bug: fix when deleting a stage resetes touranment order

hasura/triggers/tournament_stages.sql

@@ -83,6 +83,16 @@ DECLARE
     current_order INTEGER;
     next_stage_record RECORD;
 BEGIN
+    -- Resequencing after a delete only shifts "order"; the delete trigger
+    -- regenerates the brackets once for the whole tournament afterwards.
+    BEGIN
+        PERFORM 1 FROM pg_temp.resequencing_tournament_stages LIMIT 1;
+        RETURN NEW;
+    EXCEPTION
+        WHEN undefined_table THEN
+            NULL;
+    END;
+
     -- Format-only tweaks (per-round best-of settings, default best-of) don't
     -- affect bracket structure — they are read at match materialization — so
     -- they must not trigger a bracket regeneration.
@@ -203,6 +213,14 @@ DECLARE
     tournament_status text;
     stage_has_matches boolean;
 BEGIN
+    BEGIN
+        PERFORM 1 FROM pg_temp.resequencing_tournament_stages LIMIT 1;
+        RETURN NEW;
+    EXCEPTION
+        WHEN undefined_table THEN
+            NULL;
+    END;
+
     -- Format-only tweaks (per-round best-of settings, default best-of) are
     -- allowed at any point: they only apply to matches that have not been
     -- created yet, so a live tournament/league can adjust its series format.
@@ -284,6 +302,28 @@ CREATE OR REPLACE FUNCTION public.tad_tournament_stages() RETURNS TRIGGER
     LANGUAGE plpgsql
     AS $$
 BEGIN
+    -- Stage order must stay 1..N with no gaps: stages are linked by
+    -- "order" + 1, so a hole leaves the stages after it orphaned.
+    CREATE TEMP TABLE IF NOT EXISTS resequencing_tournament_stages (dummy int);
+
+    BEGIN
+        UPDATE tournament_stages ts
+        SET "order" = resequenced.new_order
+        FROM (
+            SELECT id, (ROW_NUMBER() OVER (ORDER BY "order" ASC, id ASC))::int AS new_order
+            FROM tournament_stages
+            WHERE tournament_id = OLD.tournament_id
+        ) resequenced
+        WHERE ts.id = resequenced.id
+          AND ts."order" IS DISTINCT FROM resequenced.new_order;
+    EXCEPTION
+        WHEN OTHERS THEN
+            DROP TABLE IF EXISTS pg_temp.resequencing_tournament_stages;
+            RAISE;
+    END;
+
+    DROP TABLE IF EXISTS pg_temp.resequencing_tournament_stages;
+
     PERFORM update_tournament_stages(OLD.tournament_id);
     PERFORM cleanup_orphaned_match_options(OLD.match_options_id);
     RETURN OLD;

test/tournament-stages.spec.ts

@@ -359,6 +359,52 @@ describe("tournament stages: Swiss and RoundRobin (SQL-driven)", () => {
       expect(Number(stage1.min_teams)).toBe(8);
     });
 
+    const THREE_STAGES = [
+      { type: "SingleElimination", order: 1, minTeams: 16, maxTeams: 16 },
+      { type: "SingleElimination", order: 2, minTeams: 8, maxTeams: 8 },
+      { type: "SingleElimination", order: 3, minTeams: 4, maxTeams: 4 },
+    ];
+
+    it("deleting a stage closes the gap in the remaining stage order", async () => {
+      const t = await tfx.createTournament(THREE_STAGES);
+
+      await postgres.query("DELETE FROM tournament_stages WHERE id = $1", [
+        t.stageIds[0],
+      ]);
+
+      const stages = await postgres.query<Array<{ id: string; order: number }>>(
+        `SELECT id, "order" FROM tournament_stages WHERE tournament_id = $1 ORDER BY "order"`,
+        [t.id],
+      );
+      expect(stages.map((stage) => Number(stage.order))).toEqual([1, 2]);
+      expect(stages.map((stage) => stage.id)).toEqual([
+        t.stageIds[1],
+        t.stageIds[2],
+      ]);
+    });
+
+    it("deleting a middle stage keeps the surviving stages linked", async () => {
+      const t = await tfx.createTournament(THREE_STAGES);
+
+      await postgres.query("DELETE FROM tournament_stages WHERE id = $1", [
+        t.stageIds[1],
+      ]);
+
+      const stages = await postgres.query<Array<{ order: number }>>(
+        `SELECT "order" FROM tournament_stages WHERE tournament_id = $1 ORDER BY "order"`,
+        [t.id],
+      );
+      expect(stages.map((stage) => Number(stage.order))).toEqual([1, 2]);
+
+      // Stages link by "order" + 1, so the gap used to leave stage 3 orphaned.
+      const [linked] = await postgres.query<Array<{ count: string }>>(
+        `SELECT COUNT(*) FROM tournament_brackets
+          WHERE tournament_stage_id = $1 AND parent_bracket_id IS NOT NULL`,
+        [t.stageIds[0]],
+      );
+      expect(Number(linked.count)).toBeGreaterThan(0);
+    });
+
     it("a RoundRobin stage feeds its top teams into the elimination stage", async () => {
       const t = await tfx.launch(
         [