@stencila/dockter/src/NixGenerator.ts

import Doer from './Doer'

const VERSION = require('../package').version

/**
 * Generates a default.nix for a `SoftwareEnvironment` instance
 */
export default class NixGenerator extends Doer {

  /**
   * Generate a default.nix file for a `SoftwareEnvironment` instance
   *
   * @param environ `SoftwareEnvironment` instance
   */
  generate (environ: any, folder: string): string {
    this.folder = folder

    let comments = true

    let nixfile = ''

    if (!environ) return ''

    if (comments) {
      nixfile += `# Generated by Dockter ${VERSION} at ${new Date().toISOString()}
# To stop Dockter generating this file and start editing it yourself,
# rename it to "default.nix".\n`
    }

    nixfile += `with import (builtins.fetchTarball {
  name = "stencila-18.12";
  url = https://github.com/stencila/nixpkgs/archive/18.12.tar.gz;
  sha256 = "0kygd44qc2d41dh6pccjiisdvxgpnj9njmhalr0mhrh971xxgnkz";
}) {};

stdenv.mkDerivation rec {
  name = "${environ.name}";
  buildInputs = [
    bashInteractive coreutils utillinux findutils gnugrep which openssl cacert
`

    for (let softwareRequirement of environ.softwareRequirements) {

      let platform = softwareRequirement.runtimePlatform
      if (platform === 'R') { nixfile += `    R\n` }
      if (platform === 'Node.js') { nixfile += `    nodejs\n` }
      if (platform === 'Python') { nixfile += `    python37\n` }

      let language = platform.toLowerCase().replace(/\.[^/.]+$/, '')
      if (language === 'python') { language = 'python37' }

      let pkgs = softwareRequirement.softwareRequirements.map(
        (x: any) => `${language}Packages.${x.name.toLowerCase()}`
      ).join(' ')

      nixfile += `    ${pkgs}\n`
    }

    nixfile = nixfile.trim()
    nixfile += `
  ];
}\n`

    // Write `.default.nix` for use by Nix
    this.write('.default.nix', nixfile)

    return nixfile
  }
}