import { join, extname } from 'path';
import { existsSync } from 'fs';
import assert from 'assert';
import extend from 'extend2';
import { winPath } from 'umi-utils';
import { IConfig } from 'umi-types';

interface IOpts {
  cwd?: string;
  defaultConfig?: IConfig;
  onError?: Function;
}

export function getConfigFile(cwd) {
  const files = process.env.UMI_CONFIG_FILE
    ? process.env.UMI_CONFIG_FILE.split(',').filter(v => v && v.trim())
    : ['.umirc.ts', '.umirc.js', 'config/config.ts', 'config/config.js'];
  const validFiles = files.filter(f => existsSync(join(cwd, f)));
  assert(
    validFiles.length <= 1,
    `Multiple config files (${validFiles.join(', ')}) were detected, please keep only one.`,
  );
  if (validFiles[0]) {
    return winPath(join(cwd, validFiles[0]));
  }
}

export function addAffix(file, affix) {
  const ext = extname(file);
  return file.replace(new RegExp(`${ext}$`), `.${affix}${ext}`);
}

function defaultOnError(e) {
  console.error(e);
}

export function requireFile(f, opts: IOpts = {}) {
  if (!existsSync(f)) {
    return {};
  }

  const { onError = defaultOnError } = opts;
  let ret: any = {};
  try {
    ret = require(f) || {}; // eslint-disable-line
  } catch (e) {
    onError(e, f);
  }
  // support esm + babel transform
  return ret.default || ret;
}

export function mergeConfigs(...configs): IConfig {
  return extend(true, ...configs);
}

export function getConfigByConfigFile(configFile, opts: IOpts = {}): IConfig {
  const umiEnv = process.env.UMI_ENV;
  const isDev = process.env.NODE_ENV === 'development';
  const { defaultConfig, onError } = opts;

  const requireOpts = { onError };
  const configs = [
    defaultConfig,
    requireFile(configFile, requireOpts),
    umiEnv && requireFile(addAffix(configFile, umiEnv), requireOpts),
    isDev && requireFile(addAffix(configFile, 'local'), requireOpts),
  ];
  return mergeConfigs(...configs);
}

export function getConfigPaths(cwd): string[] {
  const env = process.env.UMI_ENV;
  return [
    join(cwd, 'config/'),
    join(cwd, '.umirc.js'),
    join(cwd, '.umirc.ts'),
    join(cwd, '.umirc.local.js'),
    join(cwd, '.umirc.local.ts'),
    ...(env ? [join(cwd, `.umirc.${env}.js`), join(cwd, `.umirc.${env}.ts`)] : []),
  ];
}

export function cleanConfigRequireCache(cwd) {
  const paths = getConfigPaths(cwd);
  Object.keys(require.cache).forEach(file => {
    if (
      paths.some(path => {
        return file.indexOf(path) === 0;
      })
    ) {
      delete require.cache[file];
    }
  });
}

export default function(opts: IOpts = {}): IConfig {
  const { cwd, defaultConfig } = opts;
  const absConfigFile = getConfigFile(cwd);

  // 一定要主的 config 文件，UMI_ENV 才会生效
  if (absConfigFile) {
    return getConfigByConfigFile(absConfigFile, {
      defaultConfig,
    });
  } else {
    return {};
  }
}