// @flow

import type {
  StyleModuleMapType,
  StyleModuleImportMapType,
  HandleMissingStyleNameOptionType
} from './types';

const DEFAULT_HANDLE_MISSING_STYLENAME_OPTION = 'throw';

const isNamespacedStyleName = (styleName: string): boolean => {
  return styleName.indexOf('.') !== -1;
};

const getClassNameForNamespacedStyleName = (
  styleName: string,
  styleModuleImportMap: StyleModuleImportMapType,
  handleMissingStyleNameOption?: HandleMissingStyleNameOptionType
): ?string => {
  // Note:
  // Do not use the desctructing syntax with Babel.
  // Desctructing adds _slicedToArray helper.
  const styleNameParts = styleName.split('.');
  const importName = styleNameParts[0];
  const moduleName = styleNameParts[1];
  const handleMissingStyleName = handleMissingStyleNameOption ||
    DEFAULT_HANDLE_MISSING_STYLENAME_OPTION;

  if (!moduleName) {
    if (handleMissingStyleName === 'throw') {
      throw new Error('Invalid style name: ' + styleName);
    } else if (handleMissingStyleName === 'warn') {
      // eslint-disable-next-line no-console
      console.warn('Invalid style name: ' + styleName);
    } else {
      return null;
    }
  }

  if (!styleModuleImportMap[importName]) {
    if (handleMissingStyleName === 'throw') {
      throw new Error('CSS module import does not exist: ' + importName);
    } else if (handleMissingStyleName === 'warn') {
      // eslint-disable-next-line no-console
      console.warn('CSS module import does not exist: ' + importName);
    } else {
      return null;
    }
  }

  if (!styleModuleImportMap[importName][moduleName]) {
    if (handleMissingStyleName === 'throw') {
      throw new Error('CSS module does not exist: ' + moduleName);
    } else if (handleMissingStyleName === 'warn') {
      // eslint-disable-next-line no-console
      console.warn('CSS module does not exist: ' + moduleName);
    } else {
      return null;
    }
  }

  return styleModuleImportMap[importName][moduleName];
};

type OptionsType = {|
  handleMissingStyleName: HandleMissingStyleNameOptionType
|};

export default (styleNameValue: string, styleModuleImportMap: StyleModuleImportMapType, options?: OptionsType): string => {
  const styleModuleImportMapKeys = Object.keys(styleModuleImportMap);

  const handleMissingStyleName = options && options.handleMissingStyleName ||
    DEFAULT_HANDLE_MISSING_STYLENAME_OPTION;

  return styleNameValue
    .split(' ')
    .filter((styleName) => {
      return styleName;
    })
    .map((styleName) => {
      if (isNamespacedStyleName(styleName)) {
        return getClassNameForNamespacedStyleName(styleName, styleModuleImportMap, handleMissingStyleName);
      }

      if (styleModuleImportMapKeys.length === 0) {
        throw new Error('Cannot use styleName attribute for style name \'' + styleName +
          '\' without importing at least one stylesheet.');
      }

      if (styleModuleImportMapKeys.length > 1) {
        throw new Error('Cannot use anonymous style name \'' + styleName +
          '\' with more than one stylesheet import.');
      }

      const styleModuleMap: StyleModuleMapType = styleModuleImportMap[styleModuleImportMapKeys[0]];

      if (!styleModuleMap[styleName]) {
        if (handleMissingStyleName === 'throw') {
          throw new Error('Could not resolve the styleName \'' + styleName + '\'.');
        } else if (handleMissingStyleName === 'warn') {
          // eslint-disable-next-line no-console
          console.warn('Could not resolve the styleName \'' + styleName + '\'.');
        } else if (handleMissingStyleName === 'retain') {
          return styleName;
        }
      }

      return styleModuleMap[styleName];
    })
    .filter((className) => {
      // Remove any styles which could not be found (if handleMissingStyleName === 'ignore')
      return className;
    })
    .join(' ');
};