const browserslist = require('browserslist')

// convert the browserslist field in package.json to
// esbuild compatible array of browsers
function browserslistToEsbuild(browserslistConfig) {
  if (!browserslistConfig) {
    // the path from where the script is run
    const path = process.cwd()

    // read config if none is passed
    browserslistConfig = browserslist.loadConfig({ path })
  }

  const SUPPORTED_ESBUILD_TARGETS = ['es', 'chrome', 'edge', 'firefox', 'ios', 'node', 'safari']

  // https://github.com/eBay/browserslist-config/issues/16#issuecomment-863870093
  const UNSUPPORTED = ['android 4']

  const replaces = {
    ios_saf: 'ios',
    android: 'chrome',
  }

  const separator = ' '

  return (
    browserslist(browserslistConfig)
      // filter out the unsupported ones
      .filter((b) => !UNSUPPORTED.some((u) => b.startsWith(u)))
      // transform into ['chrome', '88']
      .map((b) => b.split(separator))
      // replace the similar browser
      .map((b) => {
        if (replaces[b[0]]) {
          b[0] = replaces[b[0]]
        }

        return b
      })
      // 11.0-12.0 --> 11.0
      .map((b) => {
        if (b[1].includes('-')) {
          b[1] = b[1].slice(0, b[1].indexOf('-'))
        }

        return b
      })
      // 11.0 --> 11
      .map((b) => {
        if (b[1].endsWith('.0')) {
          b[1] = b[1].slice(0, -2)
        }

        return b
      })
      // only get the ones supported by esbuild
      .filter((b) => SUPPORTED_ESBUILD_TARGETS.includes(b[0]))
      // only get the oldest version
      .reduce((acc, b) => {
        const existingIndex = acc.findIndex((br) => br[0] === b[0])

        if (existingIndex !== -1) {
          acc[existingIndex][1] = b[1]
        } else {
          acc.push(b)
        }
        return acc
      }, [])
      // remove separator
      .map((b) => b.join(''))
  )
}

module.exports = browserslistToEsbuild