From e0c32319e8f23932da456a935f4b1db67c3f9b6d Mon Sep 17 00:00:00 2001
From: Mathias <mathias2784@web.de>
Date: Wed, 28 Oct 2026 07:12:31 +0100
Subject: [PATCH] draft: category tree building

---
 src/models/category.py     | 51 +++++++++++++++++++++++++++++++-------
 src/models/transactions.py |  4 ++-
 2 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/src/models/category.py b/src/models/category.py
index c296834..d626417 100644
--- a/src/models/category.py
+++ b/src/models/category.py
@@ -84,6 +84,7 @@ class Category(ExportBaseModel):
         # TODO (maybe)
         ...
 
+
 class CategoryDb(BaseModelDb):
     __tablename__ = "category"
     __table_args__ = (
@@ -240,15 +241,15 @@ class CategoryBudgetDb(BaseModelDb):
 
 class CategoryTree(BaseModel):
     category: Category
-    total_amount: float
-    total_budget: float
-    sub_categories: list[ CategoryTree ] | None
-    transactions: list[Transaction] | None
+    total_amount: float | None = None
+    total_budget: float | None = None
+    sub_categories: list[CategoryTree] | None = None
+    transactions: list[Transaction] | None = None
 
     def get_total_amount(self) -> float:
         result = 0.0
         if self.transactions:
-            sum(transaction.amount for transaction in self.transactions )
+            sum(transaction.amount for transaction in self.transactions)
         if self.sub_categories:
             sum(sub_category.get_total_amount() for sub_category in self.sub_categories)
         return result
@@ -257,14 +258,46 @@ class CategoryTree(BaseModel):
         result = 0.0
         result += self.category.get_budget(date_valid)
         if self.sub_categories:
-            result += sum(category.category.get_budget(date_valid) for category in self.sub_categories)
+            result += sum(
+                category.category.get_budget(date_valid)
+                for category in self.sub_categories
+            )
         return result
 
-    def __add__(self, other):
-        ...
+    def __add__(self, other: CategoryTree):
+        if self.category != other.category:
+            return
+        sub_categories = []
+        for category1 in self.sub_categories or []:
+            for category2 in other.sub_categories or []:
+                if category1.category == category2.category:
+                    sub_categories.append(category1 + category2)
+                else:
+                    sub_categories.append(category1)
+                    sub_categories.append(category2)
+
+        return CategoryTree(
+            category=self.category,
+            total_amount=(self.total_amount or 0.0) + (other.total_amount or 0.0),
+            total_budget=(self.total_budget or 0.0) + (other.total_budget or 0.0),
+            sub_categories=sub_categories,
+            transactions=self.transactions + other.transactions,
+        )
+
 
 def build_category_tree(transactions: list[Transaction]) -> list[CategoryTree]:
     # TODO: loop through flat list a build a category tree
     result = []
     for transaction in transactions:
-        pass
+        bla = _transaction_to_tree(transaction)
+
+
+def _transaction_to_tree(transaction: Transaction) -> CategoryTree | None:
+    category = transaction.category
+    if not category:
+        return
+    result = CategoryTree(category=category, transactions=[transaction])
+    while category.parent is not None:
+        category = category.parent
+        result = CategoryTree(category=category, sub_categories=[result])
+    return result
diff --git a/src/models/transactions.py b/src/models/transactions.py
index 8ed9268..dfd7fee 100644
--- a/src/models/transactions.py
+++ b/src/models/transactions.py
@@ -5,6 +5,7 @@ from pydantic import Field, computed_field
 from sqlalchemy import Date, ForeignKey, Index, Integer, String, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
+from src.models.category import Category
 from src.models.common import Amount, ExportBaseModel, IngestdbBase, date2str, hashify
 
 
@@ -29,7 +30,8 @@ class Transaction(ExportBaseModel):
     other_name: str | None = None
     other_iban: str | None = None
     # TODO: The Pydantic model should hold a category object, NOT the category id which is owned by the DB
-    category_id: int | None = None
+    category: Category | None
+    category_id: int | None = None # remove!
 
     @computed_field  # type: ignore[prop-decorator]
     @property