#!/usr/bin/env node

/* eslint camelcase:0, max-len:0, one-var:0 */

//
// Measures impact of a Git commit (or multiple commits) on generated parsers
// speed and size. Makes sense to use only on PEG.js git repository checkout.
//

"use strict";

let child_process = require("child_process");
let fs = require("fs");
let os = require("os");
let path = require("path");
let glob = require("glob");

// Utils

let print = console.log;

function echo(message) {
  process.stdout.write(message);
}

function exec(command) {
  return child_process.execSync(command, { encoding: "utf8" });
}

function prepare(commit) {
  exec(`git checkout --quiet "${commit}"`);
}

function runBenchmark() {
  return parseFloat(
    exec("node test/benchmark/run")
      // Split by table seprator, reverse and return the total bytes per second
      .split("│")
      .reverse()[1]
      // Trim the whitespaces and remove ` kB/s` from the end
      .trim()
      .slice(0, -5)
  );
}

function measureSpeed() {
  return (runBenchmark() + runBenchmark() + runBenchmark() + runBenchmark() + runBenchmark() / 5).toFixed(2);
}

function measureSize() {
  let size = 0;

  glob.sync("examples/*.pegjs")
    .forEach(example => {
      exec("node bin/peg.js " + example);
      example = example.slice(0, -5) + "js";
      size += fs.statSync(example).size;
      fs.unlinkSync(example);
    });

  return size;
}

function difference($1, $2) {
  return (($2 / $1 - 1) * 100).toFixed(4);
}

// Prepare

let argv = process.argv.slice(2);
let cwd = path.join(__dirname, "..");
let commit_before, commit_after;

if (argv.length === 1) {
  commit_before = argv[0] + "~1";
  commit_after = argv[0];
} else if (argv.length === 2) {
  commit_before = argv[0];
  commit_after = argv[1];
} else {
  print("Usage:");
  print("");
  print("  test/impact <commit>");
  print("  test/impact <commit_before> <commit_after>");
  print("");
  print("Measures impact of a Git commit (or multiple commits) on generated parsers'");
  print("speed and size. Makes sense to use only on PEG.js Git repository checkout.");
  print("");
  process.exit(1);
}

if (process.cwd() !== cwd) {
  process.chdir(cwd);
}

// Measure

let branch = exec("git rev-parse --abbrev-ref HEAD");
let speed1, size1, speed2, size2;

echo(`Measuring commit ${commit_before}...`);
prepare(commit_before);
speed1 = measureSpeed();
size1 = measureSize();
echo(" OK" + os.EOL);

echo(`Measuring commit ${commit_after}...`);
prepare(commit_after);
speed2 = measureSpeed();
size2 = measureSize();
echo(" OK" + os.EOL);

// Finish

prepare(branch);

print(`
test/impact ${commit_before} ${commit_after}

  Speed impact
  ------------
  Before:     ${speed1} kB/s
  After:      ${speed2} kB/s
  Difference: ${difference(parseFloat(speed1), parseFloat(speed2))}%

  Size impact
  -----------
  Before:     ${size1} b
  After:      ${size2} b
  Difference: ${difference(size1, size2)}%

- Measured by /test/impact with Node.js ${process.version}
- Your system: ${os.type()} ${os.release()} ${os.arch()}.
`);