/* eslint-disable no-sync */

import * as ChildProcess from 'child_process';
import * as os from 'os';

interface IndexLookup {
  [propName: string]: string;
}

/**
 * The names of any env vars that we shouldn't copy from the shell environment.
 */
const BlacklistedNames = new Set(['LOCAL_GIT_DIRECTORY']);

/**
 * Inspect whether the current process needs to be patched to get important
 * environment variables for Desktop to work and integrate with other tools
 * the user may invoke as part of their workflow.
 *
 * This is only applied to macOS installations due to how the application
 * is launched.
 *
 * @param process The process to inspect.
 */
export function shellNeedsPatching(process: NodeJS.Process): boolean {
  return __DARWIN__ && !process.env.PWD;
}

interface ShellResult {
  stdout: string;
  error: Error | null;
}

/**
 * Gets a dump of the user's configured shell environment.
 *
 * @returns the output of the `env` command or `null` if there was an error.
 */
async function getRawShellEnv(): Promise<string | null> {
  const shell = getUserShell();

  const promise = new Promise<ShellResult>(resolve => {
    let child: ChildProcess.ChildProcess | null = null;
    let _error: Error | null = null;
    let _stdout = '';
    let done = false;

    // ensure we clean up eventually, in case things go bad
    const cleanup = () => {
      if (!done && child) {
        child.kill();
        done = true;
      }
    };
    process.once('exit', cleanup);
    setTimeout(() => {
      cleanup();
    }, 5000);

    const options = {
      detached: true,
      stdio: ['ignore', 'pipe', process.stderr],
    };

    child = ChildProcess.spawn(shell, ['-ilc', 'command env'], options);

    const buffers: Array<Buffer> = [];

    child.on('error', (e: Error) => {
      done = true;
      _error = e;
    });

    child.stdout.on('data', (data: Buffer) => {
      buffers.push(data);
    });

    child.on('close', (code: number, signal) => {
      done = true;
      process.removeListener('exit', cleanup);
      if (buffers.length) {
        _stdout = Buffer.concat(buffers).toString('utf8');
      }

      resolve({ stdout: _stdout, error });
    });
  });

  const { stdout, error } = await promise;

  if (error) {
    // just swallow the error and move on with everything
    return null;
  }

  return stdout;
}

function getUserShell() {
  if (process.env.SHELL) {
    return process.env.SHELL;
  }

  return '/bin/bash';
}

/**
 * Get the environment variables from the user's current shell and update the
 * current environment.
 *
 * @param updateEnvironment a callback to fire if a valid environment is found
 */
async function getEnvironmentFromShell(
  updateEnvironment: (env: IndexLookup) => void
): Promise<void> {
  if (__WIN32__) {
    return;
  }

  const shellEnvText = await getRawShellEnv();
  if (!shellEnvText) {
    return;
  }

  const env: IndexLookup = {};

  for (const line of shellEnvText.split(os.EOL)) {
    if (line.includes('=')) {
      const components = line.split('=');
      if (components.length === 2) {
        env[components[0]] = components[1];
      } else {
        const k = components.shift();
        const v = components.join('=');
        if (k) {
          env[k] = v;
        }
      }
    }
  }

  updateEnvironment(env);
}

/**
 * Apply new environment variables to the current process, ignoring
 * Node-specific environment variables which need to be preserved.
 *
 * @param env The new environment variables from the user's shell.
 */
function mergeEnvironmentVariables(env: IndexLookup) {
  for (const key in env) {
    if (BlacklistedNames.has(key)) {
      continue;
    }

    process.env[key] = env[key];
  }
}

/**
 * Update the current process's environment variables using environment
 * variables from the user's shell, if they can be retrieved successfully.
 */
export function updateEnvironmentForProcess(): Promise<void> {
  return getEnvironmentFromShell(mergeEnvironmentVariables);
}