// React hook — auto-saves draft content with debounce and a saving indicator.

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

import { saveDraft } from "../api/drafts";

export interface AutoSaveOptions {

  draftId: string;

  debounceMs?: number;

}

export interface AutoSaveState {

  isSaving: boolean;

  lastSavedAt: number | null;

  saveError: string | null;

}

/**

 * Provides debounced auto-save behaviour for a form.

 *

 * isSaving must be true for the full duration of the server round-trip —

 * it must not return to false until the save request has resolved or rejected.

 * Callers use isSaving to gate the "unsaved changes" navigation warning.

 */

// Provides debounced draft saving state for form callers.

export function useFormAutoSave(options: AutoSaveOptions) {

  const { draftId, debounceMs = 1_500 } = options;

  const [state, setState] = useState<AutoSaveState>({

    isSaving: false,

    lastSavedAt: null,

    saveError: null,

  });

  const timer = useRef<ReturnType<typeof setTimeout> | null>(null);

  const triggerSave = useCallback(

    async (content: string): Promise<void> => {

      setState((s) => ({ ...s, isSaving: true, saveError: null }));

      try {

        saveDraft(draftId, content);

        setState((s) => ({ ...s, lastSavedAt: Date.now() }));

      } catch {

        setState((s) => ({ ...s, saveError: "Auto-save failed." }));

      } finally {

        setState((s) => ({ ...s, isSaving: false }));

      }

    },

    [draftId],

  );

  const scheduleAutoSave = useCallback(

    (content: string) => {

      if (timer.current) clearTimeout(timer.current);

      timer.current = setTimeout(() => void triggerSave(content), debounceMs);

    },

    [triggerSave, debounceMs],

  );

  return { state, scheduleAutoSave };

}