feat(topology): add Flask app skeleton with db connection (psycopg 3)

Co-Authored-By: Claude <noreply@anthropic.com>

topology_api/config.py

@@ -0,0 +1,30 @@
+# topology_api/config.py
+import os
+
+# PostgreSQL connection (from .env)
+PGHOST = os.environ.get("PGHOST", "192.168.195.241")
+PGPORT = os.environ.get("PGPORT", "35432")
+PGUSER = os.environ.get("PGUSER", "user_armor")
+PGPASSWORD = os.environ.get("PGPASSWORD", "user_armor_1790990971")
+TOPO_DATABASE = os.environ.get("TOPO_DATABASE", "ksp_wiki_topology")
+
+_BASE_DSN = f"postgresql://{PGUSER}:{PGPASSWORD}@{PGHOST}:{PGPORT}"
+
+DATABASE_URL = os.environ.get(
+    "TOPOLOGY_DATABASE_URL",
+    f"{_BASE_DSN}/{TOPO_DATABASE}",
+)
+
+READER_DATABASE_URL = os.environ.get(
+    "TOPOLOGY_READER_DATABASE_URL",
+    DATABASE_URL,
+)
+
+WRITER_DATABASE_URL = os.environ.get(
+    "TOPOLOGY_WRITER_DATABASE_URL",
+    DATABASE_URL,
+)
+
+API_HOST = os.environ.get("TOPOLOGY_API_HOST", "0.0.0.0")
+API_PORT = int(os.environ.get("TOPOLOGY_API_PORT", "5000"))
+API_DEBUG = os.environ.get("TOPOLOGY_API_DEBUG", "false").lower() == "true"

topology_api/db.py

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+# topology_api/db.py
+import psycopg
+from psycopg.rows import dict_row
+from contextlib import contextmanager
+from topology_api.config import READER_DATABASE_URL, WRITER_DATABASE_URL
+
+
+def get_reader_connection():
+    """Return a new read-only connection with dict_row rows."""
+    return psycopg.connect(READER_DATABASE_URL, row_factory=dict_row)
+
+
+def get_writer_connection():
+    """Return a new write-capable connection with dict_row rows."""
+    return psycopg.connect(WRITER_DATABASE_URL, row_factory=dict_row)
+
+
+@contextmanager
+def read_cursor():
+    """Context manager for read queries. Returns a cursor."""
+    with get_reader_connection() as conn:
+        conn.execute("SET search_path TO topology, public")
+        with conn.cursor() as cur:
+            yield cur
+
+
+@contextmanager
+def write_cursor():
+    """Context manager for write queries. Auto-commits on success, rollback on error."""
+    with get_writer_connection() as conn:
+        conn.execute("SET search_path TO topology, public")
+        with conn.transaction():
+            with conn.cursor() as cur:
+                yield cur