BEGIN;
CREATE TABLE canvas_subgraphs (
 project text NOT NULL,
 workspace_id uuid NOT NULL,
 parent_board_id uuid NOT NULL,
 frame_id text NOT NULL CHECK (frame_id ~ '^[A-Za-z0-9_-]{1,128}$'),
 child_board_id uuid NOT NULL,
 archived_at timestamptz,
 migration_source jsonb,
 created_at timestamptz NOT NULL DEFAULT now(),
 PRIMARY KEY(project,workspace_id,child_board_id),
 FOREIGN KEY(project,workspace_id,parent_board_id) REFERENCES materials ON DELETE RESTRICT,
 FOREIGN KEY(project,workspace_id,child_board_id) REFERENCES materials ON DELETE RESTRICT,
 CHECK(parent_board_id<>child_board_id)
);
CREATE UNIQUE INDEX canvas_subgraph_active_frame ON canvas_subgraphs(project,workspace_id,parent_board_id,frame_id) WHERE archived_at IS NULL;
-- Workspace row locks serialize ownership changes. A database trigger also rejects
-- cycles and excessive depth for maintenance callers outside the HTTP service.
CREATE FUNCTION foundry_check_subgraph() RETURNS trigger LANGUAGE plpgsql AS $$
DECLARE depth integer;
BEGIN
 PERFORM 1 FROM workspaces WHERE project=NEW.project AND id=NEW.workspace_id FOR UPDATE;
 IF EXISTS(SELECT 1 FROM materials WHERE project=NEW.project AND workspace_id=NEW.workspace_id AND id IN(NEW.parent_board_id,NEW.child_board_id) AND kind<>'board') THEN
  RAISE EXCEPTION 'subgraph requires boards' USING ERRCODE='23514';
 END IF;
 WITH RECURSIVE ancestors(id,path) AS (
  SELECT NEW.parent_board_id,ARRAY[NEW.child_board_id,NEW.parent_board_id]
  UNION ALL
  SELECT s.parent_board_id,a.path||s.parent_board_id FROM ancestors a JOIN canvas_subgraphs s
   ON s.project=NEW.project AND s.workspace_id=NEW.workspace_id AND s.child_board_id=a.id
   WHERE NOT s.parent_board_id=ANY(a.path) AND s.archived_at IS NULL
 ) SELECT max(cardinality(path)-1) INTO depth FROM ancestors;
 IF depth>8 OR EXISTS(WITH RECURSIVE descendants(id,path) AS (
  SELECT NEW.child_board_id,ARRAY[NEW.child_board_id]
  UNION ALL SELECT s.child_board_id,d.path||s.child_board_id FROM descendants d JOIN canvas_subgraphs s
   ON s.project=NEW.project AND s.workspace_id=NEW.workspace_id AND s.parent_board_id=d.id
   WHERE NOT s.child_board_id=ANY(d.path) AND s.archived_at IS NULL
 ) SELECT 1 FROM descendants WHERE id=NEW.parent_board_id OR cardinality(path)+depth-1>8) THEN
  RAISE EXCEPTION 'subgraph cycle or depth exceeded' USING ERRCODE='23514';
 END IF;
 RETURN NEW;
END $$;
CREATE TRIGGER canvas_subgraph_integrity BEFORE INSERT OR UPDATE ON canvas_subgraphs FOR EACH ROW EXECUTE FUNCTION foundry_check_subgraph();
CREATE TABLE canvas_transactions (
 project text NOT NULL,
 workspace_id uuid NOT NULL,
 board_id uuid NOT NULL,
 id uuid NOT NULL DEFAULT gen_random_uuid(),
 account_id uuid NOT NULL,
 action text NOT NULL,
 idempotency_key uuid NOT NULL,
 payload_hash text NOT NULL,
 response_status integer NOT NULL,
 response_body jsonb NOT NULL,
 before_state jsonb NOT NULL,
 after_versions jsonb NOT NULL,
 relation_changes jsonb NOT NULL DEFAULT '[]'::jsonb,
 created_at timestamptz NOT NULL DEFAULT now(),
 expires_at timestamptz NOT NULL DEFAULT now()+interval '7 days',
 undone_at timestamptz,
 PRIMARY KEY(project,workspace_id,id),
 UNIQUE(project,workspace_id,account_id,board_id,action,idempotency_key),
 FOREIGN KEY(project,workspace_id,board_id) REFERENCES materials ON DELETE RESTRICT,
 FOREIGN KEY(project,account_id) REFERENCES project_accounts
);
COMMIT;