// Native
const {createHash} = require('crypto')
const path = require('path')

// Packages
const {readFile} = require('fs-promise')

 /**
  * Computes hashes for the contents of each file given.
  *
  * @param {Array} of {String} full paths
  * @return {Map}
  */

async function hashes(files, isStatic, pkg) {
  const map = new Map()

  await Promise.all(files.map(async name => {
    const filename = path.basename(name)
    let data

    if (isStatic && filename === 'package.json') {
      const packageString = JSON.stringify(pkg, null, 2)
      data = Buffer.from(packageString)
    } else {
      data = await readFile(name)
    }

    const h = hash(data)
    const entry = map.get(h)
    if (entry) {
      entry.names.push(name)
    } else {
      map.set(hash(data), {names: [name], data})
    }
  }))
  return map
}

/**
 * Computes a hash for the given buf.
 *
 * @param {Buffer} file data
 * @return {String} hex digest
 */

function hash(buf) {
  return createHash('sha1')
    .update(buf)
    .digest('hex')
}

module.exports = hashes