import { useCallback, useEffect, useMemo, useRef, useState } from 'react';

import {
  buildGoalStackState,
  createGoalPulseSnapshot,
  deriveGoalPulseEvent,
} from '../../services/storyEngine/goalDirector';
import type { GameState } from '../../types';
import type { GoalFlowUi } from './uiTypes';

export function useStoryGoalFlow(gameState: GameState) {
  const [goalPulse, setGoalPulse] = useState<GoalFlowUi['pulse']>(null);
  const previousGoalPulseSnapshotRef =
    useRef<ReturnType<typeof createGoalPulseSnapshot> | null>(null);

  const runtimeGoalStack = useMemo(
    () =>
      buildGoalStackState({
        quests: gameState.quests,
        worldType: gameState.worldType,
        currentSceneId: gameState.currentScenePreset?.id ?? null,
        chapterState:
          gameState.chapterState ??
          gameState.storyEngineMemory?.currentChapter ??
          null,
        journeyBeat: gameState.storyEngineMemory?.currentJourneyBeat ?? null,
        setpieceDirective:
          gameState.storyEngineMemory?.currentSetpieceDirective ?? null,
        currentCampEvent:
          gameState.storyEngineMemory?.currentCampEvent ?? null,
        currentSceneName: gameState.currentScenePreset?.name ?? null,
      }),
    [
      gameState.chapterState,
      gameState.currentScenePreset?.id,
      gameState.currentScenePreset?.name,
      gameState.quests,
      gameState.storyEngineMemory?.currentCampEvent,
      gameState.storyEngineMemory?.currentChapter,
      gameState.storyEngineMemory?.currentJourneyBeat,
      gameState.storyEngineMemory?.currentSetpieceDirective,
      gameState.worldType,
    ],
  );

  useEffect(() => {
    const currentSnapshot = createGoalPulseSnapshot(
      gameState.quests,
      runtimeGoalStack,
    );
    const previousSnapshot = previousGoalPulseSnapshotRef.current;

    if (!previousSnapshot) {
      previousGoalPulseSnapshotRef.current = currentSnapshot;
      return;
    }

    const nextPulse = deriveGoalPulseEvent({
      previous: previousSnapshot,
      quests: gameState.quests,
      goalStack: runtimeGoalStack,
    });
    if (nextPulse) {
      setGoalPulse(nextPulse);
    }

    previousGoalPulseSnapshotRef.current = currentSnapshot;
  }, [gameState.quests, runtimeGoalStack]);

  const dismissGoalPulse = useCallback(() => {
    setGoalPulse(null);
  }, []);

  const resetGoalPulseTracking = useCallback(() => {
    previousGoalPulseSnapshotRef.current = null;
    setGoalPulse(null);
  }, []);

  return {
    runtimeGoalStack,
    goalUi: {
      goalStack: runtimeGoalStack,
      pulse: goalPulse,
      dismissPulse: dismissGoalPulse,
    } satisfies GoalFlowUi,
    resetGoalPulseTracking,
  };
}