"use client";

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

import { saveWithConflictRetry } from "@/lib/editor/autosave";
import { parseLocalDraft as parseStoredDraft, serializeLocalDraft } from "@/lib/editor/local-draft";

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

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

export function useAutosave<Value, Draft = Value>({
  value,
  valid,
  initialVersion,
  persist,
  delay = 900,
  storageKey,
  localDraft,
  parseLocalDraft,
  restoreLocalDraft,
}: {
  value: Value;
  valid: boolean;
  initialVersion: number;
  persist: (value: Value, expectedVersion: number) => Promise<SaveResult>;
  delay?: number;
  storageKey?: string;
  localDraft?: Draft;
  parseLocalDraft?: (value: unknown) => Draft | null;
  restoreLocalDraft?: (draft: Draft) => void;
}) {
  const fingerprint = JSON.stringify(value);
  const draftFingerprint = JSON.stringify(localDraft ?? value);
  const [savedFingerprint, setSavedFingerprint] = useState(fingerprint);
  const [savedDraftFingerprint, setSavedDraftFingerprint] = useState(draftFingerprint);
  const [errorFingerprint, setErrorFingerprint] = useState<string | null>(null);
  const [saving, setSaving] = useState(false);
  const [version, setVersion] = useState(initialVersion);
  const [hydrated, setHydrated] = useState(!storageKey);
  const [manualRequest, setManualRequest] = useState(0);
  const handledManualRequest = useRef(0);
  const storageWarningShown = useRef(false);

  const restore = useEffectEvent((serialized: string) => {
    if (!parseLocalDraft || !restoreLocalDraft) return false;
    const stored = parseStoredDraft(serialized, parseLocalDraft);
    if (!stored) return false;
    restoreLocalDraft(stored.draft);
    return true;
  });

  useEffect(() => {
    if (!storageKey) return;
    const timer = window.setTimeout(() => {
      let restored = false;
      try {
        const serialized = window.localStorage.getItem(storageKey);
        if (serialized) restored = restore(serialized);
        if (serialized && !restored) window.localStorage.removeItem(storageKey);
      } catch {
        if (!storageWarningShown.current) {
          storageWarningShown.current = true;
          toast.error("ไม่สามารถเปิด Local draft ได้");
        }
      }
      setHydrated(true);
      if (restored) toast.info("กู้คืน Local draft แล้ว ระบบจะบันทึกอัตโนมัติเมื่อข้อมูลครบ");
    }, 0);
    return () => window.clearTimeout(timer);
  }, [storageKey]);

  useEffect(() => {
    if (!hydrated || !storageKey || localDraft === undefined) return;
    try {
      if (draftFingerprint === savedDraftFingerprint) {
        window.localStorage.removeItem(storageKey);
        return;
      }
      window.localStorage.setItem(storageKey, serializeLocalDraft(localDraft, version));
    } catch {
      if (!storageWarningShown.current) {
        storageWarningShown.current = true;
        toast.error("บันทึก Local draft ไม่สำเร็จ กรุณาตรวจสอบพื้นที่ของเบราว์เซอร์");
      }
    }
  }, [draftFingerprint, hydrated, localDraft, savedDraftFingerprint, storageKey, version]);

  const save = useEffectEvent(async (snapshot: Value, snapshotFingerprint: string, snapshotDraftFingerprint: string) => {
    setSaving(true);
    setErrorFingerprint(null);
    try {
      const attempt = await saveWithConflictRetry(persist, snapshot, version);
      const result = attempt.response;
      if (attempt.retried) setVersion(attempt.version);
      if (result.status === "error" || result.status === "conflict") {
        if (result.currentVersion) setVersion(result.currentVersion);
        setErrorFingerprint(snapshotFingerprint);
        toast.error(result.message ?? "บันทึกอัตโนมัติไม่สำเร็จ");
        return;
      }
      if (result.version) setVersion(result.version);
      setSavedFingerprint(snapshotFingerprint);
      setSavedDraftFingerprint(snapshotDraftFingerprint);
    } catch (cause) {
      setErrorFingerprint(snapshotFingerprint);
      toast.error(cause instanceof Error ? cause.message : "บันทึกอัตโนมัติไม่สำเร็จ");
    } finally {
      setSaving(false);
    }
  });

  useEffect(() => {
    if (!hydrated || !valid || saving) return;
    const manual = manualRequest !== handledManualRequest.current;
    if (!manual && (fingerprint === savedFingerprint || fingerprint === errorFingerprint)) return;
    if (manual) handledManualRequest.current = manualRequest;
    const timer = window.setTimeout(() => {
      void save(JSON.parse(fingerprint) as Value, fingerprint, draftFingerprint);
    }, manual ? 0 : delay);
    return () => window.clearTimeout(timer);
  }, [delay, draftFingerprint, errorFingerprint, fingerprint, hydrated, manualRequest, savedFingerprint, saving, valid]);

  let state: AutosaveState;
  if (!valid) state = "incomplete";
  else if (saving) state = "saving";
  else if (fingerprint === errorFingerprint) state = "error";
  else if (fingerprint !== savedFingerprint) state = "unsaved";
  else state = "saved";

  useEffect(() => {
    const browserWindow = window as Window & { __guideHasUnsavedChanges?: boolean };
    browserWindow.__guideHasUnsavedChanges = state !== "saved";
    if (state === "saved") return () => {
      browserWindow.__guideHasUnsavedChanges = false;
    };
    const warnBeforeLeaving = (event: BeforeUnloadEvent) => {
      event.preventDefault();
      event.returnValue = "";
    };
    window.addEventListener("beforeunload", warnBeforeLeaving);
    return () => {
      window.removeEventListener("beforeunload", warnBeforeLeaving);
      browserWindow.__guideHasUnsavedChanges = false;
    };
  }, [state]);

  return {
    state,
    saveNow: () => {
      if (!valid || saving) return;
      setErrorFingerprint(null);
      setManualRequest((current) => current + 1);
    },
  };
}