/**
 * UI 설정 — gc_app_settings.ui_preferences_json (DB 단일 소스)
 */
import {
  getAppSettingsCache,
  subscribeAppSettings,
} from '../hooks/useAppSettings';
import { saveAppSettings, type AppSettingsDto } from './backendApi';
import {
  EMPTY_UI_PREFERENCES,
  UI_PREFERENCES_VERSION,
  type UiPreferences,
} from '../types/uiPreferences';

const SAVE_DEBOUNCE_MS = 400;
let saveTimer: ReturnType<typeof setTimeout> | null = null;
let pendingPatch: Partial<UiPreferences> | null = null;

function isPlainObject(v: unknown): v is Record<string, unknown> {
  return v != null && typeof v === 'object' && !Array.isArray(v);
}

function deepMerge<T extends Record<string, unknown>>(base: T, patch: Partial<T>): T {
  const out = { ...base } as T;
  for (const key of Object.keys(patch) as (keyof T)[]) {
    const pv = patch[key];
    if (pv === undefined) continue;
    const bv = base[key];
    if (isPlainObject(bv) && isPlainObject(pv)) {
      out[key] = deepMerge(bv as Record<string, unknown>, pv as Record<string, unknown>) as T[keyof T];
    } else {
      out[key] = pv as T[keyof T];
    }
  }
  return out;
}

export function resolveUiPreferences(raw: unknown): UiPreferences {
  if (!raw || typeof raw !== 'object') {
    return { ...EMPTY_UI_PREFERENCES };
  }
  const o = raw as UiPreferences;
  return {
    ...EMPTY_UI_PREFERENCES,
    ...o,
    v: UI_PREFERENCES_VERSION,
    strategyEditor: { ...EMPTY_UI_PREFERENCES.strategyEditor, ...o.strategyEditor },
    indicator: { ...EMPTY_UI_PREFERENCES.indicator, ...o.indicator },
    chart: { ...EMPTY_UI_PREFERENCES.chart, ...o.chart },
    panels: { ...EMPTY_UI_PREFERENCES.panels, ...o.panels },
    virtual: { ...EMPTY_UI_PREFERENCES.virtual, ...o.virtual },
    tradeNotifications: { ...EMPTY_UI_PREFERENCES.tradeNotifications, ...o.tradeNotifications },
  };
}

/** DB 캐시 기준 UI 설정 (앱 설정 로드 후 유효) */
export function getUiPreferences(): UiPreferences {
  return resolveUiPreferences(getAppSettingsCache().uiPreferences);
}

/** UI 설정 부분 갱신 — 낙관적 캐시 + 디바운스 DB 저장 */
export function patchUiPreferences(patch: Partial<UiPreferences>, immediate = false): void {
  const current = getUiPreferences();
  const next = deepMerge(current as Record<string, unknown>, patch as Record<string, unknown>) as UiPreferences;
  next.v = UI_PREFERENCES_VERSION;

  const cache = getAppSettingsCache();
  const merged: AppSettingsDto = { ...cache, uiPreferences: next };
  Object.assign(cache, merged);

  pendingPatch = pendingPatch
    ? (deepMerge(pendingPatch as Record<string, unknown>, patch as Record<string, unknown>) as Partial<UiPreferences>)
    : patch;

  const flush = () => {
    saveTimer = null;
    const toSave = pendingPatch
      ? resolveUiPreferences(deepMerge(getUiPreferences() as Record<string, unknown>, pendingPatch as Record<string, unknown>))
      : next;
    pendingPatch = null;
    void saveAppSettings({ uiPreferences: toSave }).catch(err => {
      console.warn('[uiPreferences] DB 저장 실패:', err);
    });
  };

  if (immediate) {
    if (saveTimer != null) clearTimeout(saveTimer);
    pendingPatch = null;
    void saveAppSettings({ uiPreferences: next }).catch(err => {
      console.warn('[uiPreferences] DB 저장 실패:', err);
    });
    return;
  }

  if (saveTimer != null) clearTimeout(saveTimer);
  saveTimer = setTimeout(flush, SAVE_DEBOUNCE_MS);
}

export function subscribeUiPreferences(listener: () => void): () => void {
  return subscribeAppSettings(listener);
}

/** 중첩 경로 헬퍼 */
export function getUiPref<K extends keyof UiPreferences>(key: K): UiPreferences[K] {
  return getUiPreferences()[key];
}