import {
  DEFAULT_PRESET,
  applyThemeOverrideWithRuntime,
  type ApplyThemeOverrideOptions,
  type ApplyThemeOverrideResult,
  type UpdateCssVariables,
} from './applyThemeOverrideRuntime';
import type { Platform } from './types';

export { DEFAULT_PRESET };
export type {
  ApplyThemeOverrideOptions,
  ApplyThemeOverrideResult,
  UpdateCssVariables,
} from './applyThemeOverrideRuntime';

interface CommonJsModule {
  readonly require?: (id: string) => unknown;
}

function getCommonJsLoader(): ((id: string) => unknown) | undefined {
  if (typeof module === 'undefined') return undefined;

  const commonJsModule = module as CommonJsModule;
  const { require: load } = commonJsModule;
  return typeof load === 'function' ? load.bind(commonJsModule) : undefined;
}

function loadCommonJsPeer(id: string): unknown {
  const load = getCommonJsLoader();
  if (!load) return undefined;

  try {
    return load(id);
  } catch {
    return undefined;
  }
}

function detectPlatform(): Platform {
  const reactNative = loadCommonJsPeer('react-native') as
    | {
        readonly Platform?: {
          readonly OS?: string;
        };
      }
    | undefined;
  const os = reactNative?.Platform?.OS;
  return os === 'ios' || os === 'android' ? os : 'web';
}

function getUpdateCssVariables(): UpdateCssVariables {
  const uniwind = loadCommonJsPeer('uniwind') as
    | {
        readonly Uniwind?: {
          readonly updateCSSVariables?: UpdateCssVariables;
        };
      }
    | undefined;
  const uniwindRuntime = uniwind?.Uniwind;
  const updateCSSVariables = uniwindRuntime?.updateCSSVariables;

  if (typeof updateCSSVariables !== 'function') {
    throw new Error(
      'applyThemeOverride could not access the optional "uniwind" peer from this module format. ' +
        'Use the browser or react-native package condition, or pass updateCSSVariables in the options.',
    );
  }

  return updateCSSVariables.bind(uniwindRuntime);
}

/** Parse, expand, validate, and sparsely apply one target ThemeOverride. */
export function applyThemeOverride(
  override: unknown,
  options: ApplyThemeOverrideOptions = {},
): ApplyThemeOverrideResult {
  return applyThemeOverrideWithRuntime(override, {
    runtimeMap: options.runtimeMap,
    runtimePlatform: options.runtimePlatform ?? detectPlatform(),
    getUpdateCSSVariables: () => options.updateCSSVariables ?? getUpdateCssVariables(),
  });
}