Initial commit: AI Dungeon clone (FastAPI backend + React frontend)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KFsGHju9szibJJa2YJcdbg

backend/app/migrations.py

@@ -0,0 +1,66 @@
+"""Lightweight versioned schema migrations over SQLite's PRAGMA user_version.
+
+How it works:
+- A fresh database is created by `Base.metadata.create_all()` (always current)
+  and stamped with LATEST_VERSION.
+- An existing database runs every migration whose version is greater than its
+  stored user_version, in order, then is stamped.
+
+To change the schema: update models.py (keeps fresh DBs current) AND append a
+(version, sql) pair here (upgrades existing DBs). Keep migrations idempotent
+where cheap (IF NOT EXISTS etc.).
+"""
+
+from sqlalchemy import inspect, text
+from sqlalchemy.engine import Engine
+
+from .database import Base
+
+# (version, SQL to run when upgrading past it) — append only, never reorder.
+MIGRATIONS: list[tuple[int, str]] = [
+    # Phase 6: auto-summarization + memory bank (the `memories` table itself is
+    # created by create_all, which runs for existing DBs too).
+    (2, "ALTER TABLE adventures ADD COLUMN auto_summarize BOOLEAN NOT NULL DEFAULT 0"),
+    (3, "ALTER TABLE adventures ADD COLUMN memory_bank_enabled BOOLEAN NOT NULL DEFAULT 0"),
+    (4, "ALTER TABLE adventures ADD COLUMN memory_cursor INTEGER NOT NULL DEFAULT 0"),
+    (5, "ALTER TABLE adventures ADD COLUMN summary_cursor INTEGER NOT NULL DEFAULT 0"),
+    (6, "ALTER TABLE settings ADD COLUMN summary_model VARCHAR(200) NOT NULL DEFAULT ''"),
+    (7, "ALTER TABLE settings ADD COLUMN embedding_model VARCHAR(200) NOT NULL DEFAULT ''"),
+    (8, "ALTER TABLE settings ADD COLUMN memory_bank_capacity INTEGER NOT NULL DEFAULT 200"),
+    (9, "ALTER TABLE settings ADD COLUMN memory_top_k INTEGER NOT NULL DEFAULT 5"),
+    # Repair duplicate action indexes (player + AI actions of one turn used to
+    # get the same index): renumber 0..n-1 per adventure, preserving order.
+    # UPDATE..FROM: ranks are computed as a snapshot before any row is
+    # rewritten (a correlated subquery would see partially-updated rows and
+    # could produce duplicates again).
+    (10, """
+        UPDATE actions SET "index" = ranked.new_index
+        FROM (
+            SELECT id, ROW_NUMBER() OVER (
+                PARTITION BY adventure_id ORDER BY "index", id
+            ) - 1 AS new_index
+            FROM actions
+        ) AS ranked
+        WHERE ranked.id = actions.id
+    """),
+    # Reasoning-model support: separate thinking budget + stored reasoning text.
+    (11, "ALTER TABLE settings ADD COLUMN reasoning_max_tokens INTEGER NOT NULL DEFAULT 0"),
+    (12, "ALTER TABLE actions ADD COLUMN reasoning TEXT"),
+]
+
+LATEST_VERSION = max((v for v, _ in MIGRATIONS), default=1)
+
+
+def bootstrap(engine: Engine) -> None:
+    fresh = not inspect(engine).get_table_names()
+    Base.metadata.create_all(bind=engine)
+    with engine.begin() as conn:
+        if fresh:
+            conn.execute(text(f"PRAGMA user_version = {LATEST_VERSION}"))
+            return
+        current = conn.execute(text("PRAGMA user_version")).scalar() or 1
+        for version, sql in MIGRATIONS:
+            if version > current:
+                conn.execute(text(sql))
+                current = version
+        conn.execute(text(f"PRAGMA user_version = {current}"))