import React from 'react';

function storageKey(slug: string) {
  return `guestTasks_${slug}`;
}

function parseStored(value: string | null) {
  if (!value) {
    return [] as number[];
  }
  try {
    const parsed = JSON.parse(value);
    if (Array.isArray(parsed)) {
      return parsed.filter((item) => Number.isInteger(item)) as number[];
    }
    return [];
  } catch (error) {
    console.warn('Failed to parse task progress from storage', error);
    return [];
  }
}

export function useGuestTaskProgress(slug: string | undefined) {
  const [completed, setCompleted] = React.useState<number[]>([]);
  const [hydrated, setHydrated] = React.useState(false);

  React.useEffect(() => {
    if (!slug) {
      setCompleted([]);
      setHydrated(true);
      return;
    }
    try {
      const stored = window.localStorage.getItem(storageKey(slug));
      setCompleted(parseStored(stored));
    } catch (error) {
      console.warn('Failed to read task progress', error);
      setCompleted([]);
    } finally {
      setHydrated(true);
    }
  }, [slug]);

  const persist = React.useCallback(
    (next: number[]) => {
      if (!slug) return;
      setCompleted(next);
      try {
        window.localStorage.setItem(storageKey(slug), JSON.stringify(next));
      } catch (error) {
        console.warn('Failed to persist task progress', error);
      }
    },
    [slug]
  );

  const markCompleted = React.useCallback(
    (taskId: number) => {
      if (!slug || !Number.isInteger(taskId)) {
        return;
      }
      setCompleted((prev) => {
        if (prev.includes(taskId)) {
          return prev;
        }
        const next = [...prev, taskId];
        try {
          window.localStorage.setItem(storageKey(slug), JSON.stringify(next));
        } catch (error) {
          console.warn('Failed to persist task progress', error);
        }
        return next;
      });
    },
    [slug]
  );

  const clearProgress = React.useCallback(() => {
    if (!slug) return;
    setCompleted([]);
    try {
      window.localStorage.removeItem(storageKey(slug));
    } catch (error) {
      console.warn('Failed to clear task progress', error);
    }
  }, [slug]);

  const isCompleted = React.useCallback(
    (taskId: number | null | undefined) => {
      if (!Number.isInteger(taskId)) return false;
      return completed.includes(taskId as number);
    },
    [completed]
  );

  return {
    hydrated,
    completed,
    completedCount: completed.length,
    markCompleted,
    clearProgress,
    isCompleted,
  };
}