const read = require('fs').readFileSync;
const exec = require('child_process').execSync;

// See tests ../node-tests/config/utils.js
const repositoryYear = function(date = exec('git show -s --format=%ci HEAD')) {
  return date
    .toString()
    .trim()
    .split('-')
    .shift();
};
const repositorySHA = function(sha = exec('git rev-parse --short HEAD')) {
  return sha.toString().trim();
};
const binaryVersion = function(repositoryRoot) {
  return function(versionFileContents = read(`${repositoryRoot}/version/version.go`)) {
    // see /scripts/dist.sh:8
    return versionFileContents
      .toString()
      .split('\n')
      .find(function(item, i, arr) {
        return item.indexOf('Version =') !== -1;
      })
      .trim()
      .split('"')[1];
  };
};
const env = function($) {
  return function(flag, fallback) {
    // a fallback value MUST be set
    if (typeof fallback === 'undefined') {
      throw new Error(`Please provide a fallback value for $${flag}`);
    }
    // return the env var if set
    if (typeof $[flag] !== 'undefined') {
      if (typeof fallback === 'boolean') {
        // if we are expecting a boolean JSON parse strings to numbers/booleans
        return !!JSON.parse($[flag]);
      }
      return $[flag];
    }
    // If the fallback is a function call it and return the result.
    // Lazily calling the function means binaries used for fallback don't need
    // to be available if we are sure the environment variables will be set
    if (typeof fallback === 'function') {
      return fallback();
    }
    // just return the fallback value
    return fallback;
  };
};

module.exports = {
  repositoryYear: repositoryYear,
  repositorySHA: repositorySHA,
  binaryVersion: binaryVersion,
  env: env,
};