/**
 * localStorage → gc_app_settings.ui_preferences_json 1회 이전
 */
import type { AppSettingsDto } from './backendApi';
import type { UiPreferences } from '../types/uiPreferences';
import { resolveUiPreferences } from './uiPreferencesDb';

const MIGRATED_FLAG = 'gc_ui_prefs_migrated_v1';

function readJson<T>(key: string): T | null {
  try {
    const raw = localStorage.getItem(key);
    if (!raw) return null;
    return JSON.parse(raw) as T;
  } catch {
    return null;
  }
}

function removeKeys(keys: string[]): void {
  for (const k of keys) {
    try { localStorage.removeItem(k); } catch { /* ignore */ }
  }
}

/** 이미 DB에 uiPreferences가 있으면 스킵. 없으면 localStorage 병합 후 키 제거. */
export function migrateLocalStorageToUiPreferences(
  current: AppSettingsDto,
): { uiPreferences: UiPreferences; changed: boolean } | null {
  try {
    if (localStorage.getItem(MIGRATED_FLAG) === '1' && current.uiPreferences) {
      return null;
    }
  } catch { /* ignore */ }

  const base = resolveUiPreferences(current.uiPreferences);
  const patch: UiPreferences = { ...base };
  let changed = false;

  const editorMode = localStorage.getItem('gc_se_editor_mode');
  if (editorMode === 'list' || editorMode === 'graph') {
    patch.strategyEditor = { ...patch.strategyEditor, editorMode };
    changed = true;
  }

  const canvasMode = localStorage.getItem('gc_se_canvas_interaction');
  if (canvasMode) {
    patch.strategyEditor = { ...patch.strategyEditor, canvasInteraction: canvasMode };
    changed = true;
  }

  const paletteAux = readJson<unknown[]>('se-palette-auxiliary-v1');
  if (paletteAux?.length) {
    patch.strategyEditor = { ...patch.strategyEditor, paletteAuxiliary: paletteAux as NonNullable<UiPreferences['strategyEditor']>['paletteAuxiliary'] };
    changed = true;
  }
  const paletteComp = readJson<unknown[]>('se-palette-composite-v1');
  if (paletteComp?.length) {
    patch.strategyEditor = { ...patch.strategyEditor, paletteComposite: paletteComp as NonNullable<UiPreferences['strategyEditor']>['paletteComposite'] };
    changed = true;
  }

  const customTabs = readJson<NonNullable<UiPreferences['indicator']>['customTabs']>('gc-indicator-custom-tabs-v1' as never);
  if (customTabs?.length) {
    patch.indicator = { ...patch.indicator, customTabs };
    changed = true;
  }

  const mainTabOrder = readJson<string[]>('gc_indicator_main_tab_order');
  if (mainTabOrder?.length) {
    patch.indicator = { ...patch.indicator, mainTabOrder };
    changed = true;
  }

  const listOrder = readJson<string[]>('gc_indicator_settings_list_order');
  if (listOrder?.length) {
    patch.indicator = { ...patch.indicator, listOrder };
    changed = true;
  }

  const chartState = readJson<{ alertPrices?: number[]; indicators?: unknown[] }>('trading_chart_state');
  if (chartState?.alertPrices?.length || chartState?.indicators?.length) {
    patch.chart = {
      ...patch.chart,
      alertPrices: chartState.alertPrices,
      legacyIndicators: chartState.indicators as NonNullable<UiPreferences['chart']>['legacyIndicators'],
    };
    changed = true;
  }

  const panels: Record<string, number | boolean | string> = { ...patch.panels };
  for (const key of ['se-left-width', 'se-terminal-height', 'btd-left-width', 'btd-right-width']) {
    const v = localStorage.getItem(key);
    if (v != null) {
      const n = Number(v);
      panels[key] = Number.isFinite(n) ? n : v;
      changed = true;
    }
  }

  const virtualTargets = readJson<unknown[]>('gc_virtual_targets_v1');
  const virtualSession = readJson<unknown>('gc_virtual_session_v1');
  const cardView = localStorage.getItem('gc_virtual_card_view_v1');
  if (virtualTargets?.length || virtualSession || cardView) {
    patch.virtual = {
      ...patch.virtual,
      ...(virtualTargets?.length ? { targets: virtualTargets as NonNullable<UiPreferences['virtual']>['targets'] } : {}),
      ...(virtualSession ? { session: virtualSession as NonNullable<UiPreferences['virtual']>['session'] } : {}),
      ...(cardView === 'detail' || cardView === 'summary' ? { cardViewMode: cardView } : {}),
    };
    changed = true;
  }

  const readIds = readJson<string[]>('gc_trade_notify_read_v1');
  const hiddenIds = readJson<string[]>('gc_trade_notify_hidden_v1');
  if (readIds?.length || hiddenIds?.length) {
    patch.tradeNotifications = {
      readIds: readIds ?? [],
      hiddenIds: hiddenIds ?? [],
    };
    changed = true;
  }

  const displayMode = localStorage.getItem('tsd-display-mode');
  if (displayMode === 'chart' || displayMode === 'summary') {
    changed = true;
  }

  if (!changed && current.uiPreferences) {
    try { localStorage.setItem(MIGRATED_FLAG, '1'); } catch { /* ignore */ }
    return null;
  }

  if (!changed) return null;

  removeKeys([
    'gc_se_editor_mode',
    'gc_se_canvas_interaction',
    'se-palette-auxiliary-v1',
    'se-palette-composite-v1',
    'gc-indicator-custom-tabs-v1',
    'gc_indicator_main_tab_order',
    'gc_indicator_settings_list_order',
    'trading_chart_state',
    'chartLayout',
    'chartLayoutSync',
    'gc_virtual_targets_v1',
    'gc_virtual_session_v1',
    'gc_virtual_card_view_v1',
    'gc_trade_notify_read_v1',
    'gc_trade_notify_hidden_v1',
    'tsd-display-mode',
    'gc_se_flow_layout_v1',
    'gc_strat_v2',
    'gc_strategies_v1',
    'se-left-width',
    'se-terminal-height',
    'btd-left-width',
    'btd-right-width',
  ]);

  try { localStorage.setItem(MIGRATED_FLAG, '1'); } catch { /* ignore */ }

  return { uiPreferences: resolveUiPreferences(patch), changed: true };
}