar.py
index e69de29..4afebc3 100644
--- a/pillar_tool/routers/pillar.py
+++ b/pillar_tool/routers/pillar.py
@@ -0,0 +1,43 @@
+import uuid
+
+from fastapi.params import Depends
+from sqlalchemy import select, insert, delete
+from sqlalchemy.orm import Session
+from starlette.exceptions import HTTPException
+from starlette.requests import Request
+from fastapi import APIRouter
+from starlette.responses import JSONResponse
+
+from pillar_tool.db.models.top_data import State, StateAssignment
+from pillar_tool.schemas import PillarParams, get_model_from_query
+from pillar_tool.util.validation import validate_state_name
+
+router = APIRouter(
+    prefix="/pillar",
+    tags=["pillar"],
+)
+
+# Note: there is no list of all pillars, as this would not be helpful
+
+@router.get("/{name}")
+def state_get(req: Request, name: str, params: Depends(get_model_from_query(PillarParams))):
+    # TODO: implement
+    # this function should:
+    #    - get the affected host hierarchy
+    #    - get all the relevant pillar dictionaries
+    #    - merge the pillar directories
+    #    - return the merged pillar directory
+    # if any error happens, return non-200 status and an empty dictionary so that salt does not shit itself
+    db: Session = req.state.db
+
+
+@router.post("/{name}")
+def state_create(req: Request, name: str):
+    # TODO: implement
+    db = req.state.db
+
+
+@router.delete("/{name}")
+def state_delete(req: Request, name: str):
+    # TODO: implement
+    db = req.state.db
diff --git a/pillar_tool/schemas.py b/pillar_tool/schemas.py
index 03e1d86..b39047f 100644
--- a/pillar_tool/schemas.py
+++ b/pillar_tool/schemas.py
@@ -50,7 +50,11 @@ class HostgroupParams(BaseModel):
 class StateParams(BaseModel):
     pass  # No parameters needed for state operations currently
 
-
+# Pillar operations
+class PillarParams(BaseModel):
+    target: str # must be host or hostgroup
+    value: str | None # value if the pillar should be set
+    type: str | None # type of pillar if pillar should be set
 
 
 def get_model_from_query[T](model: T) -> Callable[[Request], T]:
diff --git a/pillar_tool/util/pillar_utilities.py b/pillar_tool/util/pillar_utilities.py
new file mode 100644
index 0000000..e0e4284
--- /dev/null
+++ b/pillar_tool/util/pillar_utilities.py
@@ -0,0 +1,52 @@
+from copy import deepcopy
+
+
+def apply_layer(base: dict, layer: dict):
+    """
+    Recursively applies key-value pairs from `layer` onto `base`.
+
+    For each key in `layer`:
+      - If both `base[key]` and `layer[key]` are dictionaries, recursively merge them.
+      - Otherwise, `base[key]` is overwritten (or newly inserted) with `layer[key]`.
+
+    Note: This function mutates the `base` dictionary in-place.
+
+    :param base: The target dictionary to be updated. Will be modified directly.
+    :param layer: The source dictionary whose values will be applied to `base`.
+    """
+    for key, value in layer.items():
+        # if base and layer value are dicts, apply recursively
+        if type(value) is dict and key in base and type(base[key]) is dict:
+           apply_layer(base[key], value)
+        # else replace the base value with the layer value
+        # or insert the base value
+        else:
+            base[key] = value
+
+
+def merge(*pillar_data, deep_copy=True) -> dict:
+    """
+    Merges multiple pillar data dictionaries into one.
+
+    The merging is done left-to-right: keys from later dictionaries override
+    those in earlier ones. Nested dictionaries are merged recursively using
+    `apply_layer`.
+
+    :param pillar_data: Two or more dictionaries to merge. Must contain at least one item.
+    :param deep_copy: If True (default), the first dictionary is deep-copied before merging,
+                      preserving the original input data. If False, the first dictionary
+                      is modified in-place.
+    :return: A new merged dictionary (if `deep_copy=True`) or the mutated first dictionary (if `deep_copy=False`).
+
+    Example:
+        merge({'a': 1}, {'b': 2}) → {'a': 1, 'b': 2}
+        merge({'a': {'x': 1}}, {'a': {'y': 2}}) → {'a': {'x': 1, 'y': 2}}
+    """
+    assert len(pillar_data) > 0, "At least one pillar data is required"
+    merged_pillar = deepcopy(pillar_data[0]) if deep_copy else pillar_data[0]
+
+    for pillar in pillar_data[1:]:
+        apply_layer(merged_pillar, pillar)
+
+
+    return merged_pillar
\ No newline at end of file