"use client";

import { useEffect, useEffectEvent, useState } from "react";
import { toast } from "sonner";

export type AutosaveState = "saved" | "unsaved" | "saving" | "incomplete" | "error";

interface SaveResult {
  status: string;
  message?: string;
  version?: number;
}

export function useAutosave<T>({
  value,
  valid,
  initialVersion,
  persist,
  delay = 900,
}: {
  value: T;
  valid: boolean;
  initialVersion: number;
  persist: (value: T, expectedVersion: number) => Promise<SaveResult>;
  delay?: number;
}) {
  const fingerprint = JSON.stringify(value);
  const [savedFingerprint, setSavedFingerprint] = useState(fingerprint);
  const [errorFingerprint, setErrorFingerprint] = useState<string | null>(null);
  const [saving, setSaving] = useState(false);
  const [version, setVersion] = useState(initialVersion);

  const save = useEffectEvent(async (snapshot: T, snapshotFingerprint: string) => {
    setSaving(true);
    setErrorFingerprint(null);
    try {
      const result = await persist(snapshot, version);
      if (result.status === "error") {
        setErrorFingerprint(snapshotFingerprint);
        toast.error(result.message ?? "บันทึกอัตโนมัติไม่สำเร็จ");
        return;
      }
      if (result.version) setVersion(result.version);
      setSavedFingerprint(snapshotFingerprint);
    } catch (cause) {
      setErrorFingerprint(snapshotFingerprint);
      toast.error(cause instanceof Error ? cause.message : "บันทึกอัตโนมัติไม่สำเร็จ");
    } finally {
      setSaving(false);
    }
  });

  useEffect(() => {
    if (!valid || saving || fingerprint === savedFingerprint || fingerprint === errorFingerprint) return;
    const timer = window.setTimeout(() => {
      void save(JSON.parse(fingerprint) as T, fingerprint);
    }, delay);
    return () => window.clearTimeout(timer);
  }, [delay, errorFingerprint, fingerprint, savedFingerprint, saving, valid]);

  if (!valid) return "incomplete";
  if (saving) return "saving";
  if (fingerprint === errorFingerprint) return "error";
  if (fingerprint !== savedFingerprint) return "unsaved";
  return "saved";
}