/* @flow */
/*::

type DotenvParseOptions = {
  debug?: boolean
}

// keys and values from src
type DotenvParseOutput = { [string]: string }

type DotenvConfigOptions = {
  path?: string, // path to .env file
  encoding?: string, // encoding of .env file
  debug?: string // turn on logging for debugging purposes
}

type DotenvConfigOutput = {
  parsed?: DotenvParseOutput,
  error?: Error
}

*/

const fs = require('fs')
const path = require('path')

function log (message /*: string */) {
  console.log(`[dotenv][DEBUG] ${message}`)
}

// Parses src into an Object
function parse (src /*: string | Buffer */, options /*: ?DotenvParseOptions */) /*: DotenvParseOutput */ {
  const debug = Boolean(options && options.debug)
  const obj = {}

  // convert Buffers before splitting into lines and processing
  src.toString().split('\n').forEach(function (line, idx) {
    // matching "KEY' and 'VAL' in 'KEY=VAL'
    const keyValueArr = line.match(/^\s*([\w.-]+)\s*=\s*(.*)?\s*$/)
    // matched?
    if (keyValueArr != null) {
      const key = keyValueArr[1]

      // default undefined or missing values to empty string
      let value = keyValueArr[2] || ''

      // expand newlines in quoted values
      const len = value ? value.length : 0
      if (len > 0 && value.charAt(0) === '"' && value.charAt(len - 1) === '"') {
        value = value.replace(/\\n/gm, '\n')
      }

      // remove any surrounding quotes and extra spaces
      value = value.replace(/(^['"]|['"]$)/g, '').trim()

      obj[key] = value
    } else if (debug) {
      log(`did not match key and value when parsing line ${idx + 1}: ${line}`)
    }
  })

  return obj
}

// Populates process.env from .env file
function config (options /*: ?DotenvConfigOptions */) /*: DotenvConfigOutput */ {
  let dotenvPath = path.resolve(process.cwd(), '.env')
  let encoding /*: string */ = 'utf8'
  let debug = false

  if (options) {
    if (options.path != null) {
      dotenvPath = options.path
    }
    if (options.encoding != null) {
      encoding = options.encoding
    }
    if (options.debug != null) {
      debug = true
    }
  }

  try {
    // specifying an encoding returns a string instead of a buffer
    const parsed = parse(fs.readFileSync(dotenvPath, { encoding }), { debug })

    Object.keys(parsed).forEach(function (key) {
      if (!process.env.hasOwnProperty(key)) {
        process.env[key] = parsed[key]
      } else if (debug) {
        log(`"${key}" is already defined in \`process.env\` and will not be overwritten`)
      }
    })

    return { parsed }
  } catch (e) {
    return { error: e }
  }
}

module.exports.config = config
module.exports.load = config
module.exports.parse = parse