"use client";

import { useCallback, useEffect, useState } from "react";

const STORAGE_KEY = "digital-course-video-completed";

function loadCompleted(): Set<string> {
  if (typeof window === "undefined") return new Set();
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (!raw) return new Set();
    const arr = JSON.parse(raw) as string[];
    return new Set(Array.isArray(arr) ? arr : []);
  } catch {
    return new Set();
  }
}

function saveCompleted(ids: Set<string>) {
  if (typeof window === "undefined") return;
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify([...ids]));
  } catch {
    // ignore
  }
}

export function useVideoProgress() {
  const [completed, setCompleted] = useState<Set<string>>(() => new Set());

  useEffect(() => {
    setCompleted(loadCompleted());
  }, []);

  const markCompleted = useCallback((lessonId: string) => {
    setCompleted((prev) => {
      const next = new Set(prev);
      next.add(lessonId);
      saveCompleted(next);
      return next;
    });
  }, []);

  const isCompleted = useCallback(
    (lessonId: string) => completed.has(lessonId),
    [completed]
  );

  const isPartCompleted = useCallback(
    (lessonIds: string[]) =>
      lessonIds.length > 0 && lessonIds.every((id) => completed.has(id)),
    [completed]
  );

  return { completed, markCompleted, isCompleted, isPartCompleted };
}