rofrischmann/fela

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packages/fela/src/getFontFormat.js

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/* @flow */
import isBase64 from './isBase64'

const formats: {
  [string]: string,
} = {
  '.woff': 'woff',
  '.woff2': 'woff2',
  '.eot': 'embedded-opentype',
  '.ttf': 'truetype',
  '.otf': 'opentype',
  '.svg': 'svg',
  '.svgz': 'svg',
}

const base64Formats: {
  [string]: string,
} = {
  'image/svg+xml': 'svg',
  'application/x-font-woff': 'woff',
  'application/font-woff': 'woff',
  'application/x-font-woff2': 'woff2',
  'application/font-woff2': 'woff2',
  'font/woff2': 'woff2',
  'application/octet-stream': 'truetype',
  'application/x-font-ttf': 'truetype',
  'application/x-font-truetype': 'truetype',
  'application/x-font-opentype': 'opentype',
  'application/vnd.ms-fontobject': 'embedded-opentype',
  'application/font-sfnt': 'sfnt',
}

export default function getFontFormat(src: string): string {
  if (isBase64(src)) {
    let mime = ''
    for (let i = 5; ; i++) {
      // 'data:'.length === 5
      const c = src.charAt(i)

      if (c === ';' || c === ',') {
        break
      }

      mime += c
    }

    const fmt = base64Formats[mime]
    if (fmt) {
      return fmt
    }

    console.warn(
      `A invalid base64 font was used. Please use one of the following mime type: ${Object.keys(
        base64Formats
      ).join(', ')}.`
    )
  } else {
    let extension = ''
    for (let i = src.length - 1; ; i--) {
      const c = src.charAt(i)

      if (c === '.') {
        // fetches all the string from the gotten dot to the end
        // of the string
        const strippedSrc = src.slice(i, src.length)

        // removes all query string that are usually attached to the
        // font face strings e.g ./font-location/font.woff2?some-query
        // Reference: https://github.com/robinweser/fela/issues/642
        extension = strippedSrc.includes('?')
          ? strippedSrc.split('?', 1)[0]
          : strippedSrc

        break
      }
    }

    const fmt = formats[extension]
    if (fmt) {
      return fmt
    }

    console.warn(
      `A invalid font-format was used in "${src}". Use one of these: ${Object.keys(
        formats
      ).join(', ')}.`
    )
  }
  return ''
}