import { EOL } from 'os'
import chalk from 'chalk'
import { Stats } from 'webpack'
import RequestShortener from 'webpack/lib/RequestShortener'
import WebpackError from 'webpack/lib/WebpackError'
import { formatErrorMessage, stripLoaderFromPath } from './formatUtil'

const createGetFile = (requestShortener: RequestShortener) => (
  e: WebpackError
): string | null => {
  /* istanbul ignore if */
  if (e.file) {
    // webpack does this also, so there must be case when this happens
    return e.file
  } if (
    e.module &&
    e.module.readableIdentifier &&
    typeof e.module.readableIdentifier === 'function'
  ) {
    // if we got a module, build a file path to the module without loader information
    return stripLoaderFromPath(e.module.readableIdentifier(requestShortener))
  }

  /* istanbul ignore next */
  return null
}

// helper to transform strings in errors
const ensureWebpackErrors = (
  errors: Array<string | WebpackError>
): Array<WebpackError> =>
  errors.map((e: string | WebpackError) => {
    /* istanbul ignore if */
    if (typeof e === 'string') {
      // webpack does this also, so there must be case when this happens
      return ({ message: e } as any) as WebpackError
    }
    return e
  })

const prependWarning = (message: string) =>
  `${chalk.yellow('Warning')} ${message}`
const prependError = (message: string) => `${chalk.red('Error')} ${message}`

export default function createStatsFormatter(rootPath: string) {
  const requestShortener = new RequestShortener(rootPath)
  const getFile = createGetFile(requestShortener)

  const formatError = (err: WebpackError) => {
    const lines: Array<string> = []

    const file = getFile(err)

    /* istanbul ignore else */
    if (file != null) {
      lines.push(`in ${chalk.underline(file)}`)
      lines.push('')
    } else {
      // got no file, that happens only for more generic errors like the following from node-sass
      //    Missing binding /mochapack-example/node_modules/node-sass/vendor/linux-x64-48/binding.node
      //    Node Sass could not find a binding for your current environment: Linux 64-bit with Node.js 6.x
      //    ...
      // just print 2 lines like file
      lines.push('')
      lines.push('')
    }

    lines.push(formatErrorMessage(err.message))

    return lines.join(EOL)
  }

  return function statsFormatter(
    stats: Stats
  ): { errors: Array<string>; warnings: Array<string> } {
    const { compilation } = stats

    return {
      errors: ensureWebpackErrors(compilation.errors)
        .map(formatError)
        .map(prependError),
      warnings: ensureWebpackErrors(compilation.warnings)
        .map(formatError)
        .map(prependWarning)
    }
  }
}