import { useEffect, useRef } from "react";
import { useShellStore } from "../app/shellStore";
import {
  exportDungeonEncounterCheckpointSnapshots,
  subscribeDungeonEncounterSnapshots,
} from "./dungeonEncounterRuntime";
import { DUNGEON_RUN_CHECKPOINT_VERSION } from "./dungeonRunCheckpoint";
import { useGameStore } from "./store";
import { useDungeonRunStore } from "./dungeonRunStore";

function checkpointSignature(dungeonId: string): string {
  const game = useGameStore.getState();
  const encounters = exportDungeonEncounterCheckpointSnapshots(dungeonId, 0);
  return JSON.stringify({
    dungeonId,
    difficultyId: game.activeDifficultyId,
    spawn: game.activeSpawn,
    encounters,
    run: useDungeonRunStore.getState().progress,
  });
}

/** Persists only reset-projected state when encounter progress reaches a new stable revision. */
export function DungeonRunCheckpointBridge() {
  const phase = useShellStore((state) => state.phase);
  const activeCharacterId = useShellStore((state) => state.activeCharacter?.id ?? null);
  const lastSignature = useRef("");

  useEffect(() => {
    if (phase !== "game" || !activeCharacterId) return undefined;
    const save = () => {
      const game = useGameStore.getState();
      if (game.gameMode !== "dungeon" || game.gmTestMode) return;
      const signature = checkpointSignature(game.activeDungeonId);
      if (signature === lastSignature.current) return;
      lastSignature.current = signature;
      const encounters = exportDungeonEncounterCheckpointSnapshots(game.activeDungeonId, 0);
      useShellStore.getState().saveActiveDungeonRunCheckpoint({
        version: DUNGEON_RUN_CHECKPOINT_VERSION,
        dungeonId: game.activeDungeonId,
        difficultyId: game.activeDifficultyId,
        checkpointId: encounters.find((entry) => entry.checkpointId)?.checkpointId ?? "entrance",
        spawn: game.activeSpawn,
        encounters,
        savedAt: Date.now(),
        run: useDungeonRunStore.getState().progress ?? undefined,
      });
    };
    save();
    const unsubscribeEncounters = subscribeDungeonEncounterSnapshots(save);
    const unsubscribeRun = useDungeonRunStore.subscribe(save);
    return () => { unsubscribeEncounters(); unsubscribeRun(); };
  }, [activeCharacterId, phase]);

  return null;
}